This year is now almost certain to become Earth's warmest on record after a hot July and August saw global temperatures reach the Paris Agreement target of 1.5 degrees Celsius above pre-industrial levels for the first time.
Data released last week from Copernicus, a branch of the European Union Space Programme, shows August was 1.59C warmer than 1850–1900 levels, following a 1.6C increase in July.
The recent records have now lifted the year-to-date global temperature to the end of August to 1.35C above pre-industrial levels, just 0.01C behind 2016 — the current record holder, according to Copernicus data.
While the latter months of 2016 cooled off, global temperatures this year have been building, a trend likely to continue as El Niño develops further.
This upward swing should ensure 2023 becomes the new warmest year on record, an assessment shared by the Bureau of Meteorology's senior climatologist Blair Trewin.
"If current 2023 temperature anomalies are maintained, or increase, over the last four months of the year that would be sufficient for an annual record to be set," he said.
On September 8, a separate database of global temperature run by the US government already had 2023 slightly ahead of 2016 by 0.04C.
And the gap is only likely to grow in the following months considering how El Niño years evolve.
Watershed year in Earth's climate history
It's not just air temperatures at unprecedented levels this year.
- Major global climatological records have fallen at a rapid rate across the Earth's atmosphere, hydrosphere and cryosphere, including:
- Record-high monthly air temperatures in June, July and August
- All-time record daily air temperature, passing 17C for the first time
- Record-low Antarctic sea ice in May, June, July and August
- Record-high monthly ocean temperatures in April, May, June, July and August
- All-time record daily ocean temperature, passing 21C for the first time
The world's waters have been so warm in 2023 that seven out of a possible eight months have entered the top 30 warmest on record, including four of the top five.
The cause of 2023's sudden spike in heat is not as simple as climate change plus El Niño, but rather the timing of El Niño immediately after three consecutive La Niña years.
"A large part of it is the removal of the cooling influence of La Niña which has been suppressing global temperatures over the last two to three years," Mr Trewin said.
"On decadal timescales, global temperatures are warming at about 0.20-0.25 degrees per decade, which means that 'baseline' temperatures now are around 0.15 degrees warmer than they were when the 2016 record was set."
History tells us 2024 will be warmer
The warmest year in an El Niño cycle is the second, implying next year will be even warmer.
Out of the past 15 El Niño episodes, 13 saw a rise in global temperatures in the second year, including year-on-year rises of 0.27C and 0.25C in 1997 and 2015.
A similar rise would cause 2024 to become the first year to temporarily pass the Paris Agreement target of 1.5C, and Mr Trewin is confident next year will follow the historic trend.
"In the 1997-98 and 2015-16 El Niño events, the first year of each event set a global temperature record, but that record was broken by a significant margin the following year," he said.
"Early 2023 also had some residual cooling influence from La Niña, which will be absent from at least the early months of 2024."
For Australia, there is every chance this spring and summer will challenge records and it's an almost certain temperatures will be above the past three years.
By Tom Saunders
Original article link here: https://www.abc.net.au/news/2023-09-11/global-temperatures-pass-1-5c-above-pre-industrial-levels/102836304
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