The retreat of Palcaraju glacier in Peru’s Cordillera Blanca has led to the rapid expansion of Lake Palcacocha, which now threatens the city of Huaraz with a glacial lake outburst flood (GLOF). A GLOF from the same lake resulted in >1800 deaths in Huaraz in 1941. Ongoing litigation (Lliuya v RWE) seeking financial compensation for the costs of protecting Huaraz has entered an evidentiary phase in which evidence on human influence on the retreat of Palcaraju glacier will be considered by the court.

View looking north over Huaraz towards the highest region of the Cordillera Blanca

Looking north over Huaraz towards the highest region of the Cordillera Blanca. Image by Uwebart - CC BY-SA 3.0

Dr Sihan Li (Meredith), Post-doctoral Research Assistant at the ECI, and Rupert Stuart-Smith, first year DPhil student in the NERC Doctoral Training Partnership in Environmental Research, summarise the project for us:

Our team have completed analyses with collaborators at the University of Washington’s Department of Earth and Space Sciences which constitute the first study to attribute GLOF risk to climate change. We received £2,800 from the Inspiration Fund which allowed Rupert Stuart-Smith to travel to work with Professor Gerard Roe at the University of Washington (Seattle) for two months to carry out the proposed research. Our results show that it is virtually certain (>99% confidence) that the observed retreat of Palcaraju glacier could not have happened in a natural climate. Further, our central estimate for the fraction of Palcaraju glacier’s retreat attributable to human influence on the climate system is 97.7%. This is a powerful statement of the dramatic impact of climate change on this deglaciating landscape.

We also conducted an evaluation of human influence on the retreat of the glacier prior to the 1941 GLOF (i.e. between 1880 and 1940) and found that this also far exceeded the plausible glacier length change over a 60-year period in a natural climate. As such, we reached the sobering conclusion that this GLOF was one of the earliest deadly climate change impacts to have been attributed to human greenhouse gas emissions.

Impact and follow-on work

These analyses have been written up as a journal article which will soon be submitted for publication. We hope this work will contribute to the resolution of the ongoing litigation: an influential, widely publicised and potentially precedent-setting legal case. If successful, this case would be the first to hold a company liable for the damages of climate change and has the potential to change how science is used in climate litigation.

The findings of this research will be presented at the Lund University Centre for Sustainability Studies Conference on Loss and Damage, in November 2019, and at the American Geophysical Union Fall Meeting, in December 2019. We expect that the findings of this paper will garner substantial media interest once published.

Our future work will build on this research and develop a methodology for accurate attribution of climate change damages to individual emitters for non-meteorological climate change impacts including glacial retreat and sea level rise.