In my
last post I promised to take a bit of time to discuss the 2oC
target. You would expect that such an important target was picked through the
use of a detailed scientific process with input from the brightest minds
on the planet. In this you would be wrong. The acceptance of the 2oC
target is actually one of the most deliberately muddied topics in the
climate change debate. The reason for this is because one of the
not-very-secret secrets of the climate change debate is that the 2oC
target was originally chosen based on the thinnest of technical
rationales. It was then backstopped with a thin veneer of research and buffed
up to look like it had a stamp of approval marked "SCIENCE"
before being trotted out for the public. Most distressingly, unlike a
true science-based target, which would be refined as our knowledge
base has improved and we have become more capable of understanding the climate
system, this target has held absolutely steady since it was suggested in
the late 1990's. Admittedly, since the target was not chosen based on the
science, advances in science really should not affect its value.
Now that
I have written an introduction that should get every climate activist on
the planet in a tizzy let me tell you a second secret. As targets go,
the 2oC target ends up being a pretty reasonable first
guess. While a lot of science supporting the target is pretty flaky (and
created using some pretty interesting premises) a lot of the research
indicates that the most likely range certainly is somewhere around 2oC
(it actually seems to range from 1oC to 4oC).
I'll go more into that later but wanted to reassure readers that the policy
folks aren't completely off their rockers.
For those
of you really interested in reading deeper into the debate around the 2oC
target there was a fascinating run of articles/blog postings in October 2014
that will provide interested readers with far more details than I
have room to provide here. The discussion started with a comment in Nature
by Drs. David Victor and Charles Kennel titled: Climate Policy: Ditch the 2oC Warming Goal. This was countered
almost immediately at RealClimate.org (a blog for and by some of the big
names in Climate Science) with an article by Dr. Stefan Rahmstorf titled Limiting global warming to 2 °C – why Victor and Kennel are
wrong. The New York Times Dot Earth blog (another biggie in the
climate blogosphere) then provided Victor and Kennel an opportunity to respond,
which they did at length. For those of you used to policy
discussions in the political sphere, this sounds like a pretty normal state of
affairs. Informed professionals present their thoughts in a major journal,
interested observers/experts provide counter-arguments and then the authors
reply in kind. When done consistently this type of discussion would provide
interested parties an opportunity to become informed without having to drown
themselves in the primary literature. Sadly in the field of climate science
this quality of back and forth discussion is seldom seen. Of
note, while I present this discussion as a model of how the debate might
be carried out in the climate field, my more sensitive readers will note that
the RealClimate blog posting starts with a pretty nasty run of ad hominems
and mean-spirited prose before the author actually gets down to discussing the
topic at hand. Believe it or not behaviour that would get you shunned in
virtually any non-academic, professional environment is actually considered a
step up from the normal in this field. Having read all the documents I feel
that Drs. Victor and Kennel made a far better case.
To go
back to my promise, let me quickly summarize the history of the 2oC
target. At the 1992 Rio Summit it was agreed that there was a need to "stabilize
greenhouse gas concentrations in the atmosphere at a level that would prevent
dangerous anthropogenic interference with the climate system (ref)". The problem is that at the time they
really had no idea what that would entail. It was understood that "global
warming" was the next serious environmental challenge but no one knew
exactly what that meant or even if we might be too late to make a
difference. Coming out of the Summit a number of meetings and technical
documents were sought/produced to establish what it would take to actually
"prevent dangerous anthropogenic interference in the climate".
The problem was that at that point in time the climate field was really in its
infancy. The first integrated assessment global climate models were still being
developed and the computer power needed to do the
necessarily complex calculations was not readily available. Just
consider that an iPad2 would have made the list of the world's speediest
supercomputers until 1994; so at that time the models were still
pretty basic. In the absence of the tools we take for granted these days a
number of organizations and governmental bodies went to work formulating
approaches that could be used in subsequent assessments. As described at the RealClimate
blog, the critical one ended up being from the German government's
Advisory Council on Global Change. This document took a very
qualitative look at the problem. It identified a "tolerable temperature
window" based on historic reconstructions of temperature regimes and came
up with the following argument:
This geological epoch has shaped our present-day
environment, with the lowest temperatures occurring in the last ice age (mean
minimum around 10.4°C) and the highest temperatures during the last
interglacial period (mean maximum around 16.1°C). If this temperature range is
exceeded in either direction, dramatic changes in the composition and function
of today’s ecosystems can be expected. If we extend the tolerance range by a
further 0.5°C at either end, then the tolerable temperature window extends from
9.9 °C to 16.6 °C. Today’s global mean temperature is around 15.3°C, which means
that the temperature span to the tolerable maximum is currently only 1.3 °C.
So
starting with the approximate 0.7°C that had already been observed by 1995 they
ended up with a number of 2oC, on which to hang their hat. As
described at the RealClimate blog, the rest was history. The German position
was adopted by the European Union and it became the de facto number we
see and love. Kinda scary eh! The 2oC target is simply
a sensible-sounding qualitative number based on approximate temperature
ranges for interglacial periods, buffered with a fudge factor.
The next
obvious question is: what is inherently wrong with the 2oC target?
