Friday, September 08, 2006

Three caveats

Not everyone appreciates the carefully caveated statement in the IPCC's TAR about the attribution to humans of the current warming. Let's take a closer look at the exact statement:
In the light of new evidence and taking into account the remaining uncertainties, most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations.
There are three important caveats in this statement, which are often ignored by strawman-toting advocates.
  1. "most of the observed warming": this says that humans contributed > 50% of the warming, but it leaves the door open for a significant amount to be due to non-human influences.
  2. "last 50 years": this says that we can identify the hand of humans in only the recent warming; before that, the data are too poor to unambiguously assign the cause of the warming.
  3. "likely": in the carefully nuanced language of the IPCC, "likely" denotes a confidence of about 75%. Thus, there is a possibility that this statement is wrong. This reflects the fact that our knowledge of the climate is imperfect, and it is possible though unlikely that new research could significantly revise our understanding of the climate system.
The main problem is that when advocates use the IPCC in their policy arguments, the carefully crafted language is abandoned for much stronger statements that support the advocates position. When these positions turn out to be false, the blame falls (unfairly) on the IPCC. Clearly, I think we all need to read the IPCC with the scientific precision with which it was written.

52 comments:

chrisl said...

Dr D, The temperature graphs on the previous thread were very interesting and could stand some further analysis.
Quite often large red dots appear next to large blue dots,meaning large variations in the same region
Also most of the large red dots seem to occur where there has been a large population build-up. Warming caused by urbanisation.
The regional nature of the GLOBAL warming ..and err.. cooling is very interesting

Bill F said...

You missed caveat 4: There is nothing in that statement that says increases in "anthropogenic" greenhouse gas concentrations caused the warming. The statement doesn't rule out that other sources of GHGs could have caused the warming. I don't disagree on principle with that statement, because as pointed out, it leaves room for other possibilities. My problems begin when people like Dano take that statement and make the quantum leap of saying that because of the consensus around a fairly limited and carefully worded statement of agreement, that there can be no scientific debate on what causes are more significant.

Dr. J said...

I agree Dr. D, the IPCC statements, taken as a whole and fully understood, which the policymaker dummies are too intellectually lazy to do, indicate the uncertainty and speculations in the "consensus" presented by the UN. However, you will hear little of that in the rhetoric of the AGW believers on this site, or the more politically motivated and subjective realclimate.org.

George Landis said...

Well said Mr. Anderson, a very complete review of the galactic situation and big picture the IPCC has no clues about, since their scientific base was quite narrow and subjective. I also agree with Dr. J, it seems the only people recognizing the uncertainties and thinking critically about the IPCC caveats are the skeptics, but now joined very courageously by Dr. D. Someday perhaps a true scientific consensus will emerge about this issue, not the phony one currently described using a narrow, elite slice of climatologists, computer modelers and enviro scientists.

Dr. J said...

One small point Dr. D, I had thought the IPCC defined "likely" as having a probability of 66%-90%, not 75%, as shown in their footnotes on the intro summary. I have usually used likely as a 50%-90% probability myself over the years, I know conventions vary, but it is important if you are searching for precise language.

Andrew Dessler said...

Dr. J-

Yes, "likely" is 66% to 90%, which I averaged to get 75%. Just something that I usually do to simplify the message.

Bill F-

Yes, the statement talks about increasing greenhouse gases, rather than human influences. However, there is basically no argument that the CO2 increase is caused by humans. Should I infer from your statement that you dispute that?

Regards

Dano said...

My problems begin when people like Dano take that statement and make the quantum leap of saying that because of the consensus around a fairly limited and carefully worded statement of agreement, that there can be no scientific debate on what causes are more significant.

Your problems begin when you don't understand the carbon cycle and think CH4 burps from melting permafrost/lakes means there's uncertainty around the causes of AGW, that's all.

HTH,

D

Peter K. Anderson said...
This comment has been removed by a blog administrator.
Peter K. Anderson said...
This comment has been removed by a blog administrator.
Bill F said...

