Environmental Engineering Reference
In-Depth Information
Table 9.2
Nonbiological indicators of climate change
The twelve warmest years since 1900 have occurred in the last 25 years;
the eight warmest have been since 1998.
In 2005 the global average temperature was the warmest since scientists
began compiling records in the late 1800s.
Most of the world's glaciers and ice caps are melting.
Arctic sea ice has disappeared at an average rate of 7.8 percent per
decade since 1953. Commercial shipping may be possible by 2015.
The Great Lakes are thawing two days sooner each ten years.
Average global sea levels have risen about 9 inches since 1901; more
than 10 percent of this rise occurred over the past decade.
On the Antarctic Peninsula, the average temperature has risen by about
4.5°F since 1950, and 212 of the 244 glaciers on the peninsula are
melting.
The Arctic's winter temperature is now 3 to 4 degrees Fahrenheit higher
than it was a hundred years earlier.
The area of permanently frozen ground (permafrost) in Canada has
decreased by 30 percent since 1900. Potentially arable soil is appearing.
The Great Lakes, the earth's largest concentration of freshwater, are
thawing earlier each spring, based on records dating back to 1846.
How Hot Is It?
Meteorological stations around the world have been recording daily
temperatures near the ground for hundreds of years, so the database
to determine an average earth surface temperature is very large. The
data show that the average temperature has been increasing for more
than a hundred years—not in a straight line, but the trend is clearly
upward (fi gure 9.1). The ups and downs over short intervals result
from interactions among the many feedback loops in the factors that
infl uence climate. Studies indicate that positive loops, which reinforce
higher temperatures, are more abundant than negative loops, which
mitigate them.
It is noteworthy that the temperature has been increasing more rapidly
in recent years than in the past. The rate of change in the last twenty-
fi ve years is triple the rate (in Fahrenheit) of the previous 100 years.
This rate of change surpasses the worst-case scenarios predicted only a
few years ago.
The average earth surface temperature in 2008 was 57.9ºF, an increase
of about 0.9ºF, or 1.6 percent, above the twentieth-century average. This
