Posts Tagged ‘AGW’

Climate Change: Wealth redistribution or making the poor even poorer?

August 17, 2011

In a previous thread, Andrew Adams made an insightful comment about how climate change impacts and mitigation mix in with economic development in poor countries:

Energy poverty in the developing world is a problem, along with food shortages and loss of arable land due to soil erosion and other factors, lack of clean water supplies, the prevalance of diseases such as malaria, TB and HIV/AIDS, the debt burden etc. And, of course, climate change, which both raises entirely new threats and exacerbates some of the problems mentioned above.


It is naïve to suggest that they can just go full steam ahead now and worry about the problem later once they have better developed economies. It always bears repeating that humanity doesn’t get to dictate the timescales for taking action to avert dangerous climate change – the planet does.

But of course, what they are going to do is only part of the problem; if we really care about the fate of people in developing countries we also have to ask what we are going to do about it. Unless we take action to reduce our own emissions we can hardly expect them to follow suit and in any case any action they do take will be futile, and if they are going to develop along low emission lines they are going to need our assistance in both practical and material terms. And of course it is our past (and present) actions which have brought humanity to the position it is now in so even if not everyone accepts the moral/ethical responsibility of those who are well off to assist those who are less fortunate, there is still the responsibility to deal with the consequences of our own actions. I see a lot of skeptics expressing concern for the effects that climate mitigation policies will have on developing countries but they reject the notion that the developed world should do anything to help bear the costs itself.


CO2 and temperature both increasing: D’Aleo’s attempt at falsification of AGW debunked

March 17, 2010

Below are two graphs of global average temperature and CO2 concentration. First I show the temperature anomaly from the three major datasets of surface temperature together with the CO2 concentration as measured at Mauna Loa since 1958:

The CO2 concentrations are plotted on a logarithmic axis because the temperature effect of CO2 is logarithmic. The 11 year running mean through the yearly temperature anomalies is given by the thick colored lines.

Before the 1970’s, the temperature trend was more or less flat for a few decades (see also the graphs in this earlier post). The strong increase in cooling aerosols (resulting from e.g. SO2 emissions) counteracted much of the greenhouse warming over that period. Since that time however, greenhouse forcing has been dominant, resulting in the temperature and CO2 trends following a similar pattern (at least over the multi-decadal timescale; short term variability is heavily influenced by e.g. El Nino/La Nina, major volcanic eruptions and other natural phenomena). A graph of the time evolution of relevant known climate forcings over the past 130 years can be found here.

A very popular graph that purportedly falsifies the whole “AGW dogma” is the following, showing unrelated trends of temperature and CO2 for a recent 11 year period. It’s been carefully crafted to create a certain impression:

However, this graph is entirely misleading:

- There are more factors than only CO2 that influence global average temperature.

- The expected trend in temperature does not necessarily rise above the expected level of yearly variability over the course of a decade.

- The graph purposefully starts at a record high temperature (1998) to maximize the visual impression of “falling temperatures”. It also strongly depends on the specific datasets used. This is a clear example of cherrypicking.

Using the same logic as this graph is based on, one could also falsify the theory of gravity by pointing to a bird in the sky (conveniently forgetting that there are more forces than gravity and that the bird has wings).

A quick ‘n dirty guide to falsifying AGW

January 6, 2010

(Nederlandse versie hier)

Have you ever heard of Newton’s theory of gravity? Well, it’s all made-up nonsense. You’ve been fooled.

The reasoning goes as follows:

  1. According to the theory of gravity, objects should fall to the Earth’ surface.
  2. That bird in the sky remains there, without falling.
  3. Theory of gravity is wrong.

This reasoning bears a lot of resemblance to the following, equally strong reasoning that falsifies the theory of anthropogenic global warming (AGW):

  1. According to AGW, CO2 controls the climate.
  2. For the past 10 years, global temperature remained more or less steady whereas CO2 levels went up.
  3. AGW theory is wrong.

Voila, problem solved. If only it were that simple…

What’s wrong with these arguments? They sound so logical at first sight.

  1. The theory to be falsified has been oversimplified. (There are more forces than only gravity; there are more factors influencing climate than only CO2).
  2. The observation has been oversimplified. (The bird has wings which can be used to exert an upward force; the expected trend in temperature does not necessarily rise above the expected level of yearly variability over the course of a decade).
  3. Therefore the conclusion does not hold. 

It appears that a lot of “skeptics” start with their desired conclusion and work back to which part-observations and simplifications are needed to get there. I prefer not to fall either, but the fact is, observing a bird in the sky doesn’t disprove gravity. Whether we want to or not, we’ll have to learn through falling and getting up.

Update: Gravity has apparently been shown to be a hoax based on Newton’s private correspondence being released.

