Introduction

Global Warming (GW) alarmists are in a pickle: no GW, in spite of rising CO2 levels.  True believers are using quasi-religious slogans, like “The End [of the GW pause] is Near” and “Repent [Stop emitting CO2] Before It’s Too Late.”

The observed absence of a global-warming trend (often described as “pause” or “hiatus”), beginning around Yr 2000 (or perhaps even earlier) contradicts the results of every IPCC climate model – all of them driven by a steady increase in anthropogenic carbon dioxide; see figure. 

This lack of model validation has obvious implications for model-based estimates of future climate.  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 of “pause” (used by UN-IPCC alarmists) suggests that absence of a warming trend is only temporary -- and that warming may soon resume.  This seems to be the opinion of well-known climate alarmists; climate skeptics, by and large, have not published their views about the end of the pause.

Cause of the pause

As I wrote in American Thinker of Dec 29, 2014:

Scientific efforts to discover mechanisms for the cause of the pause, some dozens of “explanations” so far, have not yet been successful.  These 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.

These various causes can be classified according to “Forcing Imbalance” (FI) at the TOA (top of the atmosphere) – where the components of FI can be tracked precisely by satellites.  [FI is the difference between incoming, absorbed solar energy and outgoing heat energy emitted into space.]

1. FI unaffected, and in accord with rising CO2: This implies the existence of “hidden heat” somewhere (deep ocean? but when and how will the trapped heat be released? gradually or suddenly?)

2. FI reduced with regard to rising CO2 by (internal) negative feedback {through an increase in OLW (outgoing long-wave) radiation [by reduced water vapor in upper troposphere], or from an increase in albedo [reflection of incoming short-wave solar radiation] by low-altitude clouds}

But can such a negative feedback really cancel nearly all of CO2 forcing?

3. FI reduced by external offsets, like volcanic aerosols or solar irradiance decline; but this raises many unanswered problems: how to match and offset the steady increase in forcing from rising CO2?

Recent research has implicated long-term cycles in the oceans, but there is no agreed mechanism -- with some papers attributing the pause to Pacific-Ocean cycles, other research pointing to changes in the Atlantic, and one recent paper saying that all the oceans are involved.

There is also a suggestion that the pause is an artifact of the way the data is analyzed, and that it only appears to exist because faster warming in the Arctic has been excluded from the various global temperature analyses.  Another possibility is that 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. 

Science historian Rupert Darwall notes that,

“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.”

All these proposed mechanisms should also be able to answer two puzzling questions:

** Why did the pause begin around Yr 2000? 
** When will it end – as implied by the word “pause”?

When will the pause end?

Gavin Schmidt is head of NASA’s Goddard Institute of Space Studies (GISS); he is the successor to renowned climate alarmist James Hansen.  His views are typical of those of many other 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 tells the press.  But it’s a pure guess (hope?), not backed by any analysis.

The IPCC has not issued any official pronouncements on the end of the pause.  The pause itself is often referred to as a (temporary) “slowing down” of ongoing anthropogenic global warming

A new class of deniers has sprung up: climate alarmists who deny the existence of the pause altogether -- by stitching natural climate oscillations into the surface temperature record in a somewhat arbitrary manner; so far, these are only blog postings.

The most grandiose treatment of the issue has come from Michael ”Hockeystick” Mann – no surprise there.  Writing in the Scientific American (March 29, 2014) he states that the Earth will cross the 2-degC temperature “danger threshold” by 2036!  He accepts the existence of the pause, but predicts an abrupt end.  I doubt he has seen the plot shown below. 

No wonder, Jeff Id, in an amusing discussion in his blog The Air Vent (March 22, 2014), refers to Mann’s essay as “climate-porn.”

You may be interested in Freeman Dyson's [Princeton Institute of Advanced Studies] comment on the controversy; he is considered the "pope" of quantum field theory, and is a self-declared climate skeptic:

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.

S. Fred Singer is professor emeritus at the University of Virginia and director of the Science & Environmental Policy Project.  His specialty is atmospheric and space physics.  An expert in remote sensing and satellites, he served as the founding director of the US Weather Satellite Service and, more