LIMATE NVESTIGATIONS ENTER 20 February, 2015 Anthony J. Broccoli Co-Chief Editor Journal of Climate Professor Department of Environmental Sciences Rutgers University 14 College Farm Road New Brunswick, NJ 08901 John C. H. Chiang Co-Chief Editor Journal of Climate Associate Professor and Graduate Advisor University of California, Berkeley 547 McCone Hall Berkeley, CA 94720 Dear Drs. Broccoli and Chiang: I am writing to you regarding a study published in your journal that appears to violate your ethical policy on con?icts of interest. This study, published in the Journal Of Climate in 2009 (Volume 22), is titled ?Centennial variations of the global monsoon precipitation in the last millennium: Results from ECHO-G model.? One of the listed authors of the work is Willie W. H. Soon of the Smithsonian Astrophysical Observatory, a part of Harvard?Smithsonian Center for Astrophysics. According to documents recently made public by the Smithsonian Institution under the Freedom of Information Act, this Journal of Climate article was itemized by Dr. Soon as a ?deliverable? for a grant to the Smithsonian Astrophysical Observatory from Southern Company Services Inc. of Birmingham, Alabama. However, the financial support for this research by Southern Company Services is not disclosed by the authors in the published study, which violates your journal?s policy on con?icts of interest. Southern Company Services is a subsidiary of the Southern Company, based in Atlanta, Georgia, one of the nation?s largest generators and distributors of electricity and a top corporate emitter of greenhouse gases. I will outline these concerns in greater detail, below. Climate Investigations Center, P.O. Box 9 1, Alexandria, VA 2 23 1 3 Email: In January 2008, the Smithsonian Astrophysical Observatory submitted a proposal to Southern Company for a $60,000 grant to ?nd research by Dr. Willie Soon. According to the proposal, ?expected outcomes? included ?Publication of both original and review papers on solar variability and climate change and various environmental impacts of that related change in leading scienti?c journals for the advancement of climate and meteorological sciences.? ATTACHMENT The agreement signed by the Harvard-Smithsonian Center and Southern Company Services states that published studies were part of the ?deliverables? that the Harvard- Smithsonian Center would provide to Southern Company Services (SCS). ATTACHMENT Speci?cally, the ?fth clause of the signed agreement reads: Deliverables. In consideration to SCS for its one (1) year funding contributions to the Project, Smithsonian will deliver to SCS a progress report of the ?ndings including a detailed summary and analysis of the results and ?ndings at the end of the one-year period. SCS shall be entitled to a no-cost, non?exclusive irrevocable license to utilize the data and results of the Project for its internal purposes. In January 2009, Harvard-Smithsonian sent Southern Company a one?year update on the progress of Dr. Soon?s work funded by Southern Company. ATTACHMENT That report reads, ?The goals of this research proposal have been completely and successfully executed with the following list of deliverables.? Among these deliverables, Dr. Soon lists the study ?Centennial variations of the global monsoon precipitation in the last millennium: Results from ECHO-G model,? Journal of Climate, vol. 22, 2356?2371, by Jian Liu, Bin Wang, Qinghua Ding, Xueyuan Kuang, Willie Soon, and Eduardo Zorita. But when we read that study, there is no disclosure that Dr. Soon?s work on the study was funded as part of a ?deliverable? to Southern Company. ATTACHMENT Indeed, there is no statement from Dr. Soon. The acknowledgement states in full: Acknowledgements: Jian Liu and Bin Wang acknowledge the ?nancial supports from the Innovation Project of the Chinese Academy of Sciences (Grant the National Basic Research Program of China (Grant 2004CB720208), and the National Natural Science Foundation of China (Grant 40672210). Bin Wang and Qinghua Ding acknowledge the support received from the National Science Foundation (N SF) climate dynamics group 1) and Your journal follows the American Meteorological Society?s policy on con?icts of interest, which is quite clear. The policy states: Climate Investigations Center, P.O. Box 91, Alexandria, VA 22313 Email: Author Disclosure Obligations: All funding sources should be identi?ed in the manuscript. Authors should disclose to the editor any ?nancial arrangement with a research sponsor that could give the appearance of a con?ict of interest. ATTACHMENT We applaud your guidelines for ethical behavior in science, but we are concerned that your con?ict of interest policy has been ignored and that Dr. Soon may have hidden his funding by Southern Company from your journal. Violations of ethical norms in scienti?c published may undermine the credibility of your journal and your professional society, the American Meteorological Society. We appreciate your attention to this matter and applaud your attention to con?icts of interest and transparency in science. We have provided a copy of this letter to the Dr. Alexander B. ?Sandy? MacDonald, President of the American Meteorological Society. If you have any ?lrther questions, please do not hesitate to contact the Climate Investigations Center. Sincerely, Kert Davies Executive Director Climate Investigations Center cc: Dr. Alexander B. ?Sandy? MacDonald, President, American Meteorological Society Climate Investigations Center, P.0. Box 91, Alexandria, VA 22313 Email: ATTACHMENT A 5:3 Smithsonian Astrophysical Observatory Sponsored Programs and Procurement Department 30 January 2008 Mr. Robert P. Gehri Principal Research Specialist Research and Environmental Affairs Southern Company Services 600 North 18?? Street Birmingham AL 35291 Dear Mr. Gehri: The Smithsonian Astrophysical Observatory (SAD), per your request, is pleased to submit the attached Proposal P6882-l -08 for a one (1) year Research Grant with Nonpro?t Organizations in the amount of $60,000 for Understanding Solar Variability and Climate Change: Signals from Temperature Records of the United States that could commence on 15 January 2008 and continue through 31 December 2008. The program will be conducted by the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts. The program will be performed under the direction of Dr. Willie Soon, as the Principal Investigator, within the Solar, Stellar, and Planetary Sciences Division, with Dr. Nancy Brickhouse as the Associate Director of the Division. Inquiries of a technical nature should be directed to Dr. Willie Soon, Mail Stop 16, Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, Massachusetts 02138-1516, telephone (617) 495?7448, email Inquiries and documents of a contractual nature should be directed to Mr. William J. Ford, Contract and Grant Specialist, Mail Stop 23, same address, telephone (617) 495-7317, e-mail Sincerely yours, Charles Alcock Director Enclosure SMITHSONIAN INSTITUTION 60 Garden Street Cambridge st 7.4917000 Telephone SI-000039 PROPOSAL TO SOUTHERN COMPANY SERVICES FOR UNDERSTANDING SOLAR VARIABILITY AND CLIMATE CHANGE: SIGNALS FROM TEMPERATURE RECORDS OF THE UNITED STATES P6882-1-08 Far the period 15 January 2008 through 31 December 2008 January 2008 Smithsonian Institution Astrophysical Observatory Cambridge, Massachusetts 02138 The Smithsonian Astrophysical Observatory . is a member of the Center for Astrophysics 81-000040 PROPOSAL TO SOUTHERN COMPANY SERVICES FOR UNDERSTANDING SOLAR VA RIABILITY AND CLIMATE CHANGE: SIGNALS FROM TEMPERATURE RECORDS OF THE UNITED STATES PP6882- [-08 For the period 15 January 2008 through 3 December 2008 Funds Requested: $60,000 Erincipal Associate Director, Solara Stellar, and Planetggr Dixisiog Dr. Willie Soon Dr. Nancy S. Brickhouse January 2008 Smithsonian institution Astrophysical Observatory Cambridge, Massachusetts 02138 Director: Dr. Charles Alcock The Smithsonian Astrophysical Observatory is a member or the Harvard-Smithsonian Center for Astrophysics Sl-000041 1P gag Smithsonian Observatory Understanding Solar Variability and Climate Change: Signals from Temperature Records of the United States A Proposal to The Southern Company Dr. Willie Soon, Principal Investigator Smithsonian Astrophysical Observatory Solar, Stellar and Planetary Sciences Division (617-495-7488; January, 2008 Research Target and Proposal: This proposal seeks $60,000 from The Southern Company for year one of this two-year project, Understanding Solar Variability and Climate Change: Signats?om Temperature Records of the United States. I propose to conduct an intensive up-to-date science review of solar variability and climate change (see Soon 2007a), with emphasis on the signals from temperature records of the U.S., that will be a clear improvement of previous studies. The goals for the ?rst year are to collect and assess the scienti?c quality of the available temperature records from the United States, aggregated into four inter-related spatial domains: l) a rural city a city that is minimally disturbed by urban development), 2) an individual state, 3) regional U.S. area, and 4) the whole conterminous U.S. The goals for the second year are to study any plausible connection of these U.S. temperature records with estimated solar irradiance history for the past l2 years from 1895 to 2006. The previously published research paper by Soon (2005) identi?es both the multidecadal variation in total solar irradiance and the l?year solar UV irradiance forcings to be important in explaining the observed Arctic surface air temperature change over the past [30 years or so. The overall goal for this 12-year program is to extend our basic understanding on how the variable solar irradiance outputs could be physically connected to the Earth climate system. The ability to con?rm or reject the statistical correlations shown in Figure I will be of enormous scientific importance. The ultimate physical understanding will arise from detailed assessments on how the solar irradiance is related to the cloud ?eld as well as how the solar irradiance may systematically and persistently modulate the land surface heat ?uxes sensible and latent heats) on multidecadal to centennial time scales. A parallel hypothesis regarding the role of rising atmospheric carbon dioxide (see Soon 2007b) in warming the surface temperatures of the United States on these 4 spatial scales will also be evaluated. Sh000042 Total Solar Ira-names: Total Bolu- Irradlanee A Sun? Climate Coincidence? 1m - "II?r'T?r??r'w 1 I-If-r- (1) Item-um. (8) mm mu 1367- 1337: i 1366 is I . ?Mg I360 . l" 52.5 .-.: $55 1365? a? 5~s ?all! m- as. Essie. a: - . 5'1363 1363 - I I 4 1800 1000 1920 1040 1000 1960 2000 1880 1900 1920 1940 1900 1980 2000 ['l'l I I an 1m (4) us. Ian-r;? :4 1m. mm1355i 1354 . mg [mail 1000 1900 1020 1040 1900 1900 3000 1800 1000 1920 1040 1960 1900 3000 Year Year Figure l: A plausible connection of the solar irradiance (red curves in all four plots; based on Hoyt and Schatten l993-rescaled to the mean absolute valueI measured by the radiometers) compared with US. temperature records in 4 spatial domains (the blue dotted curves are for I) Atchinson, KS, 2) state of Kansas, 3) Central region of the U.S., and 4) conterminous U.S.). These results extend the previous relation found for the Arctic shown in Soon (2005). The scienti?c hypothesis for this sun-climate relation will be carefully formulated and examined in the propOSed project. [Temperature Data Source: US. National Climatic Data Center, lwf.ncdc.noaa. 0v oa climate research ca 3 ca 3.html . 