"Long before it's in the papers"
January 28, 2015


Earth hottest in 5,000 years, study suggests

Sept. 25, 2006
Courtesy NASA
and World Science staff

Tem­pe­r­a­tures on Earth are hot­ter than they have been in sev­er­al thou­sand years, ac­cord­ing to a re­port in Mon­day’s ear­ly on­line is­sue of the re­search jour­nal Proceedings of the National Academy of Sciences.

A further in­c­rease of 1° Cel­si­us (1.8° Fah­ren­heit) will pro­duce dan­ger­ous sea le­vel ri­ses and spe­cies ex­ter­mi­na­tions, the au­thors wrote.

The stu­dy, led by James Han­sen of NASA’s God­dard In­sti­tute for Space Stud­ies in New York, found that warm­ing over the past three dec­ades has pushed Earth past the hot­test lev­els in the cur­rent in­ter­gla­cial pe­ri­od, or time between ice ages. The cur­rent pe­r­i­od has last­ed near­ly 12,000 years. The pre­vi­ous rec­ord tem­pe­r­a­tures dur­ing this pe­ri­od are es­ti­mat­ed to have oc­curred around five or six mil­len­ni­a ago.

Re­cent warm­ing is forc­ing spe­cies of plants and an­i­mals to move to­ward the north and south poles, the re­port said.

The study used tem­pe­r­a­tures around the world tak­en dur­ing the last cen­tu­ry. Sci­en­tists con­clud­ed that these da­ta showed the Earth has been warm­ing at what they called a re­mark­ably quick rate of about 0.36° Fahr­en­heit (0.2° Cel­si­us) per dec­ade for the past 30 years.

“This ev­i­dence im­plies that we are get­ting close to dan­ger­ous lev­els of hu­man-made pol­lu­tion,” said Han­sen. 

Hu­man-made “green­house gas­es” are caus­ing glo­b­al warm­ing, ac­cord­ing to sci­en­tists. Green­house gas­es trap heat in the Earth’s at­mos­phere and warm the sur­face. Some green­house gas­es, which in­clude wa­ter va­por, car­bon di­ox­ide, meth­ane, ni­trous ox­ide, and ozone, oc­cur nat­u­ral­ly, while oth­ers are due to hu­man ac­tiv­i­ties.

Fur­ther glob­al warm­ing “of more than 1°C, rel­a­tive to 2000, will con­sti­tute “dan­ger­ous” cli­mate change as judged from like­ly ef­fects on sea lev­el and ex­ter­mi­na­tion of spe­cies,” the sci­en­tists wrote. The re­port ex­tends a re­cent find­ing that Earth is cur­rently hot­ter than at any time in the past 400 years.

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Temperatures on Earth are hotter than they have been in several thousand years, according to a report published in Monday’s early online issue of the journal pnas. The study, led by James Hansen of NASA’s Goddard Institute for Space Studies, in New York, found that, because of a rapid warming over the past three decades, the Earth is passing through the warmest levels in the current interglacial period. which has lasted nearly 12,000 years. An “interglacial period” is a time in the Earth’s history when the area of Earth covered by glaciers was similar or smaller than at the present time. The previous record temperatures during that period are estimated to have occurred around five or six millennia ago. Recent warming is forcing species of plants and animals to move toward the north and south poles, the report added. The study used temperatures around the world taken during the last century. Scientists concluded that these data showed the Earth has been warming at what they called a remarkably quick rate of about 0.36° Fahrenheit (0.2° Celsius) per decade for the past 30 years. “This evidence implies that we are getting close to dangerous levels of human-made pollution,” said Hansen. In recent decades, human-made greenhouse gases have become the largest climate change factor, according to scientists. Greenhouse gases trap heat in the Earth’s atmosphere and warm the surface. Some greenhouse gases, which include water vapor, carbon dioxide, methane, nitrous oxide, and ozone, occur naturally, while others are due to human activities. Further global warming “of more than 1°C, relative to 2000, will constitute “dangerous” climate change as judged from likely effects on sea level and extermination of species,” the scientists wrote. The report extends a recent finding that Earth is currently hotter than at any time in the past 400 years.