Monday, August 07, 2006

Well said!

Take a look at this editorial in a recent Washington Post. The last paragraph makes a point that I've been trying to make for a while.


Anonymous said...

I don't disagree that the globe is warming, I don't know how much humans are contributing (and neither does anyone else), although my considered scientific opinion is that it is much less than 50%, since I have an educated and documented appreciation of natural variability in climate not caused by man. I think the last paragraph of the editorial (remember this is a newspaper, not JGR) is a reasonable political position. It is like an insurance policy, but no one, including the WashPost, Al Gore, or the NYT can give me an estimate of what this policy will cost me as a taxpayer and citizen, or my country as a society, and what the alternatives to this policy are. I self insure or have high deductables on much of my potential personal liability, it's an economic decision, based on likely occurrance and potential costs, vs. 100% certain costs of the insurance. As I have said before, give me and others the info, both scientific uncertainty and probabilities of climate response to CO2 reductions and the certain costs for these reductions to lifestyle, income, personal expenses, etc. and I can make the choice. If you can't do that we are just into politics and "political" scientists arguing about it and saying trust me even if I'm not objective, all with some hidden agenda to sell books, fund research, get published and cited, get tenure, get elected, etc. That's where we are, so now Dr. Dessler, where are the answers to the questions and calculations?

Andrew Dessler said...

Dr. J-

First, I would disagree with your statement that no one knows how much of the warming is manmade. The scientific consensus is that most of the recent warming can be attributed to humans.

Second, the scientific (including economics) communities have done research on all of these issues that you demand info on. There are estimates of costs and benefits, and of possible future warming and impacts. In some cases, the answer is confidently known; in others, there is great uncertainty in these estimates, of course.

It sounds like you're quite unfamiliar with what's been done on this, so I'll refer you to the IPCC's Third Assessment Report ( That's a summary (as of 2001) of our understanding of these important issues.


Anonymous said...

Dr. Dessler, "most" is not an accurate number, and as I said, if you can't tell me how much (how many fractions of a degree will the earth's climate cool per ppm of atmospheric CO2 or ton of carbon the US stops emitting and when) bang I get for my buck, they what am I investing in? I have read the 2001 IPCC report many times, it has many scenarios and assumptions, on a generalized, global basis, I could care less about that. I want to know what you say you want to talk about, specific policy actions right here in the US and what they cost us vs. what benefit I can expect. Give me a link to that info and I will take a look, but I am confident it has not been done, as I have been involved in both the Senate and House groups looking into it lately. If all this has been done, then why don't you just send it to John McCain or Henry Waxman and just be done with it. The CRA, MIT, and EIA made estimates of these costs during the abortive McCain-Lieberman bills, but the costs and assumptions were wildly different, and no likely impacts of the CO2 reductions were ever studied, just vague generalizations. Unless the public gets better specific and definitive information, no policy action can occur, it's just a pig-in-a-poke, and my advice has been to study it further until we get good answers. I am really not an idiot or stupid about this subject, as I respect you too.

Anonymous said...

Let's analyize the Post paragraph:

"The reality is that nobody knows how bad global warming will be; responsible estimates vary from manageable to catastrophic."

True. More accurately, nobody knows how much global warming will be (1.5 to 5.5 C) OR, regardless of warming, if the impact will be significantly beneficial or catastrophic to human well being.

"So the prudent move is to take action now as a kind of insurance policy."

Nothing wrong with buying a policy when we know: a)how much we are going to pay, b) what benefits we will receive, c) what the likihood is that the policy will be needed, and d) what the acutal consquences will be without it.

As it stands, a buyer would be more confident in reasonableness of insurance program to guard against astroids hiting the earth than against the impact of global warming. At least with Astroids we know the probabilities of a serous impact, the results, and costs of mitigation - unlike gw.

"Yes, reducing carbon emissions substantially is a daunting prospect given American and world dependence on fossil fuels -- so daunting that it induces a kind of denial in many people."