1 Soon (2007a) calls for the solar physics community to firmly establish this value emphasizing its great importance in establishing the mean climatology in climate models. The mean climatology in climate models can be subjected to a rather arbitrary tuning given that the absolute level of total solar irradiance is not determined to any level of con?dence, with values ranging from 1372 to 1360 m2. Ell-000043 Expected Outcomes: (1) Publication of both original and review papers on solar variability and climate change and various environmental impacts of that related change in leading scienti?c joumals for the advancement of climate and meteorological sciences. (2) DeveIOpment of tools, including power-point presentations and concise scienti?c essays, for unbiased and more accurate science accounting that will more powerfully serve informed public policy making. (3) Better public education with active participations by the Pl of this research proposal in all national and international forums interested in promoting the basic understanding of solar variability and climate change. Research Team: Dr. Willie Soon at the Smithsonian Astrophysical Observatory, which is part of the Harvard-Smithsonian Center for Astrophysics, will lead and direct this scienti?c research program. In addition, the Pl may solicit interests for collaborative effort from interested colleagues at no additional cost to the proposal. Funding Request: The funding is primarily to support approximately 3.5 months of the full-time research work of Dr. Willie Soon at the Smithsonian Astrophysical Observatory and a small amount of travel to a scienti?c meeting or publication costs. This research proposal requests $60,000 from the Southern Company for work to start January, 2008, extending for a duration of about one year. References Hoyt D. V. and Schanen K. H. (I 993) A discussion of plausible solar irradiance variations, WOO-1992. Journal of Geophysical Research 98 (Al I). l8895-18906 [with updates from Dr. Nicola Scafetta. Duke University, private communication May 3 . 2007]. Soon W. (2005) Variable solar irradiance as a plausible agent for multidecadal variatitms in the Arctic-wide surface air temperature records of the past l30 years. Geophysical Research Letters 32'. Ll67ll. Soon W. (2007a) Some Issues oFSolar lrradiance Variability and Climatic Responscs'. A Brief Review. lnivitcd Talk GC42A-05 at the American Geophysical Union Fall Meeting (December l0-l4, 2007). Soon (2007b) Implicatitms ofthe secundary role of carbon dioxide and methane forcing in climate change: Past. present, and future Physical Geography 25, 97-125. Slc000044 ESTIMATE OF COST Period of Performance: January 15, 2008 through December 31, 2008 Productive Labor: Dollars Dr. Willie Soon. Pl 494 $25,209 Program Administration 8 $495 Secretary 20 $697 Total Productive Labor 522 26.311 Leave 19.5% 5.1351 Total Direct Labor 31.442 Fringe Bene?ts 26.5% Direct Operating Overhead Base 3.9.774 Direct Operating Overhead 30% 11.932 Travel -see schedule 1.789 Printing and Reproduction - see schedule 1.050 8. A Base 54.545 at A 10% 5.455 TOTAL ESTIMATED COST $0.909 Sl-000045 TRAVEL SCHEDULE NO NO RATE TOT AIR TOT TOTAL DESTINATION TRIPS TRAVEQERB IRIP PER DIEM PER DIEM FARE AIR FARE COST Sdaml?c Malina-Sun chlaco 1 1 5 204 $1.020 $600 $500 5269 51.789 TOTAL TRAVEL $1.020 05110 8298 51.189 'Irlcludes Iaul ?annotation coals and mating mktrallon Tees PRINTING AND REPRODUCTION SCHEDULE COST TOTAL BASIS OBJECT QESGRIPTION VENDOR 098T Ell Pena charges Joumnl 81,050 Fauna 10 Per Page 105 TOTAL PRINTING AND REPRODUCTION ?1,059 SI-000046 CONTRACTUAL AND COST INFORMATION INCLUDING CERTIFICATIONS The Smithsonian Institution, an independent trust establishment was created by an act of the Congress of 1846 to carry out the terms of the will of James Smithson of England, who had bequeathed his entire estate to the United States of America "to found at Washington, under the name of the Smithsonian Institution, an establishment for the increase and diffusion of knowledge among men." After accepting the trust property for the United States, Congress vested responsibility for administering the trust in a Smithsonian Board of Regents. The Smithsonian performs research, educational and other special projects supported by grants and contracts awarded under the cost principles of the Federal Acquisition Regulation, Subpart 31.7 Contracts with Nonprofit Organizations. It is audited by the Defense Contract Audit Agency, Landover, Maryland. The Charter of the Smithsonian Institution carries a mandate for the "increase and diffusion of knowledge among men.? Therefore, any grant or contract that may be awarded as a result of this proposal must be unclassified, in order not to abridge the Institution's right to publish, without restriction, findings that result from this research project. Considering the nature of the proposed effort, it is requested that a Research Grant with reimbursement via electronic funds transfer be awarded to cover the proposed project in acaordance with Subpart Section .22(e) of OMB Circular No. A?llO dated 30 September 1999. Pursuant to Subpart C, Section .33 and .34 of OMB Circular No. A-llO dated 30 September 1999, it is requested that title to all exempt property and equipment purchased or fabricated under the proposed contract be vested irrevocably in the Institution upon acquisition. In accordance with an agreement between the Office of Naval Research and the Smithsonian, the Institution Operates with predetermined fixed overhead rates with carry-forward provisions. For Fiscal Year 1996 and beyond, the Indirect Cost and Fringe Benefits Rates are developed in accordance with the Office of Management and Budget Circular (OMB) Cost Principles for nonprofit organizations. The following approved rates, provided by ONR Negotiation Agreement dated 2 November 2007, shall be used for forward pricing and billing purposes for Fiscal Year 2008. The Fringe Benefits Rate will be applied to the Total Direct Labor Costs. The Material Overhead Rate will be applied to the cost of materials, equipment and subcontracts. The Direct Operating Overhead Rate will be applied to the Direct Labor and Benefits costs. The Rate will be applied to the base consisting of total costs except the costs associated with the materials, equipment and subcontracts. SF000047 The following Approved Rates shall be used for forward pricing and billing purposes for Fiscal Year 2008: Material Burden Rate 5.4% (Cost of Materials, equipment and subcontracts) Personnel Leave Rate 19.5% (Total Direct Labor Costs less paid leave and training [Productive Labor}) Fringe Benefits Rate (Full/Part Time Employees) 26.5% (Total Direct Labor Costs) Fringe Benefits Rate (Intermittent Employees) 8.5% (Total Direct Labor Costs) Direct Operating Overhead Rate . 30.0% (Total Direct Labor and Fringe Benefits Costs) General and Administrative Rate 10.0% (Base consists of Direct Operating Activities less Net Costs Associated with materials, subcontracts and equipment) Central Engineering Overhead Rate 28.9% (Central Engineering Direct Labor and Benefits Costs) Rate verification can be made by contacting Ms. Linda Shipp, Office of Naval Research, Indirect Costs/ONE 242, 800 N. Quincy Street, Room 704, Arlington, Virginia 22217, telephone (703) 696-8559, or e-mail Engineering services are provided by the Central Engineering Department as a Cost Center. Charges by the department to research projects are inclusive of Direct Labor, Fringe Benefits, and Central Engineering Overhead. CERTIFICATIONS Pursuant to Executive Order 12549 and implementing rule (FAR the Smithsonian Institution certifies that it presently is not debarred, suspended, proposed for debarment, declared ineligible or voluntarily excluded from covered transactions by any Federal department or agency. Pursuant to Section 1352, Title 31, United States Code (USC) and implementing rule (FAR the Smithsonian Institution certifies that no Federal appropriated funds have been paid or will be paid to any person for influencing or attempting to influence an officer or employee of any agency, a Member of Congress, an officer or employee of Congress, or an employee of a Member of Congress on his or her behalf in connection with the awarding of any Federal contract, the making of any Federal grant, the making of any Federal loan, the entering into of any cooperative agreement, and the extension, continuation, renewal, amendment or modification of any Federal contract, grant, loan or cooperative agreement. SL00004B ATTACHMENT AGREEMENT FOR FUNDING A GRANT T0 SMITHSONIAN ASTROPHYSICAL OBSERVATORY THIS AGREEMENT is entered into by and between the Smithsonian Astrophysical Observatory, located at 60 Garden Street, Cambridge. MA 021384516, hereinafter referred to as ?Smithsonian"), and Southern Company Services, Inc.. having its principal place of business at 600 North 18th Street. Birmingham. Alabama 35203. on behalf of itself. its parent and its af?liate companies. (collectively referred to as WHEREAS, the Smithsonian is interested in conducting an intensive science review of solar variability and climate change, as provided in the attached Proposal P6882vl-08 (referred to as the ?Project"); and, WHEREAS, SCS, on behalf of itself, its parent and its af?liate companies is interested in furthering the research on the Project and in obtaining advance information and is therefore willing to make a grant to fund this research. NOW, THEREFORE, Smithsonian and SCS hereby agree as follows: 1. Scope of Work. The Scope of Work for this Project shall he conducted in accordance with the attached Proposal entitled ?Understanding Solar Variability and Climate Change: Signals from Temperature Records of the United States?. which is incorporated and made a part of this Agreement. in consideration of the Research to be provided by Smithsonian. SCS agrees to make an advance payment in the sum of Sixty Thousand Dollars and to reimburse Smithsonian for its costs in accordance with the Proposal in an amount not to exceed the advance sum. 2. lgirnitg Natupe of Parties Obligtions. The obligations of SCS and the Smithsonian hereunder shall be limited to payment of the amounts and the Project effort as speci?ed in Article 1 above. SCS assumes no other obligation or responsibility of any kind to the Smithsonian or any other participants or sponsors. if any. SCS makes no warranties or Representations, Express or implied, of any kind. 3. Termination. Smithsonian understands and agrees that in the event the Project is temiinated prior to completion or is not in accordance with the attached Proposal. SCS shall be entitled to a refund of the unexpended funds. 4. No Joint Venture. This Agreement is not intended to create nor shall it be construed to create any partnership. joint venture, employment or agency relationship between or among the parties. and no party shall be liable for the payment or performance of any debts. obligations. or liabilities of any other party. unless expressly assumed in writing. 5. Delivgrables. In consideration to SCS for its one year funding contribution to the Project. Smithsonian shall deliver to SCS a progress report of the ?ndings including a detailed summary and analysis of the results and ?ndings at the end of the one year period. SCS shall be entitled to a no-cost. non-exclusive irrevocable license to utilize the data and results of the Project for its internal purposes. 6. Authority. Each party represents and warrants to the other that as of the effective date of this Agreement: it has all requisite power and authority to enter into and perform its obligations under this Agreement. and there are no actions. suits. or proceedings pending. or to the best of its knowledge threatened. which may have a material adverse effect on its ability to ful?ll its obligations under this Agreement or on its operations. business. properties. assets or condition. 10. 11. 12. 13. 