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18 November 2015, Science Daily, Sea level rise from Antarctic collapse may be slower than suggested. A new study by scientists in the UK and France has found that Antarctic ice sheet collapse will have serious consequences for sea level rise over the next two hundred years, though not as much as some have suggested. This study, published today in the journal Nature, uses an ice-sheet model to predict the consequences of unstable retreat of the ice, which recent studies suggest has begun in West Antarctica. Scientists, led by Catherine Ritz from Université Grenoble Alpes in France and Tamsin Edwards from The Open University, predict that the contribution is most likely to be 10 cm of sea-level rise this century under a mid to high climate scenario, but is extremely unlikely to be higher than 30 cm. When combined with other contributions, that’s a significant challenge for adapting to future sea level rise. But it’s also far lower than some previous estimates, which were as high as one metre from Antarctica alone. The study’s central estimate raises the Intergovernmental Panel on Climate Change (IPCC) central prediction of 60 cm global sea-level rise by just a few centimetres under the mid to high scenario they used. But the UK and France team’s method allowed them to assess the likelihood of sea-level rise from substantial parts of the ice sheet collapsing, which the IPCC could not due to a lack of evidence. They predict there is a one in twenty chance that Antarctic collapse could contribute more than 30 cm sea-level rise by the end of the century and more than 72 cm by 2200. This does not rule out larger contributions on longer time scales. Read More here

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14 November 2015, Climate News Network, Greenland glaciers’ melting speeds up again. The increasing rate at which Greenland’s glaciers are melting this century has confounded polar scientists.  A massive Greenland glacier that holds enough water to raise sea levels by half a metre is melting at speed, according to a new study. The Zachariae Isstrom in northeast Greenland has entered a phase of accelerated retreat, and is losing mass at the rate of 5 billion metric tons a year, according to US scientists. They report in the journal Science that a succession of aerial surveys combined with multiple satellite observations has established that the base of the glacier is being eroded rapidly by a mix of warmer ocean water and increasing amounts of meltwater from the surface of the Greenland ice sheet. “North Greenland glaciers are changing rapidly,” said Jeremie Mouginot, an earth system scientist at the University of California, Irvine, who led the study. “The shape and dynamics of the Zachariae Isstrom have changed dramatically over the last few years. The glacier is now breaking up and calving high volumes of icebergs into the ocean, which will result in rising sea levels for decades to come.” Read More here

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10 November 2015, The Conversation, Ocean acidification: the forgotten piece of the carbon puzzle. Ocean acidification – the rise in ocean acidity due to the increased absorption of carbon dioxide (CO₂) – is often thought of as consequence of climate change. However, it is actually a separate, albeit very closely-related problem. Ocean acidification is often referred to as “the other CO₂ problem” because, like climate change, it is primarily a result of the increased emissions of this gas. Despite their common driver, though, the processes and impacts of ocean acidification and climate change are distinct. It should not be assumed that policies intended to deal with the climate will simultaneously benefit the oceans. The current emphasis of global climate policies on a warming target is a case in point. A narrow focus on temperature stabilisation, for example, opens the door for policy interventions that prioritise the reduction of greenhouse gases other than carbon dioxide. This is because non-CO₂ greenhouse gases — like methane and nitrous oxide, which can arise from agricultural and industrial processes — typically have a higher global warming potential and might even be less costly than CO₂ to reduce. In addition, several geoengineering schemes have been proposed to reduce the impacts of a warming climate. Yet such schemes often do nothing to address emissions, and may even exacerbate carbon absorption in the oceans. Read More here

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9 November 2015, Renew Economy, Graph of the Day: Cities under water at 2°C and 4°C. Around half a billion people are at risk from sea level rise if the world continues on a business-as-usual path for carbon emissions, a new report has found – while limiting warming to the recommended 2°C would cut this risk by more than half. The US report by Climate Central, accompanied by an online interactive mapping system, shows that carbon emissions causing 4°C of warming – what business-as-usual points toward today – could lock in enough sea level rise to submerge land currently home to 470 to 760 million people as the “unstoppable rise” unfolds over centuries. The research also reveals, however, that aggressive carbon cuts limiting warming to 2°C could bring the number as low as 130 million people. The report – authored by Climate Central scientists Benjamin Strauss and Scott Kulp, and Anders Levermann of the Potsdam Institute for Climate Impact Research – assesses implications for all coastal nations and cities – post-2100 – using relationships between warming caused by carbon emissions, the long-term global sea level rise it locks in, and global elevation and population data. The news is worst for China, which is found to be most at risk with 145 million people living on land ultimately threatened by rising seas if emission levels are not reduced. Below are the mapped projections for Shanghai, at 4°C on the left, and 2°C on the right. Read More here

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