Climate uncertainties

The bottom line of my previous post was that the ‘next generation questions’ on climate change should focus on what do we do about it? I also mentioned what major aspects of climate science I thought are most uncertain:
- Regional climate effects
- Equilibrium climate sensitivity
- The role of aerosol and clouds
- Sea level rise (update: added after Heiko’s suggestion)
Tom Fuller asked me to elaborate, based on some specific questions he posed: 

1. Regional climate effects

I think we can agree that both adaptation and mitigation (emission reduction) are needed, but letting mitigation play second fiddle puts us at risk of ever increasing climate damages, which will cost future generations a lot to adapt to (if at all possible). To limit the future risks to manageable levels, mitigation is of the utmost importance.

Helping countries become richer should likewise be coupled to helping them become more sustainable. Even apart from climate change, this is self-evident: 20% of the population consumes 80% of its resources. For many of these resources, there is not enough to go around for 6 billion people to have the American consumption pattern, plain and simple.

The strong link between wealth and pollution, resource depletion and climate change should be weakened. The only way that developing countries can reach our level of wealth in a sustainable way is if the ecological impact per unit wealth decreases at least as fast as their wealth increases (see eg Michael Tobis). Otherwise the impacts will continue to increase, above and beyond what we can reasonably adapt to.

 2. Climate sensitivity

 To estimate the equilibrium (Charney) sensitivity (change in temperature after a doubling of CO2), the climate forcing needs to be known as well as the climate response after it’s had time to settle into a new equilibrium. For a slowly changing forcing such as we’re experiencing now, the equilibration time is long but not accurately known, and neither is the aerosol forcing, so 20^th century data are not particularly useful. Collecting better or more temperature data is not going to help.

Climate sensitivity is primarily constrained by paleo-climate data, while the climate response following a volcanic eruption is also a useful indicator from what I’ve understood. These constraints leave some more wiggle room at the upper end than at the lower end. Combining multiple constraints together leads to a most likely value of 3 deg for a doubling of CO2 (See eg James’ empty blog). Climate models also converge on this value (+/- 1). This has been a remarkable stable estimate over the course of decades, while the uncertainty hasn’t decreased significantly. Perhaps it won’t anytime soon. And perhaps that doesn’t matter too much as far as policy goes, because even with a realistic low estimate we’re still way behind in our policy response.

 3. Aerosols and clouds

 The short lifetime (days to weeks) of aerosols is an important reason for the uncertainty in their role in climate change. It causes their concentration to be highly variable in time and space, and it’s hard to even know what the global concentration is. Add to that their variability in size and chemical composition, and the poorly understood role of clouds, and it’s clear that the uncertainty in aerosol radiative forcing will remain a steady feature of climate science for some time to come.

 Different clouds have different climate effects. They both cool (by reflection of sunlight) and warm (by their trapping of IR radiation, much like GHG) the atmosphere. Which effect dominates depends on the type and altitude of the cloud. Their large variability and myriad of interdependencies involved makes quantifying their global effect very difficult indeed. This won’t change any time soon.

I have some hope that better and more satellite measurements will drive the better quantification in the future, but that’s just a guess. Process based cloud physics studies are equally necessary to elucidate the interdepencies.

With the industrialization, SO2 emissions soared, causing the aerosol burden to increase. More recently we’ve started to clean up our act regarding SO2, so the aerosol burden (at least in Europe and North America) is decreasing again. That’s the reason for their ‘bridging effect’ halfway through the 20^th century; it has nothing to do with a political desire. Scientists are a strange bunch; they just want to understand what’s happening.

4. Sea level rise (update)

The dynamics of sea level rise are very uncertain, but very important since they determine to a great extent the speed of sea level rise, which in turn strongly affects the risk posed to society. (Thanks to Heiko for bringing this omission to my attention) The magnitude and speed of sea level rise are amongst the most uncertain,  yet also the potentially most dangerous effects of climate change. I have written more about sea level rise before.

My ‘next generation questions’ on climate change

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)

Climate solutions

The public debate about the reality of human-induced climate change is perhaps mostly interesting from a psychology point of view: How come some people embrace the wishful thinking and flakey arguments from small splinter groups and distrust the evidence-based conclusions from the vast majority of relevant scientists? I think that in many cases the answer is that they don’t like the perceived consequences. In other cases it’s a matter of thinking along familiar lines. And for some, it may be the attraction of being the underdog, which, in extreme cases, leads some to think of themselves as (supporting) the new Galileo. And yet others may have been fooled into thinking that there still is a real scientific debate about the big picture (with not a little help from the popular media). After all, without reading the primary literature or attending relevant conferences, how would you know who is right? 

