Thursday, August 24, 2006

"Climate changes naturally"

One of the most irritating red herrings in the climate debate is the following argument:
The climate has warmed and cooled naturally over its entire history, so 1) the present-day warming must therefore be natural, and 2) we shouldn't worry about it.
Point 1 I debunked here. The science strongly supports the conclusion that humans are contributing significantly to today's warming. To understand why I object to point 2, let's consider the following image:


Following point 2 above, we should tell the pilot of that plane not to worry ... after all, the plane is in a descent, but this plane has descended lots of times before. Why should this descent cause any concern???

The answer should be obvious. This descent is quite different from previous descents, and one that the pilot will not survive. Similarly, the evidence we have is that the present-day warming is far more rapid than most past climate variations. Before people jump on me, I know there is some evidence that some past changes have been rapid (e.g., the cooling during the Younger Dryas), but these were all associated with reorganizations of the circulation of the atmosphere-ocean system that are not now occurring. Thus, it might be that today's warming has no precedent in the entire history of the Earth. Because of the quality and sparseness of data, there is significant uncertainty in this conclusion, but speaking as a citizen, just the possibility that this is true causes me grave concern about the state of the climate system.

22 comments:

George Landis said...

Of course it causes you concern Dr. Dessler, that is your "thing" and your cause celebre and your reason to exist it seems. But it causes me none what so ever, this issue is a non-issue for me, and for millions of others looking for real issues to deal with.

Best,

Dano said...

But it causes me none what so ever, this issue is a non-issue for me,

To clarify, the topic of the post is the mendacious techniques used by denialists/contrascientists.

Best,

D

Dano said...

But it causes me none what so ever, this issue is a non-issue for me,

To clarify, the topic of the post is the mendacious techniques used by denialists/contrascientists.

Best,

D

George Landis said...

There you go again dano, missing key sentences due to your reading comprehension problems, Dr. Dessler said this: "Because of the quality and sparseness of data, there is significant uncertainty in this conclusion, but speaking as a citizen, just the possibility that this is true causes me grave concern about the state of the climate system."

I don't have the right to respond to that statement? Has Dr. Dessler appointed you as the thought and thread police here?

Bill F said...

Dr. Dessler,

I have to somewhat disagree with your assessment that "it might be that today's warming has no precedent in the entire history of the Earth". You cite sparseness of data as a qualifying factor, but that is a vast understatement. The period of time for which we have the density of detailed temperature data to be able to see such a short term trend as we are currently seeing (~120-130 years) is miniscule when compared against the scale of geologic time. We have plenty of ways of looking at broad temperature trends over large time scales in the past, but a 100 year interval from data for periods even as recently as 100,000 years ago would be lost in the error scale of the methods used estimate the age and the methods used to estimate the temperature. Even if you estimate that you can see back 1,000,000 years with the level of precision and data density necessary to pick out a specific 100 year interval, you are still only looking at about 0.02% of "the entire history of the earth". The equivalent would be a man who has never been outside of a 56 mile radius around College Station, Texas who believes that he lives in the hottest place on the "entire planet earth". His 56 mile radius works out to about 9800 square miles, which is about 0.02% of the 49,000,000 square miles of habitable land on the planet. In his experience, he has never seen it hotter anywhere else, but he is hardly qualified to make such a sweeping statement about the rest of a planet he has never seen.

It is one thing to say that the current trend is unprecidented in the recent past for which we have data sufficient to estimate short term temperature trends, but your statement goes far beyond anything that can be supported with what we currently know.

