Extract from ABC News
Thinning Arctic ice, more storms in the North Atlantic and record heat across Australia during La Niña during 2020 were some of the trademarks of the world's equal-hottest year on record, experts have warned.
Key points:
- 2020 and 2016 share the title of being the world's equal-hottest years on record
- Last year's record temperatures occurred despite La Nina
- Black Summer conditions were so extreme scientists have not been able to simulate them using computer models
The European Union's Copernicus Climate Change Service said the past six years have been the world's hottest years on record, and last year equalled 2016.
Copernicus Climate Change Service director Carlo Buontempo called for climate policy action while releasing the service's report last weekend.
"It is no surprise that the last decade was the warmest on record, and is yet another reminder of the urgency of ambitious emissions reductions to prevent adverse climate impacts in the future," he said.
Globally, 2020 was 0.6 degrees Celsius warmer than the standard 1981-2010 reference period and about 1.25C above the 1850-1900 pre-industrial period.
Danish Meteorological Institute climatologist Martin Stendel said 2020's warmth was mainly related to the Arctic.
"We have had extremely warm temperatures most of the year in the Russian Arctic, in particular, in northern Siberia," Dr Stendel said.
"The ice there has disappeared in regions where normally it should not disappear."
Record melting of sea ice in 2020 amplified already high Arctic temperatures, which in turn will lead to thinner ice in 2021.
"So it's actually having also an effect into the future," Dr Stendel said.
Climate change overriding climate variability
The record temperatures this year occurred despite the cooling effect of La Niña, according to climatologist Sarah Perkins-Kirkpatrick, from the University of New South Wales.
"2016's record temperatures were actually off the back of an El Niño year, and that's when we typically expect to see hotter than average temperatures," she said.
Dr Perkins-Kirkpatrick said towards the end of 2020 a La Niña developed when temperatures would typically be expected to be cooler than the long-term average.
"We're now reaching a point where climate change seems to be overriding climate variability," she said.
2020 was Australia's fourth-hottest year on record, 1.15°C above Australia's 1961-to-1990 average, according to the Bureau of Meteorology.
Range of conditions increasing bushfire risks
Meanwhile, Australian scientists have shown increased temperatures are not the only reason climate change is increasing bushfire risk in south-eastern Australia.
A paper published in the journal Communications Earth & Environment said rising carbon dioxide levels, rising temperatures, changing rainfall patterns and behaviour of climate drivers with increased frontal activity have all elevated bushfire risk.
Lead author Nerilie Abram said there were many things at play.
"It's not just rising temperature, it's not just parts of the country becoming drier, there's a whole range of climate factors," Dr Abram, from the Australian National University, said.
She said the Black Summer fires were driven by a confluence of long-term climate trends and two main variable climate drivers entering phases that promoted fires.
"One was the extreme positive Indian Ocean Dipole event that was up in the tropical Indian Ocean, and also a very rare sudden stratospheric warming event over Antarctica that changed the positions of the winds over Australia in the spring and the summer.
"When they all came together, we saw just how extreme the outcome can be."
The paper said fire-promoting phases of Australia's main climate drivers, El Niño/Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD) and the Southern Annular Mode (SAM), have now become more frequent than any time in the past several hundred years.
"We're loading the dice so that those types of events are going to be happening more frequently on top of our long-term climate change trends," Dr Abram said.
Bushfire scientist Hamish Clarke, from the University of Wollongong and co-author of the paper, said the Black Summer was so extreme that researchers have been unable to simulate fires of that magnitude using computer models.
"We need to bring in not just the climate science and the ecology but also the social science to really understand bushfire risk and what we can do to manage it," he said.
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