The other day, a friend of mine directed me towards a blog post by Chris Mounsey that does an excellent job of misunderstanding the recent scientific study that found a discernable influence from anthropogenic warming in Antarctica. The study used 100 years of Arctic data, 50 years of Antarctic data, and four computer models to demonstrate that the observations that have been made in those regions are consistent with models in which human emissions are causing mean global warming, and inconsistent with models that include only natural forcings.
As in a great many other cases, the blog author confuses different types of certainty about climatic science. For example, while we definitely know that greenhouse gasses in the atmosphere cause more of the sun’s energy to be absorbed by the Earth, it isn’t clear what effect the inter-relationships between temperature, soil moisture, evaporation, clouds, and reflected sunlight are. The climate system includes a massive number of elements that have complex inter-relations. When it is reported that a scientific study “help[ed] reveal what drives climate change,” the claim being made is that our understanding of that whole complex system has been deepened.
The blog post questions whether warming is happening (it is), whether it might not be a good thing (above a certain level, extremely unlikely), and whether this is just a repeat of the Medieval Warm Period (it isn’t).
In general, it follows the same “toss everything into the pot” strategy found in many pieces of writing that question the scientific consensus on anthropogenic climate change. I have previously written about the inconsistency of simultaneously denying warming, denying that warming is caused by humans, and denying that warming is bad. This blog also connects to another argument made previously on this site. The blog is written by a self-identified libertarian. The need to disprove the fact that all sorts of human economic activities have important consequences on third parties is essential if climate change is not to render that entire political philosophy nonsensical.
Attribution of polar warming to human influence
Gillett et al. Nature Geoscience 1, 750 – 754 (2008)
The polar regions have long been expected to warm strongly as a result of anthropogenic climate change, because of the positive feedbacks associated with melting ice and snow. Several studies have noted a rise in Arctic temperatures over recent decades but have not formally attributed the changes to human influence, owing to sparse observations and large natural variability. Both warming and cooling trends have been observed in Antarctica, which the Intergovernmental Panel on Climate Change Fourth Assessment Report concludes is the only continent where anthropogenic temperature changes have not been detected so far, possibly as a result of insufficient observational coverage. Here we use an up-to-date gridded data set of land surface temperatures and simulations from four coupled climate models to assess the causes of the observed polar temperature changes. We find that the observed changes in Arctic and Antarctic temperatures are not consistent with internal climate variability or natural climate drivers alone, and are directly attributable to human influence. Our results demonstrate that human activities have already caused significant warming in both polar regions, with likely impacts on polar biology, indigenous communities, ice-sheet mass balance and global sea level.
Antarctica is Cold? Yeah, We Knew That
RealClimate.org
12 February 2008
You should consider having a weekly feature in which you debunk a wrongheaded climate-related post or article.
I can see some value in that.
People should feel free to point out possible targets.
That particular post was, I’ll admit, somewhat tongue in cheek (mainly because I have written huge amounts on anthropogenic climate change that isn’t, and I was short of time).
I’ll not bother attempting to disabuse you — I know a True Believer when I see ’em — but I will point out that even the Mediaeval Warm Period is still under debate and quoting one site which has an evident bias in the argument, i.e. Gristmill, to make three points doesn’t really convince.
I mean, what serious scientist would ever take anecdotal evidence about wine grapes in Britain as evidence of a warmer period? Seriously? Your argument on that is what we like to call “a straw man”.
You are correct in saying that climate science is very much more complicated than many assume and that we don’t really understand all of the systems involved, but that undermines your argument rather than reinforcing it.
If, for instance, we are to put our faith in climate modelling, shouldn’t we question why the Pacific current decadal switch wasn’t included?
Let us be very clear about one thing: taking action as outlined by many world governments is not cost-neutral: it will have very severe effects worldwide (and not just that we in the developed world will have to switch our appliances off). As with anything else, doing a cost-benefit analysis is the correct way forward.
Since you are so fond of the IPCC, I assume that you acknowledge this? After all, the IPCC does in its SRES series of economic models. World governments seem to be following the B family and utterly ignoring the A family of models, e.g. A1: why?
DK
the Mediaeval Warm Period is still under debate
I don’t deny that there are still significant debates about paleoclimatology: on what conditions prevailed in the past and why.
That being said, the Mediaeval Warm Period doesn’t prove that (a) climate change occurring now is natural, rather than anthropogenic or (b) that warming would be benign.
shouldn’t we question why the Pacific current decadal switch wasn’t included?
I think climatic scientists are quite aware of the Pacific decadal oscillation. For instance, its role in affecting annual ice conditions in the Arctic is commonly recognized. I don’t know anything about how it is included in General Circulation Models used for global climatic prediction.
What I do know is that there aren’t and GCMs out there that can explain the warming observed in recent decades in terms of natural variation alone. There is unambiguously an anthropogenic component.
taking action as outlined by many world governments is not cost-neutral: it will have very severe effects worldwide (and not just that we in the developed world will have to switch our appliances off). As with anything else, doing a cost-benefit analysis is the correct way forward.
I agree. The kind of action we need to take is likely to be very expensive, and involve considerable personal sacrifice. The cost-benefit calculations clearly favour action if we take into account the welfare of future generations and the possibility of abrupt or catastrophic climate change.
Business-as-usual emissions could produce 6˚C or more of temperature increase by 2100. There is no way that wouldn’t be utterly devastating for humanity: a very significant ‘cost’ that must be borne in mind.
World governments seem to be following the B family and utterly ignoring the A family of models, e.g. A1: why?
In terms of emissions, we are doing worse than even the worst scenarios the IPCC developed in 2001.
Modeling future emissions is very challenging, since you need to make guesses about technology, population, geopolitics, etc. About half the uncertainty in many IPCC projections exists because of uncertainty about what emission trajectory humanity will follow.
In the end, we need to follow a trajectory that leads the world to zero net carbon emissions, and we must do so before crossing any dangerous tipping points in the climate system.