11 July 2016, Carbon Brief, Shifting global cloud patterns could amplify warming, study says. A new study sheds light on one of the biggest uncertainties in predicting future changes to Earth’s climate: clouds. Clouds both warm the planet by insulating the Earth’s surface like a blanket, while simultaneously cooling it by reflecting away energy from the sun. Climate models predict that as the Earth warms in response to greenhouse gases, clouds will shift towards the poles and sit higher in the sky, further speeding up warming. But clouds are tricky to measure and until now, scientists haven’t been able to find direct evidence that these changes were actually happening in the real world. The new study published in Nature uses satellite data to identify how cloud patterns have changed in recent decades, confirming the pace of warming predicted by climate models. Satellite data Scientists use weather satellites to measure the extent, height and thickness of clouds. But these measurements suffer from several issues that can limit how useful they are for detecting long-term changes in cloudiness. Small discrepancies in the data are caused by satellite sensors degrading over time and being replaced by new, more precise instruments. Another issue is the gradual change in the orbit of satellites themselves, says the study’s lead author, Prof Joel Norris, professor of climate and atmospheric sciences at the Scripps Institution of Oceanography in San Diego. He explains to Carbon Brief: Read More here
Tag Archives: oceans
5 July 2016, Washington Post, This new Antarctica study is bad news for climate change doubters. or a number of years now, climate change skeptics have argued that there’s a key part of the Earth’s climate system that upends our expectations about global warming, and that is showing trends that actually cut in the opposite direction. This supposed contrary indicator is the sea ice that rings the Antarctic continent, and that reached a new all-time record extent of 7.78 million square miles in September 2014 (see above). As that record suggests, this vast field of ice has been expanding in recent years, rather than shrinking. That means it’s doing the opposite of what is happening in the Arctic, where sea ice is declining rapidly — and also that it’s doing the opposite of what we might expect in a warming world. [Climate change skeptics may be about to lose one of their favorite arguments] Scientists don’t fully understand why Antarctic sea ice is growing — suggested explanations have posited more glacial melt dumping cold fresh water into the surrounding seas, or the way the Antarctic ozone hole has changed the circulation of winds around the continent. In a new study in Nature Geoscience, though, researchers with the National Center for Atmospheric Research (NCAR) in Boulder, Colo., along with colleagues from the University of Washington in Seattle and Australia, suggest that the phenomenon is simply the result of natural variability of the climate system — driven, in this case, by changes in the tropical Pacific Ocean that reverberate globally. Read more here
8 June 2016, Climate News Network, Puzzle of Antarctica’s long-term ice loss. Analysis of satellite data records reveals that the worrying loss of hundreds of square kilometres of ice along West Antarctica’s coastline has been occurring for decades. Parts of Antarctica are not only losing ice to the ocean, they have been doing so for 40 years. Geoscientists from the University of Edinburgh and a US colleague report in Geophysical Research Letters that they looked at satellite imagery of West Antarctica’s coastline along a 2,000 km stretch and found that the region has lost 1,000 square kilometres of ice in four decades. The surprise is not that melting occurs, but that it has been happening for such a long time. Frazer Christie, a PhD student, and partners analysed data from NASA, the US Geological Survey and the European Space Agency to find that ice has been retreating along almost the entire coast of Antarctica’s Bellingshausen Sea since satellite records began. Some of the largest changes – where ice has thinned rapidly and retreated several kilometres since 1975 – matched those places where the ice front is deepest. “We knew that ice had been retreating from this region recently, but now, thanks to a wealth of freely available satellite data, we know this has been occurring pervasively along the coastline for almost half a century,” Christie says. Colder water He and his colleagues blame warmer ocean waters, rather than warmer atmosphere.But, paradoxically, a study from the University of Washington in Seattle, US, reports that the waters lapping the continent are not warming substantially − because of a steady upwelling of much colder water from the depths of the Southern Ocean. Read More here