The United States Senate Committee on Environment and Public Works held a hearing on 18 July at which a number of leading climate scientists gave testimony. One of them was Roy Spencer, who is best known for his work on satellite measurements of climate phenomena. He is a calm and unfussed scientist who rarely raises his voice, but just gets on and done his work. What he said in his presentation was most interesting.
Dr Spencer is no slouch in this field, where he has been working for nearly thirty years. He was a NASA scientist, with a Medal for Exceptional Scientific Achievement to show for it, and he has published lots of papers, on global temperature monitoring with satellites, on the amount of warming we might expect from greenhouse gas emissions, how to monitor hurricane strength from satellites, and quantitatively explaining ocean heat content changes. For some years now he has been a principal research scientist at the University of Alabama at Huntsville.
‘My overall view of the influence of humans on climate is that we probably are having some influence, but it is impossible to know with any level of certainty how much influence. The difficulty in determining the human influence on climate arises from several sources: (1) weather and climate vary naturally, and by amounts that are not currently being exceeded; (2) global warming theory is just that – based upon theory; and (3) there is no unique fingerprint of human caused global warming.
My belief that some portion of recent warming is due to humans is based upon my faith in at least some portion of the theory: that the human contribution to atmospheric greenhouse gas concentrations has resulted in an estimated 1% reduction in the Earth’s ability to cool to outer space, and so some level of warming can be expected to occur from that change.
Exactly how much warming will occur, however, depends upon something we call “climate sensitivity” (Spencer & Braswell, 2010; 2011), and relatively few researchers in the world – probably not much more than a dozen – have researched how sensitive today’s climate system is, based upon actual measurements. This is why popular surveys of climate scientists and their beliefs regarding global warming have little meaning: very few of them have actually worked on the details involved in determining exactly how much warming might result from anthropogenic greenhouse gas emissions.
Our most recent peer-reviewed paper on this subject, Spencer & Braswell (2013), has arrived at a climate sensitivity of only 1.3 deg. C for a doubling of atmospheric carbon dioxide, based upon a variety of global measurements, including warming of the global oceans since the 1950s. This level of warming is below the lower limit of 1.5 deg. C minimum predicted in the last (AR4) IPCC report. It is also in line with (an admitted minority of) other estimates of low climate sensitivity published in the peer review literature.
It should also be noted that the fact that I believe at least some of recent warming is human-caused places me in the 97% of researchers recently claimed to support the global warming consensus (actually, it’s 97% of the published papers, Cook et al., 2013). The 97% statement is therefore rather innocuous, since it probably includes all of the global warming “skeptics” I know of who are actively working in the field. Skeptics generally are skeptical of the view that recent warming is all human-caused, and/or that it is of a sufficient magnitude to warrant immediate action given the cost of energy policies to the poor. They do not claim humans have no impact on climate whatsoever…’
Ho goes on to discuss two of the currently popular topics in AGW.
‘The lack of statistically significant warming in the last 15 years … is sometimes glossed over with the claim that the global temperature record has a number of examples of no warming (or even cooling) over fifteen year periods. But this claim is disingenuous, because the IPCC-presumed radiative forcing of the climate system from increasing CO2 has been at its supposed maximum value only in the last 15 years. In other words, when the climate “stove” has been turned up the most (the last 15 years) is also when you least expect a lack of warming.
It is time for scientists to entertain the possibility that there is something wrong with the assumptions built into their climate models…’
‘The claim has been made that the extra energy from global warming has mostly bypassed the atmosphere and has been sequestered in the deep ocean, and there is some observational evidence supporting this view (e.g. Levitus et al., 2012). But when we examine the actual, rather weak level of warming (measured in hundredths of a degree C) at depths of many hundreds of meters, it implies relatively low climate sensitivity (Spencer & Braswell, 2013)… ‘
Even if our ocean temperature measurements of deep warming of hundredths of a degree over the last 50 years are correct, and mostly due to human greenhouse gas emissions, they probably do not support the IPCC’s pessimistic view of future warming.’
There’s much more in this patient statement that repays reading. I liked the cool reference to the Cook et al. monstrosity of a paper that I wrote despairingly about when it was published. How can peer review let through something as bad as this?