Scientists have beaten down the best climate denial argument

Scientists have beaten down the best climate denial argument

SOURCE: The Guardian DATE: December 18, 2017 SNIP: A new study published in Nature by Stanford scientists Patrick Brown and Ken Caldeira found that so far, the global climate models that best simulate the Earth’s global energy imbalance tend to predict the most future global warming. These results suggest the ECS is around 3.7°C. This is higher than the previous best estimate of 3.1°C, and if correct, would shrink our carbon budget by about 15%. The study found that the biggest contributor to the difference between the accurate and inaccurate models was in how well they simulated cloud changes. And while it’s just one study, several prior papers arrived at similar conclusions. For example, a 2010 study published in the Journal of Climate found that climate models that most accurately simulate recent cloud cover changes in the east Pacific point to an amplifying effect on global warming and thus a more sensitive...
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...