March 22, 2022

expert reaction to reports of extreme temperatures in Arctic and Antarctic

Both of the earth’s poles have experienced unusually high temperatures in recent days.

Dr Bethan Davies from the Department of Geography at Royal Holloway, said:

“The Arctic heat wave (temperatures about 30°C above normal) has been developing for a few days. There is a heat wave in the polar circle, and strong pressure gradients are driving warm air from further south into the polar circle. Colder air has been displaced and moved over parts of sub-polar northern Europe and Siberia, Canada and USA.

“It’s currently spring in the Arctic, and it’s experiencing much warmer temperatures this month so far than normal. These warm temperatures may have important consequences for Arctic sea ice (frozen ephemeral sea water). As the polar sea ice melts, more dark-coloured sea water is exposed, which absorbs more heat and can warm the planet further (we can call this polar amplification).

“In Antarctica, the situation is rather different. It is approaching winter now in Antarctica. Here, an atmospheric river, a tendril of water-laden warm air from the Pacific, has reached Antarctica. This has resulted in temperatures 40°C above normal in parts of East Antarctica. There was even rain reported in Antarctica. However temperatures are still below 0°C and likely most of the rain refroze in the snow pack. Temperatures are more similar to the kinds of temperatures we see here in mid-summer.

“These kinds of extreme weather events are occurring with more frequency in our warming world. Atmospheric rivers have been known previously in Antarctica, but not of this magnitude. This event was especially large, warm and significant. If we saw an event of this magnitude in West Antarctica, this could cause serious issues with the floating ice shelves. Ice shelves are floating extensions of land glaciers, and they hold back land ice, like a cork in a champagne bottle. If we remove the ice shelves, then we can get a lot of ice transferred to the ocean, rising sea levels. Ice shelves are vulnerable to heating from below and from increased surface melt  and these kinds of events could have serious consequences for the health of the ice shelves and damage to the snow pack.

“Overall a concerning event and a symptom of increased extreme weather in a warming world.”

Prof Jeffrey Kargel, Senior Scientist, Planetary Science Institute, Tucson, AZ, USA, said:

“To cut to the chase, I see a possibility that this kind of extreme weather could kill millions of people if it occurred elsewhere in the heat of summer. Why? How? What are the caveats, and are there rational hopes that I am wrong? How might I be wrong? (I hope I am wrong.)

“I’ll focus on what was recorded at Vostok, East Antarctica, since that is ground truth.

“Widely reported news has temperatures at Vostok, Antarctica that are 34 degrees C (61 degrees F) warmer than normal. It should not be missed that we have this “ground truth” information thanks to Russian scientific monitoring, which we certainly hope continues to be collected and shared with the world.

“This polar heating exceeds anything that climatologists had expected. I am sure climatologists soon will explain just how impossible this heating is with existing understanding– and yet it happened. It is reminiscent of last year’s heat wave in Oregon, Washington, and British Columbia. NASA’s Earth Observatory posted about it on June 27, 2021 as that heating episode got underway (https://earthobservatory.nasa.gov/images/148506/exceptional-heat-hits-pacific-northwest). That article pointed out how Lytton, BC, attained an all-time Canadian record-high temperature of 116 F, for any day. In the following days, that record fell, by a lot, when Lytton reached 121 F and then burned to the ground. It was like summertime Death Valley in BC! (https://www.nytimes.com/2021/07/10/world/canada/canadian-wildfire-british-columbia.html). The heating extended across a vast region. 

“Scientific analysis soon reported on just how bizarre that western North America heating event was, https://www.worldweatherattribution.org/wp-content/uploads/NW-US-extreme-heat-2021-scientific-report-WWA.pdf. It was emphasized that climate models do not show such heating events, but it was still possible that it was an extreme of all extreme heating events layered on top of anthropogenic climate warming; or else, some new climatic phenomenon occurred that is not captured in existing climate models.

“Now, we have this bipolar heating event, where the anomaly is even greater than in the western North America heat dome event of 2021. One has to ask, again, whether a fundamentally new phenomenon is at work, presumably connected to nonlinear effects of anthropogenic global warming. Climatologists will sort that out, but obviously with two events occurring in two successive years, we may have to abandon ideas that it is the extreme warm tail of the weather probability function. It seems to be a new weather phenomenon, and it is not included in current climate models. If it happened twice in two years, I’ll say it will happen again, and again, in various parts of the globe. I will wait for climatologists to clarify the phenomenon and hopefully explain it enough to understand and predict such events or at least define the envelope of what possibly may occur in the future, to what degree, and where.

