Heat rising - but how much?
Judging the change in the climate requires accurate data but how do you measure the temperatue of an entire planet? Or of the past? There are a surpising number of ways of taking the temperature.
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In general, if the climate warms, the whole bell shaped curve of temperature for a particular place shifts to warmer temperatures:
Taken from the SYnthesis report on Climate Change, 2001, ipcc.ch
Record hot events are more likely in a warmer world, and record cold events are less likely.
So, for example, we can say that the hot summer of 2003, which killed 22,000 - 35,000 people in central Europe, is twice as likely because of the global warming that has resulted from the man-made emissions of greenhouse gases. By 2050, we can expect summers as hot as that every other year.
Summer 2003 temperatures relative to the average of 2000 - 2004 summer temperatures
Similarly, in the U.K., we can expect the number of extremely rainy days, with associated flooding, to increase. Already, the kind of rainfall that you could have expected once every 30 years in the 19th century is happening once every 12 years now. By the end of the century, it could be expected every 4 years.
![Earl Steet flood [Image: Sylvia Knight]](http://www.open2.net/open2static/source/file/root/0/49/43/203461/earlstreet_flood_inline.jpg "Earl Steet flood [Image: Sylvia Knight]")
There has been a lot of debate recently about whether the number of hurricanes and typhoons has increased because of the effects of global climate change. In general, in a warmer world, you can expect the sea surface temperature - one of the key factors in hurricane development - to be warmer.
There is already evidence to link an increase in the power of hurricanes that have happened in the recent past to increased global temperatures - a recent study has suggested that the power of hurricanes has almost doubled over the last 30 years. Hurricanes will probably become more destructive in the future.
So, to summarise:
- Even with perfect forecasting techniques, we could never say exactly what the climate will do over the next century. This is because:
- weather is chaotic
- we don't know how the world will develop and how much greenhouse gas will be emitted
- We don't know what other, natural, factors may affect the climate in the future - volcanic eruptions, changes in solar activity etc.
- We can, at best, say what the climate is most likely to do, and what it probably won't do.
- The longer into the future a forecast is made, the less certain you can be about what will happen.
- We can expect extreme events - such as abnormally hot seasons and storms, to become more frequent in a warmer world.
All the above animations were developed by climateprediction.net and The University of Oxford Department for Continuing Education (Technology Assisted Life-long Learning Unit) as part of their climate prediction resources, and are used with permission.
The BBC and the Open University are not responsible for the content of external websites
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Content last updated: 13/12/2005
About our expert
Sylvia Knight - a climate scientist - works with the climateprediction.net project, which is trying to produce the most complete forecast of 21st century climate ever attempted. She is responsible for communicating the aims and results of the experiments to as wide an audience as possible.
Sylvia has a degree in Natural Sciences and a PhD in Meteorology, and is co-author of the Open University short course Weather and Climate Modelling.
