U.S. Fish and Wildlife Service firefighter Corey Adams sits on a tree stump as he monitors the Rim Fire on August 25, 2013 near Groveland, California.
Climate change already has an impact on Americans every day, and its effects will continue to grow as manmade emissions of greenhouse gases continue, according to a landmark report released Tuesday by the Obama administration.
The report, known as the National Climate Assessment, is the most detailed examination yet of how climate change is altering everything from water availability in the drought-stricken Southwest to coastal flooding in the stormy Northeast.
The White House is touting the report as part of President Obama’s “Climate Action Plan,” which was announced in June of last year. Next month, the administration is expected to unveil new and highly contentious regulations curbing emissions of carbon dioxide, the most important long-lived greenhouse gas, from existing power plants.
The Obama administration is also working with local communities to improve preparedness for climate change impacts, such as sea level rise, and this report supports both policy tracks, according to John Podesta, senior advisor to the president. In a conference call with reporters on Tuesday, Podesta said the National Assessment, which had been released in draft form in 2013 and subject to reviews from federal agencies and the public, offers “the most authoritative and comprehensive source of scientific information” about climate change impacts in the U.S.
The report differs from other recent assessments of climate science, such as the U.N. Intergovernmental Panel on Climate Change's Fifth Assessment Report, in that it drills down on specific impacts and projections for eight different regions in the country. “Climate change is not a distant threat, it is already affecting every region of the country and key sectors of the economy,” said White House science advisor John Holdren. “This national climate assessment is the loudest and clearest alarm bell to date.”
The report is the third such examination of how climate change is affecting the U.S. specifically, and is the product of more than four years of work by hundreds of scientists. Since the second such assessment was published in 2009, climate science findings have become clearer and more dire, Holdren said.
For example, Tom Karl, the director of the National Climatic Data Center in Asheville, North Carolina, told reporters that the last report predicted that sea levels would increase between 10 to 17 inches by 2100. The new report has greatly increased the upper end of that range, due to alarming findings about increased ice loss in Greenland and Antarctica. The new projection is for one to four feet of sea level rise during the current century, Karl said.
The report highlights the risks that sea level rise poses to coastal cities such as Miami, Norfolk, Va., and Portsmouth, N.H. Considering that just two feet of sea level rise would more than triple the frequency of dangerous coastal flooding throughout most of the Northeast, if sea level rise were to hit the upper end of the new projections, it could prove extraordinarily expensive.
Recent studies have shown that the rise in global average sea level since the late 1800s has been much greater than at any other time in the past 2,000 years, the report said. Since 1992, sea level has risen at twice the rate it had during the past century, decreasing the amount of time that residents of U.S. coastlines have to prepare for coastal flooding.
The report paints a picture of a country in the grips of a large-scale transition, with shifts in extreme precipitation patterns, heat waves, coastal flooding and wildfire seasons all detected. These changes have occurred even though only a relatively modest increase in the average U.S. temperature has occurred so far, with an increase of between 1.3 to 1.9 degrees Fahrenheit since 1895. The most recent decade was the nation’s and the world’s hottest on record, and all regions of the country have experienced warming in recent decades.
Temperatures are projected to rise by another 2 to 4 degrees Fahrenheit in most areas of the U.S. during the next few decades. Depending on the magnitude of global greenhouse gas emissions, average U.S. temperatures could skyrocket by up to 10 degrees Fahrenheit by 2100, assuming continued increases in emissions.
The increase in average temperatures is reflected in an increasingly skewed balance between high and low temperature records. "Many more high temperature records are being broken as compared to low temperature records over the past three to four decades – another indicator of a warming climate," the report says. More precisely, the number of record low monthly temperatures has declined to the lowest levels since 1911, while the number of record high temperatures in the U.S. has climbed to its highest level since the blistering 1930s, when the nation saw some of its worsts heat waves.
In much of the U.S., especially the Midwest and Northeast, more rain is falling in short-duration, heavy bursts, leading to more flooding, the report says. The Northeast and Midwest may continue to get wetter, while the Southwest becomes even more parched, raising water supply and energy concerns there. The report warns the Southwest to prepare for major disruptions ahead due to climate change:
"Increased heat and changes to rain and snowpack will send ripple effects throughout the region’s critical agriculture sector, affecting the lives and economies of 56 million people –- a population that is expected to increase 68% by 2050, to 94 million. Severe and sustained drought will stress water sources, already over-utilized in many areas, forcing increasing competition among farmers, energy producers, urban dwellers, and plant and animal life for the region’s most precious resource."
While the Southwest has a long history of naturally-driven droughts, some of which have lasted for decades, the droughts that occur now and in years ahead are likely to be hotter, thereby making them even drier than they otherwise would have been, the report says. The hot and dry conditions are also likely to lead to a significant increase in wildfire activity, which has already started to take place. According to studies cited in the report, projections include a doubling of burned area in the southern Rockies, with up to a 74% increase in burned area in California in coming decades.
A new study that was recently accepted for publication in a scientific journal found that between 1984 to 2011, the number of wildfires over 1,000 acres in size from Nebraska to California increased by a rate of seven fires per year. The total area these fires burned increased by nearly 90,000 acres a year.
The report also found that other types of extreme weather events have become more common in the U.S., which officials such as Karl linked to manmade global warming. Heat waves have become more frequent and intense, especially across the West and Southwest. In the future, the report shows the droughts and heat waves are projected to become more intense everywhere.
Jerry Melillo, who led the federal advisory committee that spearheaded this report, told reporters that it is far more clear than the past two such efforts. “We are all bearing the costs of increases in extreme heat, heavy downpours and increased coastal storm surges,” he said.
“For decades we have collected the dots, now we have connected those dots.”“For decades we have collected the dots, now we have connected those dots.”
Podesta said in addition to the press outreach activities taking place on Tuesday, which includes rare one-on-one interviews between President Obama and a select group of eight television meteorologists, the administration plans to “fan out” across the country to engage communities in a dialogue about its findings. This will involve various Cabinet members and leaders of scientific agencies, Podesta said.
Asked about opinion polls that consistently show the American public rates global warming low on its list of policy priorities, Holdren said, "I think you are going to see the polls change.”