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Warming already causing extreme weather, official report says

May 6, 2014
Courtesy of the Glob­al Change Re­search Pro­gram
and World Science staff

Glob­al warm­ing is al­ready caus­ing more more ex­treme weath­er in the United States, and af­fect­ing the country in other “far-reaching ways,” a ma­jor new re­port finds.

The re­port, known as the Na­t­ional Cli­mate As­sess­ment, came from a large go­vernment-o­verseen pan­el known as the Glob­al Change Re­search Pro­gram, es­tab­lished by Con­gress.

“Cer­tain types of ex­treme weath­er events with links to cli­mate change have be­come more fre­quent and/or in­tense,” said an over­view of the re­port, which was un­veiled May 6 at the White House.

Some in­di­ca­tors meas­ured glob­al­ly over many dec­ades that Earth’s cli­mate is warm­ing. White ar­rows in­di­cate in­creas­ing trends; black ar­rows in­di­cate de­creas­ing trends. All are meas­ured to be in the dir­ec­tions ex­pected for a warm­ing world. (Fig­ure source: NOAA NCDC, based on da­ta up­dat­ed from Ken­ne­dy et al. 2010).


These events in­clude “pro­longed pe­ri­ods of heat, heavy down­pours, and, in some re­gions, floods and droughts. In ad­di­tion, warm­ing is caus­ing sea lev­el to rise and glaciers and Arc­tic sea ice to melt, and oceans are be­com­ing more acid­ic as they ab­sorb car­bon di­ox­ide. These and oth­er as­pects of cli­mate change are dis­rupt­ing peo­ple’s lives and dam­ag­ing some sec­tors of our econ­o­my,” said the over­view.

There is over­whelm­ing ev­i­dence that hu­man ac­ti­vi­ties are the pri­ma­ry cause of the glob­al warm­ing of the past 50 years, ac­cord­ing to the re­port. “The burn­ing of coal, oil, and gas, and clear­ing of forests have in­creased the con­centra­t­ion of car­bon di­ox­ide in the at­mos­phere by more than 40 per­cent since the In­dus­t­ri­al Rev­o­lu­tion, and it has been known for al­most two cen­turies that this car­bon di­ox­ide traps heat” in the at­mos­phere, the re­port not­ed.

“The pat­tern of tem­per­a­ture change through the lay­ers of the at­mos­phere, with warm­ing near the sur­face and cool­ing high­er up in the strat­o­sphere, fur­ther con­firms that it is the build­up of heat-trapping gas­es (al­so known as “green­house gas­es”) that has caused most of the Earth’s warm­ing over the past half cen­tu­ry,” the over­view said.

“U.S. av­er­age tem­per­a­ture has in­creased by 1.3°F to 1.9°F since 1895, and most of this in­crease has oc­curred since 1970,” it added. “The most re­cent dec­ade was the na­t­ion’s and the world’s hot­test on rec­ord, and 2012 was the hot­test year on rec­ord in the con­ti­nen­tal Un­ited States. All U.S. re­gions have ex­pe­ri­enced warm­ing in re­cent dec­ades, but the ex­tent of warm­ing has not been un­iform. In gen­er­al, tem­per­a­tures are ris­ing more quickly in the north. Alaskans have ex­pe­ri­enced some of the larg­est in­creases in tem­per­a­ture be­tween 1970 and the pre­s­ent. Peo­ple liv­ing in the South­east have ex­pe­ri­enced some of the small­est tem­per­a­ture in­creases over this pe­ri­od.”

“Tem­per­a­tures are pro­jected to rise anoth­er 2°F to 4°F in most ar­eas of the Un­ited States over the next few dec­ades. Re­duc­tions in some short-lived hu­man-induced emis­sions that con­trib­ute to warm­ing, such as black car­bon (soot) and meth­ane, could re­duce some of the pro­jected warm­ing over the next cou­ple of dec­ades, be­cause, un­like car­bon di­ox­ide, these gas­es and par­t­i­cles have rel­a­tively short at­mos­pher­ic life­times.”


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Global warming is already affecting the United States in “far-reaching ways,” including through more extreme weather events, a major new report finds. The report, known as the National Climate Assessment, came from a large government-overseen panel known as the Global Change Research Program, established by Congress. “Certain types of extreme weather events with links to climate change have become more frequent and/or intense,” said an overview of the report, which was unveiled May 6 at the White House. These events include “prolonged periods of heat, heavy downpours, and, in some regions, floods and droughts. In addition, warming is causing sea level to rise and glaciers and Arctic sea ice to melt, and oceans are becoming more acidic as they absorb carbon dioxide. These and other aspects of climate change are disrupting people’s lives and damaging some sectors of our economy,” said the overview. There is overwhelming evidence that human activities are the primary cause of the global warming of the past 50 years, according to the report. “The burning of coal, oil, and gas, and clearing of forests have increased the concentration of carbon dioxide in the atmosphere by more than 40% since the Industrial Revolution, and it has been known for almost two centuries that this carbon dioxide traps heat” in the atmosphere, the report noted. “The pattern of temperature change through the layers of the atmosphere, with warming near the surface and cooling higher up in the stratosphere, further confirms that it is the buildup of heat-trapping gases (also known as “greenhouse gases”) that has caused most of the Earth’s warming over the past half century,” the overview said. “U.S. average temperature has increased by 1.3°F to 1.9°F since 1895, and most of this increase has occurred since 1970,” it added. “The most recent decade was the nation’s and the world’s hottest on record, and 2012 was the hottest year on record in the continental United States. All U.S. regions have experienced warming in recent decades, but the extent of warming has not been uniform. In general, temperatures are rising more quickly in the north. Alaskans have experienced some of the largest increases in temperature between 1970 and the present. People living in the Southeast have experienced some of the smallest temperature increases over this period.” “Temperatures are projected to rise another 2°F to 4°F in most areas of the United States over the next few decades. Reductions in some short-lived human-induced emissions that contribute to warming, such as black carbon (soot) and methane, could reduce some of the projected warming over the next couple of decades, because, unlike carbon dioxide, these gases and particles have relatively short atmospheric lifetimes.”