Why limit warming to less than 2 °C?
A sustained 2 °C warming would already be well outside the range of temperature fluctuations experienced since the last ice age, and many vulnerable ecosystems and societies are expected to suffer under this level of climate change.
Many are calling for global warming to be limited to 1.5 °C if possible. But there is a large body of evidence that the risk of dangerous climate change rises if we fail to limit warming to 2 °C above pre-industrial temperatures, and many of the world’s governments have now adopted this limit as their goal.
The need to limit cumulative emissions of carbon dioxide applies even more forcibly if we are to limit warming to a lower temperature.