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標 題: [TAM] 地球氣溫已達數千年來最高點 NASA Study Finds World Warmth Edging
發信站: 政大狂狷年少 (10/15/06 19:07:09 Sun)

NASA Study Finds World Warmth Edging Ancient Levels

撰文:Rob Gutro(NASA Goddard Space Flight Center)


A new study by NASA scientists finds that the world's temperature is
reaching a level that has not been seen in thousands of years.

The study, led by James Hansen of NASA's Goddard Institute for Space
Studies, N.Y. along with scientists from other organizations concludes
that, because of a rapid warming trend over the past 30 years, the
Earth is now reaching and 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. Recent warming is forcing species of plants and animals to move
toward the north and south poles.

Image: Because of a rapid warming trend over the past 30 years, the
Earth is now reaching and passing through the warmest levels seen in
the last 12,000 years. This color-coded map shows average temperatures
from 2001-2005 compared to a base period of temperatures from 1951-
1980. Dark red indicates the greatest warming and purple indicates the
greatest cooling. (Credit: NASA)

The study used temperatures around the world taken during the last
century. Scientists concluded that these data showed the Earth has
been warming at the remarkably rapid rate of approximately .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. Green-
house 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.

Animation: Because of a rapid warming trend over the past 30 years,
the Earth is now reaching and passing through the warmest levels seen
in the last 12,000 years. This color-coded map shows a progression of
changing global surface temperatures from 1880 to 2005, the warmest
ranked year on record. Dark red indicates the greatest warming and
dark blue indicates the greatest cooling. (Credit: NASA)

The study notes that the world's warming is greatest at high latitudes
of the Northern Hemisphere, and it is larger over land than over ocean
areas. The extra warming at high latitudes is because of effects of
ice and snow. As the Earth warms, snow and ice melt, uncovering darker
surfaces that absorb more sunlight and increase warming. Warming is
less over ocean than over land because the deep ocean can absorb great
amounts of heat, and because they are so big, they take longer to warm.

The Western Pacific Ocean, which is a major source of heat for the
world ocean and atmosphere, has warmed in the past century. Meanwhile,
the Eastern Pacific Ocean has not warmed, because cold water rises
from the deep ocean in the Eastern Pacific, keeping the surface waters

Image: Data from this study reveal that the Earth has been warming
approximately 0.2 degrees Celsius (.36 Fahrenheit) per decade for
the past 30 years. This rapid warming has brought global temperature
to within about one degree Celsius 1.8 Degrees Fahrenheit) of the
maximum estimated temperature during the past million years.
(Credit: NASA)

Hansen and his colleagues suggest that the increased temperature
difference between the Western and Eastern Pacific may lead to the
development of strong El Ninos, such as those of 1983 and 1998. An
El Nino is an event that typically occurs every several years when the
warm surface waters in the West Pacific slosh eastward toward South
America, in the process altering weather patterns around the world.

The most important result found by these researchers is that the
warming in recent decades has brought global temperature to a level
within about one degree Celsius (1.8° F) of the maximum temperature
of the past million years, which they suggest is a sensible upper
limit for additional global warming. “If further global warming
reaches 2 or 3 degrees Celsius, we will likely see changes that make
Earth a different planet than the one we know. The last time it was
that warm was in the middle Pliocene, about three million years ago,
when sea level was estimated to have been about 25 meters (80 feet)
higher than today.”

Image: The "greenhouse effect" is the warming of climate that results
when the atmosphere traps heat radiating from Earth toward space.
Certain gases in the atmosphere resemble glass in a greenhouse,
allowing sunlight to pass into the "greenhouse," but blocking Earth's
heat from escaping into space. The gases that contribute to the
greenhouse effect include water vapor, carbon dioxide (CO2 ), methane,
nitrous oxides, and chlorofluorocarbons (CFCs). (Credit: U.S. EPA)

Global warming is already beginning to have noticeable effects in
nature. Plants and animals can survive only within certain temperature
ranges. In the northern hemisphere, with the warming of recent decades,
many species are beginning to move toward the North Pole. A study that
appeared in 2003 found that 1700 plant, animal and insect species
moved poleward at an average rate of about 4 miles per decade in the
last half of the 20th century.

Hansen said, “If we do not slow down the rate of global warming, many
species are likely to become extinct. In effect we are pushing them
[the plants and animals] off the planet.”

Animation: This study notes that the greatest warming is occurring at
high latitudes of the Northern Hemisphere. Here, white, snow-covered
terrain acts a giant reflector that bounces incoming solar radiation
back into space. As the snow cover melts, the percentage of sunlight
reflected, or “albedo,” decreases. Instead, the darker ocean and
exposed ground can absorb the light and heat-up, thus adding more
energy for continued melting. (Credit: NASA)

Related Links:

+ NOAA Pacific Marine Environmental Laboratory El Nino page

+ NASA's Climate Change Resource Reel



NASA哥達德太空飛行中心(Goddard Institute for Space)James Hansen 等
人指出:從地球近 100年來的氣溫來看,地球過去30年的氣溫暖化速度非常快,
使得地球現今的全球平均氣溫已經達到此次間冰期(interglacial period,
向遷徙。最近一次冰河時期發生於 12,000 年前;而再前一次的間冰期約距今


的地區。近30年的氣溫上升速度,平均達每10年上升攝氏 0.2度左右。看起來
圖,可明顯看見百年來氣溫已經上升了攝氏 1度之多!而氣溫如果上升超過攝
氏 2度以上,就會對全球氣候產生劇烈影響!「明天過後」,將真的成為全球




目前西太平洋的海水溫度在過去 100年間已經明顯上升,不過東太平洋受到來
平洋海溫之間的差異逐年增加,將使得聖嬰現象(El Ninos)愈來愈強--西太




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