- Predicting Global Climate Change
- some likely changes may occur naturally, so difficult to tell whether an event is caued by human activities or not. The change may be the frequency with which events such as floods, storms or droughts occur and this is only detecable after many years when trend is clear. Individual/several storms do not indicate trend
- difficult to identify trends because of limited historical dataon e.g. rainfall patterns, sea ice or wind velocity. Some historical data can't be trusted. Historical data may come from indirect sources e.g. pollen anaylsis/tree growth rings
- many natural processes are interconnected, so one change may have unexpected effects
- some changes e.g. sea level rise very slow. So cause of change may have been happpening for long time before any change is noticed
- Different changes occur in different locations/time. If one area gets less rainthan another gets more. If Britain warms up may be less rain in summer as water vapour does not condense, but in winter cold enough for condensation + higher evaporation rates over ocean = more rainfall.