WASHINGTON — Americans will need to adapt quickly to already-occurring climate change that is causing more frequent and intense rainstorms and flooding and hotter, longer, and potentially more deadly summer heat waves, according to the third U.S. National Climate Assessment released on Tuesday.
The assessment also predicted dire, long-term consequences for failing to act quickly to reduce man-made greenhouse gas emissions that are fueling the changing climate. Those include heat waves and drought in California and the Southwest, wildfires and a degraded forest ecosystem in the West, a decline in species diversity, and an increase in invasive species and higher levels of air pollution in warming urban areas.
John Holdren, science adviser for the Obama Administration, which recently has begun pushing its climate-change policies, including limitations on greenhouse gas emissions, said the assessment is “the loudest and clearest alarm bell to date signaling the need to take urgent action.”
The periodic federal climate assessment, compiled by 13 federal agencies with input from more than 300 scientists, advisers, and government administrators, is mandated by a 1990 law and updates assessments released in 2000 and 2009.
The 840-page report makes a strong case that climate changes are occurring in many parts of the United States and the impacts on ecosystems, infrastructure, economics, and public health will continue to grow.
The assessment predicts that the Northeast will experience warmer winters and less snowfall. In mountainous regions, including much of Pennsylvania and West Virginia, more intense precipitation events will mean greater flood risk, particularly in valleys, where people, infrastructure, and agriculture tend to be concentrated.
And along the Atlantic seaboard, the continuing rise of sea level could triple the frequency of flooding and severely damage water, sewer, and electrical systems, and human health, said Radley Horton, research scientist at Columbia University in New York and the lead author of the assessment’s Northeast region chapter. He said flooding along the Atlantic seaboard could cause “multiple systems failures in a cascade effect,” and warned that the extreme heat waves could be deadly for young people, senior citizens, and the disadvantaged.
“I see a real risk, a growing risk of very negative outcomes for residents of the Northeast,” said Mr. Horton in a teleconference Tuesday afternoon that was hosted by Climate Nexus, an organization focused on climate-change policy and clean-energy solutions, and attended by a half-dozen other authors of the assessment.
They urged states to implement mitigation and adaptation strategies to address what the report calls “climate disruption” but noted that while most states have adopted action plans, implementation is in the early stages for most.
“We are being presented clearly with evidence that it’s time to make a change in the pathway we are on,” said Kirstin Dow, professor of geography at the University of South Carolina and lead author of the assessment’s Research Agenda for the Climate Change Chapter. “And there are opportunities to go a better way.”
Mr. Horton said in the Northeast region, West Virginia is the state that has done the least. It has not started to develop a climate-action plan. The other states in the region either have action plans or are moving toward them.
In the Midwest, the report says a warming planet will worsen a series of weather trends already showing up. Look for more extremes: searing heat, late-spring freezes, and floods and droughts across a region that includes Ohio, Michigan, Indiana, Illinois, Wisconsin, Minnesota, Iowa, and Missouri.
The growing season, already two weeks longer than in 1950, will continue to lengthen. But the gains will be offset by smaller yields for some crops, including corn. Soybean yields will improve for a while, but the gains will be offset by heat stress.
Sensitive fruits such as tart cherries in Michigan and Wisconsin increasingly will be vulnerable to early budding followed by killing freezes as in 2012, when the crop was devastated. Wetter springs could delay planting.
Wetlands, prairies, and other ecosystems will change profoundly, none more so than the northern forests. Familiar tree species such as paper birch, quaking aspen, balsam fir, and black spruce probably will migrate even farther north, giving way to oak and pine varieties now common farther south.
The report acknowledges it’s harder to project long-range changes in precipitation than temperature. But the Midwest generally has become wetter in the last century, mostly because of increasingly intense storms, and that’s likely to continue in the next century. Just how much will depend on how successfully people cut back on carbon emissions.
But weather patterns may become increasing erratic — wet in some parts of the region, dry in others. Snowfall may decline in much of the Midwest but increase in areas that get lake-effect snow. More flooding is likely, which intensifies sewer overflows, soil erosion, and water pollution from runoff.
Heat and humidity will raise the misery index in cities, with one study predicting up to 2,217 additional heat-related deaths per year in Chicago toward the end of the 21st century, although cutbacks in greenhouse gas emissions could reduce the number significantly. Higher temperatures should lengthen the pollen season and worsen the effects of degraded air quality.
More than 90 percent of the Great Lakes’ surface froze this winter, but don’t be fooled. Ice cover has retreated steadily for decades, and the trend probably will continue, despite the occasional blip.
Expect warmer surface waters and more nuisance algae blobs that harm fish and water quality. Reduced ice cover could lengthen the cargo shipping season, although the benefit could be offset if water levels drop. The effect of climate change on water levels is uncertain.
The assessment was hailed by environmental organizations and scored by industry groups, Republican leaders, and conservatives as alarmist and political and another example of government overreach.
Katharine Hayhoe, lead author of the report’s climate change science chapter and director of the Climate Science Center at Texas Tech University, acknowledged that while some skeptics who are philosophically or ideologically opposed to acknowledging climate change remain, most people understand it’s real but don’t think action is a priority.
“They know it’s an issue but they’ll worry about it later,” she said. “For those, the report shows how the climate is changing here and now, no matter what part of the country we are living in.”
The Block News Alliance consists of The Blade and the Pittsburgh Post-Gazette. Don Hopey is a reporter for the Post-Gazette. Information from The Blade’s wire services was used in this report.
Contact Don Hopey at: firstname.lastname@example.org or 412-263-1983.