Will Copenhagen be met? Is an increase in average global temperatures of two degrees by 2100 likely, possible, or just pie-in-the-sky? And what are the implications of this figure and of exceeding it.
Kevin Anderson has a fascinating and startling chapter on these questions.
First things first. There's a lot of uncertainty surrounding climate change. That doesn't just mean we have probability distributions over different scenarios. It also means, in the technical sense, that we may simply not know how technologies and production will evolve, how much greenhouse gas will be produced or what its impact on temperatures will be. And the ecological system, beyond a certain increase in temperatures, may react in ways that we cannot currently predict. Will there be "feedback effects", non-linear changes?
But here's the dope.
2° C over pre-industrial levels is actually unlikely and its likely impact has changed from being "dangerous" but "very dangerous".
Average global temperature increases over the last century have been about 2.7° C each year. Average, mind you. Given that land surface and the sea warm up at different rates that means increases in land temperatures is more (perhaps one degree more). Also, NY and the arctic might be hit by much higher increases than other places because this is only an average figure.
If we were to increase at 2.7 that would mean the business-as-usual scenario would give us around 25 years for carbon to increase to 800 ppm ! At 800 we're talking about maybe a 17% chance (Weitzman) of temperature increases of + 6° C. Which, in anyone's books, is disaster.
Of course, there isn't going to business as usual so you need to look at mitigation (though, having said that, carbon dioxide has grown at more than 3.2 % even after the economic slowdown and global material extraction has, over the period of 1980-2009 nearly doubled (an increase of 94%).
Is there time for serious mitigation and which countries are going to have to take the plunge?
Given that Co-2 can stay in the atmosphere for over a 100 years the later we delay things the more difficult stabilisation is going to become. Anderson clearly explains this: in order to reach 2° C there's only a certain amount of Co-2 that can be emitted by 2050. If we made all the cuts in the last years before 2050 (for argument's sake) that would not be the same as if we cut back gradually up to 2050 since Co-2 would have accumulated and it's the stock of it that counts.
For Stern and others for us to have a reasonable chance of not going over 2° C we have to reach peak Co-2 by 2015. Er..
And there's this widespread assumption built into the models that new technologies in the future will help resolve the problem. And if they aren't there, then what happens to the models?
Kevin Anderson has a fascinating and startling chapter on these questions.
First things first. There's a lot of uncertainty surrounding climate change. That doesn't just mean we have probability distributions over different scenarios. It also means, in the technical sense, that we may simply not know how technologies and production will evolve, how much greenhouse gas will be produced or what its impact on temperatures will be. And the ecological system, beyond a certain increase in temperatures, may react in ways that we cannot currently predict. Will there be "feedback effects", non-linear changes?
But here's the dope.
2° C over pre-industrial levels is actually unlikely and its likely impact has changed from being "dangerous" but "very dangerous".
Average global temperature increases over the last century have been about 2.7° C each year. Average, mind you. Given that land surface and the sea warm up at different rates that means increases in land temperatures is more (perhaps one degree more). Also, NY and the arctic might be hit by much higher increases than other places because this is only an average figure.
If we were to increase at 2.7 that would mean the business-as-usual scenario would give us around 25 years for carbon to increase to 800 ppm ! At 800 we're talking about maybe a 17% chance (Weitzman) of temperature increases of + 6° C. Which, in anyone's books, is disaster.
Of course, there isn't going to business as usual so you need to look at mitigation (though, having said that, carbon dioxide has grown at more than 3.2 % even after the economic slowdown and global material extraction has, over the period of 1980-2009 nearly doubled (an increase of 94%).
Is there time for serious mitigation and which countries are going to have to take the plunge?
Given that Co-2 can stay in the atmosphere for over a 100 years the later we delay things the more difficult stabilisation is going to become. Anderson clearly explains this: in order to reach 2° C there's only a certain amount of Co-2 that can be emitted by 2050. If we made all the cuts in the last years before 2050 (for argument's sake) that would not be the same as if we cut back gradually up to 2050 since Co-2 would have accumulated and it's the stock of it that counts.
For Stern and others for us to have a reasonable chance of not going over 2° C we have to reach peak Co-2 by 2015. Er..
And there's this widespread assumption built into the models that new technologies in the future will help resolve the problem. And if they aren't there, then what happens to the models?
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