327
centrations were used, thereafter a continued increase based upon the most
likely emission scenario. The overall findings are in broad agreement with
observed global surface temperature suggesting that the calculated warming until present is fully consistent with the observed warming of about
0.6°0 since the middle of the last century. Major regional variations occur
at high latitudes including cooling trends lasting several decades. Experiments with atmospheric models only indicate that atmospheric processes
may play an important role in generating the low frequency variability
which is typical for high latitude climate patterns on decadal time scales. A
preliminary analysis of radiative forcing patterns suggest a strong enhancement of the greenhouse warming from atmospheric water vapour, while the
cloud forcing indicate a negative feedback through an increased short wave
cloud forcing. The hydrological cycle is becoming more active in particular
over land, where both precipitation and evapotranspiration are increasing.
Evaporation is also increasing over ocean areas while precipitation is more
or less unchanged. A possible explanation is an enhanced monsoonal forcing due to the more rapid increase of surface energy fluxes over land. The
experiment indicate that a more rapid warming has commenced in recent
years. Although the global warming has increased during the last years in
consistency with these results, it cannot be taken as a proof, since recent
warming could also be due to natural fluctuations. However, systematic
global monitoring over the next decades is of particular importance in that
respect. Upper tropical tropospheric temperature, integrated amount of
atmospheric water vapour, Arctic ice cover and ice volumes, ocean temperatures are examples of parameters where a climate warming is likely
to be indicated. In this study we have calculated the climate change over
the period 1860-2020. An alternative approach is to compare the climate
change experiment with a control experiment using unchanged greenhouse
gas concentrations. By doing so we may also incorporate any possible effect due to long term climate drift of the coupled model not eliminated by
the flux adjustment. Such a minor drift appears to occur in the control
experiment, indicating a cooling of around O.l°C/lOOyears. The cooling
is mainly concentrated to the Southern Hemisphere and suggest that the
spin-up time of the coupled model probably was too short. If the trend is
the same in the climate change experiment the global warming at 2020 is
underestimated by some 0.15°0. It is furthermore suggested that the hydrological cycle over oceans is slightly enhanced (by about 2 units for both
precipitation and evaporation). No changes occur over land. The climate
centrations were used, thereafter a continued increase based upon the most
likely emission scenario. The overall findings are in broad agreement with
observed global surface temperature suggesting that the calculated warming until present is fully consistent with the observed warming of about
0.6°0 since the middle of the last century. Major regional variations occur
at high latitudes including cooling trends lasting several decades. Experiments with atmospheric models only indicate that atmospheric processes
may play an important role in generating the low frequency variability
which is typical for high latitude climate patterns on decadal time scales. A
preliminary analysis of radiative forcing patterns suggest a strong enhancement of the greenhouse warming from atmospheric water vapour, while the
cloud forcing indicate a negative feedback through an increased short wave
cloud forcing. The hydrological cycle is becoming more active in particular
over land, where both precipitation and evapotranspiration are increasing.
Evaporation is also increasing over ocean areas while precipitation is more
or less unchanged. A possible explanation is an enhanced monsoonal forcing due to the more rapid increase of surface energy fluxes over land. The
experiment indicate that a more rapid warming has commenced in recent
years. Although the global warming has increased during the last years in
consistency with these results, it cannot be taken as a proof, since recent
warming could also be due to natural fluctuations. However, systematic
global monitoring over the next decades is of particular importance in that
respect. Upper tropical tropospheric temperature, integrated amount of
atmospheric water vapour, Arctic ice cover and ice volumes, ocean temperatures are examples of parameters where a climate warming is likely
to be indicated. In this study we have calculated the climate change over
the period 1860-2020. An alternative approach is to compare the climate
change experiment with a control experiment using unchanged greenhouse
gas concentrations. By doing so we may also incorporate any possible effect due to long term climate drift of the coupled model not eliminated by
the flux adjustment. Such a minor drift appears to occur in the control
experiment, indicating a cooling of around O.l°C/lOOyears. The cooling
is mainly concentrated to the Southern Hemisphere and suggest that the
spin-up time of the coupled model probably was too short. If the trend is
the same in the climate change experiment the global warming at 2020 is
underestimated by some 0.15°0. It is furthermore suggested that the hydrological cycle over oceans is slightly enhanced (by about 2 units for both
precipitation and evaporation). No changes occur over land. The climate