My ‘next generation questions’ on climate change

August 19, 2009

Following an interesting conversation I’ve been engaged in with Thomas Fuller (see also the previous post), here is my take on what the next generation questions on climate change are.

Let’s distinguish the following main issues:
- To what extent is climate change occurring, and to what extent is it man-made?
- To what extent is that (going to be) a problem?
- What can or should we do about it?

The first questions are strictly scientific; the middle has a judgment value to it, and the latter is primarily a political/moral judgement (and has more to do with technology than with climate science).

 We have made much more progress in addressing the first question than in addressing the last one. The limiting factor in addressing the issues relating to climate change is not a lack of knowledge about the exact nature of the changes; rather, it is the unwillingness of society to deal with (the consequences of) this knowledge. Even if climate change is less bad than currently expected, we need to dramatically step up our policy response.

I don’t say this to downplay the uncertainties in climate science; there are many, and many of them are large (scientifically speaking). However, within realistic boundaries of the uncertainty, we still don’t do enough to deal with the issue: Any realistic change in our scientific understanding is not going to change the needed policy response, at least not in the short to medium term (~decades). As Herman Daly noted: “If you jump out of an airplane you need a crude parachute more than an accurate altimeter.” And Tom Yulsman: “With a bit of luck, maybe we can agree that regardless of [the details regarding] climate change, we need an Apollo-scale effort to develop transformational energy technologies.” How to shape that effort is the next generation question.

So the ‘next generation questions’ in my view relate to the last one: How are we going to deal with this? There are a lot of tough questions to be answered in that arena, e.g. relating to different technologies (nuclear, biomass, CCS, electric vs hydrogen transport, geoengineering, to name just a few highly contested topics), and relating to more institutional-political matters (e.g. carbon tax vs cap and trade, landuse, changes in consumption patterns, equity issues). Michael Tobis has some excellent writing on the latter topics.

Regarding the ‘next generation of questions’ strictly relating to climate science, some examples of important areas with high uncertainty are the following:
- Regional climate effects
- Climate sensitivity
- The role of aerosol and clouds
- Sea level rise (update: added after Heiko’s suggestion)

However, we need to keep in mind that uncertainty goes both ways, and that science usually progresses with small increments: Three steps forward, two steps back. It is wise to be very skeptical of any claim that the science is radically wrong. Any new piece of evidence just adds to the puzzle; it doesn’t replace existing evidence. Context and perspective are key, and they are often missing in loud proclamations against the consensus.

Let me give an example from an area of research that I’ve been working in for a number of years: Aerosol formation. For at least a decade, sulfuric acid has been regarded a key compound in the formation aerosol particles. The potential contribution of other compounds (ammonia, iodine, ions, organics) has been (and still is) hotly debated, but if someone tries to tell me that sulfuric acid has no noticeable effect on aerosol nucleation, I would not tend to take them very seriously, unless they have extraordinary evidence to back up that (scientifically radical) position. Nothing is impossible, but it’s not very likely.

I think we know a great deal more about the role of CO2 in the climate system than we do about the role of sulfuric acid in aerosol nucleation. I don’t expect a landslide change in scientific thinking on the subject. If someone does, they better bring very strong evidence to the table; a photograph or two won’t do.

(update: the next post elaborates on the major climate science uncertainties)

Next generation questions on climate change

July 12, 2009

Over at the Examiner, Thomas Fuller had a post outlining a ‘new generation of skeptical arguments against the theory of anthropogenic global warming’ (AGW), which he felt had a lot of merit. I got to his post via a comment thread at RealClimate, where he asked for input. He did get quite a lot of feedback, but unfortunately, a lot of it was packaged in a rather negative tone. (I’ll come back to communication strategies in another post.) Since he appeared to be sincerely interested, I felt compelled to react. I responded to (his framing of) his questions as follows:

You frame your questions/topics as “skeptical arguments advanced against the theory of anthropogenic global warming”. You also acknowledge that scientists are getting frustrated “answering the same ‘primitive’ objections repeatedly, only to see them resurface shortly thereafter, something that I am sure is frustrating.” I think a logical consequence is that your framing of the topic arouses a defensive reaction from climate scientists and their supporters. Based on you being aware of the scientists’ frustration in this matter, your choice of framing is rather odd, and so is your surprise about the reactions you received at RealClimate (mostly from commenters by the way; not from the RC editors). In between the snark, you did get some feedback there as to the contents of your questions/topics. It’s your choice whether to focus attention on the former (the snark) or the latter (the feedback to the content).

Most points on your list are neither new nor a threat to the theory of anthropogenic global warming. That said, some of your points have some validity in that the related uncertainties are large. Reframing your questions as “which areas in climate science have the greatest uncertainties?”, opens the door to a more constructive discussion. 

