Remaining Carbon Budget

It's not much....

Last year the IPCC stated that all anthropogenic emissions to date add up to 2200 GTon, that we have 600 GTon remaining before hitting a 50% chance of exceeding 1.5 degrees of warming, and that were adding 50 GTon each year.

The flask in the picture shows what's going on graphically. It's already nearly full with  historical emissions and each year it gets more full. Around 2030 it will overflow.

Why 1.5 degrees? 


They agree that at around 2 degrees the various feedback loops will mean warming is no longer under human control. We're at around 1 degree already. It would seem that 1.5 was deemed the "safe" limit because it was halfway between the two. 

Unfortunately there's at least a couple of reasons to think that the picture painted is overly rosy:

Firstly, the "budget" they specify comes with a number of caveats: there are a number of uncertainties in the calculation and they quantify them. These can be thought of as error bars on the input data, and the IPCC have opted in almost every case to use figures from the optimistic end of these bars. Taking the pessimistic end leads to the conclusion we have already busted the limit.

Secondly, the 2 degree threshold itself may be optimistic. It is pretty clear now that we've already locked in an essentially ice free Arctic within a few summers. The warming caused by the change of albedo (from reflective ice to non reflective water) is equivalent to 25 years worth of emissions. That could take us to the next tipping point, which could take us to the one after, and so on.

What can be done?


The IPCC tell us we need to avoid exceeding this budget, which obviously involves emissions reductions. Unfortunately emissions are still going up. The blobs of larva being thrown in to the flask in the picture are getting larger each year! With unbridled optimism they suggest we turn this around now and drop steeply to zero in thirty years or less. But even they cannot forsee this being enough without massive geo engineering projects which rely on untested and expensive technologies.

What does this all mean?


At the moment there does not exist anywhere in the world a government capable of leaving newly discovered oil or gas in the ground. We're therefore looking at the end of civilisation as we know it within decades. Our grandchildren if we're lucky enough to have any will live in a world supporting far fewer humans. How we get there is the big unknown. At present it looks like business as usual (in the wealthy part of the world) and then war,  famine, violence. An alternative is that we replace the system -  that is unable to even talk honestly about the greatest issue ever to face the human race - and start preparing. Mitigation and adaptation, started now, cannot make all this go away but it can make it less bad. By how much we do not know.

About me


I did a maths degree at Bristol, and I've been working in embedded software for 23 years. I live in Cambridge with my wife and 17 year old son. I've recently recognised the madness of continuing just "making stuff" - most of which will never be used and none of which is really needed - at a time such as this, and I've chucked in my job. I joined Extinction Rebellion a few weeks ago and I'll be joining in the International Rebellion this October. Do I think we'll fix climate change? No. But I value truth above almost anything else, and I want to spend these last years around other people who do too.

I have a nice place I can go to and that's my belief in the multiverse. Out there there's a reality as real as this in which we got our act together and are on track to sorting it out. And I belong to that reality as much and in the same manner as I belong to any of the tomorrows to which this today leads. This is spiritually reassuring, but as with a belief in determinism, it doesn't offer any guide how to act. So I am splitting my mind in two for now: one half to tell me how to act and the other how to regenerate.

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