Whence the Global Warming Pause?

Published April 16, 2015

Editor’s Note: S. Fred Singer, Ph.D., is the most prominent scientist in the world speaking out against global warming alarmism. He founded the Science and Environmental Policy Project and the Nongovernmental International Panel on Climate Change. Singer received the 2014 Lifetime Achievement in Climate Science Award at the Ninth International Conference on Climate Change, July 8, 2014, in Las Vegas.

The absence of a global-warming trend, often described as a “pause” or “hiatus,” beginning around 2000, contradicts the results of every climate model used by the Intergovernmental Panel on Climate Change (IPCC), all of which project temperature increasing apace with anthropogenic carbon-dioxide emissions; see figure. 

Until the cause of the pause is better understood and incorporated into existing models, all policies aiming to stabilize climate are useless and are nothing more than highly uncertain and hugely expensive exercises. 

The label “pause” suggests the absence of a warming is only temporary and warming may soon resume. This is the opinion of climate alarmists who promote the fear human activities are causing potentially catastrophic global warming. 

Cause of the Pause  

Alarmists have offered a succession of possible explanations for why global temperatures have not risen along with increasing carbon-dioxide levels as predicted by climate models. 

One set of explanations posits temperature has been rising along with carbon-dioxide, though the heat is being trapped by some as yet unidentified hidden heat sink; for instance, the deep ocean. If this is the case, the question arises of when and how will the stored heat be released—gradually or suddenly?

Eminent physicist Freeman Dyson of the Princeton Institute for Advanced Study rejects this view, stating, “You ask me where the extra trapped heat has gone, but I do not agree with the models that say the extra trapped heat exists.”  

A second set of explanations suggests the temperature forcing from carbon-dioxide emissions has been suppressed by one or more negative feedback mechanisms internal to the natural climate system, for instance by an increase in the reflection of incoming shortwave solar radiation by growing low-altitude cloud cover. 

This brings up the question of whether such a negative feedback really could actually cancel nearly all of the increased carbon-dioxide’s forcing effect. 

A third posited explanation is external factors, such as volcanic or human-emitted aerosols or a solar irradiance decline, are preventing temperatures from rising (or rising faster). This creates many unanswered problems for modelers: Why have these factors matched and offset the steady increase in forcing from rising carbon-dioxide so far, and can or will they continue to match them in the future?

Natural Cycles

Recent research has implicated long-term natural cycles in the oceans in suppressing temperature, but there is no agreed mechanism. Some papers attribute the pause to Pacific-Ocean cycles, other research points to changes in the Atlantic, and one recent paper implicated all the world’s oceans. 

Some have even suggested there has been no actual pause, instead positing it as an artifact of the way the data is analyzed, saying it only appears to exist because faster warming in the Arctic has been excluded from the various global temperature analyses. Another possibility is the pause is an entirely natural variation in the climate cycle around an underlying upward trend in global temperatures. None of these explanations has gained widespread acceptance.

Explanations Leave Questions Unanswered

Science historian Rupert Darwall notes “IPCC has sidelined itself in irrelevance until it has something serious to say about the pause and has reflected on whether its alarmism is justified, given its reliance on computer models that predicted temperature rises that have not occurred.”

None of these proposed mechanisms has been able to answer two questions critical to them being acceptable as possible explanations of the pause: Why did the pause begin around 2000? And when will it end, as implied by the term “pause,” and the warming predicted by the models continue? 

I wrote in American Thinker (12/29/14), scientific efforts to discover mechanisms for the cause of the pause, some dozens of “explanations” so far, have not yet been successful. These explanations include “a build-up of heat in the deep oceans, a weakening of solar activity, and aerosols of volcanic ash in the atmosphere that reflect the sun’s rays back into space. However, the impact of solar activity and volcanoes does not appear sufficient to explain the pause and the accumulation of deep ocean heat appears to be somewhat elusive—the measured increase in ocean heat content being less than required to explain the pause.”

When Will the ‘Pause’ End?

The views of Gavin Schmidt, successor to renowned climate alarmist James Hansen as head of NASA’s Goddard Institute of Space Studies, are typical of climate alarmists: 

“Within 5 to 10 years, the steady increase in greenhouse gases will overcome the [cyclical] factors that may be responsible for the pause,” he told the press. Schmidt’s assertion is a pure guess (hope?), not backed by any analysis.

The most grandiose treatment of the issue has come from Michael “Hockey stick” Mann. Writing in the Scientific American (3/29/14) he stated the Earth will cross the 2°C temperature danger threshold by 2036. He recognizes the pause but predicts an abrupt end. I doubt he has seen the plot below.

No wonder Jeff Id, in an amusing discussion on Air Vent (3/22/14), referred to Mann’s essay as “climate porn.”

S. Fred Singer, Ph.D. ([email protected]) is professor emeritus at the University of Virginia and chairman of the Science & Environmental Policy Project.