The more relevant discussion for society is about how to deal with climate change. How do we act in the face of uncertainty, but with real risks of problematic consequences? “Skeptics” could make a very useful contribution to such a discussion, if they started thinking about how to deal with climate change while at the same time minimizing the perceived consequences they dislike so much (e.g. taxes and regulations).

Waiting until disaster strikes (as desired ‘proof’) before starting to deal with the problem, is not a rational option. If a doctor is 90% certain that you have a dangerous illness, you probably want to start treatment as soon as possible. Or would you wait with treatment until the doctor is 99% or 100% certain? The problem is, doctors and scientists are never 100% certain.

 

So what do we do?

 

I’ll be writing more about this question in the near future. Specific topics that I intend to discuss are geo-engineering (intentional engineering of the Earth’s climate), biomass, transport options (biomass/hydrogen/electric powered vehicles), and others. These are not all clear-cut ‘solutions’, and their suitability in dealing with the problem is vigorously debated, including in the scientific arena. Finally some real debate, rather than the fake stuff.

Freedom and responsibility

Arguments about how to address climate change often evolve around the concepts of freedom and responsibility. I was reminded of this by a recent discussion on the climate-policy blog Prometheus, where several comments from attorney “lgcarey” hit the nail on its head. E.g. here, (s)he writes

“…the key question here is about fraudulent conduct, not free speech. Free speech does not immunize me from liability for telling the guy who is interested in buying my house that the basement is dry as bone when I know that it leaks like a sieve every time it rains.” 

Of course, the issue is not whether a layperson is liable for expressing a thought that runs counter to the consensus. In complex issues, many people tend to not believe something of which they dislike the perceived consequences (“Back to the stone age!”). It’s unfortunate and perhaps unwise, but you can hardly put them on trial for that.

The issue is whether an entity (person, industry) with a financial interest in the matter, who knowingly distorts the evidence to increase their financial profit, is liable for doing so. To that, the answer is (or should be) yes.

The background to this discussion is some resurfaced old news that an industry funded lobby group distorted evidence about the reality of man-made climate change. Just like lobby groups before them did regarding health effects of smoking. History has a tendency to repeat itself. The NY Times has since published an addendum, but it didn’t change the bottom line very much in my view.

People opposing action on climate change often claim that their right to free speech is being stifled by, uhm…, yeah, by whom, really? I guess by the climate mafia, headed by Al Gore.

People calling for action on climate change on the other hand rather frame the issue in terms of responsibility.

Of course, both values are important, and a balance needs to be found between them. Freedom without responsibility leads to reckless anarchy, and responsibility without freedom is like a prison.

I, for one, hate it when somebody tells me what to do, or what not to do. I very much like my freedom. And I don’t want to take anybody else’s freedom away. However, freedom has limits. Your right to your freedom shouldn’t interfere with other people’s right to their freedom. I think that should include the freedom and rights of future generations and of nature at large.

If you don’t want to take your responsibility, it’s far easier for peace of mind to ignore the signs that you may adversely affect others, than to live with that uncomfortable knowledge.

If I’m addicted to smoking, I may be more likely to downplay the risks of smoking than if I weren’t a smoker. I would be pretty pissed off though with all those people around me telling me that indeed it isn’t harmful, especially if I somehow sensed that they withheld or twisted information to the contrary. And if decades later, suffering the full consequences of having smoked all that time, I found out that the tobacco industry had funded efforts to mislead and confuse the public regarding the health effects of its products, how would I feel then?

Will that be how future generations feel about (some of) us?

Haven’t we learnt the risks associated with “Buy now, pay later”? Isn’t it asocial to let somebody else pay for what you buy now?

As uncle Ben said to Spiderman: “With great power comes great responsibility”.

Herman Daly on climate policy

Found via Michael Tobis’ blog: From “know how” to “do now”, an excellent speech by Herman Daly (full text available here), on the interplay between climate science, economics and policy. Take home message: We know enough to start doing something about the problem. My addition: Any realistic change in our knowledge is not going to affect that conclusion.

“Can we systematically continue to emit increasing amounts of CO2 and other greenho’use gasses into the atmosphere without eventually provoking unacceptable climate changes? Scientists will overwhelmingly agree that the answer is no. The basic science, first principles, and directions of causality are very clear. Arrhenius discovered the basics a century ago. Focusing on them creates a world of relative certainty, at least as to the thrust and direction of policy.”

Parachute or altimeter?

