The Greenhouse Effect and Global Warming - Air Pollution and Global Warming: History, Science, and Solutions - page 297

(a) (b)

Figure 12.29. (a) New Orleans, Louisiana, a city that lies below sea level. C Olivierl/Dreamstime.com. (b) An
island in the San Blas Archipelago, a Caribbean chain of nearly 400 small islands where native Kuna Indians live
semiautonomously from Panama, their host country. C Erikgauger/Dreamstime.com.

too wet. Citrus crops, in particular, require a certain
number of cooling degree days to survive. Many cit-
rus farms are no longer viable in their original location
due to winter temperature increases that have already
occurred.
Because plants grow faster when temperatures, car-
bon dioxide levels, or water vapor levels mildly increase
(plant-carbon dioxide negative feedback), some forms
of agriculture are expected to flourish in areas where
only mild increases in temperature and moisture occur.
In areas where extreme temperature increases occur,
agriculture will die out. Of particular concern are sub-
tropical desert regions of Africa, where temperatures
are already high. In these regions, agriculture is sub-
ject to the whims of the climate, and millions of people
depend on the local food supply. Small increases in
temperature could trigger famine in these areas, as has
occurred in the past.

atmospheric CO 2 (g) continues to increase unabated, the
pH is estimated to decline to about 7.85 by 2100. This
pH decrease represents a factor of 2.5 increase in the
H + concentration between 1751 and 2100.
Ocean acidification damages coral reefs ,which are
made of calcium carbonate secreted by corals. Corals
consist of living polyps, attached at their base to the
coral reef, that cluster in groups and secrete calcium
carbonate to form a solid exoskeleton. The greater the
acidity of water, the more readily calcium carbonate
dissolves by the reverse of Reaction 3.17.
Between 1990 and 2008, the coral growth of the Great
Barrier Reef off Australia declined by about 13 per-
cent, much greater than during any time in the past 400
years (De'ath et al., 2009). Ocean acidification similarly
makes it more difficult for noncoral sea life to form and
maintain shells from calcium carbonate. It also directly
damages fish that are accustomed to a narrow pH
range.
Over land, rapid, continuous increases in tempera-
ture will lead to the extinction of some species that are
accustomed to narrow climate conditions and are unable
to migrate faster than the rate of global warming.
Although enhanced CO 2 (g) levels generally invigo-
rate forests, sharp increases in temperature associated
with higher CO 2 (g) can lead to forest dieback in trop-
ical regions, affecting the rates of CO 2 (g) removal by
photosynthesis and emission by respiration.

12.5.3. Changes in Ocean Acidity
and Ecosystems
The increase in atmospheric CO 2 (g) increases the
amount of dissolved and dissociated carbonic acid in
the ocean by Reactions 3.15 and 3.16. The dissocia-
tion of carbonic acid increases the H + concentration
in the ocean, decreasing the ocean pH, resulting in
ocean acidification .The pH of the ocean today is
above 8 because of the high concentrations of cations
(Na + ,Ca 2 + ,Mg 2 + ,K + )inocean water. Due to CO 2 (g)
buildup in the atmosphere since the Industrial Revo-
lution, the pH of the ocean declined from about 8.25
to 8.14 between 1751 and 2004 (Jacobson, 2005b). If

12.5.4. Changes in Heat Stress
Global warming affects human health by increasing heat
stress. In warm climates, higher temperatures increase