Global Warming 'Hiatus' Challenged by NOAA Research - NYTimes.com - 0 views
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Scientists have long labored to explain what appeared to be a slowdown in global warming that began at the start of this century as, at the same time, heat-trapping emissions of carbon dioxide were soaring. The slowdown, sometimes inaccurately described as a halt or hiatus, became a major talking point for people critical of climate science.
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When adjustments are made to compensate for recently discovered problems in the way global temperatures were measured, the slowdown largely disappears, the National Oceanic and Atmospheric Administration declared in a scientific paper published Thursday. And when the particularly warm temperatures of 2013 and 2014 are averaged in, the slowdown goes away entirely, the agency said.
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“The notion that there was a slowdown in global warming, or a hiatus, was based on the best information we had available at the time,” said Thomas R. Karl, director of the National Centers for Environmental Information, a NOAA unit in Asheville, N.C. “Science is always working to improve.”
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senior climate scientists at other agencies were in no hurry to embrace NOAA’s specific adjustments. Several of them said it would take months of discussion in the scientific community to understand the data corrections and come to a consensus about whether to adopt them broadly.
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NOAA said the improvements in its data set included the addition of a huge number of land measurements from around the world, as a result of improving international cooperation in sharing weather records. But the disappearance of the slowdown comes largely from adjustments in ocean temperatures.
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A leading hypothesis to explain the slowdown is that natural fluctuations in the Pacific Ocean may have temporarily pulled some heat out of the atmosphere, producing a brief flattening in the long-term increase of surface temperatures.
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Yet the temperature record is plagued by many problems: thermometers and recording practices changed through time, weather stations were moved, cities grew up around once-rural stations, and so on. Entire scientific careers are devoted to studying these issues and making corrections.
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NOAA is one of four agencies around the world that attempts to produce a complete record of global temperatures dating to 1880. They all get similar results, showing a long-term warming of the planet that scientists have linked primarily to the burning of fossil fuels and the destruction of forests. A huge body of physical evidence — notably, that practically every large piece of land ice on the planet has started to melt — suggests the temperature finding is correct.
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Even if the warming slowdown in the early 21st century was real, there seems to be little question that it is ending. By a small margin, the global temperature hit a record in 2014, and developing weather patterns suggest that record will likely be broken by a larger margin in 2015.