What will climate change mean for our world?
The Intergovernmental Panel on Climate Change (IPCC) has explored various scenarios for future greenhouse gas emissions with a range of climate models. They show that:
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Carbon dioxide levels are likely to at least double from pre-industrial levels by the end of this century. This, and other factors such as more water vapour in the atmosphere, will probably raise average global temperature between 1·5 and 5·8°C by 2100.
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Warming is likely to be faster that we've experienced during the 20th century, and will probably be unprecedented in the last 10,000 years.
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Global sea level is likely to rise by 10-90cm over this century. Low-lying coasts will flood, affecting many human settlements, including some major cities. Some natural habitats will be lost.
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If temperatures over Greenland increase by more than about 3°C, which appears likely, the ice sheet will eventually disappear altogether. Global sea level would rise by several metres over a period of 1000 years or more.
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Some regions and seasons will become wetter, others drier. Summer droughts are likely to intensify in the interiors of continents. Tropical hurricanes and cyclones will probably become more severe, partly because they increase in ferocity as the temperatures of the sea below them rises.
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Intense cold weather will become less frequent. But if the Atlantic Conveyor Belt slows or stops, Europe could become colder, giving the UK a similar climate to Iceland.
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Many areas will experience more extremely hot weather (like the heat wave in Europe in 2003). But rain, when it comes, is likely to be heavier, bringing more floods.
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Food production in mid-latitudes could benefit if climate change is not too severe. However, in tropical and sub-tropical regions famines may become more frequent or severe.
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Getting enough water will become even more of a problem for people in regions where it is already scarce, particularly the sub-tropics.
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The world's vegetation zones will move. In particular, the boundaries between grasslands, forests and shrublands may shift.
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The levels, flows and temperatures of rivers lakes and streams will change, affecting biodiversity, water supplies and water quality.
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Human and animal diseases, such as malaria, will probably spread to new areas. Deaths from heat stress are predicted to increase.
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Many people may move away from flood- or drought-prone areas. These environmental migrants could increase health problems and even trigger conflicts.
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