Temperatures have rocketed throughout the northern hemisphere DENIS CHARLET/AFP/Getty Images

The current heatwave in northern Europe was made twice as likely by climate change, according to a preliminary analysis.

Temperatures have soared over much of Europe over the last month, regularly exceeding 30°C and several temperature records have been broken. The conditions have been so extreme that wildfires have broken out in Sweden and the UK.

Heatwaves are one of the most likely consequences of climate change. As the average global temperature rises due to higher levels of greenhouse gases, more extreme bouts of high temperatures follow.


But heatwaves do happen anyway. To find out if the current heatwave was made more likely by climate change, a team at World Weather Attribution led by Friederike Otto of the University of Oxford, UK has conducted a rapid-response study.

Extreme heat

They ran climate models with and without our greenhouse gas emissions and tracked how often heatwaves like the current one occurred in both cases.

“We estimate that the probability to have such a heat or higher is generally more than two times higher today than if human activities had not altered climate,” the team reports.

The intensity of the climate effect varies somewhat from country to country. “In Ireland and Denmark climate models give a very similar increase in probabilities to the observations — roughly a factor two more likely in Dublin and a factor four in Denmark,” the team writes.

The team was unable to put a figure on the increase in the risk of heatwaves in Scandinavia, because summer temperatures that far north are very variable anyway. They “can conclude that anthropogenic climate change increased the odds of a heat wave as observed in 2018 in Scandinavia but we cannot quantify by how much”.

“We have to be a bit more sceptical of studies like this that haven’t gone through rigorous peer-review,” says Michael Mann of Pennsylvania State University. “But these findings are consistent with a broader body of work indicating a profound impact of climate change on precisely these sorts of events.”

The new normal

“This analysis confirms what we already know – that we are suffering an extreme weather event caused by climate change,” says Gareth Redmond-King, a climate change specialist at WWF. “World leading academics are warning us that, like a disaster movie, this is going to get worse and we know this will impact our nature, wildlife, people and food supplies. We urgently need ambitious action to cut our emissions and to build a cleaner, greener economy to tackle climate change before we pass the point of no return that we are so very near.”

The team estimates that similar heatwaves will return soon. In particular, comparable heatwaves will now strike Dublin and the Netherlands every four to seven years in the current climate – “even though they are close to record-high compared to earlier climates”.

“In fact, I think that these sorts of analyses are overly conservative,” says Mann.

He says this summer’s extreme weather in the Northern Hemisphere is related to a near-stationary perturbation in the jet stream. Such patterns have been implicated in “many of the most extreme, persistent summer weather events in recent years, including the 2003 European heat wave, 2010 Moscow wildfires, 2011 Texas and Oklahoma drought [and the] 2016 Alberta wildfires.”

In a study published last year, Mann and his colleagues showed that such patterns are becoming more common as a result of human-caused climate change (Scientific Reports, doi.org/f9vwxh). Mann says the “amplified warming in the Arctic” seems to be a major contributor.

“Events like the massive wildfires breaking out around the Arctic Circle really have no precedent in modern history and they are consequently very difficult to anticipate in advance,” says Mann. “It is a reminder that there are many surprises lurking in the greenhouse and they are unlikely to be welcome surprises.”

Weather forecasts could soon include information about whether specific dangerous weather events are made more likely by climate change.

Beyond that, we need to “Act. On. Climate,” says Mann. That means “individual actions and, even more importantly, governmental policies to incentivise a rapid shift away from the source of the problem – fossil fuels – toward renewable energy. It’s a win-win-win-win on climate, energy, the economy and the planet.”