November 30, 2021

expert reaction to a study modelling future rainfall in the Arctic

A study published in Nature Communications uses new climate models to look at Arctic precipitation projections.

Dr Gavin Schmidt, Director of the NASA Goddard Institute for Space Studies, said:

“The changes in the Arctic are already profound and this paper examines closely what we can expect in the future. They show that the impacts are robustly tied to the overall rate of change of global temperature, and thus will depend on greenhouse gas emissions going forward. These results don’t change the expected Arctic impacts given any particular temperature rise, but rather do imply that the worst impacts can be avoided if countries match their stated intentions to cut emissions by in line with the Paris agreement and updates to the Nationally Determined Contributions (NDC) from the recent Glasgow summit. 

“This cannot be taken as evidence that the Arctic rainfall will increase ‘faster than expected’ though. This is because the CMIP6 ensemble has a number of models with climate sensitivities that are larger than can be observationally supported – this leads on average to warmer future temperatures than can be expected and so earlier transitions for Arctic change. The IPCC forecast global temperatures to rise significantly less fast than the CMIP6 ensemble mean, and this projection doesn’t take that into account. The claim of a new ‘more rapid’ forecast is unsupported.”

Prof Tim Palmer, Royal Society Research Professor, University of Oxford, said:

“This is an interesting paper and whilst the results are certainly concerning, I believe some caution is needed. Firstly, as can be seen in the authors’ paper, the CMIP models typically underestimate natural variability in the Arctic region, and, possibly linked to this, the CMIP trends in precipitation change over the Arctic over the late 20th Century are not obviously replicated in the observations (sadly, the two observational estimates used disagree substantially). Secondly, the temperature biases that most CMIP models exhibit makes estimating the transition from snow to rain (at fixed absolute temperatures) especially challenging. 

“The authors highlight a potentially important aspect of climate change that needs more careful quantification. All this points to the need for high-quality observations of precipitation for regions such as the Arctic and the development of a new class of high-resolution climate model, with smaller biases and more realistic estimates of natural variability on the regional scale. Together these will give us more confidence in the impact of carbon emissions on precipitation in places like the Arctic. We need these urgently if they are to impact on mitigation policy.”

Prof Richard Allan, Professor of Climate Science, University of Reading, said:

“As the planet warms, a more intense water cycle moves greater amounts of moisture into storms, monsoons and polar regions, increasing the amount and intensity of precipitation. Exploiting a state-of-the-art set of complex computer simulations, this new study paints a worrying picture of future Arctic climate change that is more rapid and substantial than previously thought. More rapid Arctic water cycle change is partly explained by the greater warming depicted by the latest computer models, yet this is not the whole story since the newer simulations also show larger rainfall increases for each degree of warming. The Arctic is already warming more than twice the global rate and climate change here is further heightened by sea ice loss that allows greater evaporation of moisture from the ocean but also a shift from snow to rain and melting of land ice that further alter the environment and the flows of melt water that societies and ecosystems rely upon. This research rings alarm bells for the Arctic and beyond, underscoring the urgency of the immense effort needed to limit and adapt to ongoing climate change.”

Dr Miguel Ángel Morales Maqueda, Senior Lecturer in Oceanography, Newcastle University, said:

“This is a very interesting paper. Climate models have been consistently underestimating the rate of decay of the Arctic sea ice cover in the past. The enhanced warming and sea ice loss projected by the new generation of coupled climate models indicates perhaps a correction to, sadly, more realistic predictions. There is a vast amount of freshwater that is dynamically retained in the Arctic Ocean, notably in the Canadian Basin. This freshwater is released into the North Atlantic during periods when the circulation in the Beaufort Sea weakens. If excess freshwater is brought into the Arctic by a more intense poleward transport of moisture (it does not really matter whether this water falls in solid or liquid form), it is sure to eventually make its way into the North Atlantic, potentially reducing the density of surface waters, weakening the meridional overturning circulation and affecting the entire Northern Hemisphere climate, notable that of northern Europe.”

Prof Andrew Shepherd, Director of the Centre for Polar Observation and Modelling, University of Leeds, said:

“One of the first regions to be altered by this climatic switch (from snowfall to rainfall) will be the Barents Sea, North of Russia. Its sea ice loss has already affected us by pushing Arctic weather fronts over Europe – such as the Beast from the East. And we can also expect to see the Northern Sea Route used for shipping decades sooner, which will inevitably lead to more vessels getting caught out by freezing ice as has happened this week.”

Prof Bob Spicer, Emeritus Professor, The Open University, said:

“As someone who has studied the paleoclimate of the Arctic (Alaska and Russia) for many years I can say that this research is entirely in line with what the fossil record tells us the Arctic was like during previous episodes of global warmth. Millions of years ago the Arctic was clothed in dinosaur-inhabited forests and sequestered large amounts of carbon which is now still there in the form of huge coal reserves. Climate modelling for these ancient times points to a near permanent cloud cap and high rainfall, and this is entirely consistent with the evidence we find in the rocks.”

‘New climate models reveal faster and larger increases in Arctic precipitation than previously projected’ by Michelle R. McCrystall et al. was published in Nature Communications at 4pm UK TIME on Tuesday 30 November 2021.

DOI: https://doi.org/10.1038/s41467-021-27031-y

Declared interests

None received.