Dr. D,

I don't dispute that we have caused a large portion of the increase. How large our portion is still is subject to uncertainty as we refine our knowledge about sources and feedbacks. For Dano's sake, I will point out that if our estimates of CO2 uptake by oceans have been too high by 2.5 billion tons per year and our estimates of methane contributions from arctic melt lakes may be 5 times too low, then there is still considerable uncertainty in how much of the increase in GHG concentrations is a result of human output. Dano, you still can't seem to read well enough to see that your attacks on me are based on a stereotype that you have assigned to me erroneously...but thanks for playing.

FWIW, I am not saying our role in the increase is not significant...I am saying we just can't be certain how significant it is. If we are responsible for 60% of the increase instead of 90+%, then it will make a big difference in how effective we can be by lowering our output of GHGs.

Therefore, I think it is appropriate that the statement referenced in the original post doesn't try to quantify the level of human responsibility for the GHG increase. They stick with what they believe they have reasonable scientific basis for saying, which is the right thing to do.

Peter K. Anderson said...
This comment has been removed by a blog administrator.
Mark UK said...

Surely the research showing higher levels of methane from melting permafrost does not prove either side of the debate. All it shows is exactly that, there is more methane coming out of the melting permafrost.

The melting is because of global warming and it show a feed back system right?

Andrew Dessler said...

Bill-

We agree. I don't think we can say whether humans are responsible for 51% or 90% of the warming. And there's also a chance (about 1 in 4) that it's less than 50%. I think most experts on the climate would be entirely onboard with this assessment.

Regards.

Dr. J said...

Thank you Dr. D for one of the most objective and clear positions on AGW I have heard in many years. As a skeptic, I can fully agree with it. I do urge you to try and get your much more radical associates (yes, even some at the usually conservative TAMU) to examine your assessment and try to be as honest and objective as you are. Cheers, and how 'bout those Longhorns?

coby said...

Bill F,

There is one key factor you are not considering in the atmospheric GHG concentration rise. Analysis of isotope signatures in the CO2 molecules actually in the air clearly show that the rise is from anthropogenic emissions. It is "old" carbon combined with "young" oxygen and there is no other source for such.

If new research shows oceans are taking up less CO2 than thought before, then it means something somewhere else is taking up more, it has no bearing at all on the attribution of current change. Similarily, if Arctic lakes produce more methane it means that other sources must be smaller. It is important to understand these details of the carbon cycle for future projections, definately, (will these sinks "fill"? will natural GHG sources provide large feedbacks very soon? are they now?) but it is not important for understanding the past century.

This is why Dano was not moved by the papers you cited, and I hope that clears up your misunderstanding.

Cheers

Dr. J said...

coby, in referencing the anciently studied (and not recently touched) "Suess Effect", you need to also point out the caveats, for scientific honesty and objectivity, something you tend to forget it seems. This effect is shown from tree rings starting in the 1850s, and shows a whopping 25 mil (to non isotope geochemists, this is small considering the small sample sizes and sparse data collection practices, not to mention reproduceability and thus accuracy limitations) through the early 1950s. Then it goes haywire, as nuclear testing spikes it up and down and down and up, and lately it has been going down,, but again very little research has been done on this since 1981. The questions I have of it, beyond error bar and thus statistical relevance, is the sensitive nature it has to cosmic rays, and external influences. It is also very odd that the alledged "dilution" of CO2 by the satanic variety produced by humans (but not solely it turns out by burning fossil fuels) starts rapidly in the 1850s, and of course we know the most of the CO2 was produced in the last few decades. So this method is almost unuseable as a definitve argument for AGW, case closed.

Peter K. Anderson said...
This comment has been removed by a blog administrator.
Dano said...

Boy, Dr J sure can tap dance, eh?

Best,

D

Bill F said...

Coby,

Carbon released from permafrost by melting shows up as "old carbon". CO2 emitted through biological degradation of previously frozen plant material in melting permafrost will show up as "old" carbon with "young oxygen".

