Jonathan Gregory - The physical basis of climate change
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Europe/London
Description
Owing to fossil-fuel use, land-use change and agriculture, global atmospheric
concentrations of carbon dioxide, methane and nitrous oxide have increased
markedly since 1750 and now far exceed pre-industrial values determined from
ice cores spanning many thousands of years. Warming of the climate system is
unequivocally evident from observations of increases in global average air and
ocean temperatures, widespread melting of snow and ice, and rising global
average sea level. Paleoclimate information supports the interpretation that
the warmth of the last half century is unusual compared with at least the
previous 1300 years.
Most of the observed increase in globally averaged temperatures since the
mid-20th century is very likely due to the observed increase in anthropogenic
greenhouse gas concentrations. There are discernible human influences on other
aspects of climate, including ocean warming, continental-average temperatures,
temperature extremes and wind patterns. For the next two decades a warming of
about 0.2°C per decade is projected for a range of emission scenarios.
Continued greenhouse gas emissions at or above current rates would cause
further warming and induce many changes in the global climate system during
the 21st century that would very likely be larger than those observed during
the 20th century. Anthropogenic warming and sea level rise would continue for
centuries due to the timescales associated with climate processes and
feedbacks, even if greenhouse gas concentrations were to be stabilized.