Posts Tagged ‘Gavin Schmidt’

A warm 2015 and model –data comparisons

August 7, 2015

Guest post by Jos Hagelaars. Dutch version is here.

Discussions on the Internet regarding climate change are sometimes about scientific details, sometimes about the climate sensitivity regarding the equilibrium situation hundreds of years from now, but the most prevalent discussion topic is probably: the global average temperature. Will it get warmer or colder, is there a temporary slowdown or acceleration in the rise in temperature, are the models correct or not, will the eventual warming of our earth in the future be large or small? New numbers are released on a monthly basis and every month megabytes of text are generated about them. My forecast is that 2015 again will lead to a discussion-spike.

The graph above shows the evolution of the global surface temperature anomaly for three datasets, where the average of the period 1981-2010 is defined as 0. For the year 2015 only data are presented up to and including June. So far 2015 exceeds all other years and the evolving El Niño makes it likely that 2015 will set a new world record.

Gavin Schmidt and Judith Curry on Science Advocacy

December 23, 2013

Gavin gave a fantastic talk at this year’s AGU conference about science advocacy (good report on it by Yale CMForum and Dot Earth). The video is available via the AGU youtube channel:

He argued that it’s best to be explicit about one’s values and clearly distinguish when one is talking values (“ought”) and when one is talking science (“is”). I entirely agree. I would add that it’s important to distinguish recommending a generic (e.g. mitigation) vs a specific (e.g. CCS) course of action, especially when the latter is not one’s area of expertise. I wrote about the public role of scientists before, which touches on many of these same issues.

Judith Curry also chimed in, complimenting Gavin but also giving some criticism, much of which is rather off-base imho.

Both Gavin and Judith refer to this statement by Thomas Stocker at the end of the (well worth watching) IPCC AR5 video:

Continued greenhouse gas emissions cause further climate change and constitute a multicentury commitment in the future.  Therefore we conclude that limiting climate change requires substantial and sustained reductions in greenhouse gas emissions.

Is this a normative statement (“ought”) or a factual statement (“is”)? Gavin claimed it’s the latter, Judith claimed it’s the former. It would be advocacy if the goal was left out, as in “we should reduce GHG emissions”. But that’s not what Stocker said. Instead, what he said comes down to “if this is the goal, then that is what needs to be done to achieve it”. Curry claims that adaptation, carbon sequestration or geoengineering would also be options to limit climate change. That’s only partly true. Adaptation doesn’t actually limit climate change, as the word says it means adapting to climate change. As such it helps in the short term (and is definitely important), but in the long term adaptation without mitigation is like mopping the floor while leaving the tap running (see also the Rabett). Carbon sequestration is a viable option to reduce atmospheric concentrations, but with current technologies it can only make a minor contribution. So it could limit climate change to a very limited extent one might say. Geoengineering is a more complicated story. Basically, it exchanges one type of climate change (temperature changes) with another type (hydrological changes), so it changes climate change.

Perhaps Stocker’s statement could have been made more specific by including e.g. something like “limiting climate change to what societies are adapted or can adapt to requires substantial and sustained reductions in GHG emissions” which I think is what he meant anyway.

Curry goes on to state ” And there is a missing element in this argument that warming is ‘bad’, which is a value judgment and has nothing to do with science.”

This is a strawman argument, as it’s not a (hidden) element in Stocker’s argument as given above. Again, it would be true if the goal was omitted or left implicit (but it wasn’t). If one feels that limiting climate change is not needed (because it’s not bad) than the needed cure (reducing emissions) is not needed, obviously. That is entirely consistent with what Stocker said.

Curry further offers the following list of “examples of potential hidden values that are rather inconvenient (because) these are why the public distrusts scientists as advocates”. I offer my comment with each (in italics). It’s not at all clear that these would all go in the direction of a bias in favor of the mainstream (as Curry seems to implicitly assume); to the contrary.

