Natural factors alone cannot explain the recent
warming of the EarthÕs surface
Black: Observed
surface temperature changes
Attribution of
climate change to causes involves READ
Climate models
are important tools for attributing and understanding climate change.
Understanding observed changes is based on our best understanding of climate
physics, as contained in simple to complex climate models. For the 4rth
assessment report, we had a new and very comprehensive archive of 20th
century simulations available. This has greatly helped.
This figure
gives an example.
You see observed
global and annual mean temperature in black over the 20th century
compared to that simulated by a wide range of these models. On the top, in
red, are individual model simulations and their overall mean shown fat, that
are driven by external influences including increases in greenhouse gases, in
aerosols, in changes in solar radiation and by volcanic eruptions. The
observations rarely leave the range of model simulations. The trends and
individual events like cooling in response to volcanic eruptions (POINT) are
well reproduced. The fuzzy range gives an idea of uncertainty with
variability in the climate system.