Sure it is daunting and induces 'denial' but given that the Post is pushing for insurance against a never previously experienced threat, costing a massive amount in premiums, with an unknown result...such denial sounds more rational than taking council in fear.

"But it is a particularly ugly kind of denial that leads a congressional committee to spend this kind of energy attacking scientists, instead of confronting the problems their data suggest."

It is ugly for the people's represenatives to question the results of studies funded by the people? Perhaps the editors forgot that government committees and newspapers like the Post routinely criticize government and private funded studies and authorities in a number of areas, e.g.; economics, medicine, current events, public work projects, transportation, the environment, energy, etc. Just what makes climate science so special?

If something is unattractive (as well as disappointing) it is the reflexive attack that says that any informed challenge to an orthodoxy must be "ugly" and therefore dismissed as "more denial" - hardly the kind of responsible attitude towards science that is taught to the public.

Anonymous said...

Extremely well said Mark H.

EliRabett said...

The problem Mark, is that you forgot the weighting factor. The costs of global warming increase (strongly) non-linearly with the amount. Above 2 C or so, the cost will be very negative. This changes any insurance like calculation.

Moreover, a great deal of future climate change is already built in. We are already committed to substantial additional warming and sea level rise. The earth is not in radiative balance, with the excess going mostly into warming of the oceans. Even if the entire world, let alone the US stopped emitting fossil carbon into the atmosphere, CO2 concentrations would not significantly change for hundreds of years and there would be no cooling, just a less strong warming.

Given that dr. j's considered scientific opinion is in strong disagreement with the opinions of almost everyone who studies climate this suggests one might want to significantly discount it. As to costs, the dr. might want to look at the WG II and WG III reports. The AR4 (out in January?) do a better job on this, but the TAR is a reasonably place to start, although 5 years old.

EliRabett said...

In a previous post, dr. j said

"It may be true that some decision is coming from our "policy" makers (i.e. political hacks in DC)"

but here he says wrt responses to climate change

"I have been involved in both the Senate and House groups looking into it lately"

so, is dr. j a political hack?

Anonymous said...

elirabbet, what is the point of your last your comment above?

Anonymous said...

elirabett, I am not a policy maker, elected official, or political hack. By being involved in the process through advisement and consults, I try to provide scientific insights and data to those who make policy, are elected, and are political hacks. I can also recognize eggs and feed chickens without being a chicken. Hope you understand the difference, regards.

Anonymous said...

Oops, forgot to sign last comment, sorry. And I am puzzled at your statement elirabett about disregarding my views on climate change since I don't agree with you and what you represent as the unanimous scientific community. I know numerous distinguished climate scientists who agree with me, so I know your opinions are not unanimous, but perhaps you also discount any value in science to those who question the existing dogma. If so, you need a refresher course in the scientific method, principles, and history of science. Also, the documents you reference do not contain the specific information I cited, in this field and asking for policy action, vague generalizations and averages (as in the documents you cite) will not suffice. Also, the documents you cite are too slanted and are not critically examined for errors and omissions, an independent process is necessary to get objective, verifiable data even for the gross generalizations that are made. I know you believe, but as with religion, not all agree with you.

Anonymous said...

elirabett, if you believe what you say : "a great deal of future climate change is already built in. We are already committed to substantial additional warming and sea level rise. The earth is not in radiative balance, with the excess going mostly into warming of the oceans. Even if the entire world, let alone the US stopped emitting fossil carbon into the atmosphere, CO2 concentrations would not significantly change for hundreds of years and there would be no cooling, just a less strong warming.",
what's the point of even doing anything about it. If ALL CO2 emissions stopped, totally impossible, then we are still doomed? Between your "hopeless" stance and Dr. J's cautious approach due to scientific uncertainty, I would chose his. If the policymakers believe you elirabett (not likely) they also would do nothing since doing 100% produces no significant positive climate effects in anyone's lifetime. Surely you can't believe that, do you Dr. Dessler?