As far as your thesis for the post, if you take the initial statement of "The climate has warmed and cooled naturally over its entire history, so 1) the present-day warming must therefore be natural, and 2) we shouldn't worry about it." as the end point of the average skeptic's argument, then you have created a very convenient strawman to take a quick potshot at. The reality is that most people who look at historical fluctuations in temperature and take a skeptical stance towards blaming humans for most or all of the current global warming, do so because they simply do not feel that scientists studying the issue know enough about ALL of the processes that have created past fluctuations and that we do not have enough data about those processes NOW to say with any certainty how much influence humans do or don't have. You use the word "significant" to describe human activity's current role in global warming. As a scientist, I am sure you understand that the word "significant" has a scientific meaning...as in "significant" digits in a mathematical calculation. In that usage, it is used to denote the level of precision to which somebody can calculate the result of a calculation or measurement. As an environmental scientist, when I say in a report that a site I investigated has "significant" contamination in groundwater", it means more than if I say the site has contaminated groundwater. The insertion of the word significant implies that I have enough data and measurements to feel confident that I can tell somebody HOW contaminated the water is, not just that it is contaminated in general. So in your statement, the use of the word significant to describe human influence on the recent global warming implies that you have enough data and enough precision in your calculations and measurements that you can in some way quantify our role in the process with some level of accuracy. That is where the skeptic who looks at our knowledge of historical temperature fluctuations diverges from your opinion. We can measure very accurately how much temperature has changed recently, and we can estimate fairly accurately what quantity of greenhouse gases we have emmitted in the past. But what many people have a significant amount of skepticism over is your ability to compare that recent data to a similar data set of past information with similar accuracy and precision and to draw specifically quantifiable conclusions about the specific processes and cycles that drove past temperature fluctuations. Without being able to know exactly what caused past fluctuations, and with an incomplete understanding of many of the current processes, it is hard for many of us to believe that you have enough accuracy in your data and your predicitve capability to say that our role is "significant" taken in a scientific context. I know you cite how you feel we have a good enough handle on things like the level of tectonic activity, orbital variations, solar variations, volcanic activity, and internal climate variability to rule them out as significant players in the current warming, but I don't believe our knowledge level is broad enough or deep enough to say that at all. You know perfectly well that while we have some knowledge of those historical processes and how they may work today, we have nearly zero detailed data about how they worked in the past. What little data we do have is circumstantial and prone to statisitcally significant error when we try to use it to closely correlate events a world apart to within a miniscule geologic time frame. For instance, we can look at marine fossils in ocean sediments and date them to within a thousand years or so, we can also tag specific layers of things like volcanic ash to within a few thousand years in things like ice cores and ocean sediments. When you start trying to take those pieces of data that may be across the world from each other, and then try to tie them down to a specific period of 100 years or so, you introduce alrger errors. And then when you add on interpretation of what historical processes caused the changes you observed and which process you believe was dominant in forcing the changes observed, you are introducing an error level and degree of imprecision that just simply will not allow you to draw a defensible conclusion in trying to say that we understand those processes well enough to assign them an insignificant role in what we are now seeing over a similarly miniscule period of geologic time.

I admire your professional audacity in believing that you understand ALL of the planetary and extraplanetary processes involved in earth's climate well enough that you can have enough scientific confidence in the precision of our current understanding of the climate system and ALL past variations to feel qualified to "debunk" any thought of a significant role for non-human related processes in today's climate change with a one page post on a blog. However, forgive me if I consider that particular debate still open for discussion.

Bill F said...
This comment has been removed by a blog administrator.
Bill F said...
This comment has been removed by a blog administrator.
Dano said...

There you go again dano, missing key sentences due to your reading comprehension problems

I notice that this tactic is often used against me when folk are lacking substance in their argumentation.

I don't have the right to respond to that statement [italicized supra]?

As you didn't specify to what exactly you were responding (the standard is to insert the relevant passage prior to the response), there was confusion over what you were commenting on.

Your prodigious reading comprehension skills, surely, allow you to note that my comment served to clarify the topic wrt your statement and made no judgement on the italicized, contra your assertion of Has Dr. Dessler appointed you as the thought and thread police here?

But now that you've clarified, your position is certainly interesting.

The current societal debate Andrew alludes to wrt to the future direction we will take hinges on this 'uncertainty' question. Millions of lives will likely be directly affected by the decsioning arising from this societal discussion (as they will be displaced from coastal areas).

Yet, you declare you care not one whit whether we clarify the uncertainty before we set off on a direction.

Strange, surely.

HTH,

D

Mark UK said...

The point is that with climate skeptics the goal posts keep shifting. Whatever data is provided it is never enough. At some point the mountain of scientific observations, models, analysis becomes convincing when looked at from a logical point of view.

Holding on to the views that it is all alarmist behaviour and keep repeating that we don't know everything is not the same as providing alternative theories.

