430 GREENHOUSE GASES EFFECTS
FIGURE 3 Model simulation of the mean near-surface temperatures over land for June, July and August
compared with observation.SUMMER SURFACE AIR TEMPERATURE (DEG C)
SIMULATEDOBSERVED4032241680–8–16–854032241680–8–16–85The main errors in model simulations of the present
climate are discussed in IPCC (1992, 1996) and by Mason
(2004). Simulations with the best models are close to reality
despite the rather low model spatial resolution as illustrated
by Figures 2 and 3.Model Simulations of Ocean ClimateThe role of the oceans in influencing climate and climate
change is discussed in some detail in Mason (1993). Only
the salient facts will be summarised here.
The oceans influence climate change on seasonal, decadal
and longer time scales in several important ways. The large-
scale transports of heat and fresh water by ocean currents are
important climate parameters and affect the overall magnitude,timing and the regional pattern of response of the climate
system to external forcing. The circulation and thermal struc-
ture of the upper ocean control the penetration of heat into
the deeper ocean and hence the time delay which the ocean
imposes on the atmospheric response to increases of CO 2 and
other greenhouse gases. The vertical and horizontal motions
also control the uptake of CO 2 through the sea surface and
thus influence the radiative forcing of the atmosphere.
If ocean models are to play an effective role in the predic-
tion of climate change, they must simulate realistically the
present circulation and water mass distribution and tempera-
ture fields and their seasonal variability. Ocean modelling
and validation are less advanced than atmospheric model-
ling, reflecting the greater difficulty of observing the interior
of the ocean and of inadequate computer power. They sufferC007_002_r03.indd 430C007_002_r03.indd 430 11/18/2005 10:27:58 AM11/18/2005 10:27:58 AM