Climate Battle: Round 2

In an opinion piece titled “Global Warming Is Here to Stay”, Washington Post Columnist Eugene Robinson sides with anthropogenic global warming (AGW) enthusiasts:

Yes, scientists are finally asserting a direct connection between long-term climate trends and short-term weather events. This was always a convenient dodge for climate change deniers. There might be a warming trend over decades or centuries, they would say, but no specific heat wave, hurricane or hailstorm could definitively be attributed to climate change.

“To the contrary, our analysis shows that, for the extreme hot weather of the recent past, there is virtually no explanation other than climate change,” Hansen wrote. “The deadly European heat wave of 2003, the fiery Russian heat wave of 2010 and catastrophic droughts in Texas and Oklahoma last year can each be attributed to climate change.”

Leave it to Mr. Robinson to promote a straw-man argument, although others have done the same thing. There is a difference between believing that climate change occurs and believing that climate change must be the result of Mankind’s activities.

On February 7, 2012, climatologist Judith Curry posted on her blog an explanation of the three main hypotheses pertaining to why climate change happens:

Consider the following three hypotheses that explain 20th century climate variability and change, with implied future projections:

I.  IPCC AGW hypothesis:  20th century climate variability/change is explained by external forcing, with natural internal variability providing high frequency ‘noise’.  In the latter half of the 20th century, this external forcing has been dominated by anthropogenic gases and aerosols.   The implications for temperature change in the 21st century is 0.2C per decade until 2050.Challenges:  convincing explanations of the warming 1910-1940, explaining the flat trend between mid 1940′s and mid 1970′s, explaining the flat trend for the past 15 years.

II. Multi-decadal oscillations plus trend hypothesis:  20th century climate variability/change is explained by the large multidecadal oscillations (e.g NAO, PDO, AMO) with a superimposed trend of external forcing (AGW warming).  The implications for temperature change in the 21^st century is relatively constant temperatures for the next several decades, or possible cooling associated with solar.  Challenges: separating forced from unforced changes in the observed time series, lack of predictability of the multidecadal oscillations.

III:  Climate shifts hypothesis: 20th century climate variability/change is explained by synchronized chaos arising from nonlinear oscillations of the coupled ocean/atmosphere system plus external forcing   (e.g. Tsonis,Douglass).  The most recent shift occurred 2001/2002, characterized by flattening temperatures and more frequent LaNina’s.  The implications for the next several decades are that the current trend will continue until the next climate shift, at some unknown point in the future.  External forcing (AGW, solar) will have more or less impact on trends depending on the regime, but how external forcing materializes in terms of surface temperature in the context of spatiotemporal chaos is not known. Note:  hypothesis III is consistent with Sneyers’ arguments re change-point analysis.   Challenges:  figuring out the timing (and characteristics) of the next climate shift.

There are other hypotheses, but these three seem to cover most of the territory.  The three hypotheses are not independent, but emphasize to varying degrees natural internal variability vs external forcing, and an interpretation of natural variability that is oscillatory versus phase locked shifts.   Hypothesis I derives from the 1D energy balance, thermodynamic view of the climate system, whereas Hypothesis III derives from a nonlinear dynamical system characterized by spatiotemporal chaos.  Hypothesis II derives from climate diagnostics and data analysis.

Each of these three hypotheses provides a different interpretation of the 20th century attribution and has different implications for 21st century climate.   Hypothesis III is the hypothesis that I find most convincing, from a theoretical perspective and in terms of explaining historical observations, although this kind of perspective of the climate system is in its infancy.

On July 30, 2012, Dr. Curry posted the following on her blog:

No one that I listen to questions that adding CO2 to the atmosphere will warm the earth’s surface, all other things being equal.   The issue is whether anthropogenic activities or natural variability is dominating the climate variability.  If the climate shifts hypothesis is correct (this is where I am placing my money), then this is a very difficult thing to untangle, and we will go through periods of rapid warming that are followed by a stagnant or even cooling period, and there are multiple time scales involved for both the external forcing and natural internal variability that conspire to produce unpredictable shifts.