As stated by Zimov, Schuur, and Chapin, in "Permafrost and the Global Carbon Budget" from the June 16, 2006 issue of Science magazine: "The 13C/12C isotope ratio of the permafrost reservoir is similar to that of soil, vegetation, and marine biota. Unlike these reservoirs, however, permafrost carbon is depleted in radiocarbon (14C). Methane, CO2, and dissolved organic carbon released from thawing yedoma have a radiocarbon age reflecting the time when the yedoma was formed in the glacial age, differentiating the permafrost carbon signal from emissions from other reservoirs that have a modern radiocarbon age."

As for the CO2 uptake by the ocean, thanks for recognizing the point I was trying to make. Contrary to Dano's mistaken assumption, I am not saying that because CO2 uptake estimates were wrong, that we weren't producing CO2 or that climate is not warming. I am just saying that it all feeds back into the uncertainty agreed to by Dr. D above...we know that temperature is rising, we know GHGs are rising, and we know that we put out alot of GHG. We believe that the GHG rise is causing most of the warming, but can't say if it is 51% or 90%, and because of the uncertainty in the processes, we can't really say how much GHG increase we are responsible for, although we think we are responsible for most of it. I was using the papers to highlight areas of significant uncertainty, not to deny GW or to disprove AGW.

coby said...

I just can't believe that people smart enough to log on to the internet and post a comment on a blog (doesn't take much, does it?)seriously doubt that pumping billions of tons per year of CO2 into the air is not the cause of CO2 accumulating in the air.

Dr J should read this, intended for luddites or not, and if that is not technical enough for him he should read this.

Dr. J said...

coby, I'm sorry, but recycling biased POVs from biased websites and blogs that have already been commented on and shown to be lacking is not going to impress me. If you don't have the research experience in this field it is OK to reference some scientific papers that would make your point, as I have done on the MWP, C14, C12/C13 ratios, etc. These are technical scientific points that have more than one POV in the scientific world, that's why we do research, to perfect the understanding and try and remove inconsistent internal data conflicts. To represent the C14 issue as case closed is scientifically and intellectually dishonest, but then so is saying AGW is a closed case, which I am sure you also believe. Try to do some original scientific thinking and research rather than relying on some blog, that is not science, it is debate and comment.

Dano said...

I, personally, see no bias in the evidence in Coby's links.

I also see no evidence of the information [having] already been commented on and shown to be lacking , unless you think that any old comment will do to show lackingness, no matter how wrong it is.

And the only bias in Coby's website, in my view, is the bias against denialist/contrascience arguments.

Darn that Coby, anyway - marginalizing important contrascience voices!

Best,

D

Bill F said...

"...seriously doubt that pumping billions of tons per year of CO2 into the air is not the cause of CO2 accumulating in the air."

Who has said that they doubt this Coby? My only question is how many billions of tons are anthropogenic and how many billions of tons are natural or result from feedback loops from earlier warming that can't be concretely tied to a single forcing. We know roughly how much we have pumped into the air, but we are constantly finding out how little we know about the rest of the natural system. As I pointed out to you above, complete with a peer-reviewed and published scientific source (instead of a blog), the carbon from arctic permafrost does not show a "modern" carbon ratio, and as such, is more difficult to distinguish from anthropogenic sources. Since we know warming has been occurring for over 100 years, and (as Dr. D has admitted) we are not sure how much of that warming pre-1950 is caused by human activity, it is possible that a sizeable amount of GHGs could result from feedbacks associated with the earlier warming. How sizeable? Who knows...the research goes on. Humans are still likely to be the largest source, but we really don't know by how much. Painting the situation with anymore certainty than that simply isn't supported by the current understanding of the system. As you pointed out, if one source is higher than we thought before, then either another source is smaller or somewhere in the conceptual model, we have a process that we don't understand well enough. Once again, keep in mind that arctic sources will not have the same carbon profile as other natural sources, so they will not be offset by smaller than expected outputs for those sources.

Dano said...

The CO2 ppmv atm levels have never been this high in roughly 2/3 of a million years, casting doubt on the quality of Bill F's argumentation.

Sowing doubt by uninformed questions doesn't work in this case, unless one can show any sort of testable hypothesis with data that show how today's levels are tied to such feedback loops.

that is: it's "not likely" that such an argument as found immediately above can fly.

Best,

D

Bill F said...