The other point is of course that whether or not this type of climate change (ie rapid) has happened before it is happening now. I did not live 1,000,000 years ago. I live now. So, the effects of the current changes in our climate are something I have to deal with, consider and mitigate.

Climate has changed throughout time and we have a pretty clear picture as to how and why. The current climate changes taken place fit in with the rise in CO2 concentrations caused by human activities. Therefore, to the best of our knowledge this is the most likely major cause.

Dr. J said...

Extremely well said Bill F. Dr. Dessler is probably not familiar with paleoclimatology, error bars on data, and the concepts needed to look at long term trends of hundreds or thousands or millions of years on a cyclical nature. I think the most egregious use of paleoclimatic proxy data is embodied in the infamous Mann hockeystick. To put such coarse and generalized temperature data as tree rings, corals, old pre-1930s thermometers (not to mention sampling errors, reproduceablity issues and data collection techniques that would frighten any real scientist) together with highly accurate and repeatable satellite temperature surveys to use as a poster to prove AGW is unconscionable.

Anonymous said...
This comment has been removed by a blog administrator.
Anonymous said...
This comment has been removed by a blog administrator.
Andrew Dessler said...

Bill F-

OK, OK, you make a god point about my statement that this type of warming is unprecedented. I agree that perhaps my statement went a bit too far and that we really don't know, On the other hand, I would just like to add that there's no evidence to the contrary.

As far as your point about "significant" and the human influence, I think we continue to disagree. The consensus is that humans are responsible for *most* of the recent warming. We cannot tell you an exact amount, but we can say we think it's the single most important factor. I think this statement is pretty hard to argue with, and I blogged a few weeks ago about why we are so confident in that conclusion. Check that posting out.

Regards.

Andrew Dessler said...
This comment has been removed by a blog administrator.
Bill F said...

Glad to see I am not the only one suffering from double post syndrome today. I did check out that post, and you are right, we will have to agree to disagree on how well we understand the other possible factors. I think you are probably pretty safe in saying something like "with what we know right now, we believe human activity is likely to be the most significant cause" of the current warming trend. But to claim to have "debunked" any other possible source as a significant factor with a few unreferenced claims in a blog posting is still pretty audacious. You have alot of science to back you up in your assumption, but the scientific understanding of some of the more amorphous issues like planetary heat flux is spotty at best. We can say we don't think it is significant, but the reality is that we really have no way to accurately measure it now and no way to accurately measure its effects in the past, so any conclusion drawn about its impact is a guess at best.

George Landis said...

Don't get me wrong dano, I believe we should thoroughly research, study, and quantify the uncertainty to a high level of accuracy before we charge off on "mitigation" measures that could wreck the economy and drive our society back to the early 20th century levels. And certainly that has not even really begun yet, and probably won't for some years.

But as far as I'm concerned, those living near the coasts need to move now, why wait? Hurricanes, typhoons, cyclones and tsunamis are going to get you in many places anyway, regardless of GW. If you live near sea level, don't wait, nothing the governments do will save you, you have to be accountable for your lifestyle choices.

Gareth said...

"mitigation" measures that could wreck the economy and drive our society back to the early 20th century levels.

Here's a classic example of a double standard. You require a high degree of certainty about global warming and its causes, but are happy to assert - without any credible evidence whatsoever - that the costs of mitigation are huge.

A straw man? More like a bloody haystack.

ttyler5@hotmail.com said...

Dr. Dessler,

If you are getting spam ads here (thus the multiple deletions) I think there is a "moderated" option you can choose from Blogspot.

I set up a blogspot for the Rita emergency last year (I'm in Galveston county) and left it open and it has filled up with screwy ads in the form of spam.

Andrew Dessler said...

It's not spam ... for some reason, most every post today was being posted twice, so I've gone through and deleted the duplicates. I've thought about a moderated blog, but have not quite yet decided it's necessary.

ttyler5@hotmail.com said...

Dr. Dessler,

Glad to hear you haven't been targeted by the spammers yet!

Concerning moderated blogs, the problem is your readers have to wait until you get time to approve posts and so the comments page can stay empty or way behind for long periods, and that's no fun for the readers.

