Record temperatures across much of the world over the past two weeks could make July the hottest month ever measured on Earth, according to climate scientists.
The past fortnight has seen freak heat in the Canadian Arctic, crippling droughts in Chennai and Harare and forest fires that forced thousands of holidaymakers to abandon campsites in southern France and prompted the air force in Indonesia to fly cloud-busting missions in the hope of inducing rain.
If the trends of the first half of this month continue, it will beat the previous record from July 2017 by about 0.025C, according to calculations by Karsten Haustein, a climate scientist at the University of Oxford, and others.
This follows the warmest-ever June, which was confirmed this week by data from the US space agency Nasa, following Europe’s Copernicus satellite monitoring system.
In response to the new numbers, Michael Mann, the director of the Earth System Science Center at Pennsylvania State University, tweeted: “This is significant. But stay tuned for July numbers. July is the warmest month of the year globally. If this July turns out to be the warmest July (it has a good shot at it), it will be the warmest month we have measured on Earth.”
The scientists stressed that this outcome is uncertain because conditions could change in the second half of the month, but it underscores a broader pattern of steadily rising temperatures caused by increasing emissions of carbon dioxide from power plants, deforestation, cars, planes and other sources.
Mann estimated the chance of a new record this month at about 50%. In the longer term, he said records would continually be broken. “We have shown in recent work that the record warm streaks we’ve seen in recent years cannot be explained without accounting for human-caused planetary warming. Those warm streaks are certain to not only continue but to worsen if we continue to burn fossil fuels and warm the planet.”
Nine of the 10 hottest years on record have occurred since 2000, according to the US National Oceanic and Atmospheric Administration. Data from the first six months of this year indicates this year has a 99.9% chance of entering the top five, according to Gavin Schmidt.
“It is clear that 2019 is shaping up to be a top-five year – but depending on what happens it could be second, third or fourth warmest. The warmest year was 2016, which started with a big El Niño, which we didn’t have this year, so a record year is not particularly likely,” he said.
Quick GuideHow global heating is causing more extreme weather
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Greenhouse gas emissions from burning fossil fuels, forest destruction and other human activities are trapping heat and putting more energy into the climate system.
Hotter air means heatwaves are much more likely. For example, scientists now say the unprecedented heat and wildfires across the northern hemisphere in 2018 “could not have occurred without human-induced climate change”. In Australia, the scorching summer of 2016-17 in New South Wales was made at least 50 times more likely by global heating, linking it directly to climate change.
Hotter air can also carry more water vapour, meaning more intense rain and more flooding.
Another important factor in the northern hemisphere is the impact of changes in the Arctic. The polar region is heating more rapidly, reducing the temperature difference with lower latitudes. There is strong evidence that this is weakening the planetary waves (including the jet stream) that normally meander over Europe, Asia and North America.
When these waves stall, weather gets fixed over regions and becomes extreme. This has been linked to past floods in Pakistan, heatwaves in Russia and drought in California.
Most of the planet’s trapped heat goes into the oceans and rising sea temperatures mean more energy for hurricanes and typhoons. The deluge delivered in the US by Hurricane Harvey in 2017 was made three times more likely by climate change. Rising sea level also means storms cause more coastal damage.
Natural variability would cause some extreme weather, even without global heating, but human impacts on the climate make such extremes more likely. Carbon Brief analysed more than 230 studies and found 95% of heatwaves were made more likely or worse by climate change. For droughts, 65% were definitely affected by our hotter world, while the figure for floods was 57%.
Of the many recent temperature anomalies, perhaps the most remarkable was in the Canadian Arctic community of Alert, Nunavut, which hit a record 21C on 14 July, although temperatures at this time of year are usually just a few degrees above freezing.
Last month, France shattered its previous heat record during a heatwave across much of Europe that was made at least five times – and possibly hundreds of times – more likely by human-driven climate disruption, according to scientists.
Political leaders have failed to halt the rise in emissions that is behind global heating. On Tuesday, the UK environment secretary, Michael Gove, warned that time was running out to prevent a breakdown of the climate and natural life support systems. “These twin challenges of biodiversity and climate change are massive and urgent and interrelated. The action taken so far hasn’t been sufficient, but late as it may be, there is still time,” he warned. “The scale of action required may be daunting, but the need to act is imperative.”
The UK has avoided most of the extreme heat seen in Europe in elsewhere in recent weeks. The average temperature in the first two weeks of July was 15.1C, which equals the July average, though Mark McCarthy, the head of the Met Office’s National Climate Information Centre, said there might be a modest rise because the second half of the month is usually marginally warmer than the first.
Concerns about rising temperatures and their impact on health are growing. On Tuesday, the Red Cross launched a new Heatwave Guide to help urban planners and city authorities reduce the risks, which are particularly great for the elderly, very young children, pregnant women and people who are socially isolated.
“Heatwaves are one of the deadliest natural hazards facing humanity and the threat they pose will only become more serious and more widespread as the climate crisis continues,” said Francesco Rocca, the president of the International Federation of Red Cross and Red Crescent Societies.
Previous heatwaves have killed tens of thousands of people, including 2,500 in India in 2015 and 70,000 in Europe in 2003, according to the Red Cross.