667,000 years would take us almost, but not quite, back to the most recent polar reversal. It also would take us back about 0.014% of the planet's total history. Not exactly an all-encompassing data set from which to draw conclusions about what is or isn't possible...

FWIW Dano, when you get beyond your false assumption that I am denying any and all human involvement in climate change, you and I will have more productive discussions.

Dr. J said...

I see Dano, those sites are objective, but NewsMax isn't. Strange logic, but that is to be expected of the believers. And coby, I also said nothing of denying humans were pouring CO2 into the atmosphere, that is a long way from your claims on the C14 "evidence" you parroted from a blog.

Dano said...

It's not W much, Bill F, when you consider Homo sapiens hadn't evolved prior to then. That is, there are no lessons in adaptation nor in recent ecosystem dynamics prior to, say, the Holocene.

And, why try to include data from, say, 200 MYA, when the continents weren't in the same place, most mountain ranges hadn't poked up yet, oceans were generally shallower, chemical weathering was less, biomass distribution was radically different, carbon had barely begun sequestering (thus the C cycle different), etc. That is: the comparison isn't useful & is of almost no utility (unless one has nothing else to go on).

These...interesting...attempts to sow doubt don't seem to be fertile ground for productive scientific discussions, Bill F.

Best,

D

Dano said...

Dr J,

We already pointed out that the only time you were able to provide evidence for your assertion was to use a NewsMax story (run by the Conservative News Service) to back your claim.

Hardly scientific, as you claim to desire (just above, f'r instance).

Anyway, this story you like so much, you remember, quoted two people, one a proven liar who was forced to resign their position of obstructing scientific inquiry for BushCo, and the other source shown to take money from the fossil fuel industry, numbered among the usual climate skeptics, and has recently come under scrutiny for alleged...inconsistencies in his "official" position.

Every secondary source for your assertion quoted this NM story; that is: there is only one line of inquiry (hardly scientific, eh?), a blatantly political source. And the story appeared during the SwiftBoating campaign of Hansen. I've explained this already, remember? Sure you do.

Best,

D

Dr. J said...

Obviously Dano you are not one I will respond to again, I have finally learned my lesson, Dr. D, do you have an "ignore" key?

George Landis said...

Hilarious, dano is a big believer in more than AGW, seems he also believes in the vast right wing conspiracy to discredit poor Dr. Hansen, my my such an important and powerful man targeted by the right wing dirty tricks moles, how dastardly.

Typical MO dano, you guys are too predictable, AGW + right wing conspiracies, watch out for your phone and internet taps by the CIA and FBI and NSC next, right? Or sorry, Left? Look out behind the tree, the right wingers are coming to get 'ya!

Dano said...

George,

if you have any evidence to back the assertion Dr J parrotted (remember? the assertion made by two proven liars and found nowhere else but on CNS?), he needs some help.

Maybe you can dig up something he can't, because all Dr J has is an assertion made by two proven liars. Nothing else.

And all those other assertions he made without evidence, and couldn't provide any when asked? He needs help there too. Step to the plate for Dr J, Geo.

It's embarrassing how often the board goes silent/hand-waving happens around here when asked for evidence. Help the comment board out, Geo.

Best,

D

Dr. J said...

Interesting George, wonder if Dano thinks W is behind it all, calling the shots. I am surprised at such sterotypical AGW believers actually admit to the typology, a stereotypical package of beliefs, surely Dano is an outlier in this landscape, or is he? Science is not his bag, but conspiracy theories and partisan politics are right up his alley.

ankh said...

Eh? That's "sputter ... sputter...." in response to a request to support what you wrote.

You've made assertions, will you name your source for these stories, and tell us what it is about them that makes you believe?

Peter K. Anderson said...
This comment has been removed by a blog administrator.
Andrew Dessler said...

Guys-

Let's try to keep it civil. I know from experience that it can be hard, but when civility goes the usefulness of the debate goes too.

Regards

Bill F said...