Maybe the climate system is simpler than I think it is, but I suspect not.  I do know that it is not as simple as portrayed by the Rhode, Muller et al. analysis.

By the way, Dr. Curry has been invited by an unnamed journal to write a paper on the topic of consensus in climate change. She has posted a draft of her paper on her blog. What follows is an excerpt from her draft:

Unintended consequences of the IPCC consensus

“Historically, the claim of consensus has been the first refuge of scoundrels; it is a way to avoid debate by claiming that the matter is already settled.” – Michael Crichton

The consensus approach used by the IPCC has received a number of criticisms. Oppenheimer et al. (2007) warn of the need to guard against overconfidence and argue that the IPCC consensus emphasizes expected outcomes, whereas it is equally important that policy makers understand the more extreme possibilities that consensus may exclude or downplay. Gruebler and Nakicenovic (2001) opine that “there is a danger that the IPCC consensus position might lead to a dismissal of uncertainty in favor of spuriously constructed expert opinion.”  Curry (2011) finds that the consensus approach being used by the IPCC has failed to produce a thorough portrayal of the complexities of the problem and the associated uncertainties in our understanding.

Goodwin (2011) argues the consensus claim created opportunities to claim that the IPCC’s emphasis on consensus was distorting the science itself. “Once the consensus claim was made, scientists involved in the ongoing IPCC process had reasons not just to consider the scientific evidence, but to consider the possible effect of their statements on their ability to defend the consensus claim.”  (Goodwin, 2011)   We have personally encountered this effect numerous times in our interaction with colleagues that support the IPCC consensus.

While the IPCC’s consensus approach acknowledges uncertainties, defenders of the IPCC consensus have expended considerable efforts in the “boundary work” of distinguishing those qualified to contribute to the climate change consensus from those who are not (Goodwin, 2011).  These efforts have characterized skeptics as quantitatively small (e.g. Oreskes), extreme (Hassleman), and scientifically suspect (e.g Anderegg et al.)  These efforts create temptations to make illegitimate attacks on scientists whose views do not align with the consensus, and to dismiss any disagreement as politically motivated ‘denialism.’ ( e.g. Trenberth, other REFS).  Goodwin (2011) argues that this boundary drawing produces the strong appearance that the boundary between ‘insiders’ and ‘outsiders’ is based on political views.

There are broad consequences to this boundary work.  McKitrick (20xx) argues that consensus statements by scientific organizations put words in peoples’ mouths, imposing groupthink and conformity. Consensus statements silence and marginalize members who disagree with some or all of the statement, “demoting them to second-class citizens in their own profession, regardless of their numbers or credibility as scientists.”  This marginalization acts to degrade the intellectual climate in the field, and the declaration of consensus becomes a self-fulfilling prophecy.

The scientists who disagree with some or all aspects of the IPCC consensus include not only scientists from within the field of climate science (however that might be defined), but an increasingly broad community of technical educated people from a range of science and engineering disciplines that have educated themselves on climate science.  Some of these individuals are quite vocal and are frequently quoted by the mainstream media.  This has led to increasingly vociferous attacks on these dissenting scientists by supporters of the IPCC consensus, and to the labeling of anyone who disagrees with any aspect of the consensus as a ‘denier.’ (e.g Hasselman, etc.)   The use of ‘denier’ to label anyone who disagrees with the IPCC consensus leads to concerns about the IPCC being enforced as dogma, which is tied to how dissent is dealt with.

Is Dr. Curry describing anything that is familiar to you?

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Posted by David Robertson on August 10, 2012.
Filed under Environment, Weather.
Tagged with: Climate Change • judith curry.
A refugee from Planet Melmac masquerading as a human. Loves cats*. In fair condition. A fixer-upper. Warranty still good. Not necessarily sane.[*Joke in reference to the TV sit-com "Alf", which featured a space alien who liked to eat cats. Disclaimer: No cats were harmed in the writing and posting of this profile.]

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