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(回答先: 地球温暖化、減速していない＝最新調査 投稿者 ｒｅｉ 日時 2015 年 6 月 05 日 18:14:00)
地球温暖化は停止していなかった 2014年は最も熱い年
Global warming 'pause' didn't happen, study finds
2014 to be the warmest on record
Reassessment of historical data and methodology by US research body debunks ‘hiatus’ hypothesis used by sceptics to undermine climate science
Global temperature map
The year 2014 was Earth’s warmest in 134 years of records, according to an analysis of surface temperature measurements by Nasa scientists. In a separate, independent analysis, scientists at the National Oceanic and Atmospheric Administration also found 2014 to be the warmest on record. Photograph: GISS/NASA
Karl Mathiesen
@karlmathiesen email
Thursday 4 June 2015 19.00 BST Last modified on Friday 5 June 2015 07.51 BST
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Global warming has not undergone a ‘pause’ or ‘hiatus’, according to US government research that undermines one of the key arguments used by sceptics to question climate science.
The new study reassessed the National Oceanic and Atmospheric Administration’s (Noaa) temperature record to account for changing methods of measuring the global surface temperature over the past century.
The adjustments to the data were slight, but removed a flattening of the graph this century that has led climate sceptics to claim the rise in global temperatures had stopped.
“There is no slowdown in warming, there is no hiatus,” said lead author Dr Tom Karl, who is the director of Noaa’s National Climatic Data Centre.
Dr Gavin Schmidt, a climatologist and the director of Nasa’s Goddard Institute for Space Studies said: “The fact that such small changes to the analysis make the difference between a hiatus or not merely underlines how fragile a concept it was in the first place.”
The results, published on Thursday in the journal Science, showed the rate of warming over the past 15 years (0.116C per decade) was almost exactly the same, in fact slightly higher, as the past five decades (0.113C per decade).
Adapted from Noaa National Centers for Environmental Information
In 2013, the UN’s most comprehensive report on climate science made a tentative observation that the years since 1998 had seen a “much smaller increasing trend” than the preceding half century. The results highlighted the inadequacy of using the global mean surface temperature as the primary yardstick for climate change.
Karl said: “There’s been a lot of work done trying to understand the so-called hiatus and understand where is this missing heat.”
A series of studies have since identified a number of factors, including heat transferred into deep oceans and small volcanic eruptions, that affected the temperature at the surface of the Earth.
“Those studies are all quite valid and what they suggest is had those factors not occurred the warming rate would even be greater than what we report,” said Karl.
Dr Peter Stott, head of climate monitoring and attribution at the UK’s Met Office, said Noaa’s research was “robust” and mirrored an analysis the British team is conducting on its own surface temperature record.
“Their work is consistent with independent work that we’ve done. It’s within our uncertainties. Part of the robustness and reliability of these records is that there are different groups around the world doing this work,” he said.
But Stott argued that the term slowdown remained valid because the past 15 years might have been still hotter were it not for natural variations.
Global warming slowdown probably due to natural cycles, study finds
Read more
In the coming years the world is expected to move out of a period in which the gradient of warming has not slowed even though the temperature has been moderated. This means “we could have 10 or 15 years of very rapid rates of warming,” he said.
“Even though the observed estimate is increased, over and above that there is plenty of evidence that the rate of warming is still being depressed,” he said. “The caution is around saying that that is our underlying warming rate, because the climate models are predicting substantially higher rates than that.”
Noaa’s historical observations were thrown out by unaccounted-for differences between the measurements taken by ships using buckets and ships using thermometers in their engine in-takes, the increased use of ocean buoys and a large increase in the number of land-based monitoring stations.
“Science can only progress based on as much information as we have and what you see today is the most comprehensive assessment we can do based on all the information that’s been collected,” said Karl.
Schmidt called the new observations “state of the art” and said Nasa had been in discussions with Noaa about how to incorporate the findings into their own global temperature record.
Prof Michael Mann, whose analysis of the global temperature in the 1990s revolutionised the field, said the work underlined the conclusions of his own recent research.
“They’ve sort of just confirmed what we already knew, there is no true ‘pause’ or ‘hiatus’ in warming,” he said. “To the extent that the study further drives home the fact ... that global warming continues unabated as we continue to burn fossil fuels and warm the planet, it is nonetheless a useful contribution to the literature.”
Bob Ward, policy and communications director at London’s Grantham Research Institute, said the news that warming had been greater than previously thought should cause governments currently meeting in Bonn to act with renewed urgency and lay foundations for a strong agreement at the pivotal climate conference in Paris this December.
“The myth of the global warming pause has been heavily promoted by climate change sceptics seeking to undermine the case for strong and urgent cuts in greenhouse gas emissions,” said Ward.
Since scientists began to report a slower than expected rate of warming during the last decade, climate sceptics have latched on to the apparent dip in order to question the validity of climate models.
Last February, US Republican presidential candidate Ted Cruz told CNN: “The last 15 years, there has been no recorded warming. Contrary to all the theories that – that they are expounding, there should have been warming over the last 15 years. It hasn’t happened.”
