4 January 2018, Geophysical Research Letters, Decline in Antarctic Ozone Depletion and Lower Stratospheric Chlorine Determined From Aura Microwave Limb Sounder Observations. The Antarctic ozone hole is healing slowly because levels of the man-made chemicals causing the hole have long lifetimes. We use Microwave Limb Sounder (MLS) satellite data to measure O3 over Antarctica at the beginning of winter and then compare it to O3 near the end of winter to calculate depletion. During this period, nearly all O3 change is due to depletion. MLS also measures HCl, and when ozone levels are very low, nearly all the reactive chlorine species (Cly) are converted to HCl. Clyvaries a lot from year to year from atmospheric motions. Fortunately, MLS measures nitrous oxide (N2O), a long-lived gas that also varies with the motions. Using the ratio of Cly to N2O, we find that there is less chlorine now than 9 years ago and that Cly has decreased on average about 25 parts per trillion/yr (0.8%/yr). The O3 depletion we calculate from MLS data responds to changes in the Clylevels, and the ratio of the change in ozone loss to the change in Cly matches model calculations. All of this is evidence that the Montreal Protocol is working—the Cly is decreasing in the Antarctic stratosphere and the ozone destruction is decreasing along with it. Read More here
Category Archives: Antarctica
12 July 2017, New York Times, An iceberg the size of Delaware just broke away from Antarctica. A chunk of floating ice that weighs more than a trillion metric tons broke away from the Antarctic Peninsula, producing one of the largest icebergs ever recorded and providing a glimpse of how the Antarctic ice sheet might ultimately start to fall apart. A crack more than 120 miles long had developed over several years in a floating ice shelf called Larsen C, and scientists who have been monitoring it confirmed on Wednesday that the huge iceberg had finally broken free. There is no scientific consensus over whether global warming is to blame. But the landscape of the Antarctic Peninsula has been fundamentally changed, according to Project Midas, a research team from Swansea University and Aberystwyth University in Britain that had been monitoring the rift since 2014. “The remaining shelf will be at its smallest ever known size,” said Adrian Luckman, a lead researcher for Project Midas. “This is a big change. Maps will need to be redrawn.” Read More here
1 June 2017, The Conversation, Global stocktake shows the 43 greenhouse gases driving global warming. The most comprehensive collection of atmospheric greenhouse gas measurements, published today, confirms the relentless rise in some of the most important greenhouse gases. The data show that today’s aggregate warming effect of carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) is higher than at any time over the past 800,000 years, according to ice core records. Building on half a century of atmospheric measurements by the international research community, we compiled and analysed the data as part of a group of international scientists, led by Malte Meinshausen from the University of Melbourne in collaboration with CSIRO. Together, the data provide the most compelling evidence of the unprecedented perturbation of Earth’s atmosphere. They clearly show that the growth of greenhouse gases began with the onset of the industrial era around 1750, took a sharp turn upwards in the 1950s, and still continues today. Research has demonstrated that this observed growth in greenhouse gases is caused by human activities, leading to warming of the climate – and in fact more than the observed warming, because part of the effect is currently masked by atmospheric pollution (aerosols). The new collection of records comes from measurements of current and archived air samples, air trapped in bubbles in ice cores, and firn (compacted snow). The data cover the past 2,000 years without gaps, and are the result of a compilation of measurements analysed by dozens of laboratories around the world, including CSIRO, the Bureau of Meteorology’s Cape Grim Station, NOAA, AGAGE and the Scripps Institution of Oceanography, among others. Read More here
28 May 2017, Climate News Network, Antarctica heights settle polar warming puzzle. Computer simulation shows that Antarctica is warming far slower than the Arctic region because of its much greater height. Scientists believe they have settled one of the great polar puzzles − why Antarctica is warming at a rate so much slower than the Arctic region. And the answer is a simple one: Antarctica is so much higher. To ram the point home, they used a computer simulation to hammer the entire southern continent until it was no more than a metre above sea level. At which point, in their simulation, warming at the South Pole became much more dramatic. The two poles are very different: the Arctic is an ocean almost entirely surrounded by land, while Antarctica is a vast continent entirely surrounded by frozen ocean. Landmass of ice As the north polar ocean ice melts, dark seas begin to absorb more radiation. In the southern hemisphere, the landmass of ice reflects radiation back into space to insulate the continent and keep its temperatures far below freezing. But the new study published in Earth System Dynamics journal shows that what makes the biggest difference is the elevation of the surface. Antarctica is not just an enormous continent: thanks to many millions of years of snowfall at very low temperatures, it is banked high with ancient ice. Its average elevation is 2,500 metres − far higher than the highest peaks in the UK, for example − and its highest mountain, Mount Vinson, reaches 4,892 metres, which is higher than any alpine peak in Europe. Evidence from the distant past and climate models both show that, in a warming world, the poles should warm faster than the rest of the planet. But while the Arctic is warming at twice the rate of the rest of the globe, change in Antarctica has been much more sluggish. Read More here