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Is the scientific evidence of human-induced climate change unequivocal?

Robert Watson's picture

    Photo ©  Himalayan Trails/flickr
Last December, a very large majority of the scientific community and most politicians would have agreed that the scientific evidence of human-induced climate change was unequivocal and that the only question was whether the world’s political leaders could agree in Copenhagen to meaningful legally binding greenhouse gas emission reduction targets. 

But, as we now know, the negotiations only produced an aspirational target—to limit the global mean surface temperature to no more than 2 degrees C above pre-industrial levels—and an accord that does not bind any country to reduce their emissions. 

Since then, the IPCC’s Fourth Assessment report has been criticized for errors or imprecise wording.

  • For example, the statements that the Himalayan glaciers would melt by 2035 or earlier (IPCC admitted that this was an error and not evidence-based);
  • that agricultural production in some North African countries would decrease by up to 50% by 2020 (the synthesis report did not contain the nuances and more detailed discussion in the underlying chapter);
  • and that over half of the Netherlands was below sea level rather than a quarter (this was largely a definitional issue – the Netherlands Dutch Ministry of transport uses the figure 60% - below high water level during storms). 

These inaccuracies, coupled with the controversy surrounding illegally hacked e-mails and temperature data from the University of East Anglia (UEA), have provided climate skeptics and some media with ammunition to undermine public confidence in the conclusions of the IPCC and climate science in general.