A major new federal report warning the United States could warm up to 10 degrees Fahrenheit by the end of the century if global greenhouse gas emissions continue to rise has renewed hope among environmental groups that President Obama will make climate change a priority in his second term.
The analysis details the ways man-made climate change has already altered American lives and landscapes. Written by more than 300 scientists, the report -- a draft of the third national assessment of climate change impacts in the United States -- describes a country that is hotter and more extreme than in the past in many ways.
"Evidence for climate change abounds, from the top of the atmosphere to the depths of the oceans," says the analysis, which was released Friday. "The sum total of this evidence tells an unambiguous story: The planet is warming."
Activists say they hope the findings will keep a spotlight on climate change and ensure that it doesn't get crowded out by fiscal issues, guns and immigration.
"For the last couple of years in Washington, 'climate change' was not a phrase you used in social conversation. Then Superstorm Sandy changed all that," said Lou Leonard, managing director of climate change at WWF.
"This issue is on the table as one of the top three priorities of the administration for second term," Leonard said. "That is a very good thing that was not a certainty at all six months ago. That wasn't a certainty three months ago."
Liz Perera, a policy analyst at the Sierra Club, said there have been "a lot of rumors" about whether climate change has risen to the top of President Obama's crowded second-term agenda.
Doubling the likelihood of extreme weather events
But there is no indication when the White House might make a move on climate change, especially with the looming March 1 deadline to raise the nation's debt limit.
"We're all hoping that it is a top priority for him, and it actually is about action and not just talk," Perera said, praising the new report's "blunt language." "I think it's great to see this come out before the State of the Union," she added.
According to the draft assessment, average temperatures in the United States have risen by 1.5 degrees Fahrenheit since 1895, but 80 percent of that increase has occurred since 1980, the analysis says. It lays much of the blame on greenhouse gas emissions produced by human activities.
Across the nation, oceans, rivers and lakes have warmed; the number of frost-free days and heavy downpours has increased; sea level has risen; ocean water has become more acidic; and the area covered by snow, glaciers, permafrost and sea ice has significantly decreased, concludes the report, which was compiled by an independent panel of experts.
Winter storms are stronger and strike more frequently along the West Coast and in coastal New England, while man-made climate change has doubled the likelihood of "extreme heat events," the report says.
Those shifts threaten human health and well-being, the analysis warns, citing "impacts from increased extreme weather events, wildfire, decreased air quality, diseases transmitted by insects, food and water and threats to mental health."
"As climate change and its impacts are becoming more prevalent, Americans face choices as a result of past emissions of heat-trapping gases," says the report. "Some amount of additional climate change and related impacts is now unavoidable."
Societies have choices to make
Adding to those concerns, the report says, is the reality that impacts are often worst in places that are already grappling with "economic or health-related challenges," or for species and habitats already living in stressful conditions.
Even areas or industries that could initially thrive or even reap benefits from a changing climate could eventually shift categories from "winners" to "losers," the report adds.
U.S. farmers may adapt to climate shifts over the next few decades by increasing their use of irrigation and shifting the mix of crops they grow as temperature and rainfall patterns change.
But by 2050, those temperature and precipitation shifts will become so extreme they trump those adaptations, and yields of major crops will decline, "threatening both U.S. and international food security," the report says.
But decisions made by leaders in the United States and other countries could significantly limit climate change's toll, the report adds.
"Beyond the next few decades, the amount of climate change will still largely be determined by choices society makes about emissions," it says.
Making significant reductions in greenhouse gas emissions by 2050 could limit warming to an additional 3 to 5 degrees Fahrenheit by the end of the century, while allowing emissions to continue rising would lead to a 5- to 10-degree increase -- perhaps more, because the global rise in greenhouse gas output is outpacing even the highest projection used in the new draft report, it notes.
Only the third assessment in 23 years
The document will undergo several rounds of review before it is submitted to the government for approval next year, including a three-month public comment period that starts today and a separate, independent review by the National Academy of Sciences.
Still, White House science adviser John Holdren and outgoing National Oceanic and Atmospheric Administration chief Jane Lubchenco praised the effort for "setting a new standard of scientific integrity [and] user relevance," in a statement posted Friday on the White House Office of Science and Technology Policy's website.
In some ways, the new report is notable simply because it exists. Under the terms of a 1990 law, the White House is required to submit a report to Congress detailing the impacts of climate change in the United States every four years. But the new report is just the third national assessment completed in the last 23 years.
The first, released by the Clinton administration in 2000, predicted a doubling or tripling of heat-related deaths, increased floods and droughts and the swamping of coastlines by rising seas and more intense storms.
But it would take another nine years, and a protracted federal legal battle, before the government completed a second report. The George W. Bush administration, which had sought to replace the national climate assessment with a series of 21 narrowly defined reports on climate change science, was forced to scrape together a broader analysis after federal district court Judge Saundra Brown Armstrong rejected that plan in 2007.
The Obama administration released a final version of the second assessment in 2009. The high-profile launch saw top administration officials, including Lubchenco and Holdren, and report authors briefing reporters in Washington, D.C.
The unveiling Friday of the new draft assessment was muted in comparison, but those who helped produce the report say they are thinking long-term. Administration officials working under the auspices of the U.S. Global Change Research Program have tried to create a lasting infrastructure for producing future climate reports with broad input from citizens, experts and community groups across the country.
"These reports are very large efforts, and what happens is a huge amount of energy goes into them, and then people stop working on them," said National Climate Assessment Director Katherine Jacobs, an assistant director at the White House Office of Science and Technology Policy.
"Our intent is to have a sustained assessment process," she said. "We're already working on improving the process for the next synthesis report. We're building an information system to deploy data from this report in ways more accessible to decisionmakers."
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