Glaciers

Another retrieved post – thanks Christina.

The denialists have selected a single error on one page of the IPPC’s 3000 page discussion of the impact of climate change on glaciers to attempt to discredit the entire science of climate change. Reading the text of the IPPC reports suggests this attempt is unjustified.  Moreover, the implicit suggestion that the IPPC have connived to misrepresent the science is totally unjustified given the texts of their published reports.  

The offending remarks are on page 493 of the Working Group 2 (WG2) report. The claim that the glaciers would vanish is unattributed but apparently based on a New Scientist report while the claim that they would recede to 1/5th of their current level is attributed to a WWF publication in 1995 on glaciers.  This is followed by some evidence on rates of decline of certain glaciers with the claim that ’short glaciers’ – those less than 4 kilmetres in length – might disappear.  The wrong IPPC statement seems almost to be an inadvertant slip.  In the Executive Summary for this chapter (p. 471) the offending claim is not repeated and indeed that receding glaciers might cause loss of river flow is assigned the status of only ‘medium confidence’.

The denialist claims are further analysed in this article in DeSmogBlog.  Tim Lambert also has a survey of the issue.

Yes, the IPPC were probably wrong in claiming that Himalayan glaciers would vanish or (nearly) vanish by 2035. The IPPC were wrong in borrowing this claim from popular science, New Scientist, and the WWF without checking out carefully these sources. They compounded their error by stating that the vanishing of the glaciers would occur with ‘high probability’.  

But to be fair these remarks were made in the context of an Asian case study in WG2 that was less than one column of one page in length.  WW2 is concerned with adaptation and vulnerability issues not with the science of climate change.

The Physical Science Basis report of the IPPC (WG1) has an excellent discussion of glaciers – pages 356-360 – that does not make this claim at all.   Moreover, it is structured as a solid scientific discussion that is in no way alarmist or pushing a political line.

For example it is recognised that glaciers have been declining since 1800 – although most of the mass loss has occurred after 1970. The effect of climate change on glaciers is recognised to depend on their size and the topography. Small glaciers on steep terrain will be more severely impacted on than large glaciers on flat terrain.  Indeed the large glaciersc will respond over ’several centuries’ (p 356) to climate change.  This is the view that should have been expressed in the WG2 report.

Overall the picture painted of the effectys of climate change on glaciers is a very mixed one. Climate change will have heating effects but will also increase precipitation in some areas. Therefore some glaciers can be expected to expand not contact – WG2 explicitly list some Himalayan glaciers in thisc category. Overall the IPPC suggest a contraction but are fastidious in recognising the complexity of the effects.