Extinctions from global warming
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In 2004 a group of biologists published an estimate of extinctions risk from climate change[1]. 

"The midrange estimate is that 24 percent of plants and animals will be committed to extinction by 2050," said the first author. "We're not talking about the occasional extinction.  We're talking about 1.25 million species. It's a massive number." 

Here is the abstract

Climate change over the past ~30 years has produced numerous shifts in the distributions and abundances of species1,2 and has been implicated in one species-level extinction3. Using projections of species’ distributions for future climate scenarios, we assess extinction risks for sample regions that cover some 20% of the Earth’s terrestrial surface. Exploring three approaches in which the estimated probability of extinction shows a power law relationship with geographical range size, we predict, on the basis of mid-range climate-warming scenarios for 2050, that 15–37% of species in our sample of regions and taxa will be ‘committed to extinction’.  When the average of the three methods and two dispersal scenarios is taken, minimal climate-warming scenarios produce lower projections of species committed to extinction (~18%) than mid-range (~24%) and maximum change (~35%) scenarios. These estimates show the importance of rapid implementation of technologies to decrease greenhouse gas emissions

Click here for the full article.

iGreen comment

It is estimated there are about 14 million species on Earth, of which about 1.6 million have been identified.   Thomas seems to be saying that at least 2.5 million species (18% of 14 million) are going to become extinct as a result of a 0.8-1.7 degree Celsius global temperature rise.  Since not all species have the sort of limited habitat that prevents them migrating, perhaps it’s somewhat less than that.  Thomas himself seems to think 1.25 million species (see quote above). 

However, we had a 0.6 degree temperature rise in the 20th century, at least half of it in the first half of the century, so we should be seeing some species extinctions attributed to climate change by now.   

After all tens of thousands of biologists, ecologists and assorted doomsayers like Thomas and his colleagues are jetting round the world every year looking for them.  You would expect them to have found some.  And indeed they have.  Precisely one – the golden toad, Bufo periglenes from the Tilarin Mountains of north-western Costa Rica. 

If a 0.6 degree global temperature rise over 100 years has yielded one species extinction attributable to climate change, I’m going to relax about the extinction risk from a 0.8-1.7 degree rise.     

The researchers called for "rapid implementation of technologies" to reduce emissions of greenhouse gases.  iGreens would not go that far - we think a moratorium on flights to species-extinction  conferences would be adequate.  Let them wind each other up by phone. 

[1] "Extinction Risk from Climate Change."  Thomas et al. Nature 427, 145–148.  January 8, 2004. 


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Last modified: March 25, 2006