  • personal career advancement: Unclear in which direction this would most likely go.
  • research funding: idem, though this could cause a tendency to increase the apparent magnitude of uncertainties.
  • the value in terms of professional recognition (e.g. awards from professional societies) that supporting the scientific consensus can provide (recognizing the ostracism that con result from straying): No bigger reward for a scientist than to prove the scientific consensus wrong.
  • media attention: This goes in the direction of providing relatively more media attention to contrarian voices, Judith Curry herself being a good example (assuming that she wasn’t as prevalent in the media before her U-turn away from mainstream science). This got confirmed in the large survey amongst climate scientists that I conducted last year (not yet published).
  • influence within the scientific community: This hinges on using solid arguments, so usually provides the correct incentive.
  • influence at the power tables in terms public policy: Like with media attention, extreme voices seem to have disproportionate influence. Look at the regular line-up for US senate hearings for example. If you crave media attention and political influence, being loudly contrarian is a sure way to achieve that. In the Netherlands the same tendency is apparent.
  • broader political objectives that support any/all of the above: This goes more likely in the direction of downplaying rather than overplaying AGW I would argue.

Ocean Heat Content: Can we monitor the transfer of heat through the top 700 metres?

October 12, 2011

At RC, Gavin Schmidt and Roger Pielke Sr are discussing how Ocean Heat Content (OHC) has changed in the recent past. The disagreement seems to be on how the apparent slowdown in heat uptake of the top 700 metres can be reconciled with apparent warming of the deeper ocean. It’s very informative to witness two experts debate this in public (even though the discussion is hampered by frequent misunderstandings and other derailing issues). I’ve found this a puzzling issue for a while and am still not sure if I fully grasp it, but here goes: 

On his blog, RPSr writes:

If heat is being sequested in the deeper ocean, it must transfer through the upper ocean. In the real world, this has not been seen that I am aware of. In the models, this heat clearly must be transferred (upwards and downwards) through this layer. The Argo network is spatially dense enough that this should have been seen.

Gavin responds to this statement at RC:

Obviously heat going below 700 m must have passed through the upper ocean. However, the notion that Argo could see this is odd. Argo measures temperature, not flux. The net flux into a layer is calculated by looking at the change in temperature. It cannot tell you how much came in at the top and left at the bottom, only how much remained.

Both arguments make intuitive sense. Whether indeed temperature measurements should have seen a transfer of heat depends on the precision and on the (spatial and temporal) density of the Argo network. Besides that, it also depends on the mode of heat transfer (episodic or continuous). Or perhaps better put: the extent to which the influx and outflux of heat balance each other.

Gavin does not agree with Roger’s last statement (that it should have been see), but argues instead that the signal would not likely be observable amidst the variability (response to 140): 

I have no confidence that the observations will be sufficient to distinguish the anomalous heat flux from the climatological mean with sufficient precision to be helpful.

Roger concedes that the observation network’s precision is an important precondition for heat transfer to have been observed, when he writes in response to my little summary over there: (Roger)

(…) we should still see a slight elevation in the temperature anomalies IF the Argo data precision is good enough. I do not know the precision of the temperature data measurements, and hope someone else can answer that.

And in 193 Roger writes:

First, I stated that the Argo data density was fine enough to see the movement of the heat downward, but am now unclear on this, and look forward to an Argo specialist to give us an overview of capability in this regards.

There is however a second if-statement to make, about the mode of transfer. In response to 2, Gavin wrote:

Most heat transport into the deep ocean will occur in the down-welling branches of the overturning circulation, centered in theNorth Atlanticand the Southern Oceans. Diffusive fluxes in the rest of the ocean will be much smaller.

Roger (140) says more or less the same, but arrives at a conclusion that is not shared by Gavin:

if this transfer occurs in globs associated with mesoscale and larger ocean circulation features (as suggested in the ECMWF data), we should clearly see this movement of heat.

