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We Know: Underlying Processes |
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| Living things don’t just respond to the
climate—they affect it as well. Plants consume carbon dioxide
and produce oxygen through photosynthesis. Earthbound plants
take carbon dioxide directly from the air; drifting photosynthetic
microorganisms called phytoplankton use carbon dioxide dissolved
in water. |
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The biosphere is also the source of aerosols,
such as spores, pollen, bacteria, and other particles. These
aerosols scatter incoming radiation, affecting the energy budget.
And some marine organisms produce sulfate particles, which act
as condensation centers for cloud formation. As the number of
such condensation centers increases, more, and consequently
smaller, cloud droplets are formed. A cloud made of many small
droplets is highly reflective and prevents solar radiation from
reaching the earth. Any anthropogenic (human) production of
sulphur could produce a similar effect, moderating a warming
trend.
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| Evidences
and Uncertainties |
Many species live in very sensitive ecological
niches, so even small changes in temperature or precipitation
could drastically alter their ability to survive. Oak trees
in the midwestern U.S., for example, may not tolerate an average
temperature only a few degrees higher than current temperatures.
And even increases in ocean temperatures of as little as 1°C
over two or three days can cause coral—organisms particularly
sensitive to long-term variations in climate—to lose their
symbiotic algae, which are essential for their nutrition. When
the algae die, corals are “bleached” and appear white.
(See “Current Coral Bleaching
Hot Spots” on this site to learn more.)
Because all species are linked in complex webs of predator,
prey, and habitat, impacts on one species always affect others—and
it’s extremely difficult to predict how those effects will
manifest themselves. Changing the life cycles of key species
in food chains may well affect an entire ecosystem. |
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Additionally, the ability
of many species to adapt to changing climate
through migration is much different than it
was in earlier centuries. Habitats and migration
routes are now broken up by housing, industry,
roadways, and other development. Species also
need time to make adaptations, but the rate
of climate change appears to be increasing:
Over the last 16,000 years, the rate of increase
in global temperatures has been about 1°C
for every 4,000 years—and yet, some predictions
now suggest that we may see another 1°
increase over the next one hundred years.
Some species may actually be helped by warmer
temperatures, of course—but this may
not necessarily be good news. Increasing the
populations of some species may have serious
effects on human health. |
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Each of
these pinwheel patterns centers
on a small community of soybean
farmers in eastern Bolivia.
Roads and fields have subdivided
the tropical dry forest.
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For example, even small increases in global
temperatures, especially if they’re accompanied by flooding,
may drive an increase in the mosquito populations in tropical
areas, leading to much greater transmission rates of diseases
like malaria. (See “Risk
of Malaria Transmission” on this site to learn about
another potential health risk.) And again, changing the balance
of species affects the way entire ecosystems function, with
unknown consequences.
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glossary
terms