Dano said...

dr j said:

I don't know how much humans are contributing (and neither does anyone else), although my considered scientific opinion is that it is much less than 50%,


I find this comment thread full of boilerplate, and thus disappointing. To wit:

1. The people who do this for a living disagree with statements like ">50%" - that is, not the 'unanimous' (why you'd use that term is beyond me if you do consults [can't be worth much!]) community that does this for a living, but the vast majority. Any small minority can quibble. So what.

And no, small is not an accurate number, but it is not necessary to quibble over semantics to make a point (e.g. you used 'much less' - highly inaccurate).

2. And I find it fascinating that you agree with someone who characterizes scientfic findings as 'reflexive orthodoxy'. Hopefully none of my clients choose to remunerate you for your views. So much extra work for me...



Anonymous said...

Dr. Dessler...great blog and Gig Em! I have a couple of questions and thoughts.

First comment is on the loose and misleading statement in the WaPo editorial: "The actual concentration of carbon in the atmosphere has increased enormously since the advent of the Industrial Revolution."

Using round numbers, we have gone from around 300 to 370 ppm in the last 100 years. That is about a 23% change. Large in a historical context, and certain very rapid compared to other historical changes of larger amplitude, but "enormous"...not really.

Second, I think the debate about "a solution" should recognize a couple of things. If we accept for sake of argument that CO2 produced by burning fossil fuels is the most important forcing causing the recently observed warming; and as was mentioned in another thread, we accept that if we stopped all CO2 emissions tomorrow, global warming would still occur and would likely take decades or centuries to return to even current temperature levels...why are we focusing on trying to "prevent" it? We are already apparently past that point. We also know that the easiest solution to CO2 emissions will come when an economically viable alternative to the internal combustion engine is discovered. The drive to create such an advance is already occurring and will receive its largest boost from the economics inherent in "peak oil" and continued world economic growth that exceeds supply growth in oil production. So what incentive do we have to spend billions or trillions of dollars trying to stop something that is already assumed to be past the point of no return? Why not instead spend our money focusing on preparing ourselves for the problems predicted to come about as a result of the global warming that will happen no matter what we do with out CO2 output? Why not start relocating critical infrastructure farther from coasts that may be inundated by rising sea levels? Why not start relocating large agricultural production operations out of areas that are already drought prone and are likely to become more so? Why not work with major cities in drought prone areas that are already short on water supplies to reduce wasteful uses such as lawn watering and reuse wastewater in ways that make sense? If we are going to have to do all of those things no matter what happens with our CO2 output, why not spend our money on them instead of wasting money trying to fix a problem (CO2 output from fossil fuels) that will take care of itself through improved technologies and resource limitations in due time anyways? There are lots of reasons for more stringent regulation on things like industrial pollutant emissions and plenty of reasons to encourage reductions in dependence on oil, but from a long term economic standpoint, I don't see "prevention" of global warming as one of the compelling ones.

Second, I think what gets ignored in the scientific community is the radiative heat fluctuations from the earth's interior. Several researchers have shown that changes in heat flux between the earths inner and outer core are likely to be tied very closely to changes in the earth's magnetic field intensity and orientation. While it has been assumed that things like sst oscillations and volcanic/tectonic activity would reflect any change large enough to be a forcing for global warming, the fact is that the change in global temperature from the late 1800s to now is actually very small when compared to the total radiative heating from the core/mantle interaction and small, but broad changes in radiative heating COULD entirely escape the notice of scientists, while still possibly causing the types of changes in global temperature and sst that we have seen since the late 1800s. Add to that that recent research looking at the earth's magnetic field intensity and orientation over several centuries shows a distinct trend change in magnetic field intensity beginning in the late 1800s. Is the fact that the field intensity trend underwent a significant change in slope beginning at nearly exactly the same time as the global temperature changes started happening mere coincidence? Or is it evidence of a change in the earth's interior heat engine that has not been reflected in traditional measures such as volcanic output? Again, if such a relationship exists and is functioning as a significant and underappreciated forcing for global warming, nothing we do with CO2 will have the slightest impact on it. In that case, again, spending trillions on CO2 emission reductions will neither stop the forcing from that mechanism nor protect us from the localized effects of global warming.

