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The IPCC report: A summary for everyone

  • 27 Sep 2013, 12:00
  • Ros Donald

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Today an international group of hundreds of  climate scientists has released a report covering how and why the earth's climate is changing, and how it may change in the future. 

Greenhouse gases 

Scientists have known over two hundred years that carbon dioxide is a greenhouse gas, meaning it traps heat in the atmosphere and oceans. 

Over time, scientists have come to understand more about how the gases that are emitted when people burn fossil fuels like oil and gas affect the climate.  

Scientists are more sure than ever - 95 per cent certain - that humans are causing extra warming, today's report concludes. The oceans, land and atmosphere are getting warmer, snow and ice is melting and sea levels are rising. 

For another way of thinking about this, one news report this week explains that scientists are now as sure human activity is warming the climate as they are that smoking causes lung cancer. 

Oceans 

Oceans have a big role to play in the earth's climate. They are the source of clouds and rain, and they have also absorbed a very large percentage of the warming that has occurred since the 1970s, scientists say.  

Scientists are confident that this heat is causing the huge bodies of ice in the coldest parts of the world like the Arctic, Antarctica and Greenland to melt. It's also causing glaciers that have formed over thousands of years in the mountains around the world to lose ice. 

The water in the oceans is warming and expanding, and water from ice sheets and glaciers is topping it up. So sea levels are getting higher.  

 This latest report says that scientists now agree that the sea level rise that is happening in response to warming will be higher by the end of the century than they previously thought.  

Weather

Climate change means we're getting more hot days and less cold days per year, when you look at the world as a whole, the report says. But other changes in weather will be a mixed picture around the world.  

Some places will experience more droughts and heatwaves, while others - probably including the UK - will get more frequent, more intense rainfall.

How much we're going to experience these effects will depend on how much carbon dioxide we continue to release into the atmosphere in the coming years.

The future 

If we want to limit temperature rise - and the effects, like rising sea levels and weather disruption that flow from it - we will have to reduce the amount of greenhouse gases we produce. 

A second IPCC report will have more detail about how the changes the planet is seeing will impact on things like flooding, agriculture, human society and economies. 

A third, to be released early next year will examine what we can do about it.

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