The Greenland ice sheet is melting much faster than previously thought, threatening hundreds of millions of people with flooding and bringing some of the irreversible impacts of the climate emergency very close.
Greenland ice is being lost seven times faster than it was in the 1990s, and the scale and speed of ice loss is much greater than predicted in comprehensive studies of global climate science by the Intergovernmental Panel. on Climate Change, according to the data.
That means sea level rise is likely to reach 67 cm by 2100, about 7 cm higher than the main IPCC prediction. Such a rate of increase will put 400 million people at risk of flooding each year, up from the 360 million predicted by the IPCC, by the end of the century.
Rising sea levels also increase the risk of tides and storm surges. In this sense, coastal regions around the world are more likely due to global warming to produce more ferocious storms.
"These are not unlikely events or small impacts," said Andrew Shepherd, professor of Earth observation at the University of Leeds, a lead author on the study. "These impacts are happening and will be devastating for coastal communities."
Greenland has lost 3.8 trillion tons of ice since 1992, and the rate of ice loss has increased from 33 billion tons a year in the 1990s to 254 billion tons a year in the last decade. Greenland ice contributes directly to sea level rise as it melts because it rests on a large land mass, unlike the floating sea ice that makes up much of the rest of the Arctic ice sheet.
About half of Greenland's ice loss was due to melting caused by air surface temperatures, which have risen much faster in the Arctic than the global average, and the rest was due to acceleration of ice flow as sea from glaciers, driven by ocean warming.
The oceans have absorbed most of the excess heat from our altered climate to date and much of the carbon dioxide, but they are reaching the limit of their ability to do so. Sea level rise is driven not only by melting ice but also by the thermal expansion of the seas as they warm.
The scale and speed of the ice loss surprised the team of 96 polar scientists behind the findings, published Tuesday in the journal Nature. The Ice Sheet Mass Balance Intercomparison Exercise comprised 26 separate surveys of Greenland from 1992 to 2018, with data from 11 different satellites and volume, flow, and gravity comparisons compiled by experts from the UK, NASA in the US. USA and the European Area Agency.
Erik Ivins of NASA's Jet Propulsion Laboratory in California emphasized that the findings, the most comprehensive survey to date of the ice sheet in decades, were based on observations, rather than computer modeling.
"While computer simulation allows us to make projections from climate change scenarios, satellite measurements provide prima facie evidence," he said.
The peak year of ice loss, according to observations, was 2011, when 335 billion tons of ice were lost. Since then, the average rate has slowed to 238 billion tonnes a year since 2013, but this does not include the most recent observations this summer, which showed an even more widespread meltdown.
Governments meet in Madrid for the second week of crucial UN talks on the global response to the climate emergency. Activists have been frustrated by the slow pace of negotiations, despite growing public outcry, including a 500,000-strong march through the center of the Spanish capital led by Swedish climate activist Greta Thunberg.
Rachel Kennerley, a climate activist for Friends of the Earth, said: "We are in a climate emergency: the impacts are getting stronger and faster." This latest research sits even further in a growing pile of evidence showing that we need real action, not warm words. Governments must stop dragging their feet and offer real emissions cuts and real support for vulnerable people who are already experiencing the devastating effects of climate collapse. "
The IPCC is the gold standard for climate science, but some experts worry that its findings do not take into account the potential for "tipping points," thresholds beyond which climate collapse accelerates and becomes catastrophic and irreversible.
Louise Sime, a climate scientist at the British Antarctic Survey, said of the new document: “This finding should be of great concern to all those who will be affected by rising sea levels. If this very high rate of ice loss continues, it is possible that new tipping points will be broken sooner than we previously thought. "