Monday, January 28, 2013

Global Warming Leveling Off

I have been blogging about climate change for several years.  My general view of the issue, stated early on, is as follows:

1.       Global warming has been real over the last century. 
2.      Human activity may have been a significant factor in forcing that warming. 
3.      It is very difficult to tell what the causes of the warming are and how much of an impact human activity actually had. 
4.      It is not at all certain whether the effects of warming have been or will be, on balance, good or bad for human beings. 
5.      There is no reasonable chance that global treaties or nation-specific policies will have any impact on human carbon emissions. 

I think I am right on all five counts.  The global treaty initiatives have come a cropper.  Nations committed to reducing carbon emissions have, for the most part, failed to achieve that aim.  Actual reductions in carbon emissions have come from economic distress and from the application of new technologies such as fracking. 
Now comes a finding from The Research Council of Norway that pokes a hole in the climate change balloon.  
After Earth’s mean surface temperature climbed sharply through the 1990s, the increase has leveled off nearly completely at its 2000 level. Ocean warming also appears to have stabilized somewhat, despite the fact that CO2 emissions and other anthropogenic factors thought to contribute to global warming are still on the rise.
This, in scientific terms, is what counts as a negative finding.  Despite increased carbon emissions, warming has leveled off.  The Norwegian project used the same framework as the IPCC.  What would be the effect of doubling carbon emissions from pre-industrial levels? 
Uncertainties about the overall results of feedback mechanisms make it very difficult to predict just how much of the rise in Earth’s mean surface temperature is due to manmade emissions. According to the Intergovernmental Panel on Climate Change (IPCC) the climate sensitivity to doubled atmospheric CO2 levels is probably between 2°C and 4.5°C, with the most probable being 3°C of warming.
In the Norwegian project, however, researchers have arrived at an estimate of 1.9°C as the most likely level of warming.
This confirms my points 3, 4, and 5.  We don’t really know how much human activity is contributing to climate change and we don’t have any good reason to suppose that the current trajectory of climate change will be bad.  If the Norwegians are right, we will at worst achieve a level of climate change that the IPCC thought we should aim at without any help from global treaties. 
Climate change should be taken seriously.  Science can tell us a lot but much of what it tells us is ambiguous.  Just right now, climate change looks to be something less than a crisis.  It certainly doesn’t justify hobbling our economies, which is something we weren’t going to do anyway. 

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