Of course, you could hand it over to a TA :^D :^D :^D :^D

Just kidding!

EliRabett said...

Mitigation and adaptation are both necessary to deal with the coming climate change. The problem is not that one is cheap and the other expensive, the problem is that they are both expensive. The balance between the two should be one that comes close to minimizing dislocation and expense.

If you think adaptation is cheap, what is the value of Miami Beach, the Hamptons and the Outer Banks.

Peter K. Anderson said...

The REALITY is that climate is persistent only, and if you notice the chart in the link (*) below regarding Glaciations over the past 1 Billion years, you will see that even the Primary Oscillation is presenting a 'shorter (irregular) periodicity' by noticing that the Primary Troughs (within the green blocks) are becoming 'closer'. It IS that 'modern humanity' is but one child of 'climate alteration', NOT a cause of such (as yet).. There is not any valid link to 'CO2 sources' thus made in supposition within 'greenhouse science' and there is also NOT the 'valid link' of 'CO2' to any possible warming process. If you notice the reality of the warmer ocean surface (slides in link * below).

There is nothing UNNATURAL in the production of the 'Katrina Event' (as example) that can contain ANY result of 'greenhouse supposition', and ONLY the cumulative effect from the production of Human Habitat Sprawl upon the land surface (related to Human Population growth in its rapid rise from 500 Million to over 6 Billion in ~400 years) can be seen (again with slides in *).

The present Primary Trough, only 3 million years 'long', is after a ~200 Million year long Primary Crest Period. There is little to nil regard for actual Climate Processes within current 'greenhouse climate science' and it is NOT of any value to attempt presentation of 'statistical gibberish & jargon' to pretend to being 'scientific', which is commonly seen where the 'green-in-house process) commentators are trying to be more credible than what is being actually discussed.

As example, Isotopical analysis is not able to discern more that the spread of Isotopical forms, and these are well known to present identical Chemistry. This FACT is used widely in SCIENCE (Medicine especially) and cannot tell where the (as example) Carbon atom 'came' from with regard to 'fossil fuel combustion', as in otherwise non-'process unique' molecules (CO2 is NOT unique) there is no specific VALID manner to find 'the source process specifically'.

Temperature is NOT either a valid indicator of supposed UNNATURAL 'Climate Change' in any VALID manner of SCIENCE. When 'temperature' is mentioned, realise that the 'temperature' of a System is that Kinetic Energy residual within the materials constituting that System that is NOT directly involved in the production of the processes of Turbulence within that System. In a System where-in the Mass of the most involved materials contained is proportioned in kilogramsx10^24, then alterations to Turbulence within those materials WILL release (or uptake) vast amounts of Kinetic Energy, and that this will then be observed as a RISE (or DECLINE) in the measured 'temperature' of the System with NO NEED for alteration of the RATE of overall 'new' Kinetic Energy production. Interaction of Oceanic (slower) and Atmospheric (faster) process will see the style of variation of TEMPERATURE seen so far. The trend of the Ocean surface follows the present Land Surface rise in 'shape' even, lagging by 15 years due to the productions of Conduction and Convection transporting that Kinetic Energy TO the Ocean Surface whilst the muting of that displayed trend is due to internal production of Turbulence in the Ocean surface as reaction to those inputs of Kinetic Energy (this trend is seen in plots at the link * below).

It is NOT possible for a 'greenhouse warming process' to even have been existent; the 'greenhouse effect' is inconsistent with the materials it involves as these materials present their ACTUAL behaviours, this is inclusive of those materials presented on the surface as well as with those 'bio-forms' of surface life as they exist NOW. It is NOT possible for the 'greenhouse theory' to produce in reality a 'warming effect' as it is supposed, with manipulation of Energy within the 'Infrared Region' with regard to the real materials present (including those materials involved/contained in 'life forms'. There is not then any SCIENCE that can so far show that UNNATURAL climate change is even occurring, especially incapable is any 'greenhouse related' opinion or 'rhetoricals'.

Your's,
Peter K. Anderson a.k.a. Hartlod(tm)
From the PC of Peter K Anderson
E-Mail: Hartlod@bigpond.com
(*)- http://hartlod.blogspot.com/