This summer has already been marked as another year with record-breaking heat right across the globe, from China to North Africa and North America to Europe.

In the past week at least 34 people died from spreading wildfires in Algeria, while in the Greek island of Rhodes thousands were evacuated due to wildfires following extreme heat. That follows China breaking heat records and the US fighting flash floods and heatwaves at different ends of the country.

But hot weather and heat waves have been around forever, and many are still asking whether human-caused climate change is responsible for this summer’s heat or whether it is part of natural climate patterns.

That question was addressed last week by a team of scientists whose research found that the role of human-caused climate change in this month’s heat has been “overwhelming”.

FactCheck takes a look.

How hot has it got?

The UN has predicted that July was the hottest single month globally since records began.

That followed on from the month before being the world’s hottest June. The month had been a full 0.5 degrees Celsius above the 1991-2020 average, breaking the previous record in June 2019.

The UN has said that the earth’s weather systems have now entered a natural climate phase called El Niño, which shifts every few years but broadly raises global temperatures when it occurs.

Is climate change behind the heatwaves?

Last week a global team of climate scientists working as the World Weather Attribution (WWA) initiative, organised by Imperial College London, said that the European and US heatwaves would have been “virtually impossible” without climate change.

The recent heatwave in China was made 50 times more likely because of climate change, the research also found.

One of the study authors, Dr Friederike Otto, said their results are “not surprising”.

“The world hasn’t stopped burning fossil fuels, the climate continues to warm and heatwaves continue to become more extreme. It is that simple,” she said.

The study itself is not peer-reviewed, but the findings were made using computer models to compare this month’s weather data to that of the past using peer-reviewed techniques. The WWA initiative was set up to rapidly assess weather events and work out the role human-induced climate change might have played in them.

The latest report said that these heatwaves are no longer rare, and within decades will be expected to take place every two to five years if global average temperatures rise to just 2 degrees above the level they were before the industrial revolution in the nineteenth century.  That’s made all the more startling when we consider that the world is currently on track for well over 2.5 degrees warming by the end of the century, according to the UN’s Environment Programme.

The WWA research said that the natural El Niño phenomenon may have, in some instances, made the extremes worse — but that the primary driver of them was human-caused climate change.

The study aligns with broad scientific projections on heat events in a warming world. The world’s leading climate scientists working under the UN have said that human-caused climate change will make heat extremes on land more frequent, more intense and longer lasting.

The group only assesses events where there is sufficient data to analyse, and at times has said why it could not assess events due to limited data.

In this work on recent heatwaves, the researchers noted that the data analysed was less comprehensive than for other studies, which may have impacted its findings.

But it noted that “based on past experience in similar studies the effect on the overall result is likely to be small”.

Dr Otto said: “These heatwaves are not evidence of ‘runaway warming’ or ‘climate collapse.’ We still have time to secure a safe and healthy future, but we urgently need to stop burning fossil fuels and invest in decreasing vulnerability. If we do not, tens of thousands of people will keep dying from heat-related causes each year.”

Is climate change behind the fires?

The WWA research was about the heatwaves and did not look specifically at the link between the climate crisis and the recent wildfires themselves.

There have been media reports that some of the European wildfires were started by arsonists, though this has not yet been verified by officials.

However, arson would not be out of step with known research on wildfires.

Wildfires are often ignited by humans — either through electrical problems in homes, abandoned barbecues and cigarettes or other activities — but also occur naturally through lightning strikes.

The global picture of frequency of wildfires is complex, due to a lack of consistent measurements internationally. But regardless of the number of wildfires there are, there is clear data from the UN which shows that the amount of time they burn, the area they destroy and their severity are all increasing.

So, regardless of whether a wildfire is ignited by arson or lightning, climate change is creating the conditions for fires to be much more destructive. This is what scientists often mean when they say that the climate crisis is making wildfires worse.

Professor Guillermo Rein from Imperial College London told the Science Media Centre that hot weather makes fires more likely to ignite and then worsen, as it makes vegetation “very flammable and “easier to catch fire”.

“A heat wave or an unusually hot summer leads to even more flammable forests. Strong winds greatly accelerate wildfire,” he said. “The combination of wind and dry vegetation makes wildfires much faster. They become walls of flames that cannot be stopped by ground crews or slowed down by air tankers.”

Dr Douglas Kelley from the UK Centre for Ecology & Hydrology said to the Science Media Centre that while it’s “too early” to directly link climate change to these latest fires in the same way the WWA research did with heatwaves.

But he added: “The fact there are now so many across the world, most recently in Greece and Canada, is a clear sign that climate change is causing an increase in the number of severe wildfires globally.”