Three Numbers

Bill McKibben explains a concise way to understand the climate crisis using three numbers:

2 degrees Celsius is the maximum amount of warming that most countries have agreed is necessary to prevent catastrophic change.  Since 0.8 degrees of warming have already happened and another 0.8 degrees are on the way with current carbon dioxide emissions, there's not much room to work with.  And there are climate scientists who think a 2 degree limit won't save us.

565 gigatons is the estimate for the amount of carbon dioxide that can be released by 2050 and stay within the 2 degree limit.  Unfortunately, emissions have been increasing by about three percent per year and we would use up our carbon "budget" in about sixteen years.

2795 gigatons is the estimate for the amount of carbon dioxide that would be released from burning all the existing fossil fuel reserves.  This is far beyond the carbon budget even as the search is made for more fossil fuel supplies.

McKibben tries to remain optimistic and suggests that a moral case can be made against the energy corporations.  They are the enemy needed to energize the environmental movement.  But those fossil fuel reserves are worth $27 trillion.  And it's this fourth number that explains all you need to know about our fate.

Update (July 30):  Nicholas Arguimbau has a response to McKibben.

Update (December 27):  Rebecca Solnit declares 2013 to be Year Zero in the battle against climate change.

Update (October 28, 2013):  A study from the University of Oxford estimates that the carbon budget would be exceeded in about 27 years.

Update (December 23, 2013):  Sean McElwee and Lew Daly explain the carbon bubble.  If world governments do adhere to a carbon budget, carbon assets face a $20 trillion devaluation.

Update (December 24, 2013):  Annie Leonard explains the problems with "cap and trade".

Update (December 6, 2014):  A reminder that the world has already used 65 percent of our carbon budget.

Update (September 16, 2015):  Burning through all the world's fossil fuels would melt of the ice on Earth and bring a sea level rise of 200 feet. But disaster would occur well before that happens.