<p>Stick to the facts: In a regional chapter on Asia in Working Group 2 (climate impacts) of the 4th IPCC report, written by authors from the region, it was erroneously stated that 80% of Himalayan glacier area would very likely be gone by 2035. This was of course not the proper IPCC projection of future glacier decline, which is found in the Working Group 1 report (which is the one about basic climate science, including the future projections of climate change). There we find a 45-page, perfectly valid chapter on glaciers, snow and ice (Chapter 4), with the authors including leading glacier experts (such as my good colleague Georg Kaser from Austria, who first discovered the Himalaya error in the WG2 report). There are also several pages on future glacier decline in Chapter 10 (“Global Climate Projections”), where the proper projections are used e.g. to estimate future sea level rise. So the problem here is not that the IPCC’s glacier experts made an incorrect prediction. The problem is that a WG2 chapter, instead of relying on the proper IPCC projections from their WG1 colleagues, cited an unreliable outside source in one place. Fixing this error involves deleting two sentences on page 493 of the WG2 report. This was an unfortunate citation error by the WG2 colleagues from Asia, but it was not based on an incorrect prediction by the IPCC climate scientists, as you well know.</p>
Stefan Rahmstorf is Professor of Physics of the Oceans at Potsdam University and Department Head at the Potsdam Institute for Climate Impact Research. His most recent book is The Climate Crisis.