About the mode of heat transfer Gavin writes in response to 155:

Heat transfer will be mainly continuous, not episodic.

I.e. the heat transfer is strongest in specific locations (agreed on by both), but continuous in time (which prompted a question from Roger “how do you know?”).

In a continuous case, for a while the same amount of heat may enter the top 700 m from above, as leaves it from below. As a result, no warming signal in this layer will be observed, whereas heat is being transferred through it. In an episodic case, it would in principle be observable (though still dependent on the precision and signal to noise ratio of the measurements).

In contrast to what I wrote in my little summary at RC (175), the disagreement is not so much on whether the heat transfer is concentrated in space (both seem to agree that it is), but rather on whether the heat transfer is continuous or episodic in time (Gavin thinks it’s the former; Roger doesn’t say) and on whether the data precision is sufficient (Gavin thinks it isn’t; Roger doesn’t say).

Figure 9b from Hansen et al., ACPD 2011, “Earth’s Energy Balance and Implications”. Note that this Fig gives the heat uptake, which is the slope of a figure of heat content (in Joules): A positive heat uptake means that the heat content is increasing.

Figure caption: Six year trends of ocean heat uptake estimated by Levitus et al. (2009) and Lyman et al. (2010) for upper 700 m of the ocean, and estimates based on Argo float data for the upper 2000 m for 2003–2008 and 2005–2010.

I’ll probably update this post as the discussion progresses. Over at SkS, there have also been informative discussions between Roger and the regulars over there.

Lisbon reconciliation unsettling

February 4, 2011

The Lisbon climate reconciliation workshop is over and it has created a lot of blog-fodder. I’m quite intrigued by the concept and find it a worthwhile undertaking to try to assuage the tempers in the public debate. Whether this workshop was a useful step towards that goal I wouldn’t know; I wasn’t there. The stories floating around paint a bit of in-crowd picture, with participants varying from staunch contrarians, social scientists and journalists to a small handful of climate scientists at the more agnostic side of the spectrum of professional opinion. Strong proponents of the mainstream scientific view were largely absent AFAIK, as were more activist voices. (I don’t know the views of all those present, so take this characterization for what it’s worth.)

If one were to divide the whole spectrum of opinion in three categories (overplaying uncertainty – mainstream scientific view – overplaying certainty), one could say that only the former category was well represented, and perhaps some who are edging between the first and middle category. Based on the names I recognize, it definitely wasn’t a representative sample from those engaged in the public climate change debate. Which thus defeats the purpose of reconciliation a bit I guess.

Apparently RC’s Gavin Schmidt was also invited, but declined. Gavin writes that his

decision not to go was based purely on their initial assessment of why there was conflict in the climate debate. They appeared to think that it was actually related to reconstructions of medieval temperatures and differing analyses of ice extent. Since these are not even close to the reason why climate science is politicised, I saw little purpose in trying to ‘reconcile’ on points that are completely tangential to the real causes of conflict.

Somehow Gavin’s absence was twisted by Fred Pearce, who wrote that Gavin Schmidt

said the science was settled so there was nothing to discuss.

Needless to say, Gavin has said nothing of the sort (he’s said the opposite). Anonymous conference participant “tallbloke” has outed himself as the source. In a letter to the New Scientist editors, Gavin wrote:

Since, in my opinion, the causes of conflict in the climate change debate relate almost entirely to politics and not the MWP, climate sensitivity or ‘ice’, dismissing this from any discussion did not seem likely to be to help foster any reconciliation.

As an experienced climate journalist, Pearce is well aware of the baggage that the term “settled science” carries: It is often used as a strawman attack on climate science, in which context it means something like “there’s no uncertainy and therefore no need to discuss any of these scientific issues”. Gavin and most, if not all scientists, would vehemently disagree to this.

