323
Observed
Scenario
1.5
1.5
1.0
1.0
0.5
0.5
0.0
0.0
1940
1960
19S0
2000
2020
Figure 17: Predicted and observed annual global surface temperature changes. The observed values are the same as in Fig. 3.
5.5
Temperature changes
The surface temperature increase for the decade 2010-2020 compared to
the reference period 1860-1890 is 1.56°C with an average increase over
land by 2.35°C and over sea by 1. 24°C. As can be seen from Fig. 17, the
simulated temperature up to present time agrees well with observations,
suggesting that the typical variations in temperatures up to around 1980
are dominated by natural temperature fluctuations, while thereafter the
effect of the greenhouse warming is becoming more distinct. Of particular
interest is the rapid warming between the 1980ies and the second decade
of the next century, amounting to a global average increase of 1°C!
Fig. 18 shows the temperature increase over this period in a zonally
averaged vertical cross section. A maximum warming of around 2°C occurs in the upper tropical troposphere. This maximum warming occurs at
the upper part of the deep tropical convective regions and is caused by the
reduced slope of the moist adiabats caused by the higher surface temperatures. Another area of maximum warming occurs over the high latitudes of
the Northern Hemisphere. This warming is presumably related to a general
reduction in the Arctic sea-ice cover. In this period the Arctic sea ice cover
is calculated to decrease by 0.9 X 106 km 2 or by some 10% compared to the
Observed
Scenario
1.5
1.5
1.0
1.0
0.5
0.5
0.0
0.0
1940
1960
19S0
2000
2020
Figure 17: Predicted and observed annual global surface temperature changes. The observed values are the same as in Fig. 3.
5.5
Temperature changes
The surface temperature increase for the decade 2010-2020 compared to
the reference period 1860-1890 is 1.56°C with an average increase over
land by 2.35°C and over sea by 1. 24°C. As can be seen from Fig. 17, the
simulated temperature up to present time agrees well with observations,
suggesting that the typical variations in temperatures up to around 1980
are dominated by natural temperature fluctuations, while thereafter the
effect of the greenhouse warming is becoming more distinct. Of particular
interest is the rapid warming between the 1980ies and the second decade
of the next century, amounting to a global average increase of 1°C!
Fig. 18 shows the temperature increase over this period in a zonally
averaged vertical cross section. A maximum warming of around 2°C occurs in the upper tropical troposphere. This maximum warming occurs at
the upper part of the deep tropical convective regions and is caused by the
reduced slope of the moist adiabats caused by the higher surface temperatures. Another area of maximum warming occurs over the high latitudes of
the Northern Hemisphere. This warming is presumably related to a general
reduction in the Arctic sea-ice cover. In this period the Arctic sea ice cover
is calculated to decrease by 0.9 X 106 km 2 or by some 10% compared to the