The chart below (from the IPCC report) shows a comparison of the projected warming under a scenario that assumes technically feasible but dramatic and expensive mitigation actions (the purple forecast) and one of the other scenarios in which mitigation actions are not as strong (the orange forecast). These aren't the only scenarios analysed by the IPCC, but all the scenarios apart from the purple one predict warming of more than 2 degrees by 2100.
On this, the day of publication of the first part of the fifth IPCC report on Climate Change, there was an interesting discussion on BBC2 Daily Politics Show. In it, Matt Ridley appeared to say that some global warming was not necessarily a bad thing. To try to understand this apparent contradiction to the gist of climate science opinion, I dug a bit deeper, and found articles on the internet referring to a 2012 economics paper by Richard Tol -"Targets for Global Climate Policy: An Overview". A key chart from this is shown above - figure 8 in the paper. This appears to be one of the sources of evidence fuelling this debate - around the matter of what level of resource should be put into preventing further climate change. The chart appears to suggest that global warming up to about 2 degrees has net positive economic effects, but beyond that point there are net negative effects. In layman's terms, this particular paper says that up to 2 degrees of warming is good, more than 2 degrees is bad. While this might prompt some arguments about whether or not warming of up to 2 degrees is good or bad, these arguments are largely irrelevant, because , as the latest IPCC report shows us, we're already locked into a trajectory of (most probably) above 2 degrees of warming by the end of this century (see further comment below). This is because of the cumulative carbon already pumped into the atmosphere by human activities to date, and it will be followed by further temperature rises until a new equilibrium point is reached. What seems to be quoted less frequently are Tol's other conclusions, for example that Carbon Taxation forms part of Governments' "efficient and cost-effective" responses. He goes on to suggest rates for carbon taxes suggested by his economic calculations. Tol's paper can be downloaded free here. Personally, I'm not sure I'm fussed whether the early part of the line above, of impact on GDP, wibbles or wobbles a percentage point or two. What I'm very concerned about, however, is the impact on GDP 'falling off a cliff' soon after exceeding 2 degrees of warming, if Tol is correct in his analysis. This strongly supports taking action now and investing probably a percentage point or two of global GDP on prevention (ie decarbonisation) between now and, well, until we no longer need to ...
The chart below (from the IPCC report) shows a comparison of the projected warming under a scenario that assumes technically feasible but dramatic and expensive mitigation actions (the purple forecast) and one of the other scenarios in which mitigation actions are not as strong (the orange forecast). These aren't the only scenarios analysed by the IPCC, but all the scenarios apart from the purple one predict warming of more than 2 degrees by 2100.
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About the BloggerI'm David Calver - an Accountant with a passion for sustainability. Categories
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