30 March 2016, Climate Central, Antarctica at Risk of Runaway Melting, Scientists Discover. The world’s greatest reservoir of ice is verging on a breakdown that could push seas to heights not experienced since prehistoric times, drowning dense coastal neighborhoods during the decades ahead, new computer models have shown. A pair of researchers developed the models to help them understand high sea levels during previous eras of warmer temperatures. Then they ran simulations using those models and found that rising levels of greenhouse gases could trigger runaway Antarctic melting that alone could push sea levels up by more than three feet by century’s end. The same models showed that Antarctica’s ice sheet would remain largely intact if the most ambitious goals of last year’s Paris agreement on climate change are achieved. The new findings were published Wednesday in the journal Nature, helping to fill yawning gaps in earlier projections of sea level rise. The models were produced by a collaboration between two scientists that began in the 1990s. In those models, rising air temperatures in Antarctica caused meltwater to seep into cracks in floating shelves of ice, disintegrating them and exposing sheer cliffs that collapsed under their own weight into the Southern Ocean. Similar effects of warming are already being observed in Greenland and in some parts of Antarctica, as greenhouse gas pollution from fossil fuels, farming and deforestation warms the air. Last year was the hottest on record, easily surpassing a record set one year earlier. The ice sheets are also being melted from beneath by warming ocean temperatures. “Sea level has risen a lot — 10 to 20 meters — in warm periods in the past, and our ice sheet models couldn’t make the Antarctic ice sheet retreat enough to explain that,” said David Pollard, a Penn State climate scientist who produced Wednesday’s study with UMass professor Robert DeConto. “We were looking for new mechanisms that could make the ice more vulnerable to climate warming to explain past sea level rise,” Pollard said. Read More here
Category Archives: The Science
28 March, Science Daily, Climate change: Greenland melting tied to shrinking Arctic sea ice. Vanishing Arctic sea ice. Dogged weather systems over Greenland. Far-flung surface ice melting on the massive island. These dramatic trends and global sea-level rise are linked, according to a study coauthored by Jennifer Francis, a research professor in Rutgers University’s Department of Marine and Coastal Sciences. During Greenland summers, melting Arctic sea ice favors stronger and more frequent “blocking-high” pressure systems, which spin clockwise, stay largely in place and can block cold, dry Canadian air from reaching the island. The highs tend to enhance the flow of warm, moist air over Greenland, contributing to increased extreme heat events and surface ice melting, according to the study. That, in turn, fuels sea-level rise, said Francis, who called rising seas a “monstrous” issue for coastal communities around the world. The increased melting on the Greenland ice sheet in recent years may also be linked to cooler-than-normal ocean temperatures south of the island, slowing ocean circulation. The study, published online in the Journal of Climate last month, tapped computer models and measurements in the field. “I think this study does a good job of pinning down the fact that the [Arctic sea] ice is disappearing for a whole bunch of reasons — and that is causing the surface of Greenland’s melt area to increase,” Francis said. The Greenland ice sheet holds an enormous volume of frozen water, and the global sea level would rise about 20 to 23 feet if it all melted, the study notes. Surface melting of the ice sheet has increased dramatically since the relative stability and modest snow accumulation in the 1970s, the study also notes. Read More here
28 March 2016, NASA, 2016 Arctic sea ice wintertime extent hits another record low. Arctic sea ice appears to have reached a record low wintertime maximum extent for the second year in a row, according to scientists at the NASA-supported National Snow and Ice Data Center (NSIDC) and NASA. Every year, the cap of frozen seawater floating on top of the Arctic Ocean and its neighboring seas melts during the spring and summer and grows back in the fall and winter months, reaching its maximum yearly extent between February and April. On March 24, Arctic sea ice extent peaked at 5.607 million square miles (14.52 million square kilometers), a new record low winter maximum extent in the satellite record that started in 1979. It is slightly smaller than the previous record low maximum extent of 5.612 million square miles (14.54 million square kilometers) that occurred last year. The 13 smallest maximum extents on the satellite record have happened in the last 13 years. The new record low follows record high temperatures in December, January and February around the globe and in the Arctic. The atmospheric warmth probably contributed to this lowest maximum extent, with air temperatures up to 10 degrees Fahrenheit above average at the edges of the ice pack where sea ice is thin, said Walt Meier, a sea ice scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Read More here
25 March 2016, Climate News Network, Past emissions cause mounting climate havoc. Despite signs that the world will cut its future fossil fuel use, greenhouse gases already emitted are still driving accelerating climate change.Climate change has reached the point where it may outstrip the quickening efforts to slow it by reducing emissions of carbon dioxide and other greenhouse gases, scientists say. They say humans are now releasing CO2 into the atmosphere 10 times faster than natural processes have ever done in the last 66 million years, before the extinction of the dinosaurs. The disclosure comes in the World Meteorological Organisation’s State of the Climate report, published in the journal Nature Geoscience. The lead author, Professor Richard Zeebe of the University of Hawaii, said: “Our carbon release rate is unprecedented over such a long time period [and] means that we have effectively entered a ‘no-analogue’ state. “The present and future rate of climate change and ocean acidification is too fast for many species to adapt, which is likely to result in widespread future extinctions.” “The window of opportunity for limiting global temperature rise to well below 2°C . . . is narrow and rapidly shrinking. The effects of a warming planet will be felt by all” The UN secretary-general, Ban Ki-moon, said: “Climate change is accelerating at an alarming rate. The window of opportunity for limiting global temperature rise to well below 2°C – the threshold agreed by world governments in Paris in December last year – is narrow and rapidly shrinking. The effects of a warming planet will be felt by all.” The WMO secretary-general, Petteri Taalas, said the present “alarming” rate of climate change as a result of greenhouse gas emissions was “unprecedented in modern records”. “The future is now”, he said. Yet less than a week ago the International Energy Agency announced that global energy-related emissions of carbon dioxide had shown no increase for the second year in a row. The announcement was widely hailed as significant good news, with the IEA’s executive director, Fatih Birol, describing it as “yet another boost to the global fight against climate change”.Read More here