14. Assignment and Subcontracting Prohibited. This Agreement shall not be assigned by Smithsonian nor its obligations subcontracted without the prior written consent of SCS. which shall not be Unreasonably withheld. Any assignment or subcontracting in violation of this provision shall be deemed null and void and SCS shall be entitled to a refund ofits contribution in full. Subseguent Changes in Agreement. This Agreement may be modi?ed only by an amendment executed in writing by a duly authorized representative for each party. ?artiai Invalidig. If any provision of this Agreement is found to be unenforceable then. notwithstanding such unenforceability. this Agreement shall remain in effect and there shall be substituted for such unenforceable provision a like but enforceable provision which most nearly effects the intention ot' the parties. If a like but enforceable provision cannot be substituted, the unenforceable provision shall be deemed to be deleted and the remaining provisions shall continue in effect, provided that the performance, rights. and obligations of the parties hereunder are not materially adversely affected by such deletion. and Assigns. This Agreement shall inure to the bene?t of and be binding upon the respective successors and permitted assigns, if any. of the parties, provided that this provision shall not be construed to permit any assignment which would be unauthorized or void pursuant to any other provision contained herein. Nag-uWaiver. No provision of this Agreement shall be deemed waived and no breach shall be deemed excused unless such waiver or consent is in writing and signed by the party claimed to have waived or consented. No consent by either party to, or waiver of, a breach by the other, whether express or implied, shall constitute a consent to, waiver of. or excuse for any different or subsequent breach. Fume Maleure. Neither party shall be deemed to be in default of any provision ofthis Agreement or liable for failures in performance resulting from acts orevents beyond the reasonable control of such party. Such acts shall include but not be limited to acts of God, civil or military authority. civil disturbance, war. strikes. ?res. other catastrophes, or other 'force majeure' events beyond a party's reasonable control. Sutvival of Representations. The provisions contained in this Agreement that by their sense and context are intended to survive the performance hereof by either or both parties shall so survive the completion of performance and termination of this Agreement. including the making of any and all payments due hereunder. Notices. All notices permitted or required to be given under this Agreement shall be in writing and shall be deemed duly given upon personal delivery (against receipt) or on the fourth day following the date on which each such notice is deposited postage prepaid in the United States Mail, registered or certi?ed. return receipt requested. All notices shall be delivered or sent to the other party at the address(es) shown below or to any other address(es) as the party may designate by ten (l0) days prior written notice given in accordance with this provision. if to Smithsonian: Smithsonian Institution Astrophysical Observatory 60 Garden Street Cambridge. MA 021384516 Attention: Dr. Willie Soon (for technical matters) Attention: Mr. William J. Ford (for contractual matters) [f to SCS: Southern Company Services, Inc. 600 North 13'" Street Bin Birmingham. Alabama 35203 Attention: Robert P. Gehri (for technical matters) Attention: Joseph L. Coker (for contractual matters) 15. Publicity. Smithsonian shall not publish and utilize the name or otherwise identify SCS or its af?liate companies in any publications or other advertisements without the express written consent of SCS. As further consideration to SCS. Smithsonian shall provide SCS an advance written copy of proposed publications regarding the deliverables for comment and input, if any, from SCS. 16. Duplicate Originals. Duplicate originals of this Agreement shall be executed. each of which shall be deemed an original but both of which together shall constitute one and the same instrument. Entire Agreement. This Agreement contains the entire agreement of the parties and there are no oral or written representations, understandings or agreements between the parties respecting the subject matter of this Agreement which are not fully expressed herein. IN WITNESS WHEREOF. each of the parties hereto acknowledge that they have caused this Agreement to be executed in duplicate originals by its duly authorized representative on the respective dates entered below. SOUTHERN COMPANY SERVICES, INC. THE SMITHSONIAN INSTITUTION OBSERVATORY (?Smithsonian?) I By: xi) (Signature) .7 Name: QLEQLCL will Name: William Ford (Typed or printed] (Typed or printed} Title: Mala H, gorm? Title: and grant Spgciaiist Date: 08 Date: SI-000038 ATTACHMENT 6 March 2009 Dr. Robert P. Gehri Southern Company Services, Inc. 600 North 18?? Street Bin l4N?8195 Birmingham, AL 35207 Reference: Agreement for SAD Proposal P6882-l -08 Understanding Solar Variability and Climate Change: Signals from Temperature Records of the United States Subject: Year 1 Report Dear Dr. Gehri: Transmitted herewith is one (1) copy of the subject report for the period 15 January 2008 through 14 January 2009, in accordance with the provisions of the above referenced Agreement. Very truly yours, William J. Ford Contract and Grant Specialist Enclosure cc: Mr. Joseph Coker, Southern Co, w/encl. ebc: C. Alcock, w/encl. N. Brickhouse, w/encl. W. Soon, w/encl. N. Rathle, w/encl. P. Sozanski, w/encl. File: Southco-OOI, w/encl. Sl-000051 UNDERSTANDING SOLAR VARIABILITY AND CLIMATE CHANGE: SIGNALS FROM TEMPERATURE RECORDS OF THE UNITED STATES YEAR 1 REPORT For the Period 15 January 2008 to 15 January 2009 Principal Investigator: Dr. Willie Soon January 2009 Prepared for Southern Company Atlanta, GA 30308 The Smithsonian Astrophysical Observatory is a member of the Harvard-Smithsonian Center for Astrophysics The Southern Company contact for this grant is Robert Gehri, Southern Company, 30 Ivan Allen Jr. Blvd. NW, Atlanta, GA 30308 Sl-000052 Year 1 Report "Understanding Solar Variability and Climate Change: Signals from Temperature Records of the United States" For the Southern Company Period of performance: 1/15/08 to 1/15/09 by Willie Soon, Principal Investigator Smithsonian Astrophysical Observatory Solar, Stellar and Planetary Sciences Division (617-495-7488; wsoonl?icfaharvard.edu) The goals of this research proposal have been completely and successfully executed with the following list of deliverables: (1) The publication of: ?Polar bear p0pulation forecasts: A public-policy foecasting audit? Interface, vol. 38, 382-405 by Scott Kesten Green and Willie Soon (2008) [with comments and replies] Calls to list polar bears as a threatened species under the United States Endangered Species Act are based on forecasts of substantial long-term declines in their population. Nine government reports were written to help US Fish and Wildlife Service managers decide whether or not to list polar bears as a threatened species. We assessed these reports based on evidence-based (scientific) forecasting principles. None of the reports referred to sources of scienti?c forecasting methodology. Of the nine, Amstrup et a1. [Amstrup, S. C., B. G. Marcot, D. C. Douglas. 2007. Forecasting the rangewide status of polar bears at selected times in the let century. Administrative Report, USGS Alaska Science Center, Anchorage, and Hunter et al. [Hunter, C. M., H. Caswell, M. C. Runge, S. C. Amstrup, E. V. Regehr, I. Stirling. 2007. Polar bears in the Southern Beaufort Sea 11: Demography and population growth in relation to sea ice conditions. Administrative Report, USGS Alaska Science Center, Anchorage, were the most relevant to the listing decision, and we devoted our attention to them. Their forecasting procedures depended on a complex set of assumptions, including the erroneous assumption that general circulation models provide valid forecasts of summer sea ice in the regions that polar bears inhabit. Nevertheless, we audited their conditional forecasts of what would happen to the polar bear population assuming, as the authors did, that the extent of summer sea ice would decrease substantially during the coming decades. We found that Amstrup et a1. properly applied 15 percent of relevant forecasting principles and Hunter et al. 10 percent. Averaging across the two papers, 46 percent of the principles were clearly contravened and 23 percent were apparently contravened. Consequently, their forecasts are unscienti?c and inconsequential to decision makers. We recommend that researchers apply all relevant principles properly when important public policy decisions depend on their forecasts. 1Final (2) The publication of "Reply to response to et al. (2007) on polar bears and climate change in western Hudson Bay by Stirling et al. (2008)" Ecological Complexity, vol. 5, 289-302 by Dyck, Soon et al. (2008) We address the three main issues raised by Stirling et al. [Stirling, 1., Derocher, A.E., Gough, W.A., Rode, K., in press. Response to et a1. (2007) on polar bears and climate change in western Hudson Bay. Ecol. Complexity]: (1) evidence of the role of climate warming in affecting the western Hudson Bay polar bear population, (2) responses to suggested importance of human? poiar bear interactions, and (3) limitations on polar bear adaptation to projected climate change. We assert that our original paper did not provide any ?alternative eXplanations [that] are largely unsupported by the data? or misrepresent the original claims by Stirling et al. [Stirling 1., Lunn, N.J., Iacozza, 1999. Long-term trends in the p0pu1ation ecology of polar bears in western Hudson Bay in relation to climate change. Arctic 52, 294?306], Derocher et al. [Derocher, A.E., Lunn, N.J., Stirling, I., 2004. Polar bears in a warming climate. Integr. Comp. Biol. 44, 163?176], and other peer-approved papers authored by Stirling and colleagues. In sharp contrast, we show that the conclusion of Stirling et al. [Stirling 1., Derocher, A.E., Gough, W.A., Rode, K., in press. Response to et a1. (2007) on polar bears and climate change in western Hudson Bay. Ecol. Complexity] - suggesting warming temperatures (and other related climatic changes) are the predominant determinant of polar bear population status, not only in western Hudson (WH) Bay but also for populations elsewhere in the Arctic is unsupportable by the current scienti?c evidence. The commentary by Stirling et al. [Stirling Derocher, A.E., Gough, W.A.. Rode, K., in press. Response to et al. (2007) on polar bears and climate change in western Hudson Bay. Ecol. Complexity] is an example of uni?dimcnsionu , or reductionist thinking, which is not useful when assessing effects ol?climate change on complex ecosystems. Polar bears of WH are exposed to a multitude of environmental perturbations including human interference and factors unknown seal population size, possible competition with polar bears from other populations) such that isolation of any single variable as the certain root cause climate change in the form of warming spring air temperatures), without recognizing con'lbunding interactions. is imprudent, unjustified and ol? questionable scienti?c utility. et [Dyck, M.G., Soon, W., Baydack, R.K., Legates, D.R., Baliunas, 8., Ball, if?i?llCUCk, L.O., 2007. Polar bears of western Hudson Bay and climate change: Are warming spring air temperatures the ?ultimate? survival control factor? Ecol. Complexity, 4, 73?84. 