Well, assuming you are okay with its qualitative derivation, the
obvious next issues are: 1) the question as to whether the number is
the right one? and 2) the question as to whether it makes sense using
a lagging indicator as your target? Let's deal with the second issue
first. As everyone involved in the climate change debate understands,
temperature is a lagging indicator. Moreover, as demonstrated by the
"pause" temperature can be a seriously delayed lagging indictor.
Since we don't have a good handle on climate sensitivity 2oC
could happen at 450 ppmv, it might occur at 800 ppmv or in an even less
likely scenario it could take until 1200 ppmv? As we have seen with the pause,
temperature has essentially held still for the better part of 20 years while
carbon emissions have continued pretty much unabated. This point
seems to be completely missed by Dr. Rahmstorf in his article. He harps on the
political value of the target without ever acknowledging that it is
less than a target than a shimmering mirage which may or may not exists
somewhere out there somewhere, if you squint just right. Under the current
target approach we will only be sure we have reached the edge of the
chasm after we have started falling...essentially the Wile-E-Coyote
approach to policy. If you truly believe that 2oC represents a
danger point then it would be much better to establish what emissions will
get you to that point and ensure we do not exceed those numbers. This
is the approach suggested by Meinshausen in his letter to Nature where
he suggests carbon budgets as a much better policy tool. While I cannot
attest to the validity of his actual numbers, the whole idea of
negotiating carbon budgets makes a lot more sense than negotiating to keep
ourselves below some nebulous post hoc target.
Another consideration in the debate is whether 2oC even represents an appropriate target. Since this post is already getting quite long instead of going into extreme detail on the topic I would simply direct you to a very interesting paper by Dr. Richard Tol from the University of Sussex. Since the article is pay walled, I will link to a figure from the paper which I found online.
What the
paper indicates (and is illustrated in the figure) is that minor amounts
of heating (less than 2oC) may actually result in improvements
in quality of life (as indicated by effect on % GDP). The conclusions of
the Dr. Tol paper were not surprising to me as any plant biologist will
tell you: plants grow better and have more drought tolerance under conditions
of higher atmospheric CO2 concentrations. While the exact
point at which the baseline is crossed remains under debate the positive
effects of small increases in atmospheric CO2 concentrations are
undeniable.
An
interesting consideration of the Tol graph, that I have not seen
discussed, is how the improvement in quality of life derived from the first 1oC
heating might actually be hindering attempts to slow the growth in carbon
emissions. Every week we see another attempt by alarmists to link higher
CO2 concentrations to wild and woolly weather and unexpected
global events. As I've written elsewhere, all this crying wolf does little
to help their cause and runs contrary to the peer-reviewed research.
Perhaps the policy people out there might want to acknowledge that increased CO2
concentrations are actually expected to improve things in the short
run. Framing the current conditions as a "calm before the
storm" would better allow the public to understand the risk. Instead they
keep talking about Hurricane Katrina which only reminds us about how long
it has been since Hurricane Katrina actually happened.
Good question.
ReplyDeleteBut bringing Tol's work in evidence brings me to a better one - what is the epistemic status of economic models as compared to climate models. Are they similarly informative? I think the answer is, demonstrably, no.
So seeing as your argument seems to be based in large measure on Tol's work (which is an outlier even among the published economics) should we begin with whether we believe it?
Please see
http://grist.org/climate-energy/how-much-is-climate-change-going-to-cost-us/
I guess we could sit here and throw rocks at integrated asset models all day. I only want to point out these IAMs are used to prepare the IPCC RCP's. This tells me all these predictions about future states are indeed fuzzy.
ReplyDeleteI don't believe the IPCC can structure a work flow to get useable products. So my suggestion is that you start looking for improvements on how you go about making these predictions outside the IPCC community.
Given the high dose of politics and propaganda being used, and the degree of personal animosity and hostility in the various "climate science" camps, plus economic reality, I don't think Obama, the EU, or climate science/economics can come close to reaching a successful outcome with current policies.
This means I'll keep advocating geoengineering research. It seems to be a pragmatic solution.
I am not yet convinced that "average" temperature is a meaningful metric. Nobody experiences (or suffers from) "average" temperature. The real consequences are from the highs and lows (and frequencies and durations). A 2 degree increase in "average" temperature could be essentially meaningless.
ReplyDeleteIt could be, conceivably.
ReplyDeleteBut that would be an astonishing coincidence, as the reason for the rise would be shifts in the way energy flows though the system. For this to result in very similar weather at all places on the planetary surface (given the complexity and mutability of fluid flows) seems extraordinarily unlikely.
There is surely some temperature difference for which this similarity expectation wholly fails; an 80 c increase would turn the oceans into gumbo.
We think it's hard to say whether that's this side of 2 C. What number would you put on it and why?
"Every week we see another attempt by alarmists to link higher CO2 concentrations to wild and woolly weather and unexpected global events. As I've written elsewhere, all this crying wolf does little to help their cause and runs contrary to the peer-reviewed research."
ReplyDeleteAre you claiming that peer-reviewed research does not indicate that increased energy in the system leads to destabilising effects and more chaotic and extreme weather events? What does it show, then?