On the other hand, focusing on the more uncertain rates and valuations creates “a world of such enormous uncertainty and complexity as to paralyze policy”. Perhaps that’s indeed what’s happening now. “To make the point more simply, if you jump out of an airplane you need a crude parachute more than an accurate altimeter.” Discussing the probabilities of a certain temperature change and sea level rise by 2100 may be very interesting scientifically, but it is not necessarily the most relevant for policy. If the main thrust of the change is clear (more greenhouse gases causing more warming, eventually leading to unacceptable climate changes), then society should leave the quantitative mangling over details to the scientists, and focus on what to do about it. Because any realistic change in the details is not going to affect this main thrust. 

The main thrust
Just in case you think that this main thrust is not at all certain; it is. The rates, the exact magnitude and exact consequences, the details, are uncertain, and as such are being investigated by scientists. But there’s no way that more greenhouse gases would not lead to a warming. Even a serious “skeptical” position would not change this main thrust; it would merely change the timing of “eventually”. If we burn all currently recoverable fossil fuels (dominated by coal), CO2 levels will not be double pre-industrial, but more like quadruple. (pre-industrial CO2 concentration is 280 ppm; current levels are 385 ppm.) Even with a wholly unrealistic, low climate sensitivity of 1 degree warming per doubling of CO2, put forward by die-hard “skeptics” like Lindzen, this is a recipe for disaster: The Greenland and West Antarctic ice sheets are not likely stable in the long run at 4 degrees higher temperatures than pre-industrial. Mind you, I write “in the long run”. The main uncertainty is in the rate, not in the eventual fate at such high temperatures.

If it’s bad, it’s really bad. If it’s good, it’s still pretty bad. 

The current best estimate for the equilibrium warming if CO2 levels are quadrupled (i.e. if all recoverable fossil fuels are burned) is 12 degrees over pre-industrial temperatures. Can you imagine what the world would be like? If we consider a picture, however improbable, of what would happen at the low end of the response curve (a “skeptical” viewpoint of e.g. 1 degree per doubling of CO2), we should also consider what would happen on the high end (an “alarmist” viewpoint of e.g. 6 degrees per doubling of CO2): That’s beyond my imagination. Btw, the empirically determined bounds for climate sensitivity are between 2 and 4.5 degrees per doubling of CO2. But even within the extreme bounds (e.g. 1 and 6), there’s no situation imaginable where the consequences of burning all fossil fuel reserves are benign: If it’s bad, it’s really bad. If it’s good, it’s still pretty bad. Therefore, (ab)using scientific uncertainty as an alibi to not do anything is clearly irrational.

Energy policy & economics

To come back to Herman Daly, he suggests that our energy policy should focus on “a sustainable aggregate level of energy consumption” rather than on “efficient patterns of consumption”. Increases in efficiency are over time often (more than) counterbalanced by increases in consumption (the rebound or Jevons effect). Daly goes on to say that “GDP growth at the current margin in the US is in fact uneconomic growth—that is, growth that increases social and environmental costs faster than it increases production benefits”. I have no relevant expertise to comment on that claim, but the notion that it’s better “to stop uneconomic growth and free up resources and ecological space for truly economic growth by the poor” makes certain sense, though it’s politically a hard sell, and it runs counter to how we’ve got used to think about economics. Moreover, “beyond a threshold of absolute income already passed in the West, welfare or self-evaluated happiness becomes a function of relative income rather than absolute income.” This is confirmed e.g. here: 

Hapiness and money

The solution? “Tax bads (depletion and pollution), not goods (income).” I.e. shift taxes from human capital to natural resources.

 

“To continue business as usual while debating the predictions of complex models in a world made even more uncertain by the questions we ask, is to fail to pull the parachutes’ ripcord. The empirical consequences of this last failure, unfortunately, are all too certain.”

 

Does the Deltacommission exaggerate?

(Nederlandse versie hier)

 

In the Dutch media there is some noise that the Deltacommission consciously exaggerated the dangers of sea level rise.

 

Fear mongering? 

On one of the Dutch news channels it was claimed that the commission wants to scare the citizens to make them accept the huge infrastructure project. Did they engage in fear mongering? That depends on whether the danger is being exaggerated. Pointing out a danger is not by definition fear mongering.

 

The commission is very clear that they take as a starting point a “plausible upper bound” to sea level rise. They did not present this upper bound (on the basis of scientific input) as being the most likely (as was claimed by eg Hans von Storch according to a Dutch newspaper); that would indeed have been an unfair representation.

 

‘Delta dictator’??

The same newsflash also contained the charge that the communication advice to the commission suggests that a charismatic leader, a so called ‘Delta dictator’, should quickly put the plans in motion. I couldn’t find any information about this charge on either the commission’s or the communication firm’s websites. A lot of the internet buzz refers back to the website of the news channel instead.

 

Comparison with WMD???

