Warning signs: Coral bleaching on the Great Barrier Reef. Photo: Eddie Jim An infrared image of the category-5 strength Tropical Cyclone Fantala, described as the most powerful storm recorded in the Indian Ocean. Photo: Joint Typhoon Warning Centre
93 per cent of Great Barrier Reef hit by coral bleaching
The Earth sizzled in March with the most unusually warm month in recorded history as average land surface temperatures easily exceeded levels deemed by scientists to constitute dangerous climate change.
The abnormal weather has continued into April as the most powerful tropical cyclone ever recorded in the Indian Ocean dumped rain at rates reaching 300 mm an hour, and Australian scientists declared the worst coral bleaching event ever on the Great Barrier Reef.
Combined global land and sea-surface temperatures in March were 1.22 degrees above the 20th-century average, beating the previous record for the month – set just a year earlier – by almost one-third of a degree, the US National Oceanic and Atmospheric Administration said. Each of the past 11 months have now broken global temperature records, the longest such streak in the agency’s 137 years of data collection.
Land surface temperatures for March, though, were 2.33 degrees above the 20th-century average, smashing the previous March record set in 2008 by 0.43 degrees. It was also the most unusually warm reading for any month, eclipsing February, NOAA said.
The record breaking conditions come as leaders of 150-plus nations are due to gather in New York this week to ratify the global climate pact agreed in Paris in late 2015 to limit global warming to 1.5-2 degrees, compared with pre-industrial times.
Australia has pledged to cut emissions by about 19 per cent from 2000 levels.
While March is just one month, the record warmth is a reminder of how much land temperatures are warming, David Karoly, a climate researcher at Melbourne University, said.
“Most people are not fish, most people live on land,” Professor Karoly said, noting that the sustained warming over land had been about 40 per cent more than over the oceans.
While the current spike in global heat can be partly explained by natural variability and the monster El Nino event now ebbing in the Pacific, humans have contributed about 1.25 degrees or more of global warming since pre-industrial times, he said.
“The extreme temperatures and extreme events, including the coral bleaching in the Great Barrier Reef, are indications that climate change is already happening with worse things in store,” Professor Karoly said.
The most abnormally hot regions of the world last month included Australia, which set a record with minimum temperatures almost 2 degrees above the average for 1961-90, while the Arctic region was about 3.3 degrees above average, NOAA said. (See chart below.)
The El Nino has played a role in boosting temperatures in the year. The stalling or reversal of equatorial trade winds in the Pacific that characterise such events created a huge pool of relatively warm water in the central and eastern Pacific that is now breaking up.
However, the first three months of 2016 were not only the warmest on record for surface temperatures by 0.28 degrees – set a year earlier – they also beat the same period in 1998 by 0.45 degrees during a similar strength El Nino, NOAA said.
For the first three months of this year, average land surface temperatures were 2.05 degrees above the 20th-century average and a full 0.95 degrees warmer than in 1998, the agency said.
Most powerful Indian Ocean storm
The list of extreme weather events this year continues to grow.
Tropical Cyclone Winston, which smashed into Fiji in February, was the strongest storm ever recorded in the southern hemisphere, CNN and others have reported.
And Tropical Cyclone Fantala has been spinning this week north of Madagascar, generating winds of 150 knots (278 km/h) and dumping rain at the rate of 300 mm an hour, US space agency NASA said.
At those speeds for sustained winds, Fantala exceeds the strength of any previous Indian Ocean storm recorded during the 26 years of reliable satellite data for the region, the Weather Underground blog run by US meteorologists said.
Temperatures around northern Australia and Tasmania have also been running at record warmth for the first three months of 2016, Australia’s Bureau of Meteorology said. (See chart below.)
The period of warmth of Tasmanian waters has also been remarkably long. Tasmania’s marine heatwave is literally off the charts https://t.co/hz2ewb598Epic.twitter老域名/p7i1lETs78— Tim Beshara (@Tim_Beshara) April 19, 2016
While Australian waters have been exceptionally warm, the country is likely to report its least active cyclone season.
Just three cyclones have been recorded in our region with less than two weeks of the season to go, compared with the previous weakest season with five, the bureau said.
The absence of such storms, which draw heat from the ocean, is one reason that the corals around much of Australia have started bleaching as temperatures exceeded stress levels, scientists said.
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