The nearly two-decade long pause in global warming may just be the tip of the iceberg for evidence against anthropogenic climate change. A new paper found that temperatures in the lower troposphere have not shown a warming trend in as many as 26 years.
“In the surface data we compute a hiatus length of 19 years, and in the lower tropospheric data we compute a hiatus length of 16 years… and 26 years” using satellite data sets, according to Dr. Ross McKitrick of the economics department at the University of Guelph in Canada.
McKitrick’s study used a method that he says is “robust” when it comes to “heteroskedasticity and autocorrelation,” as well as cherry-picking of beginning and endpoints that present biased temperature trends. He found that the lower troposphere stopped warming between 16 and 26 years ago, and that surface temperatures have been flat for the past 19 years.
“Application of the method shows that there is now a trendless interval of 19 years duration at the end of the HadCRUT4 surface temperature series, and of 16 – 26 years in the lower troposphere,” reads McKitrick’s study, which was published in the Open Journal of Statistics.
News of the pause in global warming has baffled climate scientists and reignited debates over the dangers of global warming. Scientists have offered a wide range of explanations for why global temperatures have been flat for nearly two decades, including ocean oscillation cycles and increased volcanic activity.
The United Nations Intergovernmental Panel on Climate Change, however, has written off the pause in global warming and does not even estimate how long global temperatures have been flat — though scientists generally say it’s lasted between 15 and 20 years.
Despite the pause, the IPCC’s latest climate report continues to sound the alarm on global warming.
“Human influence has been detected in warming of the atmosphere and the ocean, in changes in the global water cycle, in reduction in snow and ice, and in global mean-sea-level rise; and it is extremely likely to have been the dominant cause of the observed warming since the mid-20th century,” reads a draft Intergovernmental Panel on Climate Change (IPCC) report obtained by The New York Times.
“The risk of abrupt and irreversible change increases as the magnitude of the warming increases,” the draft report reads.
Since 1990, carbon dioxide levels in the atmosphere have climbed 13 percent, from 354 parts per million to just under 400 parts per million. The early 1990s saw global temperatures rise, but that rise stopped late in the same decade and it has not trended upward since.
This is not McKitrick’s first foray into examining temperature trends. He published a paper in late July that found that climate models used by scientists and governments may have been overestimating tropical tropospheric warming for the past 55 years.
McKitrick found that from “1958 to 2012, climate models not only significantly over-predict observed warming in the tropical troposphere, but they represent it in a fundamentally different way than is observed.”
Update: The troposphere is the lowest portion of the Earth’s atmosphere. Wikipedia says the “lowest part of the troposphere, where friction with the Earth’s surface influences air flow, is the planetary boundary layer… The word troposphere derives from the Greek: tropos for “change” reflecting the fact that turbulent mixing plays an important role in the troposphere’s structure and behaviour. Most of the phenomena we associate with day-to day weather occur in the troposphere.”
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