Report: How Climate Change Impacts America

U.S. Global Change Research Program
Janet Fang 06 May 2014, 23:47
 
More water scarcity in dry regions, torrential rains in wet regions, and severe heat waves all over. With an average warming of less than 2 degrees Fahrenheit in the past century, human-induced climate change is already being felt everywhere in the U.S., and the impacts are likely to worsen, according to the third U.S. National Climate Assessment (NCA) released by the Obama Administration this week. If we continue to emit greenhouse gases like we are, warming could exceed 10 degrees by the end of the 21st century. 
 
Developed over four years with input from hundreds of climate scientists from public and private institutions, the hefty 1300-page report focuses on every region across America, as well as major sectors of the U.S. economy: from energy and health, to transportation and agriculture. The message is clear: “There is mounting evidence that harm to the nation will increase substantially in the future unless global emissions of heat-trapping gases are greatly reduced.”
 
You can read the entire report here, or you click around the interactive, digital format at globalchange.gov. Here are some of the grim highlights, outlined by the White House press office. Starting with climate trends: 
 
Temperature: U.S. average has increased by 1.3 to 1.9 degrees Fahrenheit since record keeping began in 1895, and it’s expected to rise. Most of that increase starting around 1970, with the most recent decade being the warmest on record. With human-induced warming superimposed on natural climate variations, the rise hasn’t been (and won’t be) uniform or smooth across the country or over time.
Extreme Weather: Heat waves and droughts have become more frequent and intense (especially in the west), while cold waves have become less frequent and intense across the country. 
Hurricanes: The intensity, frequency, and duration of North Atlantic hurricanes, as well as the frequency of the strongest (category 4 and 5) hurricanes, have all increased since the early 1980s. Associated storm intensity and rainfall rates are projected to increase as well. 
Severe Storms: Winter storms have increased in frequency and intensity since the 1950s, and their tracks have shifted northward over the U.S. Intensity and frequency of tornadoes, hail, and thunderstorm winds are uncertain. 
Precipitation: Average precipitation has increased since 1900, with a lot of regional variation above and below the average. More winter and spring precipitation is projected for the northern U.S. and less for the southwest.
Heavy Downpours: These have increased nationally, with the largest increases in the midwest and northeast, especially over the last three to five decades. We'll be seeing Increases in the frequency and intensity for all regions.
Frost-free Season: Their lengths have increased nationally since the 1980s, especially in the west. Growing season will continue to lengthen.
Ice Melt: Rising temperatures are reducing ice volume and surface extent on land, lakes, and sea, and the loss is expected to continue. The Arctic Ocean is expected to become essentially ice free during the summer before mid-century.
Sea Level: The global level has risen by about 8 inches since 1880, when record keeping began. It’s projected to rise another 1 to 4 feet by 2100. 
Ocean Acidification: The oceans are absorbing about a quarter of the carbon dioxide emitted to the atmosphere every year, and they're becoming more acidic as a result. 
 
Here are some impacts that are specific to geographic regions. These effects have socioeconomic as well as ecosystem consequences. 
 
Northeast: Heat waves, more extreme precipitation events, and flooding from sea level rise and storm surge.
Southeast and Caribbean: Increased risk from hurricanes, decreases in water availability with increases in water competition.
Midwest: Increases in crop yields from longer growing seasons and rising carbon dioxide levels will be offset by heat waves, droughts, and floods.
Great Plains: Rising temperatures lead to increased demand for water and energy, along with increased impacts on agricultural practices.
Southwest: Drought and increased warming foster wildfires and increased competition for scarce water resources.
Northwest: Earlier snowmelt and changes in streamflow timing will reduce water supply in the summer. 
Alaska: Rapidly receding summer sea ice, shrinking glaciers, and thawing permafrost damages infrastructure and changes ecosystems.
Hawaii and Pacific Islands: Increasingly constrained freshwater supplies and increased temperatures will decrease food and water security. 
Coasts: Water supply infrastructure and evacuation routes are increasingly vulnerable to higher sea levels and storm surges and inland flooding.
 
 
Image: GlobalChange.gov
 
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