Paris climate talks: Why all the fuss over 2 measly degrees?

Goal of COP21 summit is to keep Earth from warming more than 2 C. Why?

Media | 2 Degrees

Caption: As leaders from about 150 countries around the world gather in Paris for the next two weeks, they have already agreed to on one point: global average temperatures must not be allowed to rise more than 2C over the averages of the pre-industrial era.

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As leaders from about 150 countries around the world gather in Paris for the next two weeks, they have already agreed on one point: Global average temperatures must not be allowed to rise more than 2 C over the averages of the pre-industrial era.
The question that remains for world leaders is: how?
The question for most other people is: why?
Two degrees may not seem like much of a change in a country with places that routinely experience temperature swings from 30 C in one season down to –30 C just a few months later — but we are talking about the average for the entire globe.
And that means it's a change that will be felt in the air, on land and in the water.
Watch the video above or here to see how and why two degrees matters.

Effects of temperature change