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发帖数: 29846 | 1 August 10, 2012 by David Robertson
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 21st
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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