2007.03.002] agree that some polar bear populations may be negatively impacted by future environmental changes; but an oversimpli?cation of the complex ecosystem interactions (of which humans are a part) may not be bene?cial in studying external effects on polar bears. Science evolves through questioning and proposing hypotheses that can be critically tested, in the absence of which, as Krebs and Borteaux [Krebs, C.J., Berteaux, D., 2006. Problems and pitfalls in relating climate variability to population dynamics. Clim. Res. 32, 143?149] observe, ?we will be little more than storytellers.? (3) The publication of the scienti?c manuscript "Centennial variations of the global monsoon precipitation in the lastmillennium: Results from ECHO-G model" by ian Liu, Bin Wang, Qinghua Ding, Xueyuan Knang, Willie Soon and Eduaordo Zorita (2009) in press for the peer-reviewed journal Journal of Climate. We investigate how the global monsoon (GM) precipitation responds to the external and anthropogenic forcing in the last millennium by analyzing a pair of control and forced millennium simulations with the ECHO-G coupled ocean?atmosphere model. The forced run, which includes the solar, volcanic and greenhouse gas forcing, captures the major 2 Sl-000054 modes of precipitation climatology comparably well when contrasted with those captured by the NCEP reanalysis. The strength of the modeled GM precipitation in the forced run exhibits a signi?cant quasi-bi-centennial oscillation. Over the past 1000 years, the simulated GM precipitation was weak during the Little Ice Age (1450-1850) with three weakest periods occurring around 1460, 1685, and 1800, which fell in, respectively, the Sporer Minimum, Maunder Minimum, and Dalton Minimum periods of solar activity. Conversely, strong GM was simulated during the model Medieval Warm Period (ca. 1030-1240). Before the industrial period, the natural variations in the total amount of effective solar radiative forcing reinforce the thermal contrasts both between the ocean and continent and between the northern and southern hemispheres resulting in the millennium-scale variation and the quasi?bi-centennial oscillation in the GM index. The prominent upward trend in the GM precipitation occurring in the last century and the notable strengthening of the global monsoon in the last 30 years (1961-1990) appear unprecedented and owed possibly in part to the increase of atmOSpheric carbon dioxide concentration though our simulations of the effects from recent warming may be overestimated without considering the negative feedbacks from aerosols. The simulated change of GM in the last 30 years has a spatial pattern that differs from that during the Medieval Warm Period, suggesting that global warming that arises from the increases of greenhouse gases and the input solar forcing may have different effects on the characteristics of GM precipitation. We further note that GM strength has good relational coherence with the temperature difference between the northern and southern hemispheres, and that on centennial timescale, the GM strength responds more directly to the effective solar forcing than the concurrent forced response in global mean surface temperature. (4) The publication of the scienti?c manuscript "Validity of Climate Change Forecasting for Public Policy Decision Making? by Kesten Green, Scott and Willie Soon (2009) in the peer-reviewed journal International Journal of Forecasting [Status: accepted; subject to further revision] Policymakers need to know whether prediction is possible and if so whether any proposed forecasting method will provide forecasts that are substantively more accurate than those from the relevant benchmark method. Inspection of global temperature data suggests that it is subject to irregular cycles on all relevant time scales and that variations during the late-20th Century were not unusual. In such a situation, a ?no change? extrapolation is an appropriate benchmark forecasting method. We used the U.K. Met Office Hadley Centre?s annual average thermometer data from 1850 through 2007 to examine the performance of the benchmark method. The accuracy of forecasts from the benchmark is such that even perfect forecasts would be unlikely to help policymakers. For example, mean absolute errors for 20? and 50-year horizons were and We nevertheless evaluated the Intergovernmental Panel on Climate Change?s 1992 projected long-term linear warming rate of We used the IPCC projection for our demonstration of benchmarking because it has in?uenced important policy decisions. The small sample of errors from ex ante projections for 1992 through 2008 was practically indistinguishable from the benchmark errors. Validation for long- term forecasting, however, requires a much longer horizon. We illustrate proper 3 Sl-000055 validation procedures by projecting the IPCC warming rate successively over a period analogous to that envisaged in their 0.03?C?per?year 21st Century warming scenario in which C02 levels are expected to grow exponentially. Namely 1851 to 1975. The errors from the projections were more than seven times greater than the errors from the benchmark method. Relative errors were larger for longer forecast horizons. Our validation exercise illustrates the importance for policymakers of determining predictability before making expensive decisions. (5) Preparation of the scienti?c manuscript ?Multiple and changing cycles of active stars 11. Results? by K. Olah, Z. Kollathl, T. Granzer, K.G. Strassmeier, A.F. Lanza, S. Jarvinen, H. Korhonen, S.L. Baliunas, W. Soon, S. Messina, and G. Cutispoto (2009) for publication in the peer?reviewed journal Astronomy Astrophysics (Status: submitted) ABSTRACT Aims. We study the time variations of the cycles of 20 active stars based on decades?long photometric or spectroscopic observations. Methods. A method of time-frequency analysis, as discussed in a companion paper, is applied to the data. Results. Fifteen stars de?nitely show multiple cycles; the records of the rest are too short to verify a timescale for a second cycle. The cycles typically show systematic changes. In three stars we found 2?2 cycles that are not harmonics, and which vary in parallel, indicating that a common physical mechanism arising from a dynamo construct. The positive relation between the rotational and cycle periods is con?rmed for the inhomogeneous set of active stars. Conclusions. Stellar activity cycles are generally multiple and variable. (6) Preparation of the scienti?c manuscript ?Solar Arctic-Mediated Climate Variation on Multidecadal to Centennial Timescales: Empirical Evidence, Mechanistic Explanation, and Testable Consequences? (2009) by Willie Soon for publication in the peer-reviewed journal Physical Geography (Status: submitted) The abstract of this new paper says: ?Soon (2005) showed that the variable total solar irradiance (TSI) could explain, rather surprisingly, well over 75% of the variance for the decadally-smoothed Arctic-wide surface air temperature over the past 130 years or so. The present paper provides additional empirical evidence for this physical connection, both through several newly published high-resolution paleo-proxy records and through robust climate?process modeling outputs, and proposes a mechanistic explanation, involving 1) the variable strength of the Atlantic meridional overturning circulation (MOC) or thermohaline circulation (THC), 2) the shift and modulation of the Inter- Tropical Convergence Zone (ITCZ) rainbelt and tropical Atlantic ocean conditions, and 3) the intensity of the wind-driven subtropical and subpolar gyre circulation, across both the North Atlantic and North Paci?c. A unique test of this proposed solar TSI-Arctic thermal-salinity?cryospheric coupling mechanism is the 5-to-20?year delayed effects on 4 (1) the peak Atlantic MOC flow rate centered near and (2) sea surface temperature (SST) for the trepical Atlantic. The solar Arctic-mediated climate mechanism on multidecadal to centennial timescales presented here can be compared with and differentiated from both the related solar T81 and UV irradiance forcing on decadal timescale. The ultimate goal of this scientific research is to gain suf?cient mechanistic details so that the proposed solar?Arctic climate connection on multidecadal to centennial timescales can be con?rmed or falsi?ed. A further incentive is to expand this physical connection to longer, millennial-scale variability as motivated by the multiscale climate interactions shown by Braun et al. (2005), Weng (2005) and Dima and Lohmann (2009).? (7) The prominent participation of PI in the following list of scientific talks and discussion at both national and international forums of professional scientists: All power-point talks are available upon request January 4-6, 2008: Awakening 2008 Conference, Sea Island, Georgia "The secondary role of CO2 radiative forcing in climate change: Real facts you are not even supposed to ?nd out!" March 2-4, 2008: International Climate Conference, New York City, NY "Global Warming 101: Al Gore's C02 Theory" March 15, 2008: Good Neighbor Forum, Cheyenne, WY "Global Warming Explained!" (co-panelist Lyle Laverty, Assistant Secretary of Fish, Wildlife and Park Services) March 31, 2008: Deliberative Polling Event at California University of California, PA "Global Warming Explained: The importance of getting the science right!" April 3, 2008: Department of Physics Colloquium, University of Buffalo, NY "The secondary role of C02 and CH4 forcing on climate change: Past, present and future" April 24, 2008: Sutherland Institute Global Warming Panel (with Roy Spencer as co-panelist) "Future of Utah", Salt Lake City, Utah June 19-22, 2008 Annual "Winning Ideas Weekend" of the Free to Choose Network, New York City, NY "The Sun, C02 and Global Warming" (with Dave Legates as co-panelist) (among other speakers: John Fund of WSJ and John Stossel of ABC News) June 23-28, 2008: Nice France Special session for the ISF. Session Title: "Climate Forecasting and Public Policy." 5 Sl-000057 "Do the Forecasts by the US. Government Provide Valid Evidence for the Decision to Classify Polar Bears as an Endangered Species?? J. Scott The Wharton School, U. of Philadelphia, PA, Kesten. C. Green, Business and Econbmic Forecasting, Monash University, Vic 3800, Australia and Willie Soon, Harvard-Smithsonian Center for Astrophysics, Cambridge MA July 11-13, 2008: Annual Meeting of Doctors for Disaster Preparedness, Phoenix, Arizona "Endangering the Polar Bears: How environmentalists kill" August 6-14, 2008: the 33rd International Geological Congress, Oslo, Norway co-chairing, with Professor Bob Carter of James Cook University, the science session CGC-03: ?Solar drivers of climate change and the stratigraphic record? (ii) selected by Professor David Gee of Uppsala University, the IGC SciCom Chairman, to be one of the speakers for the August 8's Theme of the Day of IGC on "Climate" and the title of my talk: ?Solar and Climate Variability: Past, present and future? invited speaker for session: "Solar irradiance variability and climatic responses: A brief review" (iv) contributing author for CGC-03 session: ?Relationship between the global monsoon intensity and the effective solar radiation in the last millennium? by ian Liu, Bin Wang and Willie Soon September 15, 2008: Marshall Institute Climate Discussion Group, "The Sun-Climate Connection" (1) September 23, 2008: University of Southern California, Ayn Rand Institute Global Warming and Policy Panel (with Keith Lockitch as co?panelist), "On the science of global climate change" September 25, 2008: University of California Berkeley, Ayn Rand Institute Global Warming and Policy Panel (with Keith Lockitch as co-panelist), "On the science of global climate change" (11) September 29, 2008: Columbus, Ohio, Annual Meeting of the Managers? Association, "On the science of global climate change" (0) November 24-26, 2008: Jakarta, Indonesia, Invited speaker at the International Symposium on Climate and Weather of the Sun-Earth System hosted by Indonesia?s National Agency for Meteorology Geophysics (as part of the sc0ping processes for the upcoming UN IPCC ARS reports). 