3rd National Climate Assessment Overview

The third U.S. National Climate Assessment report, released in early May, provides a national synthesis of climate change and its effects that are already being felt across multiple sectors within the U.S., including coastal flooding and extreme heat in the Northeast, shrinking summer sea ice and thawing permafrost in Alaska, drought and associated increases in wildfires in the southwest, decreased water availability in the Southeast, constrained freshwater supplies in Hawai’i, and changes in streamflow timing in the Northwest.

The implications of these climatic changes include threats to human health through increasing heat stress and spread of waterborne diseases; damage to infrastructure from rising sea levels and heavy downpours; regionally varying effects on agriculture—with some areas more resilient than others; magnified threats to Indigenous People’s health and well-being through loss of traditional homelands, reduced access to traditional foods, and greater health and safety hazards; ocean acidification; and ecosystem changes.

People already at risk, include the poor, elderly, the sick, and children, are more vulnerable to climate change-related health effects. While communities and various levels of government are responding to these changes, they’re not enough to counter the negative social, environmental and economic consequences of changing climate. The current trajectory of greenhouse gas emissions will put the world on track for even higher levels than the “high emissions” (A2) scenario used in the study, and aggressive emissions controls are needed to reduce the future risks of some of the worst climate change impacts, say the report’s authors.

Who made it and what’s new?

The report was compiled from peer-reviewed research and technical reports by 300 experts, guided by a 60 member federal advisory board known as the NCADAC, and extensively reviewed by the National Academy of Sciences and the 13 Federal agencies of the U.S. Global Change Research Program. The Draft report was open for public comment during 2013. The report uses climate change projections from the next-to-most-recent generation of climate models (CMIP3). Previous assessments were released in 2000 and 2009. What’s new in this assessment? The 2014 report includes over ten new chapters in addition to the 2009 report sections, including Water, Energy and Land Use; Tribal, Indigenous, and Native Lands and Resources;  Urban Systems, Infrastructure, and Vulnerability; to name only a few. The report also specifically addresses the combined effects of multiple impacts, climate change response strategies including adaptation and mitigation, and how to maintain a sustained assessment process for future NCAs.

How do I learn more?

• If you have 5-10 minutes:
  • Read the ~10 page Overview or browse effects in your home region at: http://nca2014.globalchange.gov/downloads
  • Check the Union of Concerned Scientists’ summary at:http://www.ucsusa.org/global_warming/science_and_impacts/science/us-global-change-nca-1.html
• If you have 20-60 minutes:
  • Read the ~100 page Highlights at:http://nca2014.globalchange.gov/downloads
  • Participate in the NCA educational webinars this May:http://www.ucsusa.org/global_warming/science_and_impacts/science/national-climate-assessment-webinar.html

This overview was written by Rosemary Records and Michelle Staudinger. Michelle is an author on the Biodiversity, Ecosystems, and Ecosystem Services Technical Input to the third National Climate Assessment.