It is not clear where the idea of a “global warming hiatus” originally came from, but over the last several years it has become a widely held idea. Many researchers have published papers seeking explanations for the pause but none of them have positively concluded that the break in rising temperatures was happening at all.
Now, two papers by different groups of researchers, may have lain to rest the idea that there has been any pause in riding global temperatures.
The first of the papers published in the journal Climactic Change, used a new statistical model to look at the question. The problem, when looking at the suggested hiatus, is that it is supposed to have occurred over a 15 year period is limited data. The data accumulated over that period is tiny when compared to the data accumulated prior to the year 2000.
“We had to develop a new method which takes into account the idea that the sample size during the hiatus is really not very large,” Bala Rajaratnam, assistant professor of statistics and Earth system science at Stanford University, told the Washington Post.
After developing their new model the researchers tested four different hypothesis; first that warming had stopped completely, second that warming had slowed, third that temperatures had changed over the period and fourth that there was a difference in the annual temperature.
Their analysis showed, in each case, no evidence for a global warming pause.
The second paper, published in the Bulletin of the American Meteorological Society last week also included a statistical analysis. It showed six periods in the last 45 years when a slowing trend could have been perceived despite temperatures steady rising during those four-and-a-half decades.
The researchers then took those numbers to economists for a “blind expert test”. A group of 25 professional economists were presented with the statistics. To remove any personal or political bias about global warming, the economists were told they were agricultural production numbers.
Each of the 25 was asked whether there had been a pause in the agricultural output over the last 15 years. The economists rejected the idea of a pause or hiatus, with some even calling such an idea fraudulent.
These two papers agree with several other resent publications which call into question the idea of a global warming hiatus.
“When one looks at the long-term record of global temperature, there are wiggles up and down and there are wiggles year to year and wiggles decade to decade. What we’ve seen is not unusual for a noisy up-and-down time series,” said Noah Diffenbaugh, an associate professor of Earth system science at Stanford University.
It remains unclear where the idea of a “pause” or “hiatus” in warming came from. However, according to NASA, it is very likely that 2015 will break 2014’s record as the warmest ever recorded.