As the Arctic loses ice and the ocean absorbs more solar radiation, global warming is amplified. That can affect ocean circulation, weather patterns and Arctic ecosystems spanning the food chain, from phytoplankton all the way to top predators.
If Arctic sea ice vanishes in summers by the middle of the century as expected, the world could see a vicious circle that drives enough global warming to almost wipe out the impact of China going carbon neutral.
This year’s Arctic sea ice cover shrank to the second lowest extent since modern record-keeping began in the late 1970s. Warmer ocean temperatures eat away at the thicker multiyear ice, and also result in thinner ice to start the spring melt season. Melt early in the season results in more open water, which absorbs heat from the Sun and increases water temperatures.
Mass loss from 2007 to 2017 due to melt-water and crumbling ice aligned almost perfectly with the Intergovernmental Panel for Climate Change’s (IPCC) most extreme forecasts, which see the two ice sheets adding up to 40 centimetres (nearly 16 inches) to global oceans by 2100, they reported in Nature Climate Change. Such an increase would have a devastating impact worldwide, increasing the destructive power of storm surges and exposing coastal regions home to hundreds of millions of people to repeated and severe flooding.
Between 1994 and 2017, an incredible 28 trillion tonnes (31 trillion tons) of ice was lost from the Earth’s ice sheets, glaciers, and mountains, according to a new report in the journal The Cryosphere. The extent of this worldwide melting has been described as “staggering” by the study authors, who warn that the ongoing loss of ice could lead to catastrophic rises in sea levels.
Researchers from University College London, Leeds University, and Edinburgh University studied satellite data in order to determine global changes in ice coverage over several decades. Speaking to The Guardian, study author Andrew Shepherd explained that “in the past researchers have studied individual areas – such as the Antarctic or Greenland – where ice is melting. But this is the first time anyone has looked at all the ice that is disappearing from the entire planet.”
Recent improvements to observational data, our understanding of the main contributing processes to sea-level change and methods for estimating the individual contributions, reconcile summed contributions of ice-mass loss, terrestrial water storage and thermal expansion of the ocean with observed changes in global-mean sea level. The methods described in this paper will contribute to improvements in projections of future sea-level change.
The Arctic sea ice is melting faster than climate models had predicted, researchers at the University of Copenhagen warned on Tuesday. A recent study from Britain’s University of Lincoln concluded that Greenland’s ice melt alone is expected to contribute 10-12 centimetres to the world’s rising sea levels by 2100. Another group of researchers recently concluded that the melting of Greenland’s ice cap has gone so far that it is now irreversible, with snowfall no longer able to compensate for the loss of ice even if global warming were to end today.
The title of Eugene O’Neill’s 1939 noir epic on man’s need for self-deception could be the chyron for a recent article in the Proceedings of the National Academy of Sciences (PNAS) entitled “Ice Sheet Contributions to Future Sea Level Rise from Structured Expert Judgement” by J.L. Bamber, M. Oppenheimer, R.E. Kopp, W.P. Aspinall, and R.M. Cooke. The PNAS paper describes a structured expert judgment (SEJ) uncertainty quantification of ice sheets’ contribution to sea level rise (SLR) out to 2300 under +2°C and +5°C stabilization scenarios. Expanding on the methodology of Bamber and Aspinall’s groundbreaking 2013 study, the PNAS study again treats individual experts as testable statistical hypotheses, but this time, it targets upper-tail dependence between ice sheet processes. The result is higher median assessments and expanding uncertainties, especially in the upper tail, relative to the Fifth Assessment Report of the United Nations Intergovernmental Panel on Climate Change (IPCC AR5). Its potential for capturing a more nuanced and accurate picture of uncertainty, is precisely why Riskthinking.ai employs SEJ in the development of its scenarios tools.