Climate change drove record levels of global humidity in 2024, posing a rising risk to people’s health, a new report has warned.
The latest “State of the Climate” report published by the Bulletin of the American Meteorological Society (BAMS) found 2024 set new records for levels of water vapour in the atmosphere and the number of humid days.
Climate change is driving the increased humidity, as a warmer atmosphere can hold more moisture.
And when combined with rising temperatures – with 2024 recording record heat globally – the increase in hot, humid conditions is bringing more people into “potentially life-threatening situations,” experts have warned.
People find it harder to cool down in hot and humid conditions because sweating is less effective than in dry heat, and continued physical activity during high humid heat can lead to serious health issues, the experts warn.
Dr Kate Willett of the Met Office, who is one of the report’s editors, said: “Human health can be seriously affected by high heat and humidity.
“Such a dramatic increase in the occurrence of these humid heat events is bringing more societies into challenging, potentially life-threatening, situations.
“Our report found that it’s not just high temperatures that people are having to contend with, it’s also humidity; with the frequency of high humid heat days at a record level, and intensity of those days at the second-highest level in the record, only fractionally cooler than 2023.”
The State of the Climate report showed the amount of water in the atmosphere hit record levels over both land and ocean, with almost 90% of the atmosphere wetter than the 1991-2020 average.
And the global average number of high humid heat days reached a record of 35.6 days more than normal in 2024, scientists said.
The report also highlights last year was the hottest year on record globally, and the 10th consecutive year that was more than 1C above pre-industrial levels, while the last 10 years have been the hottest 10 years on record.
In 2024, sea surface temperatures were at their highest in records dating back 171 years, and marine heatwaves were observed over more than nine tenths (91%) of the world’s oceans.
All 58 reference glaciers lost more ice than they gained in 2024, in only the second year this has happened, while Colombia’s Conejeras glacier was declared extinct, and all of Venezuela’s glaciers have officially disappeared.
It was the wettest year for extreme rainfall on record, while there was also no let up in the increase in climate-warming pollution, with the main gases carbon dioxide, methane and nitrous oxide all hitting new highs in the atmosphere, the study found.
Professor Stephen Belcher, Met Office chief scientist, said: “The changes to global climate highlighted in the BAMS State of the Climate report indicates the need for deep, rapid and sustained reductions in greenhouse gas emissions from burning fossil fuels in order to limit warming as much as possible, alongside scaled up adaptation action to protect societies and nature already exposed to impacts from record breaking extremes.”
