Why we need to keep fossil fuels in the ground

From The Guardian - 

"We need to reduce emissions to keep our planet safe for future generations - the science is clear. However, it can be quite hard to get your head around how to do that. Here's a very simple idea from writer and climate campaigner, Bill McKibben: keep fossil fuels in the ground. If we were to burn all the fossil fuel reserves we currently know about, experts forecast the Earth's temperature would warm by more than 2C and have catastrophic effects. Guardian journalists explain the 'keep it in the ground' theory in easy to understand terms."