Upon closer look, a global warming hiatus is ruled out, U.S. scientists say - LA Times - 0 views
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fresh look at the way sea temperatures are measured has led government scientists to make a surprising claim: The puzzling apparent hiatus in global surface warming never really happened
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Mainstream scientists have struggled to explain to the public how climate change can be getting worse if the warming of the planet's surface slowed at the turn of the century. Their various theories have chalked it up to dust and ash blasted into the sky by volcanic eruptions, a rare period of calm in the solar cycle, and heat absorption by the Pacific Ocean and other waters.
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“I don't find this analysis at all convincing,” said Judith Curry, a climatologist at Georgia Tech who argues that natural variability in climate cycles dominates the impact of industrial emissions and other human actions. “While I'm sure this latest analysis from NOAA will be regarded as politically useful for the Obama administration, I don't regard it as a particularly useful contribution to our scientific understanding of what is going on.”
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In the study, the NOAA researchers argue that long-standing problems with the way temperatures are measured have masked years of sea surface warming. Once those problems are corrected for, “this hiatus or slowdown simply vanishes,” said lead study author Thomas Karl, director of NOAA's National Climatic Data Center in Asheville, N.C.
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Although researchers have long known that sea surface temperatures measured by autonomous buoys run cooler than temperatures measured by ships, they have failed to account for this as they expanded their use of buoy readings over the last two decades, the study authors argued.
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“The buckets, when you pull them up, tend to evaporate their water, and if they're canvas there's even more evaporation,” Karl said. “By the time people stick a thermistor in the bucket to measure temperature, it's already slightly cool.”
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“If you start a short-time series on an anomalous value, you tend to get an anomalous trend,” Karl said.
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A growing number of climate scientists have argued that this phenomenon, as well as other hiatus effects, are evidence of a poorly understood pattern of wind, ocean current and temperature variations that have far-reaching effects on global climate. They say the oceans have absorbed heat energy from the sun, causing Arctic ice to melt and sea levels to rise.
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“One way to think about it is that global warming continued, but the oceans just juggled a bit of heat around and made the surface seem cooler for a while,” said Joshua Willis, another climate scientist at JPL.
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“All of those factors are real,” Karl said. “If those factors had not occurred, the warming rate would have been even greater. … If anything we may still be underestimating the trend.”