As UN researchers met virtually to finalise a major report on global warming, extreme weather events wreaked havoc in several continents. But to what extent was climate change the culprit? Attribution science may hold the answers
29th July 2021 (Taken from: #44)
An alarming question was posed this summer in the Eifel region of Germany, in Henan province in China and in Western Canada. The unsettling thought would have also crossed the minds of people across Greece and Turkey, in North Africa and in the southern United States. Faced with scenes of destruction wrought by extreme weather, people around the world wondered – is this what our future looks like?
The two highest temperatures ever reliably recorded on Earth were registered in July; Europe hit its highest ever temperature the following month. In August, it rained – rather than snowed – at the summit of Greenland’s ice sheet for the first time on record. In other parts of the world the summer heat reached previously uncharted highs – almost 50C in British Columbia, Canada, a province known for its moderate climate. Meanwhile, the gentle, undulating landscape of Eifel in western Germany was devastated by floods, while more than 300 people died in Henan province, where a year’s worth of rain fell in three days.
As director of the Red Cross Red Crescent Climate Centre in the Netherlands, Maarten van Aalst has spoken to many people on the front line of the climate emergency. “They ask me, ‘Is this a sign of a future that’s going to be worse? Or is this a random one-off?’” he says. In the hope of providing answers, a few years ago the experienced climate scientist joined the pioneering World Weather Attribution network, which assesses the degree to which individual extreme weather events are caused by climate change.
Wildfires in the Mediterranean
Wildfires take place every year in the Mediterranean, but 2021 was unusually destructive. In Algeria more than 90 people died fighting unprecedented fires in the Tizi Ouzou region, which according to experts caused more damage to forests than all the fires in the country from 2008 to 2020 combined. Wildfires also ravaged vast swathes of neighbouring Tunisia, where in August the capital, Tunis, recorded a record temperature of 49C, more than two degrees higher than the previous peak.
The fires in Turkey were the worst in the country’s history and left 1,700 square kilometres of forest destroyed. Tourists were evacuated by boat from resorts on the Mediterranean and Aegean coasts and Recep Tayyip Erdoğan’s government was criticised after it was revealed that it had no serviceable firefighting planes. More than 2,000 residents of the Greek island of Evia were evacuated by sea after fires consumed entire villages. There were also fires in California, where more than half of the 20 largest blazes on record have occurred in the past four years, and in Siberia, which had the worst fire season since records began, with more than 18 million hectares – a little less than the land area of England and Scotland combined – of forest destroyed.
Van Aalst says that wildfires are difficult to analyse because multiple factors – including human-made ones – can contribute to their ferocity. But it seems certain that they were exacerbated by the heat wave in the region, and that the heat wave was made more intense by climate change. On the same day Tunis recorded its highest temperature, a monitoring station in Sicily recorded the highest temperature in European history, 48.8C.
Last year the World Weather Attribution group analysed the 2020 Australian bushfires and concluded that they were made at least 30 percent more likely by climate change. “Because the heat was very significantly influenced by climate change we saw an increase in the overall fire risk,” says van Aalst.
Like wildfires, hurricanes happen every year, but as the planet heats up their intensity seems to be increasing. Hurricane Ida, the fifth strongest ever to hit the mainland US, killed at least 115 people in the US and Venezuela in late August and early September, and caused major damage in Louisiana, leaving around a million people, including the residents of New Orleans, without power for over a week.
On 9th August, an Intergovernmental Panel on Climate Change report, described as a “code red for humanity” by UN secretary-general António Guterres, stated that there is evidence that hurricanes are indeed becoming more intense as ocean temperatures rise due to climate change. The World Weather Attribution group didn’t conduct an analysis of Hurricane Ida, but it did study Hurricane Harvey, which wreaked havoc upon Texas in 2017. “We defined as the hazard the amount of rainfall dumped by the hurricane and looked at whether the models could properly simulate the rainfall associated with these hurricanes, and then did the statistics on how that was changing,” says van Aalst. The group concluded that climate change made the record rainfall three times more likely.
Flash floods in Germany and Belgium
In mid-July, flash floods in western Germany and eastern Belgium left more than 200 people dead. After record rainfall saw rivers in Germany burst their banks, the failure of the flood alert system was a worrying sign. If the fourth biggest economy in the world can’t successfully anticipate and prepare for extreme weather events, it doesn’t bode well for other countries.