Finally, as a geologist, I question the "climate science" community's grasp of the magnitude and extent of very long cycle changes in global climate, and where present day earth is in those cycles. For instance, look at the graphs on this page:

In the 0-400K year CO2 graph (with current day at the left end), prior to the large increase in the last 100 years of the graph, we were clearly already nearing the typical peak CO2 concentration of a cycle that appears to have a period of something like 100-120K years. The previous three peaks typically topped out at a concentration between about 270-300 ppm. However, in looking at the graph of temperature over the same period of time (0-400K years from the same link), despite being at or above the same CO2 concentrations as were observed in previous cyclical peaks, our temperature was 2-3 degrees C COOLER than the previous peaks. So on what basis do people like Al Gore claim we are seeing historically high global temperatures, when it would appear based on those graphs that we are actually abnormally LOW compared to similar cyclical peaks? How can we be so sure that WE are the cause of the relatively small warming we have seen (relative to historical amplitude changes), when those cycles clearly point out that given the CO2-temp relationship in past cycles, we should expect to be 2-3 degrees hotter than we are now and should be wondering why we are abnormally low.

Anonymous said...

The link came through incorrectly in my previous should have been:

Anonymous said...

Grrrr! The last part of the link should read:


Sorry for the multiple posts...

Anonymous said...

Well said Bill F., there is a vast difference in climate scientists or computer scientists who do climate models, and those of us who are trained and educated in geology, geophysics, paleontology, and paleoclimatology. Most people's eyes glaze over when you mention thousands or millions of years (including biologists), as they are educated and trained to respect short time periods (100-200 years) and a few generations, whereas we earth scientists become very skeptical of such small time samplings for any complex, long lived earth events like climate. Much of the disagreements I have are with non-earth scientists over this issue, since they are not educated in long term sequences and cycles.

Anonymous said...


My point in posting that was to point out that while CO2 and temp appear to move in relatively close coordination over large time scales like that, there is clearly a negative temperature divergence in the last few thousand years that is not explainable with CO2 alone. While the large scale cyclical behavior suggests a close relationship between CO2 and temp, there is no way of determining if a rise in CO2 caused by some other forcing caused the rise in temperature seen in past cycles, or if a rise in temperature from some other forcing resulted in a rise in CO2. What is apparent is that the most recent cycle that we would appear to be near or at the peak of would suggest that temperatures should be several degrees hotter, yet they are not. That suggests strongly to me that we do NOT have a good handle on exactly how tight the relationship is between temperature change and CO2 and which causes which. Therefore, the assumption that simply by rapidly raising CO2, we can force a global temperature change is not yet proven in the science. Just because our CO2 is "historically high" doesn't necessarily mean that temperature will follow. I am not saying it won't, I am just saying the relationship is far from proven. There are great models and theories that suggest that it will, but as a geologist, I look back at the very recent scientific history of my profession and can see from the battle to defend "continental drift" against "plate tectonics", that scientists often invest themselves so deeply in a given theory that they will blindly defend it to the exclusion of all other reasonable possibilities, which violates the very foundation of empirical scientific method.

Andrew Dessler said...

Bill F.-

Thanks for your comments. First, I think you have identified many of the questions we need to be debating now, in particular the mix of adaptation vs. mitigation. I would disagree with your statement that mitigation does not make sense --- I think a strong case can be made for an aggressive mitigation effort at present. However, we clearly need to focus on adaptation, too.

As far as your question about heat flowing from the Earth's interior, it can be shown quite convincingly that this is not an important term in the surface heat budget. But make no mistake --- scientists have indeed considered this.

Finally, we do not expect a perfect correlation between CO2 and temperature. After all, CO2 is only one of the factors that changes climate. In the last 50 years, however, the scientific community believes that CO2 is the most important factor, although other facts can still be playing significant roles.


Anonymous said...

