Geography Reference
In-Depth Information
warmer world will lead to more clouds, cooling the planet.
Increased precipitation and the amount of fresh water release by
melting ice could increase the volume of fresh water entering sen-
sitive parts of the oceans thereby slowing the thermohaline circula-
tion in the ocean and allowing northern high latitudes to cool.
There are also additional negative feedbacks caused by human
action on land. For example, deforestation may result in acceler-
ated erosion of soils which could increase the dustiness of the
atmosphere reflecting more of the Sun's energy back into space.
Furthermore, if warmth-loving broadleaved forests replace conifer-
ous ones, or if forests are replaced by agriculture, then the albedo
will increase causing cooling.
Positive feedback processes are also currently being studied. For
example, albedo will decrease due to the retreat of snow and ice
cover. Warming may cause release of carbon dioxide from
enhanced decomposition of vegetation, especially in forest regions
and the tundra (but faster growth rates in these areas may also take
up more carbon dioxide). Increased cover of woody vegetation in
the high latitudes, caused by an increase in suitable growing land
for plants due to warming, will decrease albedo. Warming may
increase the decomposition rate of
gas hydrates
leading to a
release of the potent greenhouse gas methane; this will increase
warming. Gas hydrates are solid crystal structures in which the
molecules of gas are combined with molecules of water. There is
twice as much carbon stored in gas hydrates on Earth than on all
other fossil fuels put together. The hydrate of methane is stable at
low temperatures or high pressures (e.g. in frozen ground or the
bottom of the oceans). However, global warming may melt some
of the ground that is currently frozen in high latitudes potentially
releasing the methane from the hydrates into the atmosphere. Some
peatlands may warm increasing the rate of decomposition of the
plant matter that forms them, resulting in more carbon being
released than they store each year.
IMPACTS OF CLIMATE CHANGE
The above feedbacks could in themselves be seen as impacts of
climate change. Most models predict a 2° to 4°C increase in global
temperature over the next century and a 50 per cent chance that