6 l-O 00058 ATTACHMENT 2356 JOURNAL OF CLIMATE Centennial Variations of the Global Monsoon Precipitation in the Last Millennium: Results from ECHO-G Model EDUARDO *State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, China VOLUME 22 JIAN BIN QINGHUA XUEYUAN WILLIE AND Department of Merenrriiogy. and haematimml Paci?c Harrow}: Crater. University rimevaii at Manoa, Honolulu, Hawaii Ocean University of China, Qingdao, ("ham (Trainer ?nr Astrophysics, Crunhririgr, institute for (Turn-mi Research, UKSN Research (femur, (it't'rtiracht, Germany {Eli (Manuscript received 29 November 2007, in ?nal form 3 September 2008) ABSTRACT The authors investigate how the global monsoon (GM) precipitation responds to the external and an? thropogenic forcing in the last millennium by analyzing a pair of control and forced millennium simulations with the ECHAM and the global Hamburg Ocean Primitive Equation (ECHO-G) coupled ocean?atmosphere mode]. The forced run, which includes the solar, volcanic, and greenhouse gas forcing, captures the major modes of precipitation climatology comparably well when contrasted with those captured by the NCEP reanalysis. The strength of the modeled GM precipitation in the forced run exhibits a signi?cant quasi- bicentennial oscillation. Over the past 1000 yr, the simulated GM precipitation was weak during the Little Ice Age (1450?1850) with the three weakest periods occurring around 1460, 1685, and 1800, which fell in, respectively, the Sporer Minimum, Maunder Minimum, and Dalton Minimum periods of solar activity. Conversely, strong GM was simulated during the model Medieval Warm Period (ca. 1030?1240). Before the industrial period, the natural variations in the total amount of effective solar radiative forcing reinforce the thermal contrasts both between the ocean and continent and between the Northern and Southern Hemispheres resulting in the millennium-scale variation and the quasi-bicentennial oscillation in the GM index. The prominent upward trend in the GM precipitation occurring in the last century and the notable strengthening of the global monsoon in the last 30 yr (1961+90) appear unprecedented and are due possibly in part to the increase of atmospheric carbon dioxide concentration, though the authors? simulations of the effects from recent warming may be overestimated without considering the negative feedbacks from aero- sols. The simulated change of GM in the last 30 yr has a spatial pattern that differs from that during the Medieval Warm Period, suggesting that global warming that arises from the increases of greenhouse gases and the input solar forcing may have different effects on the characteristics of GM precipitation. It is further noted that GM strength has good relational coherence with the temperature difference between the Northern and Southern Hemispheres, and that on centennial time scales the GM strength responds more directly to the effective solar forcing than the concurrent forced response in global-m ean surface temperature. 1. Introduction Monsoon climate varies on several characteristic time scales in addition to ?uctuations of random origin. In the last two decades, signi?cant progress has been made in the study of monsoon variability on intraseasonal, Corresponding author address: Dr. J. Liu, State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing 210008, China. E-mail: jianliu@niglas.ac.cn 2009 American Meteorological Society interannual, interdecadal, and orbital time scales of tens of thousands of years. A review of recent progresses in the understanding of Asian monsoon variability has been summarized in Wang (2006). However, the centennial- scale variability of the global monsoon system has been considerably less studied. On time scale of centuries, the internal feedback processes that control the interannual- to interdecadal-scale variations become less important; in the meantirne, the persistent, external forcing from centennial?scale variations in solar radiation, when viewed from the perspective of local and regional spatial domains, 1 MAY 2009 may be considerably stronger and more effective than the effect of internal feedback. Both the nature and cause of the centennial-scale variability are largely not known and understudied. In contrast to numerous studies on the global-mean temperature, we focus on global monsoon precipitation in this study. Why are we particularly concerned with the global monsoon precipitation? The monsoon rain- fall provides water resources to about two-thirds of the world?s population, so any improved knowledge on its variation will be of great societal importance. Monsoon precipitation is also of scienti?c importance as it is the key variable of the global water cycle and it provides a critical heat source for driving atmospheric circulation. What is the global monsoon? Previous studies have mostly focused on the monsoon changes in speci?c re- gions because of considerable regionality of the mon- soon variations. Yet regional monsoons are coordinated by the same annual cycle of the solar forcing and their variations are interrelated. Trenberth et al. (2000) ar- gued that the conservation of atmospheric mass, mois- ture, and energy spread over global domain with ex- changes in the lower boundary. They have de?ned the global monsoon system as a global-scale overturning circulation that varies annually. Wang (1994) ?rst at- tempted to delineate the global monsoon regime using outgoing longwave radiation data as the proxy for deep convection and precipitation. Wang and Ding (2006) further demarcated a global monsoon (GM) precipita- tion domain based on characteristics of monsoon pre- cipitation and examined the trends of the GM rainfall over land using four sets of rain gauge precipitation datasets compiled for the period 1948?2003. But how the GM changes on multidecadal to millennial time scales and what mechanisms are responsible for them remain poorly studied. One of the major roadblocks for studying GM vari- ability on centennial or millennial scale is the lack of direct observations, especially on the global scale. To make progress, we consider numerical simulations with atmosphere?ocean coupled climate models for the last millennium. These simulations may provide useful sur- rogate datasets for analyzing and understanding any changes of GM precipitation on multidecadal to cen- tennial time scales. These kinds of simulations have been constructed using a wide variety of climate models with different levels of complexity, including the second climate con?guration of the Met Of?ce Uni?ed Model Johns et al. 1997), Geophysical Fluid Dy- namics Laboratory (GFDL) model (Manabe and Stouffer 1993; Stouffer et al. 2000), Commonwealth Sci? enti?c and Industrial Research Organisation (CSIRO) model (Vimont et al. 2002), ECHAM and the global LIU ET AL. 2357 Hamburg Ocean Primitive Equation (ECHO-G) model (Rodgers et al. 2004; Min et al. 2005a,b; Wagner et al. 2005), and Meteorological Research Institute Coupled General Circulation Model, version 2.2 (MRI CGCM2.2) model (Kitoh 2006) for control simulations; and the Climate and Biosphere Model model (Bauer et al. 2003), ECHO-G model (Zorita et al. 2003; Gonzalez-Rouco et al. 2003; Zorita et a1. 2005; Gouirand et al. 2007a,b), ocean?atmosphere+sea ice model of intermediate complexity de Bilt?coupled large- scale ice?ocean model (Goosse et a1. 2005), Model for the Assessment of Greenhouse-Gas Induced Climate Change (MAGICC) model (Osborn et al. 2006), Isopycnal Model Stendel et al. 2006), third climate con?guration of the Met Of?ce Uni?ed Model Tett et al. 2007), and National Center for Atmospheric Research Cli- mate System Model (NCAR Mann et al. 2005b; Ammann et al. 2007) for forced simulations of the past millennium or past half millennium. Based on these model results, the internal variability of temperature, precipitation, mean sea level pressure, and major modes of climate variation such as the North Atlantic Oscillation (NAO), ENSO, and Indian mon- soon have been discussed (Min et al. 2005a,b; Zorita et a1. 2003; Kitoh 2006). Variabilities on interannual, decadal, multidecadal, and centennial time scales under natural and anthropogenic forcing have also been ex- amined in terms of surface and subsurface temperatures (Stouffer et al. 2000; Beltrami et al. 2006; Gonzalez? Rouco et al. 2003; Zorita et a1. 2005; Wagner et a1. 2005; Osborn et a1. 2006). Both model?model comparison (Goosse et al. 2005; Osborn et al. 2006) and model?data comparison (Liu et a1. 2005; Beltrami et a1. 2006) among convenient indexes like SST, ENSO, NAO, and Arctic Oscillation Vimont et al. 2002; Rodgers et a1. 2004', Goosse et al. 2005; Gouirand et al. 2007a,b) have been performed in order to assess the reality and ro- bustness of models? simulations. Roles of centennial? scale variations in solar activity (Wagner et al. 2001; Fleitmann et a1. 2003; Weber et a1. 2004; Wiles et al. 2004; Holzkamper et al. 2004; Delrnonte et al. 2005; Lim et al. 2005; Wang et al. 2005; Haltia-Hovi et al. 2007) and changes between volcanic pulse forcing (Crowley 2000; Goosse and Renssen 2004; Mann et al. 2005a) have also been recently investigated and argued through a combination of paleo?proxy data analyses and climate modelings. But how does the GM rainfall respond to natural and anthropogenic forcing in the last millennium? How do the spatial patterns of GM precipitation anomalies differ between the warm and cold periods in the millennium? How do the changes of GM rainfall relate to the changes 2358 of global temperature and interhemispheric temperature difference? These open questions will be explored here. To study these questions, we ?rst explore the perfor- mance of climate model in simulating annual mean and annual cycle of the precipitation in the global tropics and subtropics (section next we de?ne the global monsoon indexes (GMI) for the variability of global monsoon precipitation and its centennial-to-millennial? scale variability (section the ECHO-G simulation clearly yielded the mock-up versions of the Medieval Warm Period (MWP), Little Ice Age (LIA), and Present Warm Period (PWP)?their durations in the model will be de?ned later. We will then compare the spatial struc- ture of GM precipitation during the MWP, LIA, and PWP (section 4), and ?nally we discuss the forcing-response relationships between GMI and radiative forcings from changes in solar activity, volcanic eruptions, as well as atmosPheric C02 and CH4 concentration (section 5). Section 6 summarizes the main results of this paper. 2. Model and its validation a. Model and simulation The ECHO-G climate model (Legutke and Voss 1999) consists of the spectral atmospheric model ECHAM4 (Roeckner et al. 1996) and the Hamburg Ocean Prim- itive Equation global (HOPE-G) model (Wolff et al. 1997), both developed at the Max Planck Institute for Meteorology in Hamburg. The ECHAM4 is based on primitive equations with a mixed p?o' coordinate system. The model con?guration used for these simulations has 19 vertical levels in the atmosphere and 20 levels in the ocean, and horizontal resolutions are approximately 3.75? (atmosphere) and 28? (ocean) in both latitudes and longitudes. The ocean model HOPE-G has a grid re?nement in the tropical regions, where the meridional grid point separation reaches 05". To enable the cou- pled model to sustain a simulated climate near to the real present-day climate with minimal drift, both heat and freshwater ?uxes between the atmosphere and ocean are modi?ed by adding a constant (in time) ?eld of adjustment with net-zero spatial average (Roeckner et al. 1996; Wolff et al. 1997). Two millennial integrations with the model will be analyzed here. One is the 1000-yr control simu? lation (CTL), which was generated using ?xed external (annually cycling) forcing set to the present-day values (Zorita et al. 2003). This CT experiment can simulate annual-to?decadal climate oscillations through the in- ternal dynamics of the coupled climate system (Min et al. 2005a,b). The second simulation, named ERIK (covering the period 1000?1990), is forced by three ex- ternal forcing factors (Gonzalez-Rouco et al. 2003; von JOURNAL OF CLIMATE VOLUME 22 Storch et a1. 2004; Zorita et al. 2005): solar variability (Crowley 2000; von Storch et a1. 