At other instances (e.g. by Simon at CaS) it is defined as “widespread agreement amongst experts on the main tenets of the issue”. Most Scientists would agree that such consensus exists (it’s hard to argue with really), but it is not at all the same as the definition often used when used as a rhetorical weapon by contrarians. So a defense that that’s how it was meant doesn’t sound convincing to me.

As Stoat rightly sais:

“the science is settled” has been one of the mantras used almost exclusively by climate denialists as a term of insult for those actually doing science (…). It is a feeble attempt at a double bind: is the science settled? ha ha, then you can’t be a scientist because real science is never settled. Is the science not settled? Oh great, then we don’t need to do anything until it is.

Update: Gavin’s response to the conference invitation conforms to his initial description of why he declined. Steve McIntyre chimed in to say that Fred Pearce had read this email as well, which makes the twisted transcription into “settled science” even weirder. Eli assembled the main back and forth’s.

The public role of scientists

December 11, 2009

To what extent should scientists differentiate in their role as ‘pure’ scientists and their role as public educator, advocate, activist, or whatever other public role they may want to assume? James Hansen is not afraid to voice his political opinion. As expected, he is viciously attacked for that by political opponents, but others, even if not in agreement on everything he sais, give him credit for differentiating clearly between talking science and providing a personal opinion. I definitely do.

Roger Pielke Jr frequently takes issue with how scientists blur these roles. He often charges that scientists (especially those from RealClimate are a frequent target) “argue politics through science”, i.e. pretending to talk only science, but in the meantime providing a value-laden political stance. Now that all depends on what he means by “politics”.

Climate scientists more and more speak out about the need to (drastically) reduce emissions. IMHO, they do so based on an understanding of the science. Of course, it is also based on a value judgement, that the risks posed by unmitigated climate change are undesirable. Roger’s point (I think) is that this value judgement is not widely shared. He may be right in that, but I think that the vast majority of people opposing the need to curb emissions do so for reasons other than science, and then rationalize that decision by twisting the science around so that it fits their pre-conceived wish not to curb emissions. There are preciously few people who really accept the science, and still strongly argue against emission reduction.

Consider the analogy of a lifelong smoker who goes to see his doctor for breathing problems. The doctor may say: “All the indications point towards your lung function deteriorating. This is very likely related to you having smoked for X decades. In order to minimize the risk to your health, I urge you to quit smoking.”

That is what I see Gavin Schmidt and many other climate scientists doing. And I find it perfectly legitimate, even desirable, that scientists (as well as doctors) share their knowledge about risks with those who need to know.

If the doctor were to say as the last sentence instead “(…) I urge you to take these nicotine patches” he would act as a stealth advocate, since there are many more options to quit smoking that the patient may want to chose from.

If the patient is so hooked to his cigarettes, and would rather continue smoking than extend his statistical life expectancy by X months, he is free to do so. If however he rationalizes that decision by claiming “smoking isn’t bad for your health at all. My dad was 96 when he died in a car accident, and he chain-smoked his whole life!”, the doctor would be right to reply: “You’re mistaken. Smoking is definitely bad for your health. If you keep smoking, your life expectancy will be X month less than if you quit smoking, and you will have more breathing problems. It is your choice whether or not to quit smoking, but you should make your choice in the full knowledge of these consequences”.

This highlights a different problem. One could argue that by continuing to smoke, the patient really only impacts his own health negatively (and those who breath the second hand smoke; likely not the doctor). If the majority of people, and especially the people in power, decide to ignore the problem and not change the trajectory society is on, it is everybody who suffers. Even worse, those in different parts of the world, and those who have yet to be born, will suffer the most. That makes it much more difficult to just say “I don’t care if you quit smoking, as long as you realize the risks”. 

So climate scientists could perhaps be more specific about this, by saying e.g.: “You’re mistaken. Unabated CO2 emissions will very likely cause substantial climate change, with serious consequences. So you should decide your course of action based on this knowledge. If you don’t care about these risks, that is your perogative. However I do. Please find yourself another planet to experiment on.”


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