So Dano,

Are you then disputing that there are global cycles that occur over hundreds of thousands of years? Are we supposed to ignore cycles and processes (such as magnetic excursions) that have shown very tight correlation to global climate simply because humans weren't around then or continents may be in different positions? Are you also tying temperature directly to CO2 and saying that if CO2 goes up, temperature must also go up in linear fashion? I seem to remember me pointing out cases in the last 400,000 years where temperature was higher than today, but CO2 was not. In response, you pointed out that there were plenty of other processes and changes that had to be considered and that CO2 was not the only factor in predicting temperature. Are you now backtracking and saying that because CO2 is going up, temperature has to go up linearly with it and there is no possibility of any other process or feedback to mitigate that rise (or amplify it)?

You keep talking about how little uncertainty there is Dano, but perhaps you should talk to Dr. Dessler...he seems perfectly willing to admit that while he believes humans are the most significant cause, that there is ample uncertainty in our knowledge. Do you know something he doesn't? Why can he admit to uncertainty and you cannot?

Dano said...

Careful with all that straw, Bill F. It's fire season out here.

That is: I'm arguing none of those arguments you - for some reason - want to attribute to me.

And if you could provide evidence of where I argue there being little uncertainty, that would be great.

Best,

D

Bill F said...

Dano,

I posted numerous sources to show that we have uncertainty in what we know about GHG production by non-anthropogenic sources and about how CO2 is removed from the atmosphere. In response to Coby, I cited that uncertainty when questioning how much is or isn't attributed to man.

You cited 667,000 years of CO2 data to say that it has never been this high. What is your point in saying that if you are not attempting to say that there are no natural processes that could result in higher CO2 levels?

When I called you on it by showing that that data was a tiny sliver of the entire history of the earth, you responded by claiming that the older data was not worth much since homo sapiens hadn't developed then. What is the point of tying the data set to the rise of humans? High CO2 levels occurring prior to the evolution of humans would prove that processes unrelated to humans COULD cause high CO2 levels.

There is nothing magical about the evolution of primates in the carbon cycle or in the paleoclimatological history of the planet...planetary cycles and processes are blissfully ignorant of the evolution of species. What IS pertinent about periods before 667,000 years is that they show the appearance of planetary climate cycles that occur on much larger timeframes than anything that could be seen in data from a few hundred or a few thousand years. The tracking of temperature and other parameters over those time frames has the ability to show that climate cycles can respond to many forcings, not just CO2, and can also show that CO2 and temperature do not always move together in a linear fashion, which lends uncertainty to attempts to tie temperature change solely to CO2 without accounting for other processes. Looking at climate over those timeframes also shows very large and rapid changes in climate in the past.

Now to the point...read carefully before your start typing up your next response calling me a "denialist". I didn't cite any of that history to try to prove that GW isn't happening. I also didn't post it to try to prove that man has no role in the process or even an insignificant one. Read this next line very carefully...I posted that to express uncertainty, not to prove an alternate hypothesis. In other words, I am not saying I don't believe the theory; therefore, I am not obligated to present an alternate theory. I am simply expressing the fact that uncertainty does exist in the degree to which we can assign responsibility to human activity for GW.

Why is that a hard concept to understand Dano? Dr. Dessler above agreed that we can't assign an exact amount of GHG increase for which human activity is responsible or the exact amount of warming that can be attributed to humans, and the articles I referenced pointed out areas where that uncertainty is present. Every time I point to uncertainty in our knowledge, you make some snide remark about me being a "denialist" or otherwise spout some nonsense about how the science I have posted doesn't mean there is uncertainty, or about how all the scientific committees disgree with me; when in fact, the carefully worded statement that Dr. Dessler posted as the initial topic of this thread, clearly recognizes the level of uncertainty and uses language designed to allow room for that uncertainty in their conclusions.

Dano said...

Thank you for your reply Bill F, I'm not sure how all those words address my request for evidence that I'm arguing there is no uncertainty (You keep talking about how little uncertainty there is Dano ), but hey. It's a start.

I am simply expressing the fact that uncertainty does exist in the degree to which we can assign responsibility to human activity for GW.

Thanx for expressing it.

Quibblism aside, the fact that folk who do this for a living have factually stated that humans are the majority cause may or may not address your 'degree' point.