2004), greenhouse gas concentrations in the atmosphere including C02 and CH4 (Blunier et al. 1995; Etheridge et al. 1996), and the effective radiative effects from stratospheric volcanic aerosols (Crowley 2000) for the period AD 1000?1990. The volcanic forcing is parameterized in this simulation as a simple reduction of the annual-mean solar constant, starting in the year with a volcanic eruption and usually lasting a couple of years, according to the reconstruc- tions of volcanic aerosol forcing (Crowley 2000). This second experiment includes the major natural and anthro- pogenic forcings in the past millennium, but a number of other potentially important forcings anthropogenic tropospheric sulfate aerosols, the effect of land-use and vegetation changes, and some other greenhouse gases, such as halocarbons and ozone) were excluded in the ERIK experiment. We keep in mind that the neglected anthropogenic factors may have a signi?cant impact on the climate in the twentieth century. For example, sul- fate aerosols exert a negative temperature forcing. Ne- glect of the tropospheric sulfate aerosols in the ERIK simulation, therefore, excluded their cooling in?uences on temperature, leading to excessive warming in the last 30?50 yr of the twentieth century. The initial conditions of the ERIK simulation were taken from year 100 of the control run. Those initial conditions are, however, representative of present-day rather than preindustrial climate and the experimental design therefore included a 30-yr adjustment period during which the control run forcing was linearly re? duced until it matched the forcing imposed around AD 1000, followed by a 50-yr period with ?xed forcing to allow the model?s climate to readjust to the modi?ed forcing. The ERIK simulation then proceeded from the conditions at AD 1000 to AD 1990. Note that uncer- tainties remained unresolved with the speci?cation of initial conditions, and that the uncertainty in the initial conditions, in turn, might cause initial climate drift that could potentially in?uence the relationship between applied forcing and simulated response. This issue has been recognized by the authors of the simulation and has been addressed in the comment published in the Journal of Climate (Fig. 1 of Zorita et a1. 2007). b. Validation of the model annual?mean precipitation and annual cycle of precipitation To assess the performance of ECHO-G in modeling precipitation climatology, we examine the annual-mean precipitation and the leading EOF mode of the mean annual cycle. The leading EOF mode accounts for about 70% of the total annual variance and its spa- tial pattern can be faithfully represented by the une? 1 MAY 2009 September (JJ AS) minus December?March (DJFM) precipitation (Wang and Ding 2008). This solstice mode captures the major portion of the global monsoon; for sim- plicity, it will be referred to as the global monsoon mode. Figure 1 compares the spatial patterns of the annual mean (Fig. 1a) and global monsoon (Fig. 1b) derived from the Climate Prediction Center (CPC) Merged Analysis of Precipitation Xie and Arkin 1997), ECHO-G ERIK run, and National Centers for Envi- ronmental Prediction Reanalysis (Kanamitsu et a1. 2002). The CMAP data are considered here as the observed ?ground truth.? Pattern correlation coef- ?cients (PCC) and root-mean?square errors (RMSE) are used to gauge the model performance. The PCC of annual-mean precipitation between ERIK and CMAP (0.87) is lower than that between NCEP-2 Re- analysis and CMAP (0.89). The pattern correlation of the global monsoon mode between ERIK and CMAP (0.81) is also lower than that between NCEP-2 Reanalysis and CMAP (0.85). However, the RMSE of the annual-mean precipitation and global monsoon mode between ECHO-G ERIK and CMAP are 1.09 mm day?1 and 1.88 mm day?1, which are both smaller than those between NCEP-2 Reanalysis and CMAP data (1.16 and 2.02 mm day?1). These results suggest that the simulated precipitation climatology in ERIK run is comparable to those assimilated data in NCEP-2 Re? analysis. This overaH agreement adds con?dence to our subsequent analysis of the centennial?scale precipitation variability using the outputs generated by the ERIK run. While the ERIK run simulates the rainfall climatol- ogy realistically, biases do exist. It can be seen from Fig. 1a that the annual-mean precipitation has signi?- cant errors in the Asian monsoon region, subtropical South Paci?c convergence zone, and South Atlantic convergence zone. The monsoonal mode has signi?cant errors in the East Asian subtropical monsoon and the Mexican?North American monsoon regions. However, the overall model results on global scale are realistic and adequate for our study of the long-term modulations of the global monsoon system by externally imposed nat- ural and anthropogenic forcings. 3. Temporal variation of the global monsoon precipitation a. De?ning the GM domain and indexes The GM is the dominant mode of the annual cycle of the global tropical circulation (Wang and Ding 2008). To analyze the spatiotemporal variation of GM, the global monsoon precipitation domain and the global monsoon precipitation strength are de?ned here fol- lowing Wang and Ding (2008). Monsoonal climate is not LIU ET AL. 2359 only characterized by annual reversal of surface winds but also by a contrasting wet summers and dry winters (Webster 1987). The global monsoon precipitation do? main is de?ned by the region in which the annual range (AR) of precipitation exceeds 2 mm day?1 and the local summer precipitation exceeds 55% of annual rainfall. Here AR is de?ned as MJJ AS precipitation minus precipitation in the Northern Hemisphere (NH) and minus MJJAS precipitation in the Southern Hemisphere (SH). Figure 2 shows the global monsoon domain de?ned by CMAP data, which consists of 6 major monsoon regions: the Northern African (N1), Southern African (SI), Asian (N2), Australian (S2), North American (N3), and South American (S4) monsoon. Note that all these ma- jor regional monsoons involve continent?ocean con- trast. There is a minor region in the central South Paci?c (S3), which does not involve land?ocean thermal con- trast and is a ?pure? oceanic monsoon-like region. In the following analysis, one will ?nd that the behavior in 83 is different from those in the other major continent? ocean monsoon regions. Therefore, we exclude S3 re- gion in the aggregate measure of the intensities for the global monsoon and Southern Hemisphere monsoon. The monsoon strength can be represented by the annual range of the total monsoon precipitation. Since the annual range is largely controlled by the local sum- mer precipitation, an alternative measure of the mon- soon strength is simply the local summer monsoon rain- fall. Thus, a NH monsoon index (NHMI) is de?ned as the JJA rainfall falling in the observed NH monsoon domain including both land and ocean; a SH monsoon index (SHMI) is de?ned as the DJF rainfall falling in the ob- served SH monsoon domain, which includes southern African, Australia, and South America but not the cen- tral South Paci?c. Here the DJF is the season following the NH JJA. As such, the two hemispheric monsoon indexes measure the strength of the aggregated NH and SH monsoon domains, respectively. To quantify the strength of the global monsoon, we de?ne the global monsoon index as the sum of the two hemispheric in- dexes; that is, GMI NHMI SI-IMI. The GMI is a measure of the GM strength in terms of the precipitation within the global monsoon rainy do- main. Under climate change, the annual cycle of the tropical circulation is expected to change. The GM strength can faithfully re?ect this change as it represents the dominant mode of the tropical circulation. b. Centennial and millennial variations of the global monsoon indexes Figure 3 shows the time series of the 7- and 31-yr running means of the monsoon indexes (NHMI, SHMI, (0) Annual mean JOURNAL OF CLIMATE VOLUME 22 Global monsoon mode {In} 12hr 150 12bit rum/day min/day FIG. 1. Comparison of climatology of global precipitation (mm day?): annual mean and global monsoon mode (JJAS minus leading EOF mode of annual cycle) for (top) CMAP, (middle) ECHO-G ERIK run, and (bottom) Reanalysis. CMAP and NCEP-2 Reanalysis climatological data were derived for the period 1979?2004. ERIK 25-yr climatology was derived for the period AD 1965?90. The numbers shown in the upper-left corners and the lower?left corners indicate pattern correlation coef?cients and RMSEs with the CMAP data, respectively. GMI) for both the CTL (Fig. 3a) and ERIK (Fig. 3b) runs. The control run provides an opportunity to ex- amine the internal variability due to unforced feedback processes in the coupled system. In the control run, there is no trend in NHMI, SHMI, and GMI. Further? more, the NHMI and SHMI are not related, as evi- denced by the correlation coef?cients between them valued at about zero for both the 7- and 31-yr running- mean series. This result suggests a lack of coherency of the monsoon intensity between the two hemispheres without external forcing. From the observed data for the last 56 yr, it was found that the correlation coef?- cients between NHMI and SHMI are also very low us- ing either the raw data or the 7-yr running-mean data (Wang and Ding 2006). But the data records are simply too short to con?rm or reject any particular hypothesis concerning relation between monsoon indexes of the two hemispheres. In the ERIK run (Fig. 3b) on the other hand, the simulated, forced responses on multidecadal scales and longer are quite different. Signi?cant centennial varia- tions can be seen. These variations correspond to the evolution of the global-mean temperature, where a model MWP, LIA, and PWP can be recognized (Zorita 1 MAY 2009 LIU ET AL. 2361 Global monsoon precipitation domain 12b: 160 12bit as 0 FIG. 2. The global monsoon precipitation domain de?ned by the region in which the AR of precipitation exceeds 2mm day?1 and the local summer precipitation exceeds 55% of annual rainfall by using CMAP data. et a1. 2005). According to the model simulation, strong global monsoon signal is observed around 1030?1240, which is de?ned here as the model Medieval Warm Period with three distinguished peaks around 1050, 1140, and 1200 (Fig. 3b). On the other hand, weak global monsoons are observed during the model Little Ice Age period from 1450 to 1850. It is of particular interest to ?nd that during the Little Ice Age the GMI strength exhibits three minima, which occur around 1460, 1685, and 1800 (Fig. 3b). These rainfall minima fell in the Sporer Minimum (1420-1570), the Maunder Minimum (1645?1715), and the Dalton Minimum (1790? 1820) periods of low sunspot activity, and in the two latter cases increased volcanic activity as well (Soon and Yaskell 2004; Haltia?Hovi et al. 2007). This suggests a connection with the centennial-scale modulation of the solar and/or volcanic radiative forcings. In sharp con- trast, such historically timed GM minima were not found in the unforced CTL runs. The strengthening of mod- eled GM in the twentieth century and especially during the 1960?90 interval seems unprecedented, which corre- sponds to the sharp multidecadal increase in solar forcing during the ?rst half of the twentieth century and the large increase in atmospheric C02 and CH4 concentration since around 1800 (see further discussion in section 5 below). Additionally, the NHMI and SHMI are signi?- cantly correlated on multidecadal to centennial time scales, the correlation coef?cients between them are 0.71 for 31-yr running-mean series. Centennial variations are also signi?cant in the ERIK run. Power spectrum analyses (Wei 2007) of the 31-yr running-mean series of the hemispheric-scale monsoon indexes (GMI, NHMI, and SHMI) for the ERIK run are shown in Fig. 4. It can be seen that a 192-yr peak is sig- ni?cant above 95% con?dence level (by red noise test) for the global and SH monsoon indexes. The NHMI (Fig. 4b) has a less signi?cant 192-yr peak probably because of larger random noises on this bicentennial scale in the Northern Hemisphere. Other signi?cant periods in the GMI spectrum are marked around 107 yr (mainly be- cause of NHMI) and 74 yr (mainly because of SHMI). We have also calculated the power spectra for all three monsoon indexes using both the raw annual data and the 7-yr running-mean data with quantitatively different spectral peaks and different statistical signi?cances of the peaks, cautioning on the arti?cial effects of the real spectra convoluted with the spectra of the smoothing ?lter. However, we believe that the bicentennial and centennial scales in the modulated GMI, NHMI, and SHMI indexes are qualitatively robust and may be plausibly connected to the prescribed forcing and re- sponse of the global monsoon system studied here. On the global scale, there have been no integrated observations that can be used for either checking or 2362 CTL run NHMI JOURNAL OF CLIMATE VOLUME 22 ERIK run NHMI SHMI SHMI 0.44 mm/day ?0.2 I ll -0.3'i -0?04- -03. Year 0 {50 260 360 460 560 560 760 360 960 1000 11b0 12bo 13ho I4ho isbn idbo iiho iahu 19bo Year (AD) FIG. 3. Time series of the 7-yr running?mean monsoon indexes: CTL (free coupled) run and ERIK (forced) run for (top) NHMI, (middle) SHMI, and (bottom) GMI. The thick solid lines represent the 31?yr running means, which highlight centennial variations. confronting the model results. However, the os- cillation has been noted empirically at many individual sites Zhong et al. 2007; van Beynen et al. 2007; Mangini et al. 2007; Allen et a1. 