Earth’s climate is now changing faster than at any point in the history of modern civilization, primarily as a result of human activities. Global climate change has already resulted in a wide range of impacts across every region of the country and many sectors of the economy that are expected to grow in the coming decades.
The Fourth National Climate Assessment (NCA4), developed by the U.S. Global Change Research Program (USGCRP), is a state-of-the-science synthesis of climate knowledge, impacts, and trends across U.S. regions and sectors to inform
decision making and resilience-building activities across the country. It is the most
comprehensive and authoritative assessment to date on the state of knowledge
of current and future impacts of climate change on society in the United States.