Climatologists at the NASA Goddard Institute for Space Studies (GISS)
in New York City have found that 2007 tied with 1998 for Earth's
second warmest year in a century.
"It is unlikely that 2008 will be a year with truly exceptional global
mean temperature," said Hansen. "Barring a large volcanic eruption, a
record global temperature clearly exceeding that of 2005 can be expected
within the next few years, at the time of the next El Nino, because of the
background warming trend attributable to continuing increases of greenhouse gases."
The eight warmest years in the GISS record have all occurred since 1998,
and the 14 warmest years in the record have all occurred since 1990.
Goddard Institute researchers used temperature data from weather stations
on land, satellite measurements of sea ice temperature since 1982 and data
from ships for earlier years.
The greatest warming in 2007 occurred in the Arctic, and neighboring high
latitude regions. Global warming has a larger affect in polar areas, as the
loss of snow and ice leads to more open water, which absorbs more sunlight
and warmth. Snow and ice reflect sunlight; when they disappear, so too does
their ability to deflect warming rays. The large Arctic warm anomaly of 2007
is consistent with observations of record low geographic extent of Arctic sea
ice in September 2007.
"As we predicted last year, 2007 was warmer than 2006, continuing the strong
warming trend of the past 30 years that has been confidently attributed to
the effect of increasing human-made greenhouse gases," said James Hansen,
director of NASA GISS.
A minor data processing error found in the GISS temperature analysis in early
2007 does not affect the present analysis. The data processing flaw was failure
to apply NOAA adjustments to United States Historical Climatology Network
stations in 2000-2006, as the records for those years were taken from a
different data base (Global Historical Climatology Network). This flaw
affected only 1.6% of the Earth's surface (contiguous 48 states) and
only the several years in the 21st century.
The data processing flaw did not alter the ordering of the warmest years on
record and the global ranks were unaffected. In the contiguous 48 states, the
statistical tie among 1934, 1998 and 2005 as the warmest year(s) was unchanged.
In the current analysis, in the flawed analysis, and in the published GISS
analysis, 1934 is the warmest year in the contiguous states (but not globally)
by an amount (magnitude of the order of 0.01°C) that is an order of magnitude
smaller than the certainty.
This article is a reprint of a NASA news release from January 16, 2008.
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Temperature anomaly map for 2007. Dark red is two degrees Celsius above normal and dark blue is two degrees below normal. NASA Image. Enlarge temperature map.
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