By Dr. John P. Holdren and Dr. Kathryn D. Sullivan

Today, the Obama Administration unveiled the Third U.S. National Climate Assessment (NCA)—the most comprehensive, authoritative scientific report ever generated about climate changes that are happening now in the United States and further changes that we can expect to see throughout this century. The report—a key deliverable of President Obama’s Climate Action Plan—confirms that climate change is affecting Americans in every region of the United States and key sectors of the national economy.

This NCA embodies the concept of “actionable science” called for in the President’s Climate Action Plan. It communicates the impacts of climate change according to geographic region of the United States, and by economic and societal sector—including agriculture, energy, and health. These tailored findings help translate scientific insights into practical, useable knowledge that can help decision-makers and citizens anticipate and prepare for specific climate-change impacts.

For instance, the report finds that, on the whole, summers are longer and hotter, with longer periods of extended heat. Wildfires start earlier in the spring and continue later into the fall. Rain comes down in heavier downpours. People are experiencing changes in the length and severity of seasonal allergies. And climate disruptions to water resources and agriculture have been increasing. 

And the report confirms that across America, people are experiencing climate-change impacts that are not uniform. In the Northeast, for example, communities are affected by heat waves, more extreme precipitation events, and coastal flooding due to sea level rise and storm surge. In the Southwest, drought and increased warming foster wildfires and increased competition for scarce water resources for people and ecosystems.

These and the other essential findings in the new NCA are the result of a three-year analytical effort by a team of over 300 climate scientists and experts, informed by inputs gathered through more than 70 technical workshops and stakeholder listening sessions held across the country. The resulting product was subjected to extensive review by the public and by scientific experts in and out of government. This process of unprecedented rigor and transparency was undertaken to ensure that the findings of this report rest on the firmest possible base of expert judgment.

Understanding of climate change and its impacts on our Nation continues to grow. This National Climate Assessment is a key step to further expand the knowledge base in ways that are immediately relevant and useful to business owners, resource managers, public health officials, and community leaders who are living and working on the front lines of climate change.

We applaud the many contributors to this report and urge all Americans to get informed about how climate change is affecting their own regions by visiting www.globalchange.gov.

Reposted from the White House Office of Science and Technology Policy.