January 18, 2023

expert reaction to study of recent temperatures on the Greenland Ice Sheet

A study published in Nature suggests that the recent temperatures in central–north Greenland are the warmest in the past millennium.

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

“There is plenty of evidence that the Arctic has warmed rapidly over recent decades. This study plugs an important gap in our knowledge, because it shows that Greenland has warmed too – it’s hotter there now than at any time in the past 1000 years.

“But the ice cores that are used in this study were collected more than a decade ago, and temperatures have risen even more since then. We are now starting to see the first major impacts of this warming on the ice sheet as glaciers in the north of Greenland have started to speed up. It’s a timely reminder that even the coldest parts of our planet are not isolated from the effects of global heating, and of course the impacts in this case will arrive at our doorsteps immediately as sea levels rise.”

Prof Martin Siegert, Professor of Geosciences and Deputy VC, University of Exeter, said:

“I’m not surprised by this conclusion – given that we’ve seen two events where the bulk of the ice sheet has been melting in high summer over the last 10 years. The last one (last summer) involved the entire ice sheet. We know from ice core work – where annual ice layers can be counted – how rare melt events on the summit are. This work adds more information around temperature from around the ice sheet region, informing us that Greenland is heating significantly and in line with other regions of the Arctic. Remember, the Arctic is heating 2-4 times quicker than the global average as a consequence of burning fossil fuels. The consequences of Greenland heating is continuing to unlock the sea level potential held in its ice, which is around 7m globally. That may take some time to realise, but further heating of the ice sheet will surely lead to further melting and – at some stage – an inevitable deglaciation.”

Dr Jeffrey S. Kargel, Planetary Science Institute, Tucson, said:

“The new Greenland ice coring and analysis shows continued and accelerating warming in northern Greenland during the industrial era. The results, as the authors show, are consistent with the rapid increase in meltwater flowing off the Greenland ice sheet. Not discussed in the article, but also apparent, there is also a consistency with the rapid decline of Arctic sea ice in the late 20th and early 21st centuries and with rapid changes in large Greenland outlet glaciers that drain the Greenland ice sheet and small glaciers that are detached from the ice sheet.

“Associated with the rise in temperatures documented in this paper, but not discussed in the paper, many enormous glaciers in Greenland have sharply accelerated their flow into the sea, have thinned, and retreated, especially in the past two decades when the surge in warm conditions is reported. The new results are part of the scientific case that global human-caused climate change is amplified in the Arctic relative to the rest of the planet, and that warming has had large consequences for sea level rise and disturbances of ocean circulation, which then have global consequences for climate and coastal flooding.

“The new results also help to establish the past millennium’s natural temperature fluctuations that have occurred in Greenland as a result of many other processes combined. We know from other studies that variability of the sun’s radiant energy output, changes in atmospheric gas composition and stratospheric dust and aerosol content caused by large volcanic eruptions, and slow changes in Earth’s orbit and spin axis, and shifts in ocean currents contribute to global temperature changes, including those recorded in the composition of Greenland’s ice. The Greenland ice cores contain a confirmation of the summed effect of those natural variations, which obviously also continue and contribute to the year-to-year and decade-to-decade fluctuations. The new work underscores the unprecedented warmth in northern Greenland during the first two decades of the 21^st century compared to any period in the ice core record going back 1000 years, including the well-known Medieval Warm Period.

“In terms of the statistical reliability of these results, the researchers acquired ice core samples from many places so as to assure that the sampling is adequate, and then they showed diligence in tracking the statistics of the calculated temperatures and their trends. The work is robust within the stated uncertainties. This robustness includes the central point of the paper that northern Greenland was warmer in the first two decades of this century relative to all other periods in the past 1000 years.”

Dr Liz Thomas, head of the ice cores team at British Antarctic Survey, said:

“This robust study, by a well-respected research team, demonstrates what the scientific community have suspected for some time – that the Greenland ice sheet, like many other locations across the globe, is warming rapidly as a result of climate change caused by human activity.

“Ice cores provide one of the best tools to reconstruct the climate prior to the instrumental era. The study uses ice cores to place the instrumental temperature records in a longer context. While some of the warming since the 1800’s can be explained in terms of natural variability, the temperatures observed in the most recent decade are outside of the expected range.

“The advantage of this study, over previous Greenland temperature reconstructions, is that it includes multiple ice core records stacked together. This reduces the signal-to-noise (which may overwhelm a single record) and provides a reliable temperature record.

“Continued warming over the Greenland ice sheet increases the risk of ice sheet melt, which will have a direct impact on sea level rise. In addition to increasing sea levels, a reduction in the Greenland ice sheet volume can alter weather and climate patterns across the northern hemisphere. Freshwater entering the ocean (as melt run-off) can change the strength and direction of oceanic currents, while the height of the ice sheet can alter the strength and direction of the winds. Both have an important imprint on UK weather and climate.”

‘Modern temperatures in central–north Greenland warmest in past millennium’ by M. Hörhold et al. was published in Nature at 4pm UK time on Wednesday 18 January 2023.

DOI: https://doi.org/10.1038/s41586-022-05517-z

Declared interests

Prof Martin Siegert: “no conflicts.”

Dr Jeffrey Kargel: “I have no relevant interests, no conflicts pertaining to the story or my comments about it.”

Dr Liz Thomas: “no interests.”

For all other experts, no reply to our request for DOIs was received.