[toomuchtodo]

Because its a fuzzy target. Much better to target a reduction of carbon emissions to zero. That can be measured.

[joggery]

Here's one existing measure of temperature:

http://climate.nasa.gov/vital-signs/global-temperature/

Two decimal places looks pretty sharp to me!

[joantune]

Yes they are, because throughout most of history, variations were very low, as you can see there, because, you know: It's a graph!

If you notice, the graph is not distorted, it's linear. 1 Celsius degree changes our climate in a mix of predictable and unpredictable ways that you don't want for our planet.

Plus: there's the added problem that the changes can be exponential after a while, melted Ice melts other ice more easily, permafrost defreezing releases methane that is worse than CO2 to the atmosphere, Ice changing color, etc.