Sunnier Skies Driving Greenland Surface Melt

Sunnier Skies Driving Greenland Surface Melt

SOURCE: Climate Central DATE: June 28, 2017 SNIP: In the past two decades, the Greenland ice sheet has become the biggest single contributor to rising sea levels, mostly from melt across its vast surface. That surface melt is, in turn, driven mostly by an uptick in clear, sunny summer skies, not just rising air temperatures, a new study finds. While some of the water Greenland is flushing out to sea comes from warming ocean waters lapping away at the glaciers that drain the ice sheet, most is due to the melt across its surface during the summer. Stefan Hofer, a PhD candidate at the University of Bristol in England, and his colleagues looked into what the main drivers of that surface melt were, in particular the effect of cloud cover on melt. In satellite data spanning the past two decades, they saw a significant decrease in cloud cover over Greenland starting in the mid-90s, which would mean more sunlight was falling on the ice and driving melt. Climate models the team used suggest that every 1 percent reduction in cloud cover leads to another 27 gigatons of melt (the U.S. uses about 1.3 gigatons of water per day, according to data from NASA and the U.S. Geological Survey). That sensitivity to cloud cover was “pretty astounding,” William Colgan, a senior researcher with the Geological Survey of Denmark and Greenland who wasn’t involved in the study, said in an...
Climate models have underestimated Earth’s sensitivity to CO2 changes, study finds

Climate models have underestimated Earth’s sensitivity to CO2 changes, study finds

SOURCE: Yale News DATE: April 7, 2017 SNIP: A Yale University study says global climate models have significantly underestimated how much the Earth’s surface temperature will rise if greenhouse gas emissions continue to increase as expected. Yale scientists looked at a number of global climate projections and found that they misjudged the ratio of ice crystals and super-cooled water droplets in “mixed-phase” clouds — resulting in a significant under-reporting of climate sensitivity. The findings appear April 7 in the journal Science. Equilibrium climate sensitivity is a measure used to estimate how Earth’s surface temperature ultimately responds to changes in atmospheric carbon dioxide (CO2). Specifically, it reflects how much the Earth’s average surface temperature would rise if CO2 doubled its preindustrial level. In 2013, the Intergovernmental Panel on Climate Change (IPCC) estimated climate sensitivity to be within a range of 2 to 4.7 degrees Celsius. The Yale team’s estimate is much higher: between 5 and 5.3 degrees Celsius. Such an increase could have dramatic implications for climate change worldwide, note the...
Methane warms climate even more than previously thought

Methane warms climate even more than previously thought

SOURCE: Engineering & Technology DATE: January 11, 2017 SNIP: According to a study led by researchers from the University of Reading, methane, the main component of natural gas, is actually 32 times more potent as a climate warming agent than carbon dioxide, instead of 28 times as previously believed. That means that methane’s contribution to global warming is 25 per cent higher than previously estimated. “Clouds play a particularly important role in causing this enhanced warming effect,” said Professor Ellie Highwood from the University of Reading, one of the co-authors of the study. “Clouds reflect some of the sun’s rays back towards space, but by absorbing some of these scattered rays low down in the atmosphere, methane has an extra warming effect – a factor that was not considered by earlier...
Clouds Won’t Save Us from Global Warming

Clouds Won’t Save Us from Global Warming

SOURCE: Scientific American DATE: April 7, 2016 AUTHOR: By John Upton, Climate Central SNIP: Analysis of the first seven years of data from a NASA cloud-monitoring mission suggests clouds are doing less to slow the warming of the planet than previously thought, and that temperatures may rise faster than expected as greenhouse gas pollution worsens—perhaps 25 percent faster. See also: Climate models underestimate global warming by exaggerating cloud...
Clouds having a greater impact on Greenland than previously thought

Clouds having a greater impact on Greenland than previously thought

SOURCE: Accuweather.com DATE: January 13, 2016 SNIP: New research led by the University of Leuven (Belgium) and assisted by the University of Wisconsin-Madison indicates that cloud cover over the Greenland Ice Sheet is playing a larger role than previously thought by raising the temperature of the ice sheet some 2 to 3 degrees compared to days with no clouds. The above process is likely accounting for as much as 30 percent of the ice sheet melt, according to the University of Wisconsin News. The impact of this could be a global sea level rise of an additional foot over the next 80 years, according to co-author Tristan L’Ecuyer of the University of...