Category Archives: The Science

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3 February 2016, Nature Communications, Evidence for the stability of the West Antarctic Ice Sheet divide for 1.4 million years. Past fluctuations of the West Antarctic Ice Sheet (WAIS) are of fundamental interest because of the possibility of WAIS collapse in the future and a consequent rise in global sea level. However, the configuration and stability of the ice sheet during past interglacial periods remains uncertain. Here we present geomorphological evidence and multiple cosmogenic nuclide data from the southern Ellsworth Mountains to suggest that the divide of the WAIS has fluctuated only modestly in location and thickness for at least the last 1.4 million years. Fluctuations during glacial–interglacial cycles appear superimposed on a long-term trajectory of ice-surface lowering relative to the mountains. This implies that as a minimum, a regional ice sheet centred on the Ellsworth-Whitmore uplands may have survived Pleistocene warm periods. If so, it constrains the WAIS contribution to global sea level rise during interglacials to about 3.3 m above present. Read More here

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28 January 2016, Climate Home, Scientists pour cold water on ocean geoengineering idea. One keenly-argued possible way of moderating the build-up of carbon dioxide in the atmosphere may not work, scientists have concluded. They say there is evidence that seeding the oceans with iron so that the algae that live there will multiply and devour more CO2 − thus preventing it reaching the atmosphere and intensifying the human contribution to global warming – is not as promising a solution as its supporters hope. The extra iron can certainly stimulate the algae to grow more vigorously, but at a cost. More algae in one part of the oceans may mean there will be fewer in other areas, the researchers say. Report: Scientists warn against geoengineering as short-term climate fix. They report in Nature journal that the depths of the central Pacific Ocean contain ancient sediments that cast doubt on iron’s ability to slow the Earth’s steady temperature rise. In parts of the oceans that lack the iron that plants need, algae are scarce. Experiments have shown that dumping iron into these areas can encourage algal growth, so large-scale fertilisation could theoretically reduce atmospheric CO2. The seafloor sediments the team studied show that, during past ice ages, more iron-rich dust blew from cold and barren landmasses into the oceans, apparently producing more algae in these areas and, presumably, a creating natural cooling effect. But the researchers say increased algal growth in one area can inhibit growth elsewhere, because ocean waters are always on the move and algae also need other nutrients, such as nitrates and phosphates. Read More here

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25 January 2016, The Guardian. Sea level rise from ocean warming underestimated, scientists say. Thermal expansion of the oceans as they warm is likely to be twice as large as previously thought, according to German researchers. The amount of sea level rise that comes from the oceans warming and expanding has been underestimated, and could be about twice as much as previously calculated, German researchers have said. The findings in the Proceedings of the National Academy of Sciences, a peer-reviewed US journal, suggest that increasingly severe storm surges could be anticipated as a result. Sea level can mount due to two factors – melting ice and the thermal expansion of water as it warms. Until now, researchers have believed the oceans rose between 0.7 to 1mm per year due to thermal expansion. But a fresh look at the latest satellite data from 2002 to 2014 shows the seas are expanding about 1.4mm a year, said the study. “To date, we have underestimated how much the heat-related expansion of the water mass in the oceans contributes to a global rise in sea level,” said co-author Jurgen Kusche, a professor at the University of Bonn. The overall sea level rise rate is about 2.74mm per year, combining both thermal expansion and melting ice. Read More here

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23 January 2016, Carbon Brief, Arctic and Med face hotspot worries. Uneven heating of the Earth’s surface as a result of climate change could see some regions facing seriously high rises in average temperatures. Forget the notion of a 2˚C global average temperature rise. In parts of the Arctic, regional average warming passed that limit 15 years ago. New research suggests that if the world really does warm to an average of 2˚C, then mean temperatures in the Mediterranean region could be 3.4˚C warmer than in pre-industrial times. And in some parts of the Arctic, 2˚C average warmingcould translate as a 6˚C rise. Sonia Seneviratne, head of the land-climate dynamics group at Switzerland’sInstitute for Atmospheric and Climate Science (ETH Zurich), and colleaguesreport in Nature journal that they have been thinking about the meaning of a 2˚C global average warming. Because it is an average, some regions will inevitably be hotter than this average. So she and her fellow researchers have been trying to calculate what further emissions of greenhouse gases in the atmosphere – the exhausts from fossil fuel combustion that drive global warming – will mean for the people who live in specific parts of the planet. Average warming They focused on what climate models could tell them about extremes of temperature and precipitation in selected regions on the global map. The answer is disconcerting: to limit average temperature rises for the Mediterranean to 2˚C, the world will have to sharply reduce its fossil fuel combustion and contain the global average warming to 1.4˚C. Since the planet is already on average 1˚C warmer than it was in pre-industrial times, this puts the challenge of climate change in an ever more urgent context. Professor Seneviratne pointed out two years ago that extremes might be more significant in climate change than global averages.” We could potentially see even greater regional variation than these findings show” And she is not the only researcher to look for the significance of local climate change implicit in a shift in planetary averages. A team of oceanographers in 2013 examined much the same pattern of variation and predicted that, for some regions,real and enduring climate change could arrive by 2020. Read More here