Yes Dano, thank you very much for your education! Here is a great link from Dr. Dessler's colleagues at A&M about the Anthropocene. Now please read my post again and see that I am not in any way asserting that CO2 is a single factor agent. Quite the contrary, I am saying that those who automatically assume that rising CO2 means rising temperature are oversimplifying the system. PLEASE go look at the graphs. The "anomolous" period I am talking about is not the last 100 years or so that are being called the "Anthropocene", but the last 10,000 years or so. In that time period, our temperatures are 2-3 degrees C COLDER than what would be suggested by the CO2 relationship alone. You can only draw two possible conclusions from that data.

You can either assume that CO2 concentration alone is not an accurate predictor of temperature change. Or you can conclude that the increasing effects of various ecological changes (including land use changes, agricultural practice changes, etc.) that are largely attributed to human population expansion since the last ice age were a net NEGATIVE effect on temperature when ALL of the other processes were taken into account besides CO2. Either way, to say that simply because we are raising CO2 we should expect temperature to rise ignores the fact that over the last 10,000 years or so, either temperature is not being primarily driven by increased CO2 concentrations or anthropogenic changes in the planet's ecosystem are a net negative effect on temperature overall. In either case, reducing CO2 output into the atmosphere by the marginal amounts we are likely to be capable of over the next 2 decades is simply no guarantee of stabilizing global temperature and most studies point to the fact that even eliminating them altogether will have only a marginal effect at slowing down the global warming that is predicted to occur in the next several decades.

I can see Dr. Dessler's point about mitigation and adaptation, but to me, the cost to mitigate to the degree necessary to create a significant potential future benefit is just not reasonable, especially given the uncertainty present in the modeling and in the problematic asspects of achieving global unanimity of action. Let me put it this way. If somebody told you that your house was right at the edge of the 100 year flood plain and that you could not buy flood insurance of any kind. If your only two options were to 1) spend 5 times the price of your house to divert a portion of the watershed's flow away from your property (with no guarantees that nobody would build more subdivisions upstream and simply increase the overall flow in the watershed); or 2) Spend 5 times the cost of your house to relocate to a new area with a house that is 5 times as nice as your current one and isn't in a floodplain; which would you choose? Obviously its a strawman that could be pushed any direction you want, but the point is that if the industrial nations commit to huge reductions in CO2, and other nations simply pick up the slack, we haven't fixed anything, and now we are left without the economic power to adapt as well as we would have been able to, because the non-industrial nations stole our economic power when they picked up the slack from our reduction in CO2 emissions. Without global commitment and global action guaranteed (which is impossible), adaptation is the only strategy that makes any sense at all.

Anonymous said...

Forgot the link:

Anonymous said...

I don't quite understand your example about the financial advisor. To use that situation, I think a more appropriate set of choices to compare to the debate over how to adress potential global climate change would be the following:

If you were concerned about whether your daughter would get a scholarship to college, you have the following two choices: 1) Begin saving money now so that you can pay for her college if she doesn't get a scholarship (adaptation) or 2) Start a campaign to convince all colleges to let all students in free of charge so that she can go to any college she wants and you won't have to pay (mitigation). It is highly unlikely that you will convince all colleges to stop charging tuition and fees, and you can't predict exactly which college she will want to go to or which ones you might be able to convince to let her in for the logical choice is to begin saving money to pay for it yourself. You adapt your practices to the likely outcome instead of trying to force everybody around you to adapt their practices to solve your approaching dilemna.

As for the forcings, you and I are obviously talking about different periods of time. I wasn't aware that we could do html codes here, so let me make my links more direct, so perhaps you will actually look at them and see what I am talking about.

