Heatwaves: Why this summer has been so hot

It is hot. Very hot. And we are only a few weeks into summer. Texas and
part of the south-west of the US are enduring a searing heatwave. At one
point, more than 120 million Americans were under some form of heat
advisory, the US National Weather Service said. That is more than one in
three of the total population.

In the UK, the June heat didn’t just break
all-time records, it smashed them. It was 0.9C hotter than the previous
record, set back in 1940. That is a huge margin. There is a similar story
of unprecedented hot weather in North Africa, the Middle East and Asia. No
surprise, then, that the European Centre for Medium-Range Weather forecasts
said that globally, June was the hottest on record. And the heat has not
eased. The three hottest days ever recorded were in the past week,
according to the EU climate and weather service, Copernicus.

These highs are in line with what climate models predicted, says Prof Richard Betts, climate scientist at the Met Office and University of Exeter.

“We should not be at all surprised with the high global temperatures,” he says. “This is all a stark reminder of what we’ve known for a long time, and we will see ever more extremes until we stop building up more greenhouse gases in the atmosphere.”

When we think about how hot it is, we tend to think about the air temperature, because that’s what we experience in our daily lives.

But most of the heat stored near the surface of the Earth is not in the atmosphere, but in the oceans. And we’ve been seeing some record ocean temperatures this spring and summer.

The North Atlantic, for example, is currently experiencing the highest surface water temperatures ever recorded.

That marine heatwave has been particularly pronounced around the coasts of the UK, where some areas have experienced temperatures as much as 5C above what you would normally expect for this time of year……………………………………………………………

Most of the extra heat trapped by the build-up of greenhouse gases has gone into warming the surface ocean, he explains. That extra heat tends to get mixed downwards towards the deeper ocean, but movements in oceans currents – like El Niño – can bring it back to the surface.

“When that happens, a lot of that heat gets released into the atmosphere,” says Prof Lenton, “driving up air temperatures.”

It’s easy to think of this exceptionally hot weather as unusual, but the depressing truth is that climate change means it is now normal to experience record-breaking temperatures.

Greenhouse gas emissions continue to increase year on year. The rate of growth has slowed slightly, but energy-related CO2 emissions were still up almost 1% last year, according to the International Energy Agency, a global energy watchdog.

And the higher the global temperature, the higher the risk of heatwaves, says Friederike Otto, a climatologist at the Grantham Institute of Climate Change at Imperial College London.

“These heatwaves are not only more frequent, but also hotter and longer than they would have been without global warming,” she says.

Experts are already predicting that the developing El Niño is likely to make 2023 the world’s hottest year.

They fear it is likely to temporarily push the world past a key 1.5C warming milestone.

And that is just the start. Unless we make dramatic reductions to greenhouse gas emissions, temperatures will continue to rise.

The Met Office said this week that record June temperatures this year were made twice as likely because of man-made climate change.

These rising temperatures are already driving fundamental and almost certainly irreversible changes in ecosystems across the world………………………………….

The world is effectively in a race.

It is clear we are speeding towards an ever hotter and more chaotic climate future, but we do have the technologies and tools to cut our emissions.

The question now is whether we can do so rapidly enough to slow the climate juggernaut and keep the impacts of global warming within manageable boundaries.

BBC 9th July 2023https://www.bbc.com/news/science-environment-66143682