A draft of the Third National Climate Assessment (NCA) has been released by the Climate Assessment Development Advisory Committee (NCADAC). The committee says this is the most peer-reviewed analysis of climate change impacts on the United States. The assessment was written by 240 scientists and other experts from academia; local, state, and federal government; business; and the non‐profit sector. The public can review the draft and submit comments, and the final draft is expected to be released in early 2014.
Several key findings include new and stronger evidence that global climate is changing, extreme weather and climate events are increasing, and that the increase is related to human activities. In addition, the report finds:
- Global climate is changing, and this is apparent across the US in a wide range of observations. The climate change of the past 50 years is due primarily to human activities, predominantly the burning of fossil fuels and is expected to accelerate if action is not taken.
- Some extreme weather and climate events have increased in recent decades, and there is new and stronger evidence that many of these increases are related to human activities.
- Impacts related to climate change are already evident in many sectors and are expected to become increasingly challenging across the nation throughout this century and beyond.
- Climate change threatens human health and well-being in many ways, including impacts from increased extreme weather events, wildfire, decreased air quality, diseases transmitted by insects food and water and threats to mental health.
- Infrastructure across the U.S. is being adversely affected by phenomena associated with climate change, including sea level rise, storm surge, heavy downpours, and extreme heat.
- Reliability of water supplies is being reduced by climate change in a variety of ways that affect ecosystems and livelihoods in many regions, particularly the Southwest, the Great Plains, the Southeast, and the islands of the Caribbean and the Pacific, including the state of Hawaii.
- Adverse impacts to crops and livestock over the next 100 years are expected. Over the next 25 years or so, the agriculture sector is projected to be relatively resilient, even though there will be increasing disruptions from extreme heat, drought, and heavy downpours. U.S. food security and farm incomes will also depend on how agricultural systems adapt to climate changes in other regions of the world.
The public review period will last until April 12, 2013. The Global Change Research Act of 1990 requires that a report must be presented to the President and the Congress every four years that provides a thorough overview of the status of climate science and climate change impacts.