As Germans digested shocking images of collapsed buildings and cars tossed upside-down, chancellor Angela Merkel described the situation as “terrifying”. Environment minister Svenja Schulze tweeted: “Climate change has arrived in Germany.”
In August, the World Weather Attribution initiative published its findings on the European floods. Global warming, they concluded, made this extreme weather event up to nine times more likely. Van Aalst stresses that “up to nine times” is not the same as “nine times” and that it’s possible climate change didn’t have as large an impact as some of the newspaper headlines suggested. It should still be considered a rare occurrence – the group said that in the current climate the floods were a one-in-400-year event in that particular part of Europe.
Ordinarily it would take more than a year for a peer-reviewed study of a specific weather event to be published, but time is of the essence for van Aalst and his volunteer colleagues. Using methods that combine observational data, the analysis of climate models, on-the-ground reports and research, they work around the clock to publish their findings as soon as possible.
The idea is to publish before the extreme weather event drops out of the news cycle, a period in which policymakers are more likely to come under pressure to acknowledge the threat of climate change – and more likely to do something about it. The group, which was founded by climatologists Friederike Otto and the late Geert Jan van Oldenborgh, has received criticism for the rapidity of its analyses. Van Aalst insists that they use peer-reviewed methods and that no corners are cut.
Heat waves in North America
Canada had experienced heat waves in the past – but nothing like this. Temperatures had never risen above 45C, but on 29th June, Lytton in British Columbia recorded 49.6C, over a degree higher than the record in Las Vegas, more than a thousand miles to the south. Lytton was almost entirely destroyed by wildfires a day later. Climate scientists described the unique weather in the Pacific Northwest as a ‘heat dome’, an area where static high-pressure traps hot air like a lid on a saucepan.
The ‘heat dome’ stretched down the western United States, causing hundreds more deaths in Washington and Oregon. The majority of the deceased in Canada and the US were elderly. In British Columbia’s biggest city, Vancouver, hotels became fully booked as people desperately sought air conditioning. According to a Human Rights Watch report, British Columbia did not have a heat action plan in place, and that lack of preparedness “contributed to unnecessary suffering and possibly deaths”.
Only a week after the heat wave, the World Weather Attribution network reached its verdict: the ‘heat dome’ would have been “virtually impossible without human-caused climate change”. Van Aalst, who contributed to the study, says his best guess is that the kind of heat wave experienced in the Pacific Northwest is “still extremely uncommon, but without climate change it would have been impossible”. “I’d be very surprised if we get another one like this in the coming five years,” he adds. “But we might be underestimating how quickly this is becoming more possible.”
Extreme weather attribution is a relatively new branch of climate science which has, according to Van Aalst, become much more focused on extremes. “Twenty years ago if an individual extreme [weather event] happened, the typical Met Office response would be that you can’t say anything about climate change in the context of one extreme, and you should look at the average weather over a period of 30 years. What we do is study these individual extreme events and look at how the statistics are changing based on long-term trends and our observations.”
The World Weather Attribution group’s report on the North American heatwave says that adaptation and mitigation measures are urgently needed to prepare societies around the world for a very different future. “There are going to be extreme weather shocks and surprises, and we need to have systems that anticipate things at shorter timescales,” says van Aalst. “Heat wave early warning systems don’t exist in many countries, and in many countries where they do exist the awareness of how important it is to heed those warnings and what to do when they [are given] is low.”
Van Aalst believes that more severe changes to our lives may soon be required. “There is only so much we can adapt by staying where we are and doing what we do. At some point we’ll have to move, or change our livelihoods, or radically change the way we cope with problems. We might need to move away from the coast, for example.”
In November van Aalst travelled to Scotland for Cop26, the UN’s conference on climate change. The stated objective of the Glasgow summit was to keep global warming to 1.5C above pre-industrial levels and reach net zero greenhouse gas emissions by 2050. “The nature of climate discussions, and also of a lot of the messaging, is about avoiding long-term catastrophe,” says van Aalst. “My focus at Cop26 was more about the here and now, and on balancing what we do to prevent that even more terrible future with what we need to do to cope with what’s already here.”
“As a climate scientist at a humanitarian organisation, I already feel the heat of the Canadian heat wave or the Australian bush fires,” van Aalst continues. “We see people struggling with disasters that have already become worse [due to climate change]. The reality is that we’re struggling already and we need to step up or the problem will get out of hand. We’ve seen some progress in Glasgow, but, given the scale of the problem, not nearly enough. This is the [nature of the] multilateral process: small steps. But the problem is growing faster than our solutions.”
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