CO2 for last 400,000 years (present day at left end)

Temperature for last 400,000 years (present day at left)

Note that in those two graphs, at intervals of about 100,000 years, we see peaks in both CO2 and Temperature. Also note that between about 18,000 years ago and about 2000 years ago, CO2 rose from around 180ppm to 280ppm. That is a 55.6% increase. Over that same time period, temperature rose nearly 8 degrees C. However, the previous three times that CO2 concentrations had approached 270-280ppm, the temperatures were 2-3 degrees warmer than they are today. So lets look at more recent data and see what it says:

CO2 for the last 2000 years:

Temperature for the last 2000 years:

What we see is a climate that can vary by as much as 3.5 degree C over the course of a few decades with no change in the CO2 concentrations. While there may be other forcings that explain why the global temperature was able to vary so widely with no change in atmospheric CO2, what I have not seen is an explanation for why the global temperature change from 18,000 years ago to 2000 years ago results in a temperature that is 2-3 degrees C LOWER than what would be predicted by previous peaks. The concentrations of human activities and resulting land use changes were just not significant enough during that time period due to relatively low populations to have caused such a dramatically large deviation from what is otherwise a quite well correlated set of trends for the last 400,000 years. Therefore, I think we have to accept that there is either some climatological process that was not happening in previous cycles that resulted in the temperature at 10,000 years ago being 2-3 degrees C lower than would be expected, or you have to assume that the relationship between CO2 and temperature over the also 400,000 years is remarkably close, but NOT a cause and effect relationship. In either case, looking at the wide variations of climate from 2000 years ago to present, and the corresponding lack of change in CO2 until 150 years ago, it is clear to me that we cannot make the assumption that CO2 alone will cause global temperature to rise until we understand the climate feedback processes that caused the current CO2 vs. T relationship to be so different than what was seen in the previous 400,000 years.

I know you keep spouting land use changes and aerosols and other buzzwords, but what land use changes were occuring 10,000 years ago that were not occuring at the end of each previous "ice age"? What "aerosols" were being put into the air 10,000 years ago that resulted in global T stopping its rise 2-3 degrees C short of what 400,000 years of fairly closely correlatable data would suggest? When we can answer those questions with an explanation that accounts for ALL of the processes that affect climate and not simply a few of what we believe to be the most influential ones, then I will become much less skeptical of our ability to predict the affects of CO2 100 years from now.

Let me give you a funny story about models that maybe will explain some of my skepticism. As a hydrogeologist, I spend alot of time looking at models that try to predict groundwater flow. Those models are 100% at the mercy of how well the system in which the groundwater flows is understood. I was told a story of a friendly wager between two professors at A&M: one who wanted to setup a monitoring system to measure flow outward from an artificially constructed pond over sandy soil, for comparison to satellite imagery; and one who wanted to simply model the water flowing out of the pond for the comparison. After collecting what was believed to be the representative soil data necessary to predict the flow regime, the "modeler" put out his model of what he believed would happen, the "measurer" assembled his measurement system, and they filled the pond with water and sat back to see who was right. When reviewing the satellite photos, they saw no change in the pond or the soil surrounding it. The measurement system also showed no changes in the soil. Finally after a week or two, they took a trip out to look at the pond that had been constructed over the sandy soil. It was still full of water. The "sandy" soil that had been expected to allow water to flow rather rapidly through it was found to have a very small amount of exansive clay (less than 5% if I recall correctly). That seemingly insignificant amount of clay exapnded enough to seal the pore space in the soil and prevent the water from leaving the pond over the timeframe they had hoped to conduct their experiment. The moral of the story to me is that not only were two professors who were very knowledgeable fooled by mother nature, but it was a factor that both believed to be insignificant in the overall system they were looking at that ended up dominating the system. Given the degree of uncertainty we have about our climate and the extremely short time period (geologically speaking) over which we have detailed data for study, I simply don't believe we have enough expertise to say conclusively which factors are major and which are minor. While I accept that Dr. Dessler's knowledge and expertise on this topic are much greater than my own, I don't think you can dismiss the possibility that small changes in the earth's heat content could occur without resulting in a measureable change in the traditional measures used to assess such a change. What may seem like small or insignificant difference may have an effect that we would not expect based on our current understanding of the system and ability to simulate the thousands of variables involved.

Sorry for the long post, but it seems that this blog has attracted a fairly logical and reasonable following that can appreciate a more detailed discussion of these kinds of topics instead of engaging in 2 sentence "soundbyte" style sniping at each other.

Anonymous said...

