Important new publication on Rain on Snow phenomena with CHARTER input

An important new article with substantial CHARTER input has just been published in the journal Nature Communications. The article is titled New climate models reveal faster and larger increases in Arctic precipitation than previously projected. In other words, climate models are predicting that snowfall will be replaced by rain fall in the future, and this will occur at a faster rate than previous models suggested. You can download the article here (open access)

This phenomena is referred to as ‘Rain on Snow’ or ROS and it is something that is predicted to happen more often with potentially disastrous impacts on biodiversity in the Arctic. By way of example, tens of thousands of reindeer have died as a result of repeated ROS events in the Yamal peninsula and Finland in recent years, with potentially catastrophic consequences for reindeer herding peoples and cultures. The phenomona is also hazardous for other wildlife as rain refreezes and turns to ice, creating a physical barrier to pastures and nutrition. While ROS events are not unheard of, the frequency with which they are happening is.

The left-hand column shows the changes in ae snowfall and cg rainfall at the end of the century in ac December–February (DJF) and eg September–November (SON) in CMIP6. Straight line hatching indicates regions where differences are not statistically significant at the 95% confidence level. The right-hand column shows the difference in bf snowfall and dh rainfall at the end of the century (2091–2100) relative to the start of the century (2005–2014) between CMIP5 and CMIP6 (CMIP6–CMIP5) for bd December–February and fh September–November. Hatching indicates statistical significance at 95% confidence level.

From the abstract:

As the Arctic continues to warm faster than the rest of the planet, evidence mounts that the region is experiencing unprecedented environmental change. The hydrological cycle is projected to intensify throughout the twenty-first century, with increased evaporation from expanding open water areas and more precipitation. The latest projections from the sixth phase of the Coupled Model Intercomparison Project (CMIP6) point to more rapid Arctic warming and sea-ice loss by the year 2100 than in previous projections, and consequently, larger and faster changes in the hydrological cycle. Arctic precipitation (rainfall) increases more rapidly in CMIP6 than in CMIP5 due to greater global warming and poleward moisture transport, greater Arctic amplification and sea-ice loss and increased sensitivity of precipitation to Arctic warming. The transition from a snow- to rain-dominated Arctic in the summer and autumn is projected to occur decades earlier and at a lower level of global warming, potentially under 1.5 °C, with profound climatic, ecosystem and socio-economic impacts.

The lead author is Michelle McCrystall of the University of Manitoba and CHARTER input was provided by Julienne Stroeve and Bruce Forbes. Quoted in Canada’s Globe and Mail, Forbes was quoted:

Bruce Forbes, a research professor at the University of Lapland in Rovaniemi, Finland, and a co-author on the study, said that it has become common practice for reindeer herders in the region to supplement their animals’ diets to make up for what they can no longer acquire through natural grazing. Further east, in Russia’s Yamal Peninsula, there have been reportsof mass starvation among herds, with tens of thousands of reindeer perishing.Dr. Forbes said that compared with similar modelling studies conducted a decade ago, the new study “demonstrates that even our most pessimistic projections of a warming Arctic, with more rain during winter – falling either on bare ground or on snow – are not keeping pace with reality.”

Climate study forecasts a rain soaked Arctic, Globe and Mail, Dec 1, 2021

The paper has already received considerable mainstream media attention(see below).

  • Rain fell at Greenland’s summit this year for the first time. It’s going to happen more often, study says. CNN
  • Rainfall could replace snowfall in the Arctic by 2060: Global warming will change the main form of precipitation in the area up to two DECADES earlier than previously thought, study warns. Daily Mail online
  • The Arctic could get more rain and less snow sooner than projected. Here’s why that matters. Washington Post
  • Rainfall in the Arctic will soon be more common than snowfall. Changes will happen decades earlier than previously thought. UManitoba News.
  • Rain to replace snow in the Arctic as climate heats, study finds. The Guardian
  • Climate study forecasts a rain-soaked Arctic. Globe and Mail (paywall)

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