Warming will trigger some processes which speed further warming,
and other effects which mitigate it. The balance between these
positive and negative feedbacks is a major cause of uncertainty
in climate predictions. For example, as the diagram shows,
decreasing ice cover will mean exposed land absorbs more heat
and speeds warming further. In contrast, for example, plants'
CO2 intake is likely to increase as higher temperatures increase
growth rates, somewhat countering the warming effect. 1 Light
coloured ice reflects back the Sunís energy efficiently. 2
Exposed land is darker coloured and absorbs more energy. 3 As
the ice melts, more land is exposed. This absorbs more heat,
melting more ice. 4 The altitude of the melting ice is reduced
so it becomes harder for new ice to form.