Контрольная работа по "Английскому языку"

David E. Steitz

Headquarters, Washington              November 5, 2001

(Phone: 202/358-1730) 

Lynn Chandler

Goddard Space Flight Center, Greenbelt, Md.

(Phone: 301/286-2806) 

RELEASE: 01-212 

SATELLITES SHED LIGHT ON A WARMER WORLD 

     While winter may be approaching, researchers using

data from satellites and weather stations around the world

have found the air temperature near the Earth's surface

has warmed on average by 1 degree F (0.6 degree C)

globally over the last century, and they cite human

influence as at least a partial cause. 

Dr. James Hansen of NASA's Goddard Institute for Space

Studies, New York, and Marc Imhoff of NASA's Goddard Space

Flight Center, Greenbelt, Md., along with several other

researchers analyzed records for 7,200 global weather

stations and used satellite observations of nighttime

lights around the planet to identify stations with minimal

local human influence. Their findings appeared in a recent

issue of the Journal of Geophysical Research-Atmospheres. 

"Warming around the world has been widespread, but it is

not present everywhere," Hansen said. Warming in the past

50 years has been rapid in Alaska and Siberia, but

Greenland has become cooler. The lower 48 United States

have become warmer recently, but only enough to make the

temperature comparable to what it was in the 1930s.  

Hansen and Imhoff are making a special effort to minimize

any distortion of the record caused by urban heat-island

effects as they research global warming. It is recognized

that recorded temperatures at many weather stations are

warmer than they should be because of human developments

around the station. Hansen and Imhoff used satellite

images of nighttime lights to identify stations where

urbanization was most likely to contaminate the weather

records.  

Urban heat-island effects are created when cities grow and

asphalt roads, tar roofs and other features are

substituted for areas where plants would otherwise grow.

Trees provide shade and cool the air through evaporation.

The hard dark surfaces like pavements store heat during

the day, which is released at night, keeping the city

hotter for longer periods of time. 

U.S. Defense Meteorological Satellites measure the

brightness of nighttime lights all over the Earth's

surface. Hansen and Imhoff used the night-light brightness

to classify the location of each weather station as urban,

near-urban or rural. "We find larger warming at urban

stations on average," said Hansen, "so we use the rural

stations to adjust the urban records, thus obtaining a

better measure of the true climate change." 

Evidence of a slight, local human influence is found even

in small towns and it is probably impossible to totally

eliminate in the global analyses. Although Hansen and

Imhoff have not yet applied satellite data in most of the

world, they adjusted the long-term trend of urban stations

to be consistent with the nearest rural stations. They

estimate that remaining urban influence on the global

record is not more than about 0.18 degree F (0.1 degree

C). 

Hansen and his colleagues classified the global climate

into three time segments between 1900 and 2000. Each

segment revealed a small swing in the Earth's global

temperature over a period of time.  

From 1900 to 1940, the data showed the world warmed. "That

warming may be in part a response to released greenhouse

gases and in part natural climate variability," Imhoff

said. 

Between 1940 and 1965, the globe cooled by about 0.18

degree F (a change of 0.1 degree C), which some scientists

attribute to the increased aerosols (fine particles in the

air) during this time. Aerosol forcing can lead to more

cloud cover and block incoming radiation. Aerosol

increases are related to the rate of growth of fossil fuel

use, which peaked in this period. Hansen noted

fluctuations in ocean heat-transport may also contribute

to such climate swings over decades. 

The third period, from 1965 to 2000, showed a large and

widespread warming around the world. During this time

warming intensified in the El Nino region of the (eastern)

Pacific Ocean, and the Indian, Atlantic and Arctic oceans

also warmed. 

This research was conducted as part of NASA's Earth

Sciences Enterprise, a long-term research effort dedicated

to understanding how natural and human-induced changes

affect our global environment. 

More information and images are available at:

http://www.gsfc.nasa.gov/topstory/20011027heatisland.html

                          -end- 

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