2007; Vonmoos et al. 2006; Wang et a1. 2005; Lim et al. 2005; Holzkamper et al. 2004; Delmonte et al. 2005; and Damon 2003; Agnihotri et al. 2002; Wagner et al. 2001; Chambers and Blackford 2001; Hong et al. 2001, 2000; Ram and Stolz 1999; Yu and Ito 1999; Leventer et al. 1996). The period of 74 yr is very signi?cant (60~80 yr) in the South Asian and East Asian monsoon region for both temperature and precipitation (Zhu and Wang 2002; Goswami 2004; Ding et al. 2007). The ECHO-G results might provide useful clues for further assembling empirical proxy data on the global scale and for in- terpretation of underlying physical mechanisms to the 200?yr oscillation. 4. Variations in the spatial structure of the 30-yr climatology of the global monsoon The spatial structure of annual?mean precipitation anomaly and the global monsoon precipitation anom- aly with reference to the corresponding long-term means (1000?1990) during the three periods of MWP, LIA, and PWP are shown in Fig. 5. The annual-mean pre- cipitation anomalies during the MWP, LIA, and PWP depict how the mean precipitations during these three epochs deviate from the long-term mean precipitation 2363 GMI In ERIK run 99% con?dence -- 95% con?dence -- 90% con?dence 960.0 24001311569 73.3 60.0 50.5 43.6 30.4- 3445 31.0 Periodicity (yr) 1MAY2009 LIU ET AL 150 II 140? 1 3 13020- 10' NHMI In ERIK run 150 . . . i 140 11.0 120- no. i con?dence mu- -- 95% con?dence - - 90% con?dence Normalized Fourier power spectrum Periodicity (yr) SHMI in ERIK run 99% con?dence .. 95% con?dence 90% con?dence Normalized Fourier power spectrum 000.0 24001311900 73.0 00.0 50.5 40.0 30.4 34.3 01.0 Periodicity (yr) FIG. 4. Spectrum analyses on the 31-yr running mean of the monsoon indexes for ERIK simulation: GMI, NHMI, and SHMI. (1000?1990). Note that the global monsoon precipitation anomaly is de?ned by the A precipitation anomaly in the NH and DJ precipitation anomaly in the SH, which depicts the strength of the local summer monsoon pre? cipitation or roughly the annual range of the monsoon precipitation. The MWP and LIA periods are plotted around the maximum of GMI intensity at 1200 and the minimum of GMI at 1685, respectively (see Fig. 3). Figure 5a compares the annual?mean precipitation distribution for the three periods. The annual-mean precipitation between and is 3.12 mm, 3.09, and 3.12 mm day-1 for MWP, LIA, and PWP, respec- tively (Table 1), which indicates the increase of the total rainfall between and during the warm periods of MWP and PWP. The annual-mean precipitation in all the 6 continental monsoon domains is 3.78, 3.75, and 3.80 mm day?1 (Table 1) for MWP, LIA and PWP, re- spectively, which means that the annual?mean precipi- tation in the global monsoon domain decreased during the relatively cold LIA period compared to the MWP and PWP periods. Although with a slight difference in the timing for LIA and MWP and probably beyond the spatial resolution of our model outputs, the recent high- quality reconstruction of monsoon rainfalls for south- west China (between the moisture transport pathway of Dongge Cave and Heshang Cave; broadly represented by our N2 monsoon region) by Hu et a1. (2007) sug- gested a relatively wetter and dryer conditions for the MWP and LIA, respectively. Figure 5b compares the local summer precipitation changes connected to the changes in the local mon- soon strength. During the MWP and PWP periods, monsoon strengthens nearly globally in each of the con- tinental regional monsoons. This is especially so for the present-day monsoon climatology. On the other hand, during the LIA, there is a general decrease in each 2364 Annual mean precipitation anomaly eon- JOURNAL OF CLIMATE VOLUME 22 Global monsoon precipitation anomaly FIG. 5. Comparison of precipitation patterns for the three 30-yr epochs: (top) MWP (1185?1214), (middle) LIA (1685-1714), and (bottom) PWP (1961?90). The annual-mean precipitation anomaly and the global monsoon precipitation anomaly with reference to the corresponding long-term means (1000?1990). The global monsoon precipitation is de?ned by the HA precipitation in the NH and DJ precipitation in the SH. The enclosed red lines outline the monsoon domains. of the monsoon regions except the oceanic S3. The precipitation anomaly of global monsoon during the MWP, LIA, and PWP is 0.014, -0.021, and 0.029 mm day?1, respectively. This fact suggests that forced re- sponses of the regional monsoons have a cohesive pat- tern and they are coordinated by the superposed changes in the external forcing. Thus, the global mon? soon index offers the measure of a global-scale trend common to the regional monsoons except oceanic monsoon region S3. We next note that, although the increase in GMI is similar between MWP and PWP, the spatial patterns have some differences (Fig. 5b). The present?day cli- mate features largest increase of the annual-mean pre- cipitation over the equatorial western Paci?c, while during MWP rainfall over the equatorial western Paci?c warm pool decreases signi?cantly. Changes in the mon- soon strength in the Mexican monsoon also differ sig- ni?cantly for the simulated monsoon climatologies for the MWP and PWP. Table 1 shows that the oceanic monsoon S3 behaves differently from all other 6 continental monsoon regions. In the continental monsoon regions, LIA precipitation is less than MWP and PWP period, but the oceanic 1 MAY 2009 TABLE 1. The annual?mean precipitation (mm day?1) of re- gional and global monsoon regions (exclude S3) and belt during the MWP (1185?1214), LIA (1685?1714), and PWP (1961?90). The notation N1represents the northern African, Asian, North American, Southern African, Australian, central South Paci?c, and South American monsoon regions, respectively. LIA Region MWP PWP N1 3.187 3.181 3.285 N2 3734 3.642 3.790 N3 5.108 5.047 5.056 S1 3.463 3.334 3.408 S2 3.599 3.405 3.473 S3 6.088 6.137 6.087 S4 3.885 3.832 3.985 Global monsoon (without 83) 3.782 3.747 3.798 belt 3.122 3.092 3.117 monsoon region (S3) is just opposite. For this reason, we had excluded S3 from our integrated monsoon indexes, namely the SHMI and GMI. 5. Attribution and mechanisms Figure 6 compares the time series of the direct solar radiative forcing, indirect radiative forcing from volca- nic eruptions, effective radiation forcing (the sum of the solar and volcanic forcing), and atmospheric C02 concentration, along with the global monsoon index, global-mean temperature, and interhemispheric tem- perature difference (NH minus SH). All time series were smoothed with a 31-yr running?mean ?lter in order to better highlight centennial-to-millennial variations. The correlation coefficients between GMI and the sus- pected relational or causal factors are shown in the lower-right corners of Fig. 6 and presented in greater details in Table 2. a. Variations of the forcing factors The amplitude of variations of the solar irradiance at centennial and longer time scales is still being debated (Krivova et a1. 2007; Solanki and Krivova 2006; Bard and Frank 2006). The amplitude of these variations is usually scaled numerically by the difference between present values and the Late Maunder Minimum. In this simulation this difference (1960?90 mean minus 1680? 1710 mean) is Thus, in the simulation the solar radiation reaching the top of the atmosphere shows signi?cant variation on millennium time scale with a maximum around 1100?1250 and the present day to- gether with a minimum around 1450 (Fig. 6a). The latest value in the simulation (1990) is about 1 rn?2 higher LIU ET AL. 2365 1368' Solar constant 1336 - 1364- 0.72 1 I Volcanic effect use (0) 1364* Effective solar radlation 1362* 1360 - I 0.285- 270- 13.2? 13- 12.3- 12.5- 12.4- 287.4- 3 287.1- 285.8- 286.5- 286.2- 4.4- -OIB '1 I055 Your (AD) FIG. 6. Smoothed time series of the solar radiative forcing (W volcanic effect (W effective solar radiation (W C02 concentration (ppm), GMI (mm day?l), global-mean temperature (K), and interhemispheric tempera? ture difference (K). All time series are 31-yr running means from AD 1000 to 1990. The numbers shown in the lower-right corners indicate correlation coef?cients of GMI with the four external forcing factors and two temperature indexes, respectively. The interhemispheric temperature difference is de?ned by the NH averaged temperature minus the SH averaged temperature. (6) CO. concentration (pp-II) Global monsoon lndex(GMl) (mm/dc!) Global mean temperature 0.86 NH mlnus SH temperature 2366 JOURNAL OF CLIMATE VOLUME 22 TABLE 2. Correlation coef?cients between GMI and other variables in ERIK run. Those values that are statistically signi?cant at the 95% con?dence level are indicated in bold numbers. The method of signi?cant test follows Chen (1982). Solar Volcanic Effective solar Global-mean Correlation coef?cient constant activity radiation C02 CH4 temperature temperature Original data 0.328 0.245 0.335 0.294 0.251 0.382 0.427 7-yr running mean 0.579 0.384 0.638 0.518 0.438 0.724 0.659 31-yr running mean 0.724 0.374 0.777 0.618 0.500 0.862 0.834 than the MWP period. There are centennial ?uctuations superposed on the millennium variation. Spectral anal- ysis shown in Fig. 7a con?rms that the variance is con- centrated on centennial and bicentennial time scales and with prominent peaks occurring on 192 and 120 yr. Similar to our calculations of the power spectra for the monsoonal indexes in Fig. 4, we have also found quantitatively different results for both the peaks and their statistical signi?cances for all the indexes in Fig. 7 using both the raw annual-mean and the 7-yr smoothed series. We believe that these quantitative differences will not strongly affect the key conclusion in the nar? row context of our study of the bicentennial and cen- tennial scales of forcing and response of the global monsoon system. The episode of volcanic forcing changes from year to year; its 31-yr running mean shows primarily a variation on bicentennial time scales (Fig. 6b). The spectral analysis con?rms peaks on 192 and 107 yr, respectively, which are both signi?cant at the 95% con?dence level (Fig. 7b). What gives rise to the periodicity in the ef- fective volcanic forcing is very curious because volcanic eruptions have been thought to be more or less chaotic and unpredictable with no regularity in time. The effective solar forcing reaching the top of the atmosphere, which is the sum of the solar forcing at the top of the atmosphere and the radiative equivalent of volcanic activity, shows both a long-term variation (presumably on a millennial time scale owing mainly to the variation of the solar radiation) and quasi-bicentennial (192 yr) and quasi-centennial (107 yr) variations (pri- marily due to the superposed variations of both the volcanic and solar forcings; see Figs. 6c and 7c). These spectral peaks are signi?cant at the 99% con?dence level by red noise test, but we rather place emphasis on physical mechanisms than statistics. The atmospheric C02 concentration in the prein- dustrial period is ?at (around 285 ppm) except a rela- tively low period between 1600 and 1800 at about 275?280 ppm; see Fig. 6d). The smoothed C02 series has increased near exponentially since 1850?1975 (around 330 ppm). Atmospheric CH4 is also important, for it is responsible for about 25% of the increase anthropo- genic radiative forcing between preindustrial period and the present (Solomon et al. 2007). b. Response of the global monsoon precipitation to external forcing How does the global monsoon precipitation respond to the changes in the aforementioned forcings? Fig. 6e shows that the GMI tends to vary in phase with the effective radiative shortwave forcing (solar forcing plus volcanic forcing), especially on the