World experiences hottest May on record, extending exceptional 12-month streak

Temperatures were more than 1.5°C higher than the period before people started burning fossil fuels

Volunteers distribute cold drinks to bypassers at a 'heatwave relief camp' along the road during a hot summer day in Lahore in May. AFP

The world just experienced its hottest May on record, extending an exceptional 12-month streak in which every month the temperature reached a new high, according to European Union's climate change monitoring service.

Copernicus Climate Change Service said the global average temperature for the month was 0.65°C above the 1991–2020 average and 1.52°C higher than the 1850-1900 period before people started burning fossil fuels. That marks the 11th consecutive month the world has breached the so-called “stretch target” threshold set by the Paris Agreement to limit the deadliest effects of climate change.

The month saw several countries experience temperatures of over 40°C for a period, with heatwaves affecting countries including Israel, Palestine, Lebanon and Syria and large regions of Asia.

The global average temperature for the last 12 months, from last June to this May is the highest on record, at 0.75°C above the 1991–2020 average and 1.63°C higher than the 1850-1900 period before people started burning fossil fuels.

“It is shocking but not surprising that we have reached this 12-month streak,” said Carlo Buontempo, Copernicus Director.

While this sequence of record-breaking months will eventually be interrupted, the overall signature of climate change remains and there is no sign in sight of a change in such a trend.”

Over time the string of hottest months will be remembered as “comparatively cold” but if the world manages to stabilise the concentrations of greenhouse gases in the atmosphere in the very near future it might be able to return to these “cold” temperatures by the end of the century, he said.

UN Secretary-General António Guterres said every turn of the calendar for the past year has turned up the heat.

The planet is trying to tell us something, he said, “but we don't seem to be listening”.

“We’re shattering global temperature records and reaping the whirlwind. It’s climate crunch time. Now is the time to mobilise, act and deliver,” added Mr Guterres.

It comes after the UK’s Met Office confirmed that the country had its warmest May and spring on record, with an average temperature of 13.1°C for the UK, beating the previous record in 2008 by a full 1°C, making it the warmest May in records dating back to 1884.

The Met Office said the month's high average temperatures were influenced particularly by warm conditions in the northern half of the UK, and by high overnight temperatures.

Meteorological spring, which covers the months of March, April and May, was also the warmest – and one of the wettest, on record, the figures show.

It was the sixth wettest on record, and the wettest since 1986, with an average of 301.7mm of rain in March, April and May, almost a third, or 32 per cent, more than usual for the season.

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El Nino

El Nino, the natural weather phenomenon that contributed to 2023 being the hottest year on record, has recently subsided, paving the way for its opposing, cooling La Nina phase to begin.

But in the context of a warming planet due to human-caused climate change, scientists say that cooling effect may be miniscule.

El Nino can weaken consistent trade winds that blow east to west across the tropical Pacific, influencing weather by affecting the movement of warm water across this vast ocean. This weakening warms the usually cooler central and eastern sides of the ocean, altering rainfall over the equatorial Pacific and wind patterns that change temperature and rain around the world.

The extra heat at the surface of the Pacific releases energy into the atmosphere that can temporarily drive up global temperatures, which is why El Nino years are often among the warmest on record.

It occurs every two to seven years, and lasts nine to 12 months.

The latest El Nino, which began in June 2023, peaked among the five strongest such events on record, according to the World Meteorological Organization.

Although El Nino has been dissipating, the first four months of 2024 have continued to break heat records - unsurprisingly as the cycle typically drives up temperatures the year after it develops.

The El Nino-Southern Oscillation (ENSO) is "not an on-off switch", said said Michelle L'Heureux, lead ENSO forecaster for the US NOAA weather agency. "It takes a while for the global atmospheric circulation to adjust."

Scientists anticipate that the neutral period between the two cycles will begin between May and July.

Above-normal temperatures are forecast to persist through July across the northern and southern hemispheres, with just equatorial regions anticipated to see near-to-below normal temperatures, according to WMO.

La Nina sees the eastern Pacific Ocean cool for a period of about one to three years, generating the opposite effects to El Nino on global weather.

It leads to wetter conditions in parts of Australia, southeast Asia, India, southeast Africa and northern Brazil, while causing drier conditions in parts of South America.

It can also contribute to more severe Atlantic hurricanes, and NOAA has forecast an "extraordinary" storm season ahead this year.

La Nina tends to bring down global temperatures, although Ms L'Heureux warned against hopes of relief in areas like southeast Asia that have recently be battered by scorching heatwaves.

"The world is warming and ENSO is acting secondary to that," she said.

"Even this year with La Nina potentially developing, we're still expecting basically a top-five global mean temperature record," she said.

NOAA says there is a 69 percent chance of La Nina beginning sometime between July and September.