Scientists said that this year was on track to become the warmest on record as the global surface air temperatures breached the threshold of 1.5C for each of the past 12 months and seas had reached their warmest for 15 months in a row.
June was the 13th consecutive month to be the hottest on the books, the Copernicus Climate Change Service said. At a surface air temperature of 16.66C, this was 0.14C above the previous June high set last year.
This was despite the early signs of the naturally occurring La Niña cooling weather phenomenon in the Pacific Ocean, which takes over from the El Niño warming effect.
“We have had six months now [in 2024] and each one of them has been record-breaking,” said Carlo Buontempo, director of CCCS. “So, in order for 2024 not to be record-breaking, we need to have [an] incredibly large negative anomaly for the remaining six months, which is unlikely.”
The only other time where monthly surface air temperature records have stretched to such a long period was during 2015-16, when each one of 15 months was the hottest — although from a lower base.
The global average temperature for the past 12 months was 1.64C above the 1850-1900 pre-industrial average, with each of the months at least 1.5C warmer than the pre-industrial average.
Buontempo said repeated months with temperatures above 1.5C was “unusual”.
“We have never seen such an anomaly,” he said, adding this was “not a good sign” for global efforts to limit temperature rises.
“At this rate of warming, we will exceed the 1.5C threshold in terms of the Paris Agreement in the early 2030s,” he said, referring to the accord agreed by almost 200 countries to limit global temperatures.
Although each of the past 12 months has been above this level, the long-term average temperature is assessed by scientists over a period of one or two decades.
The average sea surface temperature for June was 20.85C, the highest on record for the month. New daily temperature records were set for the seas from March 2023 until late June this year, when a slight cooling occurred.
This was a sign of the expected shift to La Niña, Buontempo said. “There is a cooling effect from La Niña [on sea temperatures] and that is largely expected and to a great extent anticipated. But the ocean as a whole remains very warm.”
“And while we may not understand all the reasons for [that warmth], certainly the fact that the climate is warming and keeps warming and a lot of this extra energy gets into the oceans may be part of the answer.”
The expected shift to La Niña should also lead to cooling of surface temperatures, he added. “This streak of record-breaking months will sooner or later end, hopefully sooner rather than later. But this doesn’t mean that the problem is over because, fundamentally, the climate system is warming up.”
“If our goal is to keep below 1.5C, it is not enough to hope for an end of El Niño,” he said, adding that the world needed to reduce greenhouse gas emissions from the burning of fossil fuels as soon as possible.
Copernicus said temperatures were most above average over parts of south-east Europe, the western US, Mexico, Brazil, northern Siberia, the Middle East, northern Africa and western Antarctica in June.
But conditions were wetter in Iceland, central and most of south-western Europe, with heavy rainfall leading to floods in regions of Germany, Italy, France and Switzerland.
Antarctic sea ice extent was 12 per cent below average, the second-lowest extent for June.
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