Released in November, the Federal Government’s Climate Science Special Report (CSSR) concluded that “it is extremely likely that human activities… are the dominant cause of the observed warming since the mid-20th century.” Unsettling climate-related weather events have become increasingly common over the last few years, and according to the United States Global Change Research Program (USGCRP), these trends are expected to continue in the coming decades. Thousands of studies have been conducted around the world that document a wide array of changes in the environment, and conclusions reached in the CSSR are based on extensive evidence. This report directly contradicts the Trump administration’s stance on the issue, as the recently released National Security Strategy did not include climate change as a major threat to the U.S.

The USGCRP was established under the Global Change Research Act of 1990 (Act) with the purpose to develop and coordinate a research program that would attempt to understand, assess, predict and respond to global change. The USGCRP is composed of 13 federal agencies and led by the Subcommittee on Global Change Research of the National Science and Technology Council. USGCRP responsibilities under the Act include (a) coordinating global change research across the federal government, (b) developing and distributing mandated products, and (c) helping to inform decisions.

One of the products mandated by the Act includes a quadrennial assessment, known as the National Climate Assessment (NCA), submitted to the President and the Congress. The Act requires the NCA to (1) integrate, evaluate and interpret the findings and discuss the associated scientific uncertainties; (2) analyze the effects of global change on the natural environment, agriculture, energy production and use, land and water resources, transportation, human health and welfare, human social systems and biological diversity; and (3) analyze current, and predict future, trends in global change, both human-induced and natural. The Fourth NCA (NCA4) is due to be released in 2018.

The CSSR is a major component of, and represents, Volume I of NCA4. The report offers a comprehensive assessment of the science of climate change with a focus on the U.S. Some of the report’s findings are notable:

  • The last three years have been the warmest years on record globally.
  • We are living in the warmest period of modern history.
  • Greenhouse gas (GHG) emissions are a major factor in the observed warming.
  • Global average sea level has risen seven to eight inches since 1900.
  • A sea level rise of eight feet by 2100 cannot be ruled out.
  • The frequency and intensity of high temperature events are virtually certain to increase.
  • The frequency and intensity of heavy rainfall is increasing.
  • Annual average temperatures are expected to rise 2.5°F by 2050.
  • Chronic long-term drought is increasingly possible.
  • The magnitude of climate change beyond 2050 will depend on global GHG emissions.
  • Besides human activity, there is no convincing alternative explanation for the warming observed over the last century.

A draft of NCA4 Volume II, Climate Change Impacts, Risks and Adaptation in the United States, has been released for public comment and review by the National Academies of Sciences, Engineering and Medicine. The final version of Volume II is expected to be released in December 2018 and will utilize the CSSR findings to analyze the impacts of global change on regions and topics in the U.S.