Actual and projected energy demand
Feedbacks
Thousand million tonnes
One factor which complicates climate science – and there-
of oil equivalent fore leads to wide ranges of uncertainty – is the existence of
feedbacks. These are interactions between different parts
Projections
15
of the climate system, which can mean a process or event
sets off changes which in their turn influence the initial trig-
ger. One example is the reduction of ice and snow, both
Oil
12 on land and at sea. Ice, being white, reflects up to 90 per
cent of the Sun’s radiation reaching its surface back out into
space, preventing it from intensifying atmospheric warming.
9
Coal
But when it melts it may expose earth, vegetation, rock or
water, all of which are darker in colour and therefore more
likely to absorb radiation instead of reflecting it. So the ini-
6
tial melting can cause a feedback which helps to quicken
Gas
its pace. Another possible feedback is the thawing of the
3
Nuclear permafrost in high northern latitudes. As it melts, it could
Biomass Hydropower
release big quantities of carbon dioxide and methane which
Other
at the moment are retained below the frozen soil layer. If that
0
renewables
happened, it would accelerate the warming already under
1980 1990 2000 2010 2020 2030
way. Another expected feedback: Higher temperatures of
both land and ocean have the tendency to reduce their up-
Note: All statistics refer to energy in its original form (such as coal) before
being transformed into more convenient energy (such as electrical energy).
take of atmospheric carbon dioxide, increasing the amount
of CO
2
that remains in the atmosphere. These are all posi-
Source: International Energy Agency (IEA), World Energy Outlook 2008.
tive feedbacks because they intensify the original process.
Negative feedbacks, on the other hand, are changes in the
environment that lead to a compensating process and miti-
gate the change itself.
22 Planet in Peril
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