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New research proves the link between man-made climate change and Andes flood-risk

The town of Huarez, nested high in the Peruvian Andes at 10,000ft altitude, is at risk. Water, once held securely within the Palcaraju glacier now rests in the nearby and unstable Lake Palcacocha, threatening the town with a devastating outburst flood that could inundate it. The risk is so acute that it is now the subject of a landmark legal case currently taking place in the German courts. Saúl Luciano Lliuya, a farmer from Huaraz, is suing RWE, Germany’s largest electricity producer, for the costs of preventing harms which would result if an outburst flood took place.

One of the key issues at the heart of this case is the question of fault. Should this high-emission company be held responsible, or could natural climate change have caused the glacier to retreat, resulting in the unstable lake? According to a new study from the University of Oxford and the University of Washington (which was undertaken independently of the legal case but which will now be used as evidence) the answer to the latter is unequivocally no. The researchers conclude

8 . Geographical that it is ‘virtually certain’ that the retreat of Palcaraju glacier to the present day cannot be explained by natural variability alone. In turn, they demonstrate that this retreat has increased the flood risk, establishing a direct link between emissions and the need to implement protective measures, as well as any damages caused by flooding in the future.

‘It’s up to the courts to decide how scientific evidence is interpreted,’ says Rupert Stuart-Smith, lead author of the study, ‘but this is the first attribution study which looks at the role of human-caused climate change – greenhouse gas emissions – all the way through to the hazards of a glacial outburst flood. What we found was that, from a scientific point of view, the role of climate change in causing this flood risk is very clear indeed.’

To establish this link the researchers took a threestage approach, separating the causal chain into stages. ‘The first is the link between emissions and the global and regional change in the climate. So in particular, the change in the temperature around the glacier itself,’ says Rupert. This involved using standard Intergovernmental Panel on Climate Change methods. ‘Then we look at the relationship between this change in temperature, and the retreat of the glacier, which

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