An introduction to climate change Human activities are releasing
greenhouse gases into the atmosphere. Carbon dioxide is produced
when fossil fuels are used to generate energy and when forests
are cut down and burned. Methane and nitrous oxide are emitted
from agricultural activities, changes in land use, and other
sources. Artificial chemicals called halocarbons (CFCs, HFCs,
PFCs) and other long-lived gases such as sulphur hexafluoride
(SF6) are released by industrial processes. Ozone in the lower
atmosphere is generated indirectly by ,amongst other things,
automobile exhaust fumes and other Rising levels of greenhouse
gases are already changing the climate. By absorbing infrared
radiation, these gases control the way natural energy flows
through the climate system. In response to humanity's emissions,
the climate has started to adjust to a "thicker blanket" of
greenhouse gases in order to maintain the balance between energy
arriving from the sun and energy escaping back into space.
Observations show that gl