Human-induced climate change is amplifying natural weather events, leading to heat waves that are scorching Asia, Europe and North America, and this could make 2023 the hottest year since records began to be kept, scientists say.

Here, experts explain how 2023 could be so hot and warn that these record temperatures will worsen even if humanity sharply reduces emissions of planet-warming gases.

EL NINO AND MORE

After a record warm summer in 2022, this year the Pacific warming phenomenon known as El Nino returned and warmed the oceans.

"This may have provided some additional warmth to the North Atlantic, but this is probably only a small part of the effect, as the El Nino event has only just begun," Robert Rohde of the US temperature monitoring group Berkeley Earth said in an analysis.

The group calculated that 2023 has an 81 per cent chance of being the warmest year since thermometer records began in the mid-19th century.

DUST AND SULPHUR

Warming in the Atlantic may also have been exacerbated by a reduction in two substances that typically reflect sunlight away from the ocean: dust blowing in from the Sahara desert and sulphur aerosols from ship fuel.

Rohde's analysis of temperatures in the North Atlantic region noted that "dust from the Sahara has been at exceptionally low levels in recent months".

Karsten Haustein of Germany's federal Climate Service Centre said this was due to unusually weak Atlantic trade winds.

Meanwhile, new maritime restrictions in 2020 reduced emissions of toxic sulphur. "This does not explain the entire current North Atlantic increase, but it may have increased its severity," Rohde said.

STATIONARY ANTICYCLONES

Warming oceans are influencing weather patterns on land, causing heatwaves and droughts in some places and storms in others. Richard Allan, professor of climatology at the University of Reading, said the warmer atmosphere absorbs moisture and dumps it elsewhere.

Scientists have drawn attention to the length and intensity of persistent anticyclone systems that cause heat waves.

"Where areas of stagnant high pressure persist over continents, the air sinks and warms, melting clouds, causing the intense summer sun to scorch the land, heating the ground and the air above," Allan said, adding that heatwaves "stay in place" for weeks.

"In Europe, the hot air from Africa is now staying in place and high pressure conditions mean that the heat from the warm sea, land and air continues to increase," added Hannah Cloke, a climate scientist at the University of Reading.

THE ROLE OF CLIMATE CHANGE

Climate change has made deadly heatwaves "more frequent and more intense in most land areas since the 1950s", scientists at the Intergovernmental Panel on Climate Change (IPCC) said in their global summary report this year.

Robert Vautard, director of France's Pierre-Simon Laplace climate institute, said this month's heatwaves were "not a single phenomenon, but several phenomena acting simultaneously". "But they are all amplified by a single factor: climate change."

Higher global temperatures are making heatwaves longer and more intense. Although it is the main driver, climate change is a variable that humans can influence by reducing emissions from fossil fuels.

"We are moving out of the usual and well-known natural oscillations of climate and into more unexplored and more extreme regions," said Melissa Lazenby, senior lecturer in climate change at the University of Sussex.

"However, we have the ability to reduce our human impact on climate and weather and not create more extreme and prolonged heatwaves."

HEAT PREDICTION

Berkeley Earth has warned that the current El Niño could make the Earth even hotter in 2024. The IPCC said that while governments could limit climate change by reducing countries' greenhouse gas emissions, heatwaves risked becoming more frequent and intense.

"This is just the beginning," said Simon Lewis, chair of global change science at University College London.

"Deep, rapid and sustained cuts in carbon emissions to net zero could halt warming, but humanity will have to adapt to even more severe heatwaves in the future."

 

Source: https://www.sciencealert.com/