Enlarge /. Average temperatures from March 19 to June 20.
In general, 2020 was a damn good year. In Siberia, however, there is another reason to make comparisons with the inferno: record warmth and its consequences. Forest fires have burned approximately 8,000 square miles, supported by a pod of silk moths that consume the needles of conifers. Falling permafrost also contributed to massive diesel pollution when a tank burst on unstable ground.
The immediate cause of this extreme year was last winter's jet stream pattern, which kept Siberia mild from late winter to spring, melted ice and snow early, and further increased warmth. Then, in June, there was a persistent high pressure when a wiggle of the jet stream north brought warmer air from the south to Siberia. During this heat wave, the Russian city of Verkhoyansk apparently reached 38 ° C – a premiere for every station above the Arctic Circle.
As with many extreme weather events in recent years, a team of scientists has done a quick analysis of the role of climate change in all of this. The researchers analyzed both the record temperature and warm temperatures from January to June across the region and concluded that "in both cases, this event would have been effectively impossible without man-made climate change."
These researchers, organized as part of the World Weather Attribution project, have standardized their approach to these analyzes. This enables them to work incredibly quickly – sometimes only a week after an event – and gives their results, which are also presented to scientific journals for the slow process of peer review, a certain amount of trust.
The question with every weather event is not really: "Did climate change cause this?" but how likely it is that climate change has contributed to its severity. In order to answer this, the weather records in this area must usually be examined for trends and climate model simulations carried out with and without human activities.
The team first analyzed the six-month period for the entire Siberian region, which was slightly above 5 ° C above the 1981-2010 average. Because of the warming trend there, the scientists found that this warm stretch is still unusual – probably less than an event that happened once in a century. But it's far more likely now than 1900. Simulations from dozens of models matched, albeit with a variety of accurate estimates. The team conservatively focuses on the lower end of the range of all these estimates and concludes that the 2020 event is at least 600 times more likely than the 1900 climate. That may sound dramatic, but remember it is the low end. The average estimate was actually a factor of 99,000 increase in probability.
In other words, a similarly rare event in the 1900 climate would have been about 2.5 to 3.5 ° C (4.5 to 6 ° F) cooler and would have only reached about 2 ° C on average from 1981 to 2010.
The situation is similar with the record temperature in Verkhoyansk on June 20 (which has been verified by the Russian weather service but not yet by the World Meteorological Organization). Verkhoyansk has had a weather station since 1869, but since there are gaps in the data before 1926, the analysis starts there.
Because it is a single station, the limited number of data points causes the error bars in estimates to skyrocket. Given the warmest June temperatures in climate model simulations, the increase in the probability of June temperatures is essentially infinite. Researchers return to the lowest estimates again and find that global warming has made this event “more than a thousand times more likely”.
This is strikingly high compared to analysis of other heat waves. For example, last year's European heat wave seemed about 100 times more likely in the current climate.
To see what these events could look like with a few more decades of high greenhouse gas emissions, the researchers have extended the calculations of the climate model into the future. As is to be expected, the already sensational numbers will become even more extreme by 2050. The warmth that Siberia experienced from January to June is growing to about 160 million times more likely than 1900. And an event with The rarity of 2020 would be another 2 ° C and 7 ° C above the 1981-2010 average .
Simply put, these record-breaking temperatures have been clearly increased by global warming. This fits in with the knowledge that heat waves are one of the extreme weather events that increase most sharply due to climate change.
Team member Friederike Otto said in a press release:
This study again shows how much climate change is changing in relation to heat waves. Given that heat waves are by far the deadliest extreme weather events in most parts of the world, they must be taken very seriously. As emissions continue to rise, we need to think about strengthening our resistance to extreme heat around the world, even in arctic communities – which would have been nonsensical not long ago.