Sure, there is uncertainty whether it is "54%" or "66%" or "75%", but it is more than "50%", accordion to the folk who do this for a living. Sure, that may change in the future, but right now that's what they're saying, which is what I'm saying.

Best,

D

Bill F said...

I am not trying to make a case that it is <50% Dano. I am simply trying to point out that it isn't 100% either, and we don't really know for sure how much less than 100% it is. I believe Dr. Dessler's comment was that we don't know if humans are responsible for 51% or 90%. The reason that is important is that if we are going to set a target for reducing our GHG emissions in order to bring about a desired reduction in the future warming of the planet, it is critical to know with some certainty what our role is. If human activity is responsible for 90+% of the warming, then we can feel comfortable that whatever we do will likely have a significant effect eventually. However, if we are responsible for only 60%, then there is a sizeable amount of warming that could continue to occur with or without our input.

Perhaps you have missed it when I have said it before, but I think there are dozens of great reasons to significantly cut our use of fossil fuels, to drastically reduce pollutant emissions from power plants and industrial facilities, and to enforce better conservation of all resources right now. I just think that mitigating the potential effects of global warming is pretty low on that list when compared to things like human health effects from air and water pollution, ecological damage, and geopolitical conflicts related to oil supply and demand that are immediate consequences of what we are doing right now. The changes made would accomplish the same thing regardless of the reason for making them and using other reasons to effect the same changes seems to be a path of less resistance.

Dano said...

Bill F,

As to your first para., you may want to contact your elected representatives. They are making decisions from econometric models that commonly have Rs and Ts in the .3-.4-.5 range.

By golly, if we are going to set a target for, say, growth in order to bring about a desired outcome, it is critical to know with some certainty what our input role is. So, if you don't know what the probabilities are for a desired outcome (and if you don't even know what the desired outcome is beyond, say, just plain ol' growth), relative to the costs/externalities (risk adjusted), then you are missing major parts of the equation to solve the problem.

Since we don't really have certainty but are acting anyway, well, the electeds need your advice, and how.

As to your second para., many of the things you name are coincident, and working on causation will decrease fossil fuel use.

Best,

D

Andrew Dessler said...

Peter Anderson-

Mysteriously missing? I think it says pretty clearly "deleted by blog administrator." I don't feel that your posts are appropriate for the discussion that I want to have here. If you feel truly driven to post here, I'll let you post a link to your blog, and people interested in your point of view can go there. Otherwise, your extremely long posts will be deleted.

Regards

Peter K. Anderson said...
This comment has been removed by a blog administrator.
Peter K. Anderson said...
This comment has been removed by a blog administrator.
Peter K. Anderson said...
This comment has been removed by a blog administrator.
Peter K. Anderson said...
This comment has been removed by a blog administrator.
Peter K. Anderson said...
This comment has been removed by a blog administrator.
Andrew Dessler said...

Peter Anderson-

Instead of continuing posting, can you please read my post to you up above?

Thanks!

Peter K. Anderson said...
This comment has been removed by a blog administrator.
Dano said...

Andrew, it doesn't help your bandwidth expenditure any, but IME most usenet folks see certain names and scroll right to the bottom.

[you can delete this]

D

Bob KC said...

I believe Dr. Dessler's comment was that we don't know if humans are responsible for 51% or 90%.

I would just like to point out that he also said that there is a 1 in 4 chance that humans are responsible for less than 51%. Also, these are not scientifically calculated odds - they are educated guesses (beliefs?) by the people most likely to know.

EliRabett said...

Well, being late to the tea party, allow me to quote the Summary for Policy Makers

"Concentrations of atmospheric greenhouse gases and their radiative forcing have continued to increase as a result of human activities.

"The atmospheric concentration of carbon dioxide (CO2) has increased by 31% since 1750. The present CO2 concentration has not been exceeded during the past 420,000 years and likely7 not during the past 20 million years. The current rate of increase is unprecedented during at least the past 20,000 years."

Note that the statement that the present CO2 concentration has not been exceeded during the past 420,000 years is absolute.

As to the future:

"Emissions of CO2 due to fossil fuel burning are virtually certain7 to be the dominant influence on the trends in atmospheric CO2 concentration during the 21st century."