Key Points

The agency released a monthly climate bulletin on Wednesday showing a record-hot June in Western Europe, with average temperatures hitting 20.49 degrees Celsius, 2.81 degrees above the 1991-2020 norm, driven by two severe heatwaves.

"These events typically occur in mid-July or August," Julien Nicolas, senior scientist at C3S, told Xinhua news agency. "Now they're starting much earlier, which aligns with long-term warming trends."

The heatwaves, one in mid-June and another stretching from late June into early July, affected much of western and southern Europe, including Spain, Portugal, France, Italy, Germany, Austria, Switzerland and the UK.

Nicolas attributed the two rounds of heatwaves to persistent high-pressure systems, or "heat domes," which trap warm air and intensify surface temperatures under clear skies and dry conditions.

Adding to the heat was an unprecedented marine heatwave in the western Mediterranean. On June 30, sea surface temperatures averaged 27 degrees Celsius, the highest for the month on record, with a daily anomaly of 3.7 degrees, the largest ever measured in any month, according to C3S.

Nicolas noted that the Mediterranean Sea remains a "climate change hotspot," with a more rapid and persistent long-term warming trend. In 2024, the entire basin saw record sea temperatures during late summer, particularly in August. This year, however, anomalies have emerged earlier in the season and have been concentrated in the western Mediterranean.

These conditions intensified the heatwaves, particularly overnight, leading to more "tropical nights" -- when temperatures stay above 20 degrees Celsius, Nicolas added.

"Tropical nights pose serious health risks," Nicolas said, noting that elevated nighttime temperatures can disrupt sleep and prevent the body from recovering from daytime heat.

He also pointed to the role of Arctic amplification, a phenomenon in which diminishing snow and ice exacerbate warming, in altering atmospheric patterns, including the jet stream. A more meandering jet stream may contribute to prolonged and extreme weather events, Nicolas said.

Looking ahead, Nicolas said that seasonal forecasts from C3S indicate a warmer and drier-than-average summer, particularly across eastern and southeastern Europe.

"We should expect more heatwaves ... as the climate continues to warm," he said.

The climate scientist called for urgent efforts to mitigate the root causes of climate change and adapt society to cope with a warmer world and more frequent weather extremes.

"We need to tackle the source of climate warming, the continued rise in greenhouse gas emissions from human activities, and reduce emissions as quickly as possible," he said.

"Clearly, climate action is more urgent than ever," he added.

- IANS