Geography Reference
In-Depth Information
human action; the rate of its production increases in agricultural
areas when nitrogen fertilizer is used. Humans have also emitted
fumes and smoke from industrial processes and transport. These
aerosols
partly shield the planet from the Sun's energy scattering
and reflecting it. However, not all aerosols behave in the same
way. Aerosols from vegetation burning, 'black carbon', and the
'brown clouds' that come from urban sources may have the oppos-
ite effect. The former seem to cause cooling while the latter result
in warming.
Almost every time there is a flood or storm, the media seem to
blame it on global warming. At the same time, the media love to
create polarised storylines and so if there are some people, includ-
ing scientists, who do not accept that climate change is being
driven by human action the media will push their views into the
spotlight. However, it needs to be made absolutely clear that the
overwhelming scientific consensus is that the production of green-
house gases by humans is the primary cause of recent global
warming. Masses of evidence have been compiled by the IPCC
which consists of climate experts from around the world who use
all of the available evidence and have come to this conclusion. The
IPCC have also shown that Global Climate Models, which simu-
late the production of greenhouse gases, show the same pattern of
global warming as we have observed. When these models are run
without adding human production of greenhouse gases, the models
show no appreciable global warming (see www.ipcc.ch).
Predicting how the climate will behave in the near future is an
important and growing research area. It is important to understand
the feedbacks within the Earth's system in order to do this. Negat-
ive feedbacks reduce any warming effect while positive feedbacks
cause accelerated warming. It is interesting to note that there are
several possible major negative feedbacks which are being investi-
gated for their role. For example, warming will lead to a more
active hydrological cycle with more evaporation and rainfall. Rain-
fall contains small amounts of carbon dioxide which when it meets
rock can erode it transforming the carbon dioxide into calcium
carbonate which then gets washed into rivers and oceans. Enhanced
rainfall and rock weathering will therefore have the net effect of
slightly depleting the atmosphere of carbon dioxide. Increased
evaporation and
transpiration
(water release from plants) in a
