Climate Change Over the Next 100 Years
Where is the climate headed? If the world proceeds on a "business as
usual" path, atmospheric CO2 concentrations will likely
be more than 700 ppm by 2100, and they will still be rising. This is nearly
double the current level and much more than double the preindustrial level of
280 ppm . State-of-the-art climate models suggest that this will result in an
increase of about 3.5oF in global temperatures over the next century.
This would be a rate of climate change not seen on the planet for at least the
last 10,000 years. It is the combined threat of elevated concentrations of greenhouse
gases and this unprecedented rate of increase that causes great concern.
What are the projected extent and pattern of warming over the
globe? The higher latitude regions will warm relatively more than areas
nearer to the equator. The land surface will warm more than the oceans, and
there will be less variation in temperature from night to day.
Even if the rate of emissions is slowed enough
to limit atmospheric concentrations to about 550 ppm, or roughly double the
preindustrial level, the U.S. could experience temperature increases of 5o
F to 10o F. These warmer temperatures would lead to soil drying in
some regions, with drying estimated at 10 percent to 30 percent for the United
States during the summer growing season.
Some modeling experiments have examined the consequences of CO2 levels
well beyond 700 ppm, which
are likely to occur after 2100 if current emissions trajectories are not altered.
If the CO2 concentration were to continue to rise to four times the preindustrial
level, or more than 1100 ppm, the estimated temperature increase for the United
States would be 15oF to 20oF and soil drying could approach
30 percent to 50 percent during the growing season

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