February 17, 1997
Vol. 6, No. 8
For Additional Information:
Dr. John Christy, UAH, (205) 922-5763
[email protected]
Dr. Roy Spencer, NASA, (205) 922-5960
[email protected]
Global Temperature Report: January 1997
Global temperature variation, in Celsius; trend since 1979, -0.04 degrees
C per decade
January Global Composite Temp.:
-0.30 degrees C (about 0.54 degrees Fahrenheit) below 10-year average for
January.
Northern Hemisphere:
-0.45 degrees C (about 0.81 degrees Fahrenheit) below 10-year average for
January.
Southern Hemisphere:
-0.16 degrees C (about 0.29 degrees Fahrenheit) below 10-year average for
January.
December Temperatures (revised):
Global Composite: -0.11 degrees C below 10-year average
Northern Hemisphere: +0.01 degrees C above 10-year average
Southern Hemisphere: -0.23 degrees C below 10-year average
(All temperature variations are based on a 10-year average (1982-1991)
for the month reported.)
Notes on data released February 17, 1997:
The Northern Hemisphere's coldest month in more than 18 years may in part
be due to a persistent low pressure system over the northwestern Atlantic
Ocean, according to Dr. John Christy, an associate professor of
atmospheric science in the Earth System Science Laboratory at UAH.
"What we may be seeing is the North Atlantic Oscillation," said Christy.
"This is a wintertime phenomenon in the Northern Hemisphere.
"The North Atlantic was under relatively high pressure through most of
the winters in the '80s and early '90s. Scientists who study this
reported that it had switched to low pressure last winter," said Christy.
"Changes in pressure distribution change the large scale wind systems,
which contribute to temperature changes. The North Atlantic low pressure
pattern typically includes cold temperatures over Russia and, to a lesser
extent, western Canada and the North Pacific.
"When something effects the weather in one area the way this low Atlantic
pressure is believed to, it's going to have a corresponding countereffect
on neighboring regions.
"In North America, the Quebec region's climate is influenced by the
Northwest Atlantic. The area further to the west will be likely to do the
opposite (i.e., warming over Quebec contributes to cooling over Western
Canada). We saw that pattern in December and now again in January."
While temperatures over the North Atlantic from Hudson Bay to Finland
were as much as 2.5 degrees C above seasonal norms, the corresponding
region of cold over central Russia was as much as 4.5 degrees C below the
January norm, while the troposphere above the North Pacific between
Hawaii and the Aleutian Islands was as much as 3.5 degrees C cooler.
That pool of Pacific cold air was at the eastern end of a large band of
slightly (0.5 to 1.5 degrees C) cooler than normal temperatures that
girdled most of the northern tropics and subtropics, from the Pacific
Ocean just west of Central America eastward through the Caribbean, Gulf
of Mexico and Atlantic to Morocco, Central Africa, India, and the
Philippines.
While the 0.45 degrees C temperature anomaly for January in the Northern
Hemisphere was only the seventh largest cool anomaly, it came during the
coldest month of the year for that half of the globe.
As summer deepens in the Southern Hemisphere, that hemisphere's average
temperature in January warmed slightly but still remained slightly below
seasonal norms.
As part of an ongoing NASA/UAH joint project, Christy and Dr. Roy
Spencer, a space scientist in the Earth Science Laboratory of the Global
Hydrology and Climate Center in NASA's Marshall Space Flight Center, use
data gathered by microwave sounding units on NOAA's TIROS-N satellites to
get accurate temperature readings for almost all regions of the Earth.
Once the monthly temperature data is collected and processed, it is
placed in a "public" computer file for immediate access by atmospheric
scientists in the U.S. and abroad.
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