Latest news with #ArcticSeaIce
News.com.au
a day ago
- Science
- News.com.au
‘No statistically significant decline': Arctic sea ice loss dramatically slows since 2005
A dramatic slowdown in Arctic sea ice loss over the past 20 years has been observed by scientists, who say the finding 'may sound surprising' but is consistent with human-induced global warming trends. Researchers from the University of Exeter, in a study published this month in the journal Geophysical Research Letters, analysed Arctic sea ice cover using two different datasets of satellite measurements, from 1979 to the present. 'Over the past two decades, Arctic sea ice loss has slowed considerably, with no statistically significant decline in September sea ice area since 2005,' they wrote. 'This pause is robust across observational data sets, metrics, and seasons.' Focusing on September, when sea ice cover is at its minimum, they found sea ice declined by 0.35 and 0.29 million square kilometres per decade between 2005 and 2024. Compared with the longer-term rate of decline since 1979 of 0.78 to 0.79 million square kilometres per decade, that marked a 55 per cent to 63 per cent slowdown. The 20-year period was the slowest rate of sea ice loss since records began, and four to five times slower than the peak 20-year period of 1993 to 2012. The researchers said the findings were consistent with climate models that show pauses in sea ice loss across multiple decades can happen, offset by 'natural climate variations' even as greenhouse gas emissions continue to rise. Climate models suggest the chances of such a slowdown were about 20 per cent. Comparing the current slowdown to similar pauses in model simulations, 'we see that it could plausibly continue for another five to 10 years, although the same slowdown makes a faster-than-average sea ice decline more likely in the coming years', they wrote. 'Summer sea ice conditions in the Arctic are at least 33 per cent lower than they were at the beginning of the satellite record nearly 50 years ago,' Dr Mark England, who led the study while at the University of Exeter and is now at UC Irvine, said in a statement. 'Given this — and the indisputable fact of human-driven climate change — it may seem surprising to find a temporary slowdown in Arctic sea ice loss. 'It is, however, entirely consistent with climate model simulations and is likely due to natural climate variability superimposed on the human-driven long-term trend. This is only a 'temporary reprieve' and before long the rate of sea ice decline will catch up with the longer term rate of sea ice loss. 'It's like the analogy of a ball bouncing down a hill where the hill is climate change, given by Professor Ed Hawkins. The ball continues going down the hill but as it meets obstacles in its path, the ball can temporarily fly upwards or sideways and not seem to be travelling down at all — that trajectory is not always smooth but we know that at some point the ball will careen towards the bottom of the hill.' When the current slowdown ends, climate modelling suggests the rate of sea ice loss could accelerate to 0.6 million square kilometres per decade faster than the longer-term trend. The researchers estimate that the current pause has a nearly one in two chance of lasting another five years, and a 25 per cent chance of lasting another 10 years. While most of the evidence from climate models suggest natural climate variations had played a large part in slowing the 'human-driven loss of sea ice', the modelling was inconclusive whether 'changes in the human influence on climate (the 'forced response') have also contributed'. 'Overall, while it may sound surprising that Arctic sea ice loss has slowed down even as global temperatures hit record highs, the climate modelling evidence suggests we should expect periods like this to occur somewhat frequently,' they wrote. It comes as a separate study from researchers at UNSW Sydney and the ANU, published today in the journal Nature, warns of 'catastrophic consequences' for Antarctica unless urgent actions are taken to cut global carbon emissions. 'Rapid change has already been detected across Antarctica's ice, oceans and ecosystems — and this is set to worsen with every fraction of a degree of global warming,' said lead author Dr Nerilie Abram, chief scientist at the Australian Antarctic Division (AAD). Dr Abram said the sudden loss of sea ice in the region has a range of knock-on effects. 'This includes making the floating ice shelves around Antarctica more susceptible to wave-driven collapse,' she said. She warned the West Antarctic Ice Sheet (WAIS) was at severe risk of collapse as global carbon dioxide levels continue to rise. This loss would raise sea levels by more than three metres, threatening coastal cities and communities worldwide. 'Such a collapse would result in catastrophic consequences for generations to come,' she said.
The Guardian
2 days ago
- Science
- The Guardian
Dramatic slowdown in melting of Arctic sea ice surprises scientists
The melting of sea ice in the Arctic has slowed dramatically in the past 20 years, scientists have reported, with no statistically significant decline in its extent since 2005. The finding is surprising, the researchers say, given that carbon emissions from fossil fuel burning have continued to rise and trap ever more heat over that time. They said natural variations in ocean currents that limit ice melting had probably balanced out the continuing rise in global temperatures. However, they said this was only a temporary reprieve and melting was highly likely to start again at about double the long-term rate at some point in the next five to 10 years. The findings do not mean Arctic sea ice is rebounding. Sea ice area in September, when it reaches its annual minimum, has halved since 1979, when satellite measurements began. The climate crisis remains 'unequivocally real', the scientists said, and the need for urgent action to avoid the worst impacts remains unchanged. The natural variation causing the slowdown is probably the multi-decadal fluctuations in currents in the Atlantic and Pacific oceans, which change the amount of warmed water flowing into the Arctic. The Arctic is still expected to see ice-free conditions later in the century, harming people and wildlife in the region and boosting global heating by exposing the dark, heat-absorbing ocean. Dr Mark England, who led the study while at the University of Exeter, said: 'It is surprising, when there is a current debate about whether global warming is accelerating, that we're talking about a slowdown. 'The good news is that 10 to 15 years ago when sea ice loss was accelerating, some people were talking about an ice-free Arctic before 2020. But now the [natural] variability has switched to largely cancelling out sea ice loss. It has bought us a bit more time but it is a temporary reprieve – when it ends, it isn't good news.' The research, published in the journal Geophysical Research Letters, used two different datasets of Arctic sea ice levels from 1979 to the present day. The scientists analysed the sea ice area for every month of the year and the slowdown was seen in all cases. To see if such a slowdown could be a result of natural variation, they examined the results of thousands of climate model runs. 'This is not an extremely rare event – over a century, it should happen a couple of times,' said England, now at the University of California, Irvine. Furthermore, all the simulations showed sea ice loss accelerating again after the slowdown. Prof Julienne Stroeve, of University College London, said: 'We know climate records, be it in global temperatures or sea ice, can remain the same for several years in a row as a result of internal climate variability.' Stroeve's analysis of the long-term trend from 1979 to 2024 shows that about 2.5 sq metres of September ice is lost for every tonne of CO2 emitted. Sign up to Down to Earth The planet's most important stories. Get all the week's environment news - the good, the bad and the essential after newsletter promotion Prof Andrew Shepherd, of Northumbria University, said: 'We know that the Arctic sea ice pack is also thinning, and so even if the area was not reducing, the volume still is. Our data show that since 2010 the average October thickness has fallen by 0.6cm per year.' The rate of the rise in global surface temperature has also slowed down in the past, before resuming a rapid rise. A major El Niño event in 1998 was followed by a decade or so of similar global temperatures, which was nicknamed 'the pause'. However, the planet continued to accumulate heat throughout and global temperatures have since risen rapidly. England rejected any suggestion the sea ice slowdown suggested climate change was not real. 'Climate change is unequivocally real, human-driven, and continues to pose serious threats. The fundamental science and urgency for climate action remain unchanged,' he said. 'It is good to explain to people that [the slowdown] is happening, else they are going to hear it from someone who is trying to use it in bad faith as a way to undermine our very solid understanding of what's happening with climate change.'
