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Estimates of direct economic damage from temperature change. Courtesy of the National Climate Assessment.

U.S. releases climate report

On Friday, Nov. 23, the U.S. government released the Congress-mandated Fourth National Climate Assessment, compiled by 13 federal agencies. The 1,656-page document explains the current effects of global warming, as well as projections for its toll on the economy, health and the environment (NYT, “U.S. Climate Report Warns of Damaged Environment and Shrinking Economy,” 11.23.2018). This document is the second volume of the National Climate Assessment—the U.S. Global Change Research Program issued volume one last year—which the Global Change Research Act of 1990 requires the government to publish every four years.

The findings from the previous report, published in May 2014, illustrated the economic costs and impacts that climate change has been causing around the world, prompting the Obama administration to finalize the Clean Power Plan and to help form the Paris Agreement (NYT).

However, the current administration’s policies, which include withdrawing from the Paris Agreement, promoting coal and reducing environmental regulations, directly conflict with the document’s findings and suggested course of action. Princeton Professor of Geosciences and International Affairs Michael Oppenheimer stated, “This report will weaken the Trump administration’s legal case for undoing climate change regulations, and it strengthens the hands of those who go to court to fight them” (NYT).

The report includes plans of action to reduce risk both through adaptation actions and through emissions mitigation. According to the official website, “Adaptation refers to actions taken at the individual, local, regional, and national levels to reduce risks from even today’s changed climate conditions and to prepare for impacts from additional changes projected for the future” (NCA, “Reducing Risk Through Adaptation Actions”). Although implementation of these practices have increased since the Third National Climate Assessment, the urgency of the findings presented in the report necessitate large-scale response, the report details.

Projected changes in U.S. annual average temperatures. Courtesy of the National Climate Assessment.

In the section focusing on air pollution, the experts write, “Unless counteracting efforts to improve air quality are implemented, climate change will worsen existing air pollution levels. This worsened air pollution would increase the incidence of adverse respiratory and cardiovascular health effects, including premature death” (NPR, “Climate Change Is Already Hurting U.S. Communities, Federal Report Says,” 11.23.2018). To address these effects, they include in the report actions to prevent such adverse effects, such as local authorities issuing air quality alerts (NCA, “Air Quality”).

Some of the most alarming results of the report come in the sections on heat waves, wildfires and rising sea levels. Over the next few decades, heat waves are projected to increase by 2.2 degrees Fahrenheit, and the number of days below freezing will decrease while the number of days above 90 degrees will grow. Climate change has also led to a doubling of the effect of wildfires on the Southwest, which poses an immediate danger to residents. These harsh realities appeared in the recent California fires, both of which were announced as fully contained last week. In the case of rising sea levels, coastal flooding could force millions of people to migrate to dry land (The Atlantic, “The Three Most Chilling Conclusions From the Climate Report,” 11.26.2018).

While grim, the report is designed to educate the government and the public and to urge them to act as soon as possible while we are still able to reduce or prevent dire climate change consequences.

To review the document, see its comprehensive website with interactive features and the downloadable report at https:// nca2018.globalchange.gov/.

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