“In what follows, I presume that the 2021 event and this ongoing polar event is in the same basket of phenomena–whatever that is; and then I’ll offer a few caveats. With this presumption, we must ask, what would happen if something like the 2021 and 2022 events was centered in, say Houston, Texas, in the midst of summer, when normal high is 95 degrees F? Okay, let’s just consider the 2021 event, for a reason I will explain below. The epicenter of the 2021 event was in Lytton, BC, where the worst day reached a temperature 44 degrees F (24.4 degrees C warmer than the normal high temperature for late June. Just do simple addition: 95 + 44 = 139 F. It might be a couple degrees less if it’s not a matter of adding degrees of temperature, but of added emitted black-body radiation; let’s call that a little detail. Considering Houston’s normal humidity, I’ll venture a guess: step outdoors in that, even in the shade, and you’ll be dead in a few minutes. I won’t similarly calculate using the more extreme polar heating currently going on, because the poles are apt to heat more than subpolar latitudes. Now, with temperatures possibly attaining the 130’s in Houston, I’ll take it as a given that the electrical grid will collapse. So, no cooling of buildings. There will be some thermal inertia which keeps building interiors cooler than the outside daytime high, but will very many people survive high humidity and indoors temperature say, even in the low 120’s F? If water is available, evaporative cooling (wet loose clothing, towels on the face, and hand fans) could help. How many people would die if the heat dome spanned from Houston to Atlanta? Or Charleston, South Carolina to Boston? Or New Delhi to Ho Chi Minh City?

“Caveat #1: I mentioned one: the polar anomaly event may exceed in magnitude what is likelier at subpolar latitudes. We can certainly hope and have some justification for the hope, but until we know how/why these events are happening, it is not clear what can happen.

“Caveat #2: The Vostok anomaly is about 34 degrees C (61 F). But this is where the surface is still below freezing, and phase changes of state of water are minimal (no melting, and minimal sublimation), so little energy from whatever is driving the heating is going into phase changes. That means more energy can heat the air in Antarctica when melting doesn’t happen. Since water is available in most subpolar latitudes (oceans, lakes, rivers, ground water, vegetation moisture, clouds), most subpolar latitudes will see less warming if just for this effect.

“Caveat #3: Are the current polar and the western N America 2021 events actually related? I assumed above that they are. What if they are two distinct phenomena, and both are extremes, and the polar one is purely a polar phenomenon? That leaves us with one event like 2021, and we are back to a point where we can wonder whether that was a one-in-a-thousand event plus 2 degrees C anthropogenic warming. Then we can rest a little easier.

“Caveat #4: The 2021 event occurred in early summer, a time when seasonal weather is still transitioning from spring to summer. The 2022 event is around the southern autumn equinox, a time when radical seasonal weather changes are always happening. Maybe these events are partly about full summer type weather being shifted to earlier in the summer and springtime, and to late summer and autumn. We know this is happening. If it happens to great degree during anomalous heat-dome events, it can explain part of the weird hot anomalies, but not all. It also would not really get around the fact that this is extreme weather caused, presumably, by anthropogenic climate change. However, it might mean that such a heat dome event happening in the middle of summer might not produce as much of a temperature anomaly as the 2021 and 2022 events.

“Other implications, caveats notwithstanding: Let’s say the polar phenomenon is purely polar. Whew! We’re spared that! But what does it mean for polar ice sheet melting? In the case of Antarctica, the 2022 event means nothing about melting, because temperatures still remained below freezing, at least over most of the ice plateau surface. But if such an event happened earlier in the austral summer, massive melting would happen. In fact, we have seen many extreme melt periods in Greenland in recent years. It is likely that the current polar events is another extreme-warm period in a spectrum of magnitudes. Since these are not modelled on climatic/extreme weather events, it is in addition to what the climate and glaciological models predict for melting ice sheets. So, it underscores the likelihood that polar ice sheets will melt much faster than most people have been predicting. That adds to the rate of sea level rise.

