June 28, 2016 Dear Members of Congress, We, as leaders of major scientific organizations, write to remind you of the consensus scientific view of climate change. Observations throughout the world make it clear that climate change is occurring, and rigorous scientific research concludes that the greenhouse gases emitted by human activities are the primary driver. This conclusion is based on multiple independent lines of evidence and the vast body of peer-reviewed science. There is strong evidence that ongoing climate change is having broad negative impacts on society, including the global economy, natural resources, and human health. For the United States, climate change impacts include greater threats of extreme weather events, sea level rise, and increased risk of regional water scarcity, heat waves, wildfires, and the disturbance of biological systems. The severity of climate change impacts is increasing and is expected to increase substantially in the coming decades.1 To reduce the risk of the most severe impacts of climate change, greenhouse gas emissions must be substantially reduced. In addition, adaptation is necessary to address unavoidable consequences for human health and safety, food security, water availability, and national security, among others. We, in the scientific community, are prepared to work with you on the scientific issues important to your deliberations as you seek to address the challenges of our changing climate. American Association for the Advancement of Science American Chemical Society American Geophysical Union American Institute of Biological Sciences American Meteorological Society American Public Health Association American Society of Agronomy American Society of Ichthyologists and Herpetologists American Society of Naturalists 1 The conclusions in this and the preceding paragraph reflect the scientific consensus represented by, for example, the U.S. Global Change Research Program, the U.S. National Academies, and Intergovernmental Panel on Climate Change. Many scientific societies have endorsed these findings in their own statements, including the American Association for the Advancement of Science, American Chemical Society, American Geophysical Union, American Meteorological Society, American Statistical Association, Ecological Society of America, and Geological Society of America. American Society of Plant Biologists American Statistical Association Association for the Sciences of Limnology and Oceanography Association for Tropical Biology and Conservation Association of Ecosystem Research Centers BioQUEST Curriculum Consortium Botanical Society of America Consortium for Ocean Leadership Crop Science Society of America Ecological Society of America Entomological Society of America Geological Society of America National Association of Marine Laboratories Natural Science Collections Alliance Organization of Biological Field Stations Society for Industrial and Applied Mathematics Society for Mathematical Biology Society for the Study of Amphibians and Reptiles Society of Nematologists Society of Systematic Biologists Soil Science Society of America University Corporation for Atmospheric Research