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Since 2000, the National Climate Assessment Has Grown Significantly More Certain—and Much More Grim

Since the first National Climate Assessment was released, the United States has endured 16 of the 17 warmest years on record, and the latest assessment paints a bleak picture of the future.
Firefighters light backfires as they try to contain the Thomas wildfire in Ojai, California, on December 9th, 2017.

Firefighters light backfires as they try to contain the Thomas wildfire in Ojai, California, on December 9th, 2017.

In case you missed it over the holiday weekend, on late Friday afternoon, the federal government released a worrying new report about climate change. Over 1,600-plus pages, the report explains in blunt terms all the ways that climate change will harm the environment, devastate the economy, and imperil the lives of millions of Americans.

The fourth National Climate Assessment shares many similarities with the first, which was released in 2000. Both studies find that temperatures in the United States could rise by as much as 9 degrees Celsius by the end of the century; that droughts and heatwaves will become more common; that sea-level rise and storm surges will threaten coastal communities and infrastructure. But the differences in the tone and framing of the reports is stark. The 2000 National Climate Assessment takes for granted the role that man-made emissions plays in climate change, noting on page three that "future emissions will have to be curbed to stabilize climate."

The fourth assessment—released under a climate skeptic president and a White House that's expected to discount its findings—states in the very first sentence that "Earth's climate is now changing faster than at any point in the history of modern civilization, primarily as a result of human activities."

The findings are unlikely to sway the Trump administration, in contrast to the Obama administration, which boosted the findings of the second and third national climate assessments, released in 2009 and 2014, and capitalized on the climate momentum generated by those assessments to pass legislation such as the Clean Power Plan.

The assessment was originally slated for release in December at the American Geophysical Union's annual conference, and it's still unclear who exactly ordered the report to be released two weeks early—on the day after the Thanksgiving holiday, the busiest shopping day of the year. The timing led many to speculate that the White House was attempting to bury the findings, which offer a sharp rebuke to the Trump administration's policy positions on energy and climate.

President Donald Trump has used claims that environmental regulations stifle economic growth to justify rolling back environmental protections. In June last year, for example, as Trump announced his intention to pull the U.S. out of the Paris Agreement, he cited the "draconian financial and economic burdens the agreement imposes on our country." But the latest climate assessment shows that, in reality, unchecked climate change will cost the U.S. upwards of $500 billion a year in crop losses, infrastructure damage, extreme weather damages, and other harms by the end of the century.

Temperature rise will also be very bad for our health: Heat-related deaths will rise as extreme heat waves become more common. The warming climate will be a boon to disease-spreading insects like mosquitoes and ticks. Allergy season will be supercharged, and air quality will diminish, thanks in large part to an uptick in wildfires like the one that left California's Bay Area enveloped in a toxic smog. For a few days in November, the Camp Fire, the deadliest and most destructive in the state's history, left Northern California with the dirtiest air in the world.

California has already seen its wildfire season expand and intensify in recent years, but the fire-prone West likely won't be the only part of the U.S. dealing with more infernos. According to the assessment, the Southeast could be facing a wildfire season of its own by the end of the century—a finding that was not yet foreseen in the 2000 National Climate Assessment. But even back then, climate scientists were warning readers to expect the unexpected. "Because climate is highly complex, it is important to remember that it might surprise us with sudden or discontinuous change," said the first report. "We simply do not know how far the climate system or other systems it affects can be pushed before they respond in unexpected ways."

Hence one of the main takeaways of this year's report: We can no longer turn to the past to prepare for the future. "The assumption that current and future climate conditions will resemble the past is no longer valid," the report states.

Since the first climate assessment was released, the U.S. has endured 16 of the 17 warmest years on record, but the latest report also notes that it's not too late to act. "Future impacts and risks from climate change are directly tied to decisions made in the present," it states.