“And I mentioned that water is available in most subpolar latitudes to reduce heating through evaporative cooling. One of these sources is evapotranspiration by plants: what happens to food crops and nature? By available water, I mean massive wilting. What about soil moisture? When it’s depleted, this source of cooling is gone, and what does that mean for agriculture and nature?

“When temperatures reach the 120’s and 130’s F, evaporation of shallow ponds and lakes can be rapid and complete. Wetlands will suffer, and so will human settlements that draw from wetlands. Few wild animals can survive such temperatures.  The ecological damage would be pervasive. 

“In my example, I took Houston. What if such a heat dome settled over my city of Tucson around July 1, when temperatures normally are about 106 F?

“Finally, these bizarre events are believed linked to anthropogenic climate change and changes in extreme weather due to changes in atmospheric circulation. If all this is due to 1.2 degrees of global warming, what happens when we reach or exceed 2 degrees?”

Prof Meric Srokosz, Professor of Physical Oceanography at the National Oceanography Centre, said:

“Discussing the high temperatures being measured at the poles this week, Professor Meric Srokosz, Professor of Physical Oceanography at the National Oceanography Centre, said: “Short-term large fluctuations in temperature are not deemed critical in terms of climate change. In order to melt ice sheets there must be sustained changes in surface air temperatures. Exceptionally high short-term changes may be indicative of climate change effects, but it could be natural variability. Surface air temperature variability in the Arctic and Antarctic is usually a few degrees, so it is true that the temperatures recorded this week are significantly higher than normal.

“Sea level rise is a long-term phenomenon, in which ice sheets melt over a number of years. Short-term extreme temperature events do not impact this phenomenon, as it is statistically difficult to tie one single extreme event to climate change. However, based on climate model projections, a series of such events would fit the expectation that extreme temperature events will become more common.”

Prof John Turner, British Antarctic Survey, said:

“There are periodic intrusions of warm air into the interior of the Antarctic, with some of them having reached the South Pole and the high plateau of East Antarctica. But the event in March was particularly remarkable because warm air was drawn from mid-latitudes over several days by a deep stationary storm system off the Antarctic coast. Despite being cooled as it crossed the Southern Ocean, the air was still relatively warm when it reached the Antarctic Plateau. Since the late 1950s there has been a significant increase in the number of high temperature days at Vostok station on the Antarctic Plateau, the largest increase of any station outside the Antarctic Peninsula. Climate models suggest that this trend is likely to continue in the coming decades.”

Prof Julienne Stroeve, Professor of Polar Observation & Modelling, University College London (UCL), said:

“It is unusual to have such large departures from average occur at the same time at both poles, and in the Arctic it may have led to the maximum sea ice extent reached considerably earlier than average.

“While we may expect such warming extremes to occur more frequency under climate change, it is too early to say this particular event is related to climate change. Weather is always unpredictable. And it’s important to remember that air temperatures, while warmer than average, remain below zero.”

Prof Martin Siegert, co-director of the Grantham Institute for Climate Change and the Environment, Imperial College London, said:

“Polar warmth like this will not be generated in the polar regions. It will come from low/mid-latitudes, and be transported north (Arctic) and south (Antarctic). While this process is not unusual in the Arctic, it is very in the Antarctic, where the continent is effectively isolated climatically by the southern ocean and the high elevation of the ice sheet that prevents warm weather systems from penetrating. The magnitude of the temperatures is also staggering in both poles. While the events are ‘weather’, if under climate change the polar regions experience more events like this it could have devastating impacts, especially in coastal regions in Antarctica where the warmth will be felt the greatest, and on ice shelves where melting would occur. In the Arctic, the impacts on sea ice and permafrost, and the climate feedbacks that result are also worth noting. These are unusual events, but if they become regular occurrences they would impact both regions considerably.”

Dr Lisa Schipper, co-ordinating lead chapter author for the IPCC sixth assessment report and Oxford Environmental Research Fellow, said:

“The IPCC report on Impacts, Adaptation and Vulnerability released in February underscores that the window of opportunity to act on climate is rapidly closing. If these extreme temperatures don’t wake people up about this urgency, at the same time as war threatens to encourage more fossil fuel extraction and use, I don’t know what will.”

Declared interests

None received.