NASA Finds 2012 Sustained Long-Term Climate Warming Trend

Jan. 15, 2013

Steve Cole
Headquarters, Washington
202-358-0918
stephen.e.cole@nasa.gov

Leslie McCarthy
Goddard Institute for Space Studies, New York
212-678-5507
leslie.m.mccarthy@nasa.gov

RELEASE: 13-021

NASA FINDS 2012 SUSTAINED LONG-TERM CLIMATE WARMING TREND

WASHINGTON -- NASA scientists say 2012 was the ninth warmest of any
year since 1880, continuing a long-term trend of rising global
temperatures. With the exception of 1988, the nine warmest years in
the 132-year record all have occurred since 2000, with 2010 and 2005
ranking as the hottest years on record.

NASA's Goddard Institute for Space Studies (GISS) in New York, which
monitors global surface temperatures on an ongoing basis, released an
updated analysis Tuesday that compares temperatures around the globe
in 2012 to the average global temperature from the mid-20th century.
The comparison shows how Earth continues to experience warmer
temperatures than several decades ago.

The average temperature in 2012 was about 58.3 degrees Fahrenheit
(14.6 Celsius), which is 1.0 F (0.6 C) warmer than the mid-20th
century baseline. The average global temperature has risen about 1.4
degrees F (0.8 C) since 1880, according to the new analysis.

Scientists emphasize that weather patterns always will cause
fluctuations in average temperature from year to year, but the
continued increase in greenhouse gas levels in Earth's atmosphere
assures a long-term rise in global temperatures. Each successive year
will not necessarily be warmer than the year before, but on the
current course of greenhouse gas increases, scientists expect each
successive decade to be warmer than the previous decade.

"One more year of numbers isn't in itself significant," GISS
climatologist Gavin Schmidt said. "What matters is this decade is
warmer than the last decade, and that decade was warmer than the
decade before. The planet is warming. The reason it's warming is
because we are pumping increasing amounts of carbon dioxide into the
atmosphere."

Carbon dioxide is a greenhouse gas that traps heat and largely
controls Earth's climate. It occurs naturally and also is emitted by
the burning of fossil fuels for energy. Driven by increasing man-made
emissions, the level of carbon dioxide in Earth's atmosphere has been
rising consistently for decades.

The carbon dioxide level in the atmosphere was about 285 parts per
million in 1880, the first year in the GISS temperature record. By
1960, the atmospheric carbon dioxide concentration, measured at
NOAA's Mauna Loa Observatory, was about 315 parts per million. Today,
that measurement exceeds 390 parts per million.

While the globe experienced relatively warm temperatures in 2012, the
continental U.S. endured its warmest year on record by far, according
to NOAA, the official keeper of U.S. weather records.

"The U.S. temperatures in the summer of 2012 are an example of a new
trend of outlying seasonal extremes that are warmer than the hottest
seasonal temperatures of the mid-20th century," GISS director James
E. Hansen said. "The climate dice are now loaded. Some seasons still
will be cooler than the long-term average, but the perceptive person
should notice that the frequency of unusually warm extremes is
increasing. It is the extremes that have the most impact on people
and other life on the planet."

The temperature analysis produced at GISS is compiled from weather
data from more than 1,000 meteorological stations around the world,
satellite observations of sea-surface temperature, and Antarctic
research station measurements. A publicly available computer program
is used to calculate the difference between surface temperature in a
given month and the average temperature for the same place during
1951 to 1980. This three-decade period functions as a baseline for
the analysis. The last year that experienced cooler temperatures than
the 1951 to 1980 average was 1976.

The GISS temperature record is one of several global temperature
analyses, along with those produced by the Met Office Hadley Centre
in the United Kingdom and the National Oceanic and Atmospheric
Administration's National Climatic Data Center in Asheville, N.C.
These three primary records use slightly different methods, but
overall, their trends show close agreement.

For images related to the data, visit:

http://go.nasa.gov/10wqITW


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