Northern hemisphere heatwaves more likely due to climate change | Polarjournal
The map shows the temperature anomalies over Siberia and the American Pacific coast. The measured values were up to 15°C above the average temperature (yellow – red). Meanwhile, temperatures in other regions such as Spain and the UK have been well below expected levels. Map: NASA Earth Observatory

For weeks, temperature records in various parts of the northern hemisphere have been making international headlines. From 49°C in Lytton, Canada, to just under 18°C on Kotelny, one of the New Siberian islands in the Northeast Passage, the stations are rolling over with maximum temperatures. An international study has shown that the likelihood of such heatwaves has been massively increased by climate change and will become increasingly likely in the future. Further work has simultaneously demonstrated other negative impacts of such temperatures on Arctic landscapes and wildlife.

The work of 27 international climate researchers working together in the World Weather Attribution network set out to investigate whether global climate change was linked to the extraordinary heatwave and high temperatures on the Pacific coast of the US and Canada. In doing so, they used generally accepted models and simulations. The team, which also included researchers from the Institute for Atmospheric and Climate Research at ETH Zurich, showed that the occurrence of this event would have been very unlikely without climate change. Furthermore, the team showed that even in today’s climate situation, the whole event had a 1 in 1,000 chance of occurring at all, and it would have been 150 times less likely that this heat wave would have occurred at all had the human factor of climate change not existed. The team’s report has been published only recently and an independent peer review is still pending. But several organizations such as NASA and the World Meteorological Organization stand behind the report.

Due to heat waves in Siberia, the number of forest and bush fires in the Russian tundra has been increasing in recent years. The video shows where the fires have raged in June and how the smoke has enveloped whole regions (red areas). Video: Copernicus.eu

But places along the Pacific coast are not the only ones in the northern hemisphere to be hit by heat waves. Temperatures in the Russian Arctic also have been well above normal for months. For example, on Kotelny Island, which is located in the Arctic Ocean, the temperature measured was almost 18°C instead of the usual scanty 1°C. And even in the interior of Siberia, temperatures are more than 15°C above average. This has already led to numerous forest and bush fires. The extent of the fires only becomes clear on satellite images, which show how far ash and smoke are drifting. According to scientists, this situation is likely to become the “new normal” in Siberia and other Arctic regions.

New heat records were also set in northern Europe. In Norway, 9 out of 11 provinces were affected by above-average temperatures during the day and night, even the northernmost regions of Finnmark and Troms. The thermometer in Finnish Lapland also rose above normal in the double-digit range. Fortunately, the temperatures were not as high as on the North American continent.

In addition to the people, who have hardly any cooling possibilities, it is above all the animals and plants that suffer from the excessive temperatures. Polar bears can only cool off in the water or on the remaining ice and snow. Musk oxen with their thick, dark fur also suffer greatly from the heat. And thick-billed murres are much more likely to die with temperatures above 21°C.

“Our results provide a strong warning: our rapidly warming climate is bringing us into uncharted territory that has significant consequences for health, well-being, and livelihoods.”

Philip et al (2021) “Rapid attribution analysis of the extraordinary heatwave on the Pacific Coast of the US and Canada June 2021”

But what is the origin of these heat waves in the first place? They are the result of a persistent northward bulge in the polar jet stream, explains Jennifer Francis of the Woodwell Climate Research Centers. “This is associated with a blocking pattern in the jet stream that has been prevalent over Scandinavia this year and has contributed to unusually warm conditions there, particularly in Finland,” states Francis in a citation by NASA Earth Observatory. The heat wave in the USA and Canada is also such a blockade, called “Omega”. This is a very slow moving high pressure system, writes the World Weather Attribution team. This per se is not an unusual meteorological phenomenon. But what caused the intensity of the heat, the researchers can not say. But they agree that such extreme events will hit the northern hemisphere, and thus the Arctic, even more frequently in the future. “Our results provide a strong warning: our rapidly warming climate is bringing us into uncharted territory that has significant consequences for health, well-being, and livelihoods.,” the team concludes in their report.

Dr Michael Wenger, PolarJournal

Link to report: Philip et al. (2021) Rapid attribution analysis of the extraordinary heatwave on the Pacific Coast of the US and Canada June 2021

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