millennium time scales. The correlation coef?cient between GMI and the effective radiation is 0.78 for the 31-yr smoothed series, which is better than the correlation with the solar forcing (0.72) and much better than the correlation with the volcanic forcing (0.37; see Fig. 6 and Table 2). The better correlation between the GMI and solar forcing comes from their millennium variations. The spectrum of the GMI has pronounced peaks on 192, 107, and 74 yr (Fig. 7d), which corresponds well to the sig- ni?cant spectral peaks from effective radiative forcing at around 192, 107, and 80 yr. The variation of the GM precipitation may thus be linked to three factors. First, its millennium variation (peaks in MWP and present and dips in LIA interval) can be well explained by changes in the direct solar ir- radiance. The three GMI minima during the LIA con? cur with the three minima in shortwave forcing, which further supports the impact of the effective solar forcing on the global monsoon precipitation. Second, a com- parison of Figs. 7a?c with Fig. 7d suggests that the quasi- bicentennial (192 yr) oscillations in the GM precipita- tion appear to be primarily induced by the solar forcing with ampli?cation by the volcanic forcing. The quasi- centennial (107 yr) oscillation may be related primarily to volcanic forcing with ampli?cation by the solar forcing. Third, while the direct solar irradiance in the last two decades of the simulation is higher than that of MWP by about 1 the effective solar irradiance in the late twentieth century is 0.52 m?2 lower than that during MWP because of the increase in effective volcanic forcing in the late twentieth century (see Fig. 6). On the other hand, the GM rainfall rate in the PWP is 0.016 mm day?1 higher than that during the LIU ET AL. 2367 Solar constant Global monsoon index 153 150 14ml 110 130- 1.10 120 0 120-1 0 0 g- 110. -- 99% con?dence 3- 11n~ 1 99% con?dence 3 ?m 1 .. con?dence 3 I. con?dence 3 an. 90% confidence 3 so- 909? ?00?den?? n. 3 an. '5 1'950.0 240.0137.195.o 73.6 60.0 50.5 43.5 36.4 34.3 31.0 960-0 240-0137-196-0 73-8 69-0 59-5 43.6 38.4 34.3 31.0 Periodicity (yr) Periodicity (yr) Volcanic effect Global mean temperature 150 :40 1' .a '1 a 0 120? - 0 0 II 3.11 0 99% con?dence 3- 99% con?dence .7, mo 95% confidence 3 -- 95% con?dence 59 90% con?dence 3 90% confidence .10- ?5 ?5 20' ., X's. 10- I I _45.0 41 a 960.0 240.0 137.1 96.0 73.9 60.0 50.5 43.6 38.4 34.3 31.0 960.0 24o.o137.196.0 73.5 50.0 50.5 43.5 38.4 34.3 31.0 Periodicity (yr) Periodicity (yr) Effective solar radiation no NH minus SH temperature 150 140 l. 1491' 1.10 l] 120-' 110 I 3- no 1 99% confidence 8- 111:- - 99% con?dence '5 100- -- 95% con?dence 16 1cm- 1 -- 95% con?dence 95. 90% con?dence 3 90' 90% 9?"?dence 413In. 960.0 240.0 137.1950 73.8 50.0 50.5 43.6 35.4 34.3 31.0 960-0 2.40.0137-1963 73-8 60-0 50-5 43.6 38.4 34.3 31.0 Periodicity (yr) Periodicity (yr) FIG. 7. Spectra of the 31-yr running?mean external forcing factors and atmospheric responses. Solar constant, volcanic effect, effective solar radiation, GMI, global?mean temperature, NH minus SH temperature. MWP (Table 1), which indicates that the solar and pecially after 1975. This fact may suggest that the rapid volcanic forcing can explain the simulated GM rainfall increase of atmospheric C02 and CH4 might have a from 1000 to 1950, but fails to account for most of the positive contribution to the recent increase in the GM observed increase of GM precipitation in 1961?90, es- precipitation. 2368 c. The mechanism by which effective radiative forcing modulates GM rainfall In the preindustrial period, changes in the total amount of effective shortwave radiative forcing can re- inforce the thermal contrast between the continent and ocean, thereby resulting in the centennial- to millennial- scale variations in the global monsoon strength. Land has much smaller heat capacity than the ocean. When effective radiative ?ux increases during the local sum- mer, the magnitude of land warming is much stronger than that in the adjacent ocean, thus the thermal contrast between continent and ocean gets reinforced (Table 3). This thermal contrast further enhances the pressure differences between land monsoon regions and the sur- rounding oceans (Table 3) and thus strengthens the monsoon circulation in the presence of Coriolis force and associated rainfall. As such, each regional compo- nent of the global monsoon system will intensify from the increased radiative heating and thus the composite global monsoon will be strengthened as well. Quantitatively, the change in GM rainfall rate be- tween MWP and LIA is about 0.035 mm day?1, which is about 0.93% change in precipitation strength (Table 1), while the change of solar irradiance between MWP and LIA is about 2.71 m?2 (Table 3), which is about 0.2% of the solar constant. Given a 0.2% increase in the ex- ternal forcing, the increase in GM rainfall is 4?5 times larger. Such ampli?ed response is similar to a near- resonant response of a dynamical system to an external forcing. What processes have catalyzed and ampli?ed the response? We argue that the effective radiative forcing-induced land?ocean thermal contrast causes an initial increase in monsoon precipitation. This initial increase is further reinforced by the increase in moisture supply because the warming induced by the effective radiative heating tends to increase atmospheric mois- ture content. The increase of moisture supply can in- duce a positive feedback between the latent heat release (in precipitation) and monsoon ?ow convergence, thus further amplify the latent heating release, which may ultimately amplify the atmospheric circulation response. Therefore, the humidity feedback is a key ampli?er linking solar irradiance and monsoon. A vigorous in- crease in rainfall is expected in response to a moderate change in radiative heating. d. Relationship between changes in global temperature and monsoon rainfall It can be observed from the results in Fig. 6 and Table 2 that the change of the global monsoon strength tends to roughly vary in accord to the changes in the global- mean surface temperature. The correlation coef?cient JOURNAL OF CLIMATE VOLUME 22 TABLE 3. The anomalies of effective solar radiation (AS) and summer mean (JJA for NH and DJF for SH) differences of sea level pressure and temperature between land and sea for MWP, LIA, and PWP intervals in reference to 1000?1990. The difference between the land and ocean was computed based on the averaged quantity over all land grids minus that over all oceanic grids. Increment MWP LIA PWP AS (w 1.576 ?1.138 1.052 (hPa) 0.273 ?0.150 0.309 AT.?cl arm (K) 0.080 ?0.137 0.217 mam?Pm) (hPa) 0.457 ?0.307 0.779 (K) 0.016 ?0.078 0.147 between the 31-yr running-mean GMI and global-mean temperature is 0.86. However, the global monsoon rainfall follows effective radiative forcing more closely than the global-mean temperature does. This point is particularly well ful?lled during the LIA (Figs. 6c,e,f). Overall, the correlation coef?cient between the 31?yr running-mean GMI and effective solar radiation is 0.78, while that between global-mean temperature and ef- fective solar radiation is 0.69. The global monsoon is essentially driven by the in- terhemispheric temperature difference and differential heating between the NH and SH. To understand the changes in the global monsoon strength or GMI, one should naturally seek for the root cause from the inter- hemispheric contrast in the temperature and precipita- tion. It is found that the GMI varies coherently with the interhemispheric temperature difference. The variation of the interhemispheric temperature difference has 192- and 107?yr periodicities; both are signi?cant above 99% con?dence level (Fig. 7f). This result means that the quasi-bicentennial and quasi-centennial GM changes coherently with the interhemispheric temperature dif- ference. The interhemispheric temperature difference is related to the solar activity change and the land?ocean distribution. Poleward of earth?s surface is covered largely by land and the proportion of land there is 47%. In contrast, poleward of land proportion is much smaller (only In response to increased radiative forcing, the NH warms up more than the SH because of the smaller heat capacity of land. As such, the NH minus SH temperature should vary in concert with the effective radiative forcing, and is thus correlated closely with the GM precipitation changes. 6. Conclusions In this paper, we study how the global monsoon (GM) precipitation responds to the external forcing in the last millennium by analyzing a pair of control and forced millennium simulations. The forced ERIK run has been 1 MAY 2009 shown to capture precipitation climatology realistically (Fig. 1) despite the incomplete accounting of all forcing factors. More speci?cally, two variables are used to gauge the model?s performance in simulation of the precipitation. One is the global-mean precipitation and the other is the leading mode of the annual cycle of precipitation. The leading mode of the annual cycle is characterized by a solstitial monsoonal mode whose strength can be described by a global monsoon precip- itation index. We demonstrate that the ERIK run cap- tures the two modes of climatology comparably well when compared with those captured by the NCEP re- analysis. This adds con?dence to the analysis of the change in the annual cycle in the model?s millennium simulation. The 31-yr running averaged global monsoon index in the forced run reveals both the variability on the mil- lennial time scale and signi?cant quasi-bicentennial (192 yr) and quasi-centennial (107 yr) variability. Over the past millennium, the simulated global monsoons are observed to be strong in the model Medieval Warm Period (ca. 1030?1240), while the simulated global mon- soon intensity gets weaker during the model Little Ice Age (ca. 1450?1850). During the LIA interval there are three GMI minirna occurring around 1460, 1685, and 1800, which correspond, respectively, to the Sporer Minimum (1420?1570), Maunder Minimum (1645?1715), and Dalton Minimum (1790?1820) periods of solar activity minirna and increased volcanic activity. The prominent increase of the global monsoon strength in the last century and the remarkably strengthening of the global monsoon in the last 30 yr of simulation ending in 1990 seem large; the latter may signify a possible impact from the rapid increase in atmospheric green- house gases. Before the industrial period, the changes in the sum of the direct solar radiative forcing and volcanic forcing (effective radiative forcing) can explain the natural global monsoon precipitation variations well. Simulated changes of the GM strength in the last century have a spatial pattern that differs from that during the MWP, suggesting the different effects of global warming on monsoon precipitation patterns contributed by both the increases of atmospheric greenhouse gases and the in- coming solar radiation. On a centennial time scale, the change of the global monsoon strength follows the effective radiative forcing better than the changes of the global-mean surface temperature. Physically, the GMI has a good correla- tion with interhemispheric temperature difference as elaborated in the previous section. We leave two main areas of research for future at- tention in order to bring forth a more complete char- LIU ET AL. 2369 acterization and understanding of global monsoon and its variation on centennial to millennial time scales. First, a more complete set of relevant forcing factors and physical processes must be included in the model simulation. Then a more direct and meaningful com- parison of the model simulated outputs with all the available regional monsoon proxies can be performed. Acknowledgments. Jian Liu and Bin Wang acknowl? edge the ?nancial supports from the Innovation Project of Chinese Academy of Sciences (Grant 315),the National Basic Research Program of China (Grant 2004CB720208), and the National Natural Sci? ence Foundation of China (Grant 40672210). 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