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Loss of Species

Page history last edited by PBworks 13 years, 8 months ago

Loss of Species


QUOTE: "If we do not slow down the rate of global warming, many

species are likely to become extinct. In effect we are pushing them

off the planet." James Hansen, Goddard Institute for Space Studies


 

NASA Study Finds World Warmth Edging Ancient Levels

09.25.06

 

A new study by NASA climatologists finds that the world's temperature

is reaching a level that has not been seen in thousands of years.

http://www.nasa.gov/centers/goddard/news/topstory/2006/world_warmth.html

 

The study appears in the current issue of the Proceedings of the

National Academy of Sciences, authored by James Hansen of NASA's

Goddard Institute for Space Studies, N.Y. and colleagues from

Columbia University, Sigma Space Partners, Inc., and the University

of California at Santa Barbara (UCSB). The study 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. This

warming is forcing a migration of plant and animal species toward the

poles.

 

The study includes worldwide instrumental temperature measurements

during the past century. These data reveal that the Earth has been

warming at the remarkably rapid rate of approximately 0.2° Celsius

(.36° Fahrenheit) per decade for the past 30 years. This observed

warming is similar to the warming rate predicted in the 1980s in

initial global climate model simulations with changing levels of

greenhouse gases.

 

"This evidence implies that we are getting close to dangerous levels

of human-made (anthropogenic) pollution," said Hansen. In recent

decades, human-made greenhouse gases (GHGs) have become the dominant

climate change factor.

 

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 enhanced warming at high latitudes is

attributed to effects of ice and snow. As the Earth warms, snow and

ice melt, uncovering darker surfaces that absorb more sunlight and

increase warming, a process called a positive feedback. Warming is

less over ocean than over land because of the great heat capacity of

the deep-mixing ocean, which causes warming to occur more slowly

there.

 

Hansen and his colleagues in New York collaborated with David Lea and

Martin Medina-Elizade of UCSB to obtain comparisons of recent

temperatures with the history of the Earth over the past million

years. The California researchers obtained a record of tropical ocean

surface temperatures from the magnesium content in the shells of

microscopic sea surface animals, as recorded in ocean sediments.

 

One of the findings from this collaboration is that the Western

Equatorial Pacific and Indian Oceans are now as warm as, or warmer

than, at any prior time in the Holocene. The Holocene is the

relatively warm period that has existed for almost 12,000 years,

since the end of the last major ice age. The Western Pacific and

Indian Oceans are important because, as these researchers show,

temperature change there is indicative of global temperature change.

Therefore, by inference, the world as a whole is now as warm as, or

warmer than, at any time in the Holocene.

 

According to Lea, "The Western Pacific is important for another

reason, too: it is a major source of heat for the world's oceans and

for the global atmosphere."

 

In contrast to the Western Pacific, the researchers find that the

Eastern Pacific Ocean has not shown an equal magnitude of warming.

They explain the lesser warming in the East Pacific Ocean, near South

America, as being due to the fact this region is kept cool by

upwelling, rising of deeper colder water to shallower depths. The

deep ocean layers have not yet been affected much by human-made

warming.

 

Hansen and his colleagues suggest that the increased temperature

difference between the Western and Eastern Pacific may boost the

likelihood 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. According to Hansen "That means that

further global warming of 1 degree Celsius defines a critical level.

If warming is kept less than that, effects of global warming may be

relatively manageable. During the warmest interglacial periods the

Earth was reasonably similar to today. But 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."

 

Global warming is already beginning to have noticeable effects in

nature. Plants and animals can survive only within certain climatic

zones, so with the warming of recent decades many of them are

beginning to migrate poleward. A study that appeared in Nature

Magazine in 2003 found that 1700 plant, animal and insect species

moved poleward at an average rate of 6 kilometers (about 4 miles) per

decade in the last half of the 20th century.

 

That migration rate is not fast enough to keep up with the current

rate of movement of a given temperature zone, which has reached about

40 kilometers (about 25 miles) per decade in the period 1975 to 2005.

"Rapid movement of climatic zones is going to be another stress on

wildlife" according to Hansen. "It adds to the stress of habitat loss

due to human developments. If we do not slow down the rate of global

warming, many species are likely to become extinct. In effect we are

pushing them off the planet."

 

Find this article (with graphics) at:

http://www.nasa.gov/centers/goddard/news/topstory/2006/world_warmth.html

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