A quick glance at the points your raise:

Data gathering and analysis. Points 1-4 are pretty meaningless for reasons explained at length elsewhere. The revised ocean heat content data (nr 5) don’t show a decrease of ocean heat content AFAIK, and moreover, trends have to be decided upon at appropriately long timescales. I’m not familiar enough with Tropical troposphere trends to comment on, though Santer et al (2008) found no discrepancy between modeled and measured tropical tropospheric temperatures.

Climate sensitivity and feedbacks. There is considerable uncertainty in the precise value of climate sensitivity, so in my newly proposed frame, this would be a valid point. However, taking all constraints on climate sensitivity into account, it seems very unlikely that it is far outside the boundaries you quote: 1.5 to 4.5 degrees for a doubling of CO2. The chance for all previous work to be shown totally wrong by one new piece of work is perhaps not nil, but it definitely is very small.

Plateau in current temperatures. Trends have to be decided upon at appropriately long timescales. The apparent plateau is close to meaningless for deciding on climatic trends. This truly is an old classic that gets scientifically minded persons’ defenses up.

Tipping points. The exact nature and especially timing of tipping points is extremely uncertain, so yes, this is an area where the existing knowledge is very limited. However, the limited knowledge we do have (mainly based on paleoclimate) points to the existence of tipping points, eg related to the amount of ice cover. The policy relevance may be limited to “If it’s bad, it’s really bad. If it’s good, it’s still pretty bad”.

Other climate forcings. No news there. Those other forcings are taken into account and indeed, they are additive to the changes from GHG emissions. They do not negate the radiative properties of those greenhouse gases however. Also keep in mind that many of the stronger feedbacks respond to temperature, so the amplification (or dampening) of the temperature response does not differ greatly between different forcings. That means that there is not a huge amount of wiggle room to decrease (or increase) the importance of the role of greenhouse gases (at least not without violating basic physics).

I would add one more point: Aerosols. The uncertainty surrounding them and their impact on climate change is very large. But again, don’t expect a landslide change in current wisdom just because of that. That would be wishful thinking.

It is good to keep in mind that uncertainty is not the same as knowing nothing, and that uncertainty can go both ways: for the better or for the worse. We’ll have to make decisions in the face of uncertainty, whether we like it or not. Climate policy should be about rational risk assessment, based on solid science.

The NIPCC report: don’t be fooled

June 13, 2009

(Nederlandse samenvatting hier)              (For a sneak preview, see the bottom line below)

The new ammunition put forward by “skeptics” seems to be the Heartland InstitutesNIPCC report 2009 (“Climate change reconsidered”). It is made to resemble, at least in format and in name, the IPCC report. According to Dutch “skeptic” (and contributor to the report) Hans Labohm it completely shatters the AGW (anthropogenic global warming) theory (e.g. here, in Dutch). That’s a very bold assertion, which should be backed up by very strong evidence for it to be taken seriously. Let’s take a look at the executive summary…

Second opinion
The preface starts as follows: “Before facing major surgery, wouldn’t you want a second opinion?”
Now that’s funny. I recently described the IPCC process using the same analogy: If you get a second opinion on your health condition, and it confirms what your specialist said in the first place, your trust in the diagnosis probably increases. Now imagine that you collect the interpretations of medical professionals all over the world, and by and large they their conclusions converge to the same broad picture. This happens to be how the IPCC comes to its conclusions.
Their opening statement is actually a strong argument for going with the consensus position on a complex topic. Yet they use it to argue in the opposite direction; very peculiar.

It continues: “When a nation faces an important decision that risks its economic future, or perhaps the fate of the ecology, it should do the same.” (i.e. getting a second opinion)
Huh? Risking our economic future? If they’re talking about the costs of emission reduction, they are seriously exaggerating. Who is being alarmist here? There will be winners and losers, yes, but that’s something entirely different. Everybody has a choice to join the winners or the losers. Different from the horse races, it’s easy this time to predict who (in the long run) will be the winners and who will be the losers. Take your pick.

The usual stuff
The previous NIPCC report has already been commented on by RealClimate, and it doesn’t seem like there’s much news under the sun this time. The same old and tired arguments feature in the current report. The RealClimate article has many links that debunk the various talking points, and I’m not going to repeat all of them here. A presentation from the lead author, Fred Singer, has been briefly discussed at RealClimate as well. It’s a good example of yet another groundhog day. For those who have followed the staged ‘climate debate’, the list of authors is revealing: Many of the usual suspects, with a history so to speak.

There are the usual, to be expected arguments, like that it’s all the sun’s fault. And logical fallacies, like ‘the climate changed before without human activity being involved, so therefore it must be natural now as well’. Try that line of argument in a court of law against a pyromaniac, by saying that forest fires have always happened naturally. It won’t fly, and it reveals that this report is not about science. The good thing is, with such erroneous lines of reasoning, no specialized knowledge is needed to see that.