So much for the links...I guess I am using the wrong codes or something.

If you put "Images/Temp_0" before the "-2000" and "-400k" for the temperature links and "Images/CO2_0" before the "-2000" and "-400k" for the CO2 links, they will work. I am not sure why they keep getting cut off.

Anonymous said...

I think you and I see adaptation and mitigation the same way for the most part. To me, adaptation is the "action" taken by a person or group of people to adjust what they do to "changes" that are (or are perceived to be) out of their control. Mitigation is the attempt by a person or group of people to control the "changes" so that they do not have to change their "actions". In other words, adaptation for the college example would be saving money over time in small increments so that you don't have to sell everything you own to fund your daughters college over a four year period. You accept that the need to fund college is something you may have no control over if she doesn't get a scholarship, so you take action now so that you will be able to pay for it later. You adapt to what you expect to come in the future. In my mind, that is comparable to a country recognizing that their coastal facilities may be vulnerable to sea-level rises from global warming and as a result, taking action to protect those facilities or to move them inland. That is their adaptation to expected future conditions.

In the college example, mitigation would be trying to change the college funding system so that it is more favorable to you at the time your daughter enters college. In other words, instead of adapting to what you expect to be the situation at that time (college will be expensive), you try to take steps to change the conditions you expect to be present at that time (making college cheaper) through your actions between now and then. In the global warming example, my definition of mitigation is that instead of protecting or relocating the facilities that are sensitive to sea level rises (adaptation), we try to figure out how we can change our current habits (i.e. cutting the burning of fossil fuels, changing land management practices, etc.) so that the conditions in the future are not a hazard to the facilities. In other words, we take action now (mitigation) to change the future conditions so that protection or relocation of facilities is not necessary.

Adaptation relies on our ability to predict where and how severe the hazards will be (which is easy in some cases and more difficult in others as seen in Dr. Dessler's most recent posting), whereas mitigation relies on our ability to predict the future impacts of our current practices. In cases like sea level rises, it is easy to predict which areas are at risk simply by their elevation and the expected rise. It is much harder to predict how successful any actions we take today to mitigate that rise will be. In cases of agriculture, determining where arid regions will appear is likely to be more difficult, but in some cases, it is easy to see that we should not expect certain areas that are already drought prone to suddenly become tropical rainforests. Therefore, adaption practices would dictate that we start trying to shift agricultural production away from those areas and stop encouraging future ag. development there with incentives. On the other hand, predicting the effects of mitigation on a regional scale is likely to be VERY error-prone, and could have severe consequences for failure if adaptations were not undertaken.

For instance, it is already obvious that certain areas of the SW US are non-ideal for ag production, and are only able to continue through enormously irrigation intensive practices that in many cases are subsidized heavily by federal water projects. In those areas, if current practices are forecast to result in a 3-5 degree C rise in temperature and a decline in rainfall from the already meager quantities that do fall there, obviously the future of ag production there is in jeopardy. If we adapt by moving ag production from those areas to areas that are likely to become more conducive to ag productivity and by stopping the consturction of additional government subsidized water projects that would encourage more ag development there, then it doesn't matter if we are off in our predictions by a degree or two in either direction, because there won't be any production left there. However, if we adopt a mitigation strategy that is predicted to only result in a 1 degree rise and we feel that ag practices can be maintained through more conservative irrigation strategies; then we are at the mercy both of the accuracy of our predictions as well as the willingness of the rest of the world to abide by the restrictions inherent in the mitigation strategy. If the world doesn't reach the mitigation goals or if our prediction is off by a degree or two, we could face disastrous results in which we lose a significant agricultural production area with no immediate possibility of quickly re-establishing it elsewhere.

I know that as Dr. Dessler says, these are all value judgements, but to me, adaptation as a solution offers a much higher degree of certainty that the money spent will achieve the desired result, is not dependent on unanimous world concurrence with a given strategy (when nations have a long history of failing to live up to international treaties when it costs them money to do so), and is much more adaptable to changes in the capabilities of prediction science in the coming decades.