Warmer global temperatures increase the Earth’s natural emissions of Methane and Water Vapour, two the most menacing Greenhouse Gasses.  This is called a climatic ‘Feedback Loop’. There are both Positive and Negative feedback loops. Positive feedback amplifies the situation that caused it while Negative feedback mitigates the situation. The problem being that the Positive feedback mechanisms that cause Climate Change outnumber and overshadow the Negative ones.  

Here’s some examples:

• The polar ice reflects much of the sun’s light that hits it.  With out the ice, the Earth absorbs more of the Sun’s rays, raising the temperature which causes the ice to melt even faster.  This is called the Albedo Effect.
• As the Earth’s temperature increases, the permafrost which occupies about 20% of the Earth’s surface melts.  This melting releases trapped Methane which then causes the Earth’s temperature to rise even more.
• Water vapour is a significant greenhouse gas.  As the temperature increases, evaporation increases and therefore more water vapour exists in the atmosphere. 

The image below shows how some feedback processes can have both Positive and Negative feedback effects.

Click here to see the article that this image came from.
 
Here’s a link to a web page that has a summary of Climate Feedback and if you Google “Climatic Feedback” you will come up with lots of interesting information.