Cruz’s rival for the Republican nomination, Jeb Bush, was using the pause to argue for inaction as early as 2009.
The Global Warming Policy Foundation (GWPF), the UK thinktank set up by Nigel Lawson to lobby against action on climate change and which hosts a flat-lining temperature graph on the masthead of its website, was dismissive of the study.
Dr David Whitehouse, an astrophysicist and science editor for the GWPF, said: “This is a highly speculative and slight paper that produces a statistically marginal result by cherry-picking time intervals.” He claimed the temperature graph was at odds with those of the Met Office and Nasa, despite both organisations saying the new study’s results were consistent with their data.
http://www.theguardian.com/environment/2015/jun/04/global-warming-hasnt-paused-study-finds
Study Finds No Pause in Global Warming
More comprehensive temperature measurements suggest previous results were inaccurate
A study in the journal Science, using more comprehensive measurements, concludes that the upward trend of global temperatures did not slow this century, contrary to previous analyses. What has changed? WSJ’s Jason Bellini has #TheShortAnswer.
By GAUTAM NAIK
Updated June 4, 2015 4:28 p.m. ET
509 COMMENTS
A new study concludes that the upward trend of global temperatures didn't slow this century, contrary to previous analyses that suggested the world is in the midst of a global warming hiatus.
Earlier observations showed that global surface temperatures increased by an average of 0.1 degree Celsius per decade from 1950-1999, a rise believed to stem from a surge in greenhouse gas emissions linked to human activity. But puzzlingly, for the period 1998-2014 the warming rate was recorded at a slower 0.06 degrees per decade even though greenhouse gas emissions continued to rise.
That apparent slowdown—which computer models didn’t predict—has been seized upon by those who are skeptical about man-made climate change and sparked debate about how long the pause might last. While several studies have tried to explain the plateauing of global temperatures, there is no consensus about the cause. Explanations have ranged from an increased uptake of heat by the oceans to lower levels of atmospheric water vapor and natural climate variability.
The latest study, published Thursday in the journal Science, suggests that previous research wasn’t accurate because of irregularities in how some temperatures are measured at land and sea. In the new analysis, the researchers tried to account for them and bolstered the earlier measurements with fresh temperature data from around the globe.
“We found that the rate of warming over the past 15 years was no different than the rate of warming in the second half of the 20th century,” said Thomas Karl, director of the National Oceanic and Atmospheric Administration’s National Climatic Data Center and lead author of the study.
The latest research is unlikely to be the last word on whether the global warming pause is real or not.
“The work itself is solid and consistent with some of the research we’ve been doing, but I would be cautious about the authors’ statement that their study doesn’t support the notion of a slowdown,” said Peter Stott, a climate scientist at the Met Office, the U.K.’s national weather center, who wasn’t involved in the Science paper.
For example, the notion of a global warming pause can depend on which time period is studied. “If you look at [NOAA’s] own data, the warming rate has been slower in the last 15 years than it was in the previous 15 years,” said Dr. Stott.
A March photo from the Australian government's Antarctic Division shows the Totten Glacier, the most rapidly thinning glacier in East Antarctica. ENLARGE
A March photo from the Australian government's Antarctic Division shows the Totten Glacier, the most rapidly thinning glacier in East Antarctica. PHOTO: AGENCE FRANCE-PRESSE/GETTY IMAGES
Nonetheless, Dr. Stott and most other climate scientists believe that the planet has continued to warm since the late 19th century. They argue that natural climate fluctuations can lead to brief periods lasting a decade or more when the rate of temperature increase can fall, stall or accelerate. The empirical evidence for global warming, they add, isn’t reflected in temperature data alone but a range of other phenomena, including shrinking ice sheets, rising sea levels and warmer oceans.
Temperature data, however, remains a crucial barometer, and the new findings could prompt a re-evaluation. In 2013, a report by the United Nations’s Intergovernmental Panel on Climate Change noted that global surface temperature “has shown a much smaller increasing linear trend over the past 15 years [1998-2012] than over the past 30 to 60 years.”
The new study says the IPCC conclusion is no longer valid.
The results are based on land temperature data from about 10,000 stations—more than twice the number used in previous analyses—and on improvements to sea surface temperature data obtained from thousands of commercial ships and ocean buoys.
Measuring temperature is tricky business, especially at sea. Ships used to mainly collect data by dropping a bucket over the side of the ship, bringing up some water, and measuring the temperature of that water. But from 1950 onward, more measurements were made via engine intake thermometers.
In recent decades, scientists have also begun to use more buoys rather than ships for ocean observations. Buoys tend to report a slightly cooler temperature than ships. Unlike previous analyses, the latest study accounts for those cooler readings to yield a more reliable set of data. That is significant because of the increasing number of buoys used in such calculations.
There are still gaps. Coverage of the Arctic—which is warming twice as fast on average as the rest of the world—remains poor. “We still need to refine” global temperature trends by including more Arctic readings, Dr. Karl said.
Write to Gautam Naik at gautam.naik@wsj.com
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