Degrees of uncertainty
What I didn’t expect, however, was to see otherwise interesting research be put in a context as if it somehow “falsifies the AGW theory”. In many cases, it hardly has any relevance to the attribution of current climate change, or to future projections.

Ironically, their main argument against climate modeling is its associated uncertainty (mistaking it for knowing nothing, and ignoring that uncertainty goes both ways). That doesn’t stop them from putting forward hypothetical feedbacks that have no evidence whatsoever of operating on a globally significant scale. By the way, climate modeling is mocked in the report as merely being “the opinions of scientists transformed by mathematics and obscured by complex writing”. Doesn’t sound like they know what a climate model really is.

The report goes on to describe many hypothetical feedbacks in the climate system. Of course, they are all negative: They counteract the initial warming, independent of the cause for the warming. Their combined effect, is the hope, should be evidence that the climate sensitivity is an order of magnitude (!) smaller than the commonly accepted range (between 1.5 and 4.5 degrees C for a doubling of CO2). Not just 50%, no, a factor of 10, I kid you not. My alarm bells go off. Let’s see what the implications of such low climate sensitivity would be. Any climate forcing (whether natural or human induced) would be so strongly damped as to hardly have any effect on global temperatures. But then how come the globe is warming, and has warmed and cooled in the past? A logical consequence of their theory (negligible climate sensitivity) is that it’s hardly possible for the earth’s climate to change. Indeed, there is no physics-based climate model that can satisfactorily model both the current and past climates with such low climate sensitivity.

Many of the proposed feedbacks involve the cooling effects of aerosols. They suggest that these cooling effects are larger than reported by the IPCC. That is contradicted by climate models providing a very decent match to the observed cooling following a major volcanic eruption (emitting sulfate aerosol in the stratosphere). Moreover, some have argued that a strong aerosol radiative forcing means that the climate sensitivity has to be large in order to still be able to explain the temperature trend of the last 100 years, so they seem to be shooting in their own foot.

They come up with all kinds of hypothetical feedback mechanisms involving more natural aerosol emissions in response to global warming: Dimethylsulfide from marine phytoplankton (although a very intriguing possibility, this has never been confirmed to be a significant feedback mechanism, and there is ample evidence to the contrary, which is omitted from the report), biological aerosols (idem), carbonyl sulfide (idem), nitrous oxide (idem), and iodocompounds (idem), about which they write the following:
“Iodocompounds—created by marine algae— function as cloud condensation nuclei, which help create new clouds that reflect more incoming solar radiation back to space and thereby cool the planet.”
Nou breekt mijn klomp (“Now my clogg breaks”), as I would say in Dutch. This route to atmospheric particle formation may be important at coastal sites with exposed seaweed, but its global importance is questionable to say the very least; at present it could best be considered an interesting thought experiment. Moreover, freshly nucleated particles have to grow by about a factor of 100,000 in mass before they start affecting climate, and a lot can happen to them before they reach the necessary size.

All very interesting research topics, but to claim that they are somehow evidence for negligible climate sensitivity is an extreme example of over-interpretation. In these active areas of research, where no firm conclusions have been reached yet on global significance, they selectively cite only those articles that they can somehow spin to support their desired conclusion. I feel that I’ve read enough of this report to know what it’s worth.

Bottom line
This report exhumes a very strong and unfounded faith in negative feedbacks from nature, which are hypothetical with sometimes sketchy, often contradictory, and sometimes no evidence of actually operating at a globally significant scale. This highlights an inconsistent view of uncertainty, and an unwillingness to weigh the evidence: “If it causes cooling, the uncertainty (or lack of evidence) doesn’t matter; if it causes warming, it’s too uncertain (and no evidence strong enough) to matter”.

How would you know?
Let’s apply some of my own recommendations for non-specialists on judging sources:
- The report clearly misses the forest for the trees.
- It gives a hidden argument for going with the consensus (“second opinion”), but somehow twists that around.
- It’s characterization of the IPCC process has the smell of a conspiracy to it and is full of strawmen arguments.
- To their credit (and my surprise), I couldn’t find any obvious confusion of timescales, such as confusing weather and climate.
- It contains some embarrassing mistakes in basic logic.
- The two way cause-effect relationship between temperature and CO2 is not properly recognized.
- Their strong claim of shaking the foundations of climate science is extremely unlikely; They don’t provide compelling evidence for such an extraordinary claim; They vastly overestimate the likelihood of cooling effects (feedbacks), and underestimate, deny or ignore warming effects.
- They grossly exaggerate the economic risks of emission reduction, and downplay the risk of unmitigated climate change.
- Some of the authors have historical credentials in a relevant discipline, more than a few have not. The list of signatories at the end is very thin on relevant expertise.
- The Heartland Institute is a conservative think-tank and not a reliable source of scientific information.


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