Five Key Takeaways from the United States National Climate Assessment

The United States Global Change Research Program released its third National Climate Assessment (NCA) this week. The report, a collaborative effort by federal agencies and hundreds of experts, focuses on the science of climate change impacts in the United States that are happening now, and those that are expected throughout this century. For more information, a website has been created that sets out the main findings of the report. The report makes five key points:

Warming has been driven by human activity.

Human activities are the primary cause of warming over the past 50 years. The concentration of CO2 in the atmosphere has increased by more than 40 percent since the industrial revolution, through the burning of fossil fuels and continued deforestation. Emissions from other heat-trapping gases such as methane and nitrous oxide from agriculture and other human activities add to the mix of greenhouse gases that have accumulated in our atmosphere and have contributed to rising temperatures.

2. Climate change impacts are happening now.

Temperatures in the United States have already increased 1.3 to 1.9 degrees Fahrenheit since 1895 (most of it since 1970) and in most areas of the United States temperatures are projected to rise by another 2 to 4 degrees Fahrenheit over the next few decades. This includes more extreme weather events, prolonged periods of heat, floods and droughts.  Ocean surface waters have also become 30 percent more acidic as atmospheric CO2 has been absorbed.

3. Climate change impacts will continue into the future.

Temperatures across the United States as well as in oceans and freshwater lakes are projected to rise. This will be accompanied by more heavy downpours, severe droughts, and wildfires. Sea levels are projected to rise by another 1 to 4 feet this century.

4. Climate change will adversely affect the economy and quality of life.

These impacts will have negative repercussions for human health, water supply, agriculture, transportation, energy, and coastal areas where nearly 5 million Americans and billions of dollars worth of property are located. Climate change will increase the risk of heat stress, respiratory stress from poor air quality, and the spread of airborne diseases.

5. Vulnerable regions and sectors will be disproportionately affected.

Climate change will be felt differently across the United States. For example, declining water supplies combined with increased heat and drought will result in health impacts and reduced agricultural yields in the country’s southwest, sea level rise and storm surges will cause flooding in the Gulf Coast and Atlantic seaboard and the thawing of permafrost will damage critical infrastructure in Alaska.

So How Do We Cope with Climate Change?

The report finds that existing plans for adapting to and mitigating climate change are currently insufficient if the United States wants to avoid the far-reaching consequences of climate change. The report outlines further actions to reduce emissions and increase resilience which could make measurable improvements to economic development and overall quality of life.

In January, Brookings Senior Fellow Beth Ferris recommended that the United States should play a leadership role in addressing the challenges of climate change ahead of the 2015 climate summit in Paris, particularly through “more drastic carbon emission cuts at home,” but also by finding “agreement with other states, particularly China, given its leadership role for developing states in the global climate change regime.”

There are also a number of domestic measures the United States can take through existing Executive Authority described in the President’s climate action plan, as outlined by Brookings Fellow Joshua Meltzer. Brookings scholars have also written extensively on how to reduce emissions in the United States, while simultaneously improving state finances, by using a carbon tax rather than energy efficiency tax credits. For the time being, the EPA regulates greenhouse gas emissions under the “already contested and decided” Clean Air Act.