科普知识学英语 全球气温上升1.5度将导致西伯利亚永久冻土消融.docVIP

Evidence from Siberian caves suggests that a global temperature rise of 1.5 degrees Celsius could see permanently frozen ground?thaw（融解）?over a large area of Siberia, threatening release of carbon from soils, and damage to natural and human environments. A thaw in Siberias permafrost (ground frozen throughout the year) could release over 1000 giga-tonnes of the greenhouse gases carbon dioxide and methane into the atmosphere, potentially enhancing global warming. ? The data comes from an international team led by Oxford University scientists studyingstalactites（钟乳石）?and?stalagmites（石笋）?from caves located along the permafrost frontier, where ground begins to be permanently frozen in a layer tens to hundreds of metres thick. Because stalactites and stalagmites only grow when liquid rainwater and snow melt drips into the caves, these formations record 500,000 years of changing permafrost conditions, including warmer periods similar to the climate of today. ? Records from a particularly warm period (Marine Isotopic Stage 11) that occurred around 400,000 years ago suggest that global warming of 1.5°C compared to the present is enough to cause substantial thawing of permafrost far north from its present-day southern limit. ? A report of the research is published in this weeks Science Express. The team included scientists from Britain, Russia, Mongolia and Switzerland. ? The stalactites and stalagmites from these caves are a way of looking back in time to see how warm periods similar to our modern climate affect how far permafrost extends across Siberia, said Dr Anton Vaks of Oxford Universitys Department of Earth Sciences, who led the work. As permafrost covers 24% of the land surface of the Northern hemisphere significant thawing could affect vast areas and release giga-tonnes of carbon. ? This has huge implications for ecosystems in the region, and for aspects of the human environment. For instance, natural gas facilities in the region, as well as power lines, roads,