2ºC – Outside a Safe Climate

Posted on December 11, 2011

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We are on the edge now of climactic conditions the world has not seen in a long long time.  Some people say, “Well, the world has been there before and survived it.”  That’s true.  It has survived climate events associated with the deaths of 94% of ocean life.  But you’d hardly want to be there while it’s going on, or send your children out to play in it.

In Durban, we have just seen the world’s leaders arrive at a deal which—in its present form—is guaranteed not to succeed against climate change.

Scientists and experts on climate change have for a while now been using a 2ºC-of-warming figure.  That’s the amount of warming we must keep it to, they said, to avoid the worst climate disasters.

We’re already at 0.9ºC of warming.  The deal in Durban will probably put us at 3ºC.  Hello, disasters.

And the painful reality is that 2ºC was a lousy estimate in the first place.  It never represented a safe limit.  It was reasonable when first presented because we didn’t know then about sensitivities in the environment that are all too obvious to scientists now.

A more reasonable figure, according to accumulating evidence, is 1.5ºC.  That’s the outer limit of where we want to go if we want to avoid, in the short term at least, some of the more dangerous multiplier effects in the climate system.

And even a 1.5ºC rise can only be temporary.  A similar increase in temperature during the Eemian interglacial period was associated with sea-levels 4 to 6 metres higher than what we have today.  To put that in perspective, a sea level rise of less than two metres would displace 100s of millions of people and radically endanger every seacoast city on Earth.  And we’ve already placed enough CO² in the atmosphere to buy ourselves three times that kind of trouble.  The oceans would be lapping on our doorsteps already but for the fact that the world is a big place and the system takes a while to warm up.

The bottom line is, never mind present and future emissions, we already have unacceptable levels of carbon in the atmosphere.  We not only have to slow down emissions (which is as far as Durban got to discussing), we not only have to stop producing them altogether (which we don’t yet know how to do), we’re also going to have to figure out a way to take them out of the atmosphere altogether.

Otherwise, merely with what we’ve put there already, never mind what we are furiously adding to it everyday and every decade, our climate system will tip over to a new and more ferocious climate without any further assistance from us.

4 degrees.  7 degrees.  11 degrees.  25 metre sea level rise.  Parts of the planet rendered uninhabitable for life.  Super storms.  Mass extinctions in an ocean turned acid.

And while the world will survive it and humanity will survive it, life as we have come to know it will disappear.  And I suspect we won’t like the life we get in its place.

It’s so much wiser to fight it while we still can.  Now.