Extract from ABC News
This year could be a watershed moment in Earth's climate history.
Major global climatological records are breaking at a rapid rate, a trend likely to continue during the coming years as the world's oceans and atmosphere rebound sharply following a triple La Niña.
This year has already produced record-high global ocean temperatures and record-low Antarctic sea ice. And in recent weeks, a sudden surge of record-high air temperatures could propel 2023 to become the warmest year on record.
2023 heating up rapidly
Global air temperatures have been well above the baseline average all year, building a platform to challenge the current annual record from 2016.
Data from National Oceanic and Atmospheric Administration [NOAA] shows the year-to-date ranking for 2023 is currently 4th (behind 2016, 2017 and 2020).
While May was globally the second or third warmest on record — depending on the dataset used — preliminary data for June shows the world's air temperature has been at record-high levels.
June 10 set a new mammoth record 0.4C above the previous record on this day, at 16.8C.
As the Pacific transitions from La Niña to El Niño, this year's ranking will climb.
And based on historical figures of how El Niño years evolve, 2023 could finish as the warmest year on record, passing the current warmest year of 2016.
"In recent moderate to strong El Niño events (2015, 2009, 1997), the eventual annual temperature was 0.05 - 0.10C warmer than the January-May values," Bureau of Meteorology senior climatologist Blair Trewin said.
"A similar outcome in 2023 would see the 2016 record surpassed."
Oceans simmer through record-warm April and May
While air temperatures have only just started reaching unprecedented levels, satellite data shows 2023 has already seen an extended run of record-warm global ocean temperatures.
"April and May global sea surface temperatures [SST] were the warmest on record for their respective months," Mr Trewin said.
"For the year-to-date [January to May] global SST has been the third-warmest on record, just behind 2019 and 2020."
June is also on track to break a monthly record, as daily values have been running at a staggering 0.2C above the previous global high.
The trend shows no sign of slowing, with this year likely to be the warmest on record for our oceans.
This is a somewhat surprising result, as historically the rebound from cooler La Niña years has not occurred so rapidly.
"Historically, following La Niña events, ocean and global air temperatures have been relatively cool," Mr Trewin said.
"However, for global SST, the seven warmest years on record are the seven years since 2016.
"Increasing surface temperatures mean a La Niña year now is warmer than an El Niño year in the 1980."
Antarctic sea-ice shrinking
One of the major impacts of the warm oceans is the lack of sea-ice forming around Antarctica.
This summer, the minimum amount of sea-ice was recorded at a new low, while the waters surrounding Antarctica are failing to freeze at the usual rate heading into winter.
The current deficit of ice for mid-June is close to 1 million square kilometres, larger than New South Wales, and would have a probability of occurring randomly one in every thousand years.
"We can confirm that the sea-ice extent is the lowest on record," Mr Trewin said.
He said it was about four standard deviations below the long-term mean.
The lack of ice marks a dramatic shift from the trend during recent decades when Antarctic sea-ice had not displayed a climate change driven reduction, similar to that observed around the North Pole.
Mr Trewin is confident the warmer waters are responsible, as they move south "across the Antarctic Circumpolar Current in the southern Indian, south-west Pacific and southern Atlantic" oceans.
"A more saline ocean mixed layer may also be involved."
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