hUman ImpaCtS on the BIoSphere 479how does global warming affect the earth?- Global warming is the long-term rise in Earth’s surface
temperature due to the rapid accumulation of greenhouse
gases in the atmosphere. - Due to warming, a major shift in Earth’s climate may be
under way.
Take-Home messageglobal climate change A
shift in the Earth’s climates.
global warming A long-
term rise in temperature
near the Earth’s surface.
greenhouse effect The
buildup of heat in the lower
atmosphere due largely to
the accumulation of carbon
dioxide, methane, water
vapor, and other gases.agriculture in parts of Africa where many people are des-
perately poor and farm small plots for food.
Glaciers all over the world are retreating (Figure 25.11),
and polar ice is rapidly melting. One result of these changes
is rising sea level in many coastal areas. The IPCC projects
an average rise of 0.6 to 1.9 feet by 2100. If this estimate is
accurate, in your lifetime the sea may submerge up to a
third of the world’s coastal wetlands and coral reefs, begin
to flood many large coastal cities and agricultural lands,
and erode large chunks of coastlines such as the Atlantic
coast of the United States.
Disappearing glaciers also will
wipe out a major source of fresh
water for domestic and agricultural
use in India, parts of South America
and Africa, as well as western North
America.
Although this discussion may
seem depressing, it is important to
remember that many smart people
are working on strategies for slow-
ing global warming and climate
change. Explore on Your Own at the end of this chapter sug-
gests ways you can assess your personal contribution to
both these phenomena.Today there is general agreement that the increase in
greenhouse gases is a factor in global warming, a long-
term rise in temperature near Earth’s surface. Since direct
measurements started in 1861, the lower atmosphere’s
temperature has risen by more than 1°F, mostly since 1946.
Nine of the ten hottest years occurred between 1990 and
the present. In 2007, the combined findings of nineteen
different climate research programs and the Intergovern-
mental Panel on Climate Change (IPCC) were clear: It is
almost certain that Earth’s surface will warm by 3.6–8.1°F
by the year 2100. Irreversible global climate change is
under way, and it is happening much faster than expected.
What will climate change mean for us?
Continued temperature increases will have drastic effects
on the climate of every region on Earth. Here we can men-
tion only a few examples of the projected impacts.
To begin with, climate change may benefit agriculture in
regions where winters become milder. In the Arctic, where
sea ice once made the ocean impassable for much of the
year, warming will ensure open channels and opportuni-
ties for fisheries. Several nations already are planning to
expand commercial fishing operations there.
Elsewhere the impacts may be much less desirable. As
evaporation increases, so will overall precipitation. Intense
rains and flooding are expected to become more frequent
in some regions, while other regions likely will experience
more frequent and intense droughts. Current research
suggests that severe, extended droughts may wipe out
Figure 25.11 Glaciers are in retreat in high mountains
all over the world. On Alaska’s Kenai Peninsula, a sign
marks the 1908 location of the terminus of Exit Glacier.
The retreating glacier’s current terminus is barely visible
in the background.Change in temperature (C̊)Year4.04.55.03.53.02.52.01.51.00.50
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