3. UKCIP98 Scenarios
There are four UKCIP98 scenarios, representing a range of uncertainty in amount and rate of future greenhouse gas emissions and in the sensitivity of the climate system to perturbation. Table 1 shows the global mean values for temperature, sea level rise and CO2 for 2050 for each scenario; the UK increases are expected to be similar. The dates given for the scenarios represent 30-year periods, e.g. "2050s" covers the period 2040 to 2069.
At the UK level generally the warming is greater in winter than in summer (except for the Medium-Low scenario in 2080) (Hulme and Jenkins, 1998). The rate of warming ranges from 0.1°C/decade for the Low scenario to 0.3°C/decade for the High scenario (Figure 1). Annual (Figure 2) and winter precipitation increases for all periods and scenarios but they are very modest for the Low and Medium-Low scenarios. Winter precipitation increases by 20% for the 2080 High scenario, which is larger than would be expected from natural variability (Hulme and Jenkins, 1998).
Summer precipitation is lowest in the south of the UK. However the decline only exceeds the range of natural variability in summer in the Southeast for 2080 in Medium-High and High scenarios (Hulme and Jenkins, 1998). Autumn precipitation changes are similar to those in winter and spring changes are very small.
Figure 1:Change in average annual temperature (°C with respect to the 1961-90 average) for the four UKCIP98 scenarios (Hulme and Jenkins, 1998).
Figure 2: Change in average annual precipitation (percent with respect to the 1961-90 average) for the four UKCIP98 scenarios (Hulme and Henkins, 1998). 3.1. Current trends
The period 1985 - 1994 showed a global and UK increase in average temperature of 0.2°C, compared to the average for the 1961 - 1990 period. Over this time there has been approximately a 5 % rise in atmospheric CO2 (DOE, 1996). There can, however, be significant differences in these temperature changes at a regional level. Central England has shown a slight rise in temperature since the 1940s (Jones and Hulme, 1997), with the Central England temperature record showing 0.5°C warming in the 20th century and similar increases recorded at Manchester airport records (Shackley et al., 1998). Although Scottish sites showed a slight cooling from the 1940s, since the mid-1980s warmer temperatures have been recorded (Hill et al., 1999). There has been a general decrease in the number of snowy winters in the UK since the mid-1980s (except 1995/1996), which has been associated with the increase in westerly airflow (Mayes, 1998). The work of Palutikof et al. (1997) suggests that wind speeds have increased in both frequency and severity in recent years.
Published 13 February 2001
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