Global warming: Already past the tipping point to runaway warming?

Humanity has for so long delayed cutting fossil fuel use and researching alternative fuels that we must immediately and drastically slash fossil fuel consumption AND figure out how to entirely eliminate fossil fuel consumption within decades:

[Research by Germany’s Potsdam Institute for Climate Change Impact Research] suggests the G8 target of halving global emissions by 2050 (from 1990 levels) would leave a significant risk of breaching the 2C figure.

“Only a fast switch away from fossil fuels will give us a reasonable chance to avoid considerable warming,” said Dr Mainshausen.

“If we continue burning fossil fuels as we do, we will have exhausted the carbon budget in merely 20 years, and global warming will go well beyond 2C.”

Oxford University physicist Myles Allen says we must cut carbon emissions rapidly and figure out how to eliminate emissions entirely within a few decades. Otherwise, we’ll roast this planet:

“It took us 250 years to burn the first half trillion [tons of carbon], and on current projections we’ll burn the next half trillion in less than 40 years… To avoid dangerous climate change, we will have to limit the total amount of carbon we inject into the atmosphere, not just the emission rate in any given year… Climate policy needs an exit strategy; as well as reducing carbon emissions now, we need a plan for phasing out net emissions entirely.”

So far, global temperature has risen 0.7 degrees Celsius. Over 100 countries have pledged to do whatever necessary to keep temperatures from rising more than 2 degrees Celsius, but scientists now estimate accomplishing this will require keeping total CO2 emissions below 1 trillion tons. A 1 trillion ton limit requires humanity leave ¾ths of its known coal in the ground.

Even if we find the restraint not to burn our massive cheap coal reserves, 1 trillion tons of C02 could produce incredible warming. Reasonable estimates of the heating impact of 1 trillion tons range from 1.3C degrees to 3.9C degrees.

I fully expect the world’s efforts will prove too little, too late. We’ll likely see 4C degrees of warming within our lifetimes.

Horrifyingly, that probably means we’ll see even worse during our lifetimes because the analysis above doesn’t factored in feedback effects that could dramatically amplify the impact of humanity’s CO2 releases:

One big unknown is the stage at which dangerous tipping points would be reached that lead to further warming – for example the release of methane hydrate deposits in the Arctic. “My own feeling is that if we get to a 4 degree rise it is quite possible that we would begin to see a runaway increase,” said [the British government’s former chief scientific adviser, Sir David] King.

Given humanity’s unwillingness to slash its energy consumption before the crisis is completely obvious to all, I suspect it’s already too late to save Earth from ecological and biological catastrophe.

Our deepest shame is that we’ve denied reality for the 45 years we’ve known about this threat. We failed to use those 45 years to develop new energy sources and dramatically upgrade society’s energy efficiency (e.g., replacing cars and sprawl with vibrant cities and convenient public transportation).

We’ve now boxed ourselves into a corner. Since Americans couldn’t make even modest sacrifices one or two or three decades ago, why should anyone expect humanity to make far, far more draconian sacrifices now? The Chinese certainly feel entitled to pull themselves out of poverty by burning coal just as Americans did. A grand global bargain is possible, but I’m not optimistic. I’m praying for a breakthrough in solar or cold fusion or helium-3 harvesting.

Posted by James on Thursday, April 30, 2009