The newsflash ended with a comparison with the situation in the US just before the Iraq war. The Bush government tried to gain public support for invading Iraq by charging that “the Iraqi dictator has weapons of mass destruction”, whereas the evidence for this claim was very weak. It stands in no comparison with the scientific foundation on which estimates of sea level rise are based. Even though the uncertainties regarding its precise rise and timing are large, the evidence that sea level will continue to rise is very strong indeed. This is a totally different cup of tea compared with the unfounded charge of WMD. A bad ending of a tendentious newsflash.

 

Risk

The discussion should really be about what risk we are willing to take. Is it enough to protect ourselves against the most plausible sea level rise (according to current wisdom), or should we take into account a “plausible upper bound”? Should our horizon end at 2100, or should we also take into account what may happen thereafter? Should we only adapt to what may happen, or should we also try to prevent the worst (and bad) case scenarios? These are normative questions that should be discussed, on the basis of scientific knowledge with her inherent uncertainties. The Deltacommission clearly exposes her view on these issues (with the notable exception of mitigation). Instead of accusing them of fear mongering, the critics could perhaps have said that they are willing to take a higher risk. Okay, let’s discuss that then.

Sea level rise and the Dutch Deltacommission

(Nederlanse versie hier)

 

The Dutch Deltacommittee released their report on how to protect the Netherlands against the rising waters. The advice goes quite far, from the inevitable heightening of dikes to increasing the waterlevel of the major lake by 1.5 meters.

 

Starting point

The starting point is an estimate of sealevel rise of 0.55 to 1.1 metres by 2100 and of 2 to 4 metres by 2200. To their credit, the prognosis doesn’t stop in 2100, and neither does sealevel rise. In a business as usual scenario the sealevel will continue to rise (long) after 2200. The report mentions that they use a “plausible upper bound” of sealevel rise. A comparable range (0.5 to 1.4 metres by 2100) is found by extrapolating the observed correlation between temperature and sealevel rise.

 

The consequences of ice dynamics (e.g. mechanical instability of large ice sheets due to  more meltwater, associated with large uncertainties) is included in their estimate. That is the main reason that they are higher than the KNMI and IPCC estimates for 2100 (40 to 85 cm and 25 to 76 cm for 2100, respectively). A new article in the journal Science gives 80 cm as the most likely sealevel rise for 2100, and 2 metres as the upper bound (including uncertainties related to ice dynamics). Besides uncertainties regarding ice melt, the future greenhouse gas emissions are of course an important variable, and one that we can influence (for better or for worse).  Realclimate has a discussion of sealevel rise here and a thorough review of the IPCC estimates here.

 

Adaptation…?

Can the Netherlands adapt to such high sealevels? The Deltacommitte is very positive about that, at least up to a 4 metre (!) sealevel rise. I think that at some point the possibilities for adaptation become limited. For example, can the Netherlands continue to exist amidst a sealevel that is 6 metres higher than now? That’s what sealevels were 125,000 years ago, when the global average temperature was “only” 1 to 2 degrees higher than now. Such a massive change in sealevel probably takes centuries, if not millennia, to achieve, but it makes sense to me that we’d try to avoid it from happening nevertheless. Therefore we cannot afford to keep the earth very long or very high above the 1-2 degrees higher temperature. For how long or how high can we, before the big icesheets (Greenland and the Antarctic) start melting irreversibly? Nobody knows. But it’s not worth an experiment, I’d say.

 

Mitigation…!

The emphasis in the committee’s report is strongly on adaptation to rising sealevels, although emission reduction (mitigation) is of course also necessary. Otherwise it’s like mopping while the tap is running, as we say in Dutch. Is it perhaps better to relocate certain economic activities to safer grounds instead of pumping large sums of money into keeping them in the current low lying and vulnerable area? One comment I heard is from a member of parliament, who wondered whether our (grand)children would be happy  to pay for the measures we’d be taking now (because part of the money would be borrowed is the plan). I think that if anything, they will complain that we did too little for the problems facing us than too much.

 

To what extent should we anticipate (and thus adapt to and trying to prevent) future problems, that haven’t manifested themselves to their full extent? That’s a debate that’s worth having. Science doesn’t tell us which risks are worth taking and which are not; that’s very much an individual choice. Science does have an important role in informing us about the chances of a certain outcome; in other words, about the risk. The difficulty is that an individual’s choice in this matter has consequences for the risks of others, but their own risk is only marginally affected: the “tragedy of the commons”. Governments also have to make choices regarding the safety of their citizens. The same tragedy plays there too: The risk we run is strongly dependent on what other countries do. But let’s not use that as an excuse to then not do anything ourselves. And let’s not use scientific uncertainty as an excuse either. It does not decrease the risk; to the contrary.