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.
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 0.36
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....
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 (1.8F) 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.”
Excerpt from the NASA GISS Release, Sep. 25, 2006