Hot off the projector – new AGW data

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  • Sat, Dec 27, 2008 - 12:42pm

    #1

    Damnthematrix

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    Hot off the projector – new AGW data

Hot off the projector #3: Atmospheric CO2 to 800 kyr ago

Just
a few minutes ago Chappellaz et al presented the deepest dregs of
greenhouse gas concentration data from the EPICA ice core in
Antarctica, extending the data back to 800,000 years ago. In Al Gore’s
movie you saw what was at that time the longest record of atmospheric
greenhouse gas concentrations, back to 650 kyr, and their
astonishing correlation with Antarctic temperature. This iconic
superstar record has probably consumed as many eyeball-hours as any in
climate science, alongside other classics such as the Jones et al.
global temperature trends, the Moana Loa recent CO2 record, and the hockey stick. The Antarctic CO2 record has spawned countless internet rants about the CO2 lag behind temperature, and the circle of cause and effect between CO2 and climate. And the new data say …

The first point to write home about is that the correlation between Antarctic temperatures and CO2 continues unabated. One could imagine a world in which CO2
had no impact on climate, although if you buy that Dick Lindzen has a
bridge he wants to sell you. In such a world, it could be that the
correlation between CO2 and temperature since 650 kyr was
just a coincidence, Mother Nature playing a cruel joke, and maybe in
that case a little more data would cause the spurious correlation to
start to unravel. That didn’t happen. CO2 continues to be
high in warm times and low in cold times. There were no gasps of
astonishment from the audience at the continued striking correlation.
Ho-hum, of course it still works.

That being said, there are some interesting subtleties in the latest data. The CO2 concentrations were generally lower than average between 800 and 650 kyr. The lowest CO2
value ever measured in an ice core is now 172 ppm, from 667 kyr ago. If
you average over the glacials and interglacials, there appears to be a
very long-term cycle in atmospheric CO2, low from 600-800,
peaking around 400 kyr ago in stage 11, the 50 kyr-long “super
interglacial” when the Earth’s orbit was nearly circular as it is now,
and then subsiding a bit since then. Perhaps this variability is driven
by variations in rock weathering, the longest-term geological carbon
cycle. Interestingly, there is no corresponding million-year cycle in
Antarctic temperatures, when they are averaged in a similar way. CO2 is a dominant controller of global climate, but it is not the only game in town.

There were also millennial timescale wiggles in atmospheric CO2
and methane concentration during the descent from the stage 19
interglacial to the stage 18 glacial time. There are strikingly similar
to the Dansgaard-Oeschger wiggles from 30-70 kyr ago in isotope
stage 3. The duration is similar, about a thousand years, and the
trajectories of the events are the same, with sharp warming and
associated rise in greenhouse gases, then slower recovery. As in stage
3, they occur through the slow cooling transition between extreme
climates, not in the full-blown glacial or interglacial states. These
abrupt climate changes appear to be business-as-usual for the global climate system.

What would be really cool is if there were enough ice to continue
probing back into the deeper past. Around 800 kyr ago, the climate
cycles on Earth switched from being dominated by 40 kyr cycles, to the
stronger 100 kyr cycles of the more recent times. The time period from
800 – 1000 kyr ago is called the mid-Pleistocene transition, and
since the rhythms of the Earth’s orbit didn’t change, it must have
something to do with the way that climate on Earth operates, maybe
something about the carbon cycle. What would be really cool is if we
could get CO2 and methane records back to say 2 million
years ago, through this crucial transition time. Alas, 800 kyr is as
far back as the useful ice in this location goes. The bottom tens of
meters of the ice, like the bottoms of all ice cores, are too scrambled
to interpret.

  • Sat, Dec 27, 2008 - 12:45pm

    #2

    Damnthematrix

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    Re: Hot off the projector – new AGW data

And now for all you Climate Change Deniers/Skeptics:

 

The lag between temperature and CO2. (Gore’s got it right.)

When I give talks about climate change, the question that comes up most frequently is this: “Doesn’t the relationship between CO2 and temperature in the ice core record show that temperature drives CO2, not the other way round?"

On the face of it, it sounds like a reasonable question. It is no
surprise that it comes up because it is one of the most popular claims
made by the global warming deniers. It got a particularly high profile
airing a couple of weeks ago, when congressman Joe Barton brought it up
to try to discredit Al Gore’s congressional testimony. Barton said:

    In your movie, you display a timeline of temperature and compared to CO2
    levels over a 600,000-year period as reconstructed from ice core
    samples. You indicate that this is conclusive proof of the link of
    increased CO2 emissions and global warming. A closer
    examination of these facts reveals something entirely different. I have
    an article from Science magazine which I will put into the record at the appropriate time that explains that historically, a rise in CO2 concentrations did not precede a rise in temperatures, but actually lagged temperature by 200 to 1,000 years. CO2 levels went up after the temperature rose. The temperature appears to drive CO2, not vice versa. On this point, Mr. Vice President, you’re not just off a little. You’re totally wrong.

Of course, those who’ve been paying attention will recognize that
Gore is not wrong at all. This subject has been very well addressed in
numerous places. Indeed, guest contributor Jeff Severinghaus addressed
this in one of our very first RealClimate posts,
way back in 2004. Still, the question does keep coming up, and Jeff
recently received a letter asking about this. His exchange with the
letter writer is reproduced in full at the end of this post. Below is
my own take on the subject.

First of all, saying "historically" is misleading, because Barton is actually talking about CO2 changes on very long (glacial-interglacial) timescales. On historical timescales, CO2
has definitely led, not lagged, temperature. But in any case, it
doesn’t really matter for the problem at hand (global warming). We know
why CO2 is increasing now, and the direct radiative effects of CO2 on climate have been known for more than 100 years. In the absence of human intervention CO2
does rise and fall over time, due to exchanges of carbon among the
biosphere, atmosphere, and ocean and, on the very longest timescales,
the lithosphere (i.e. rocks, oil reservoirs, coal, carbonate rocks).
The rates of those exchanges are now being completely overwhelmed by
the rate at which we are extracting carbon from the latter set of
reservoirs and converting it to atmospheric CO2. No discovery made with ice cores is going to change those basic facts.

Second, the idea that there might be a lag of CO2 concentrations behind temperature change (during glacial-interglacial
climate changes) is hardly new to the climate science community.
Indeed, Claude Lorius, Jim Hansen and others essentially predicted this
finding fully 17 years ago, in a landmark paper that addressed the
cause of temperature change observed in Antarctic ice core records,
well before the data showed that CO2 might lag temperature. In that paper (Lorius et al., 1990), they say that:

    changes in the CO2 and CH4 content have played a significant part in the glacial-interglacial
    climate changes by amplifying, together with the growth and decay of
    the Northern Hemisphere ice sheets, the relatively weak orbital forcing

What is being talked about here is influence of the seasonal
radiative forcing change from the earth’s wobble around the sun (the
well established Milankovitch theory of ice ages), combined with the
positive feedback of ice sheet albedo (less ice = less reflection of
sunlight = warmer temperatures) and greenhouse gas concentrations
(higher temperatures lead to more CO2 leads to warmer
temperatures). Thus, both CO2 and ice volume should lag temperature
somewhat, depending on the characteristic response times of these
different components of the climate system. Ice volume should lag
temperature by about 10,000 years, due to the relatively long time
period required to grow or shrink ice sheets. CO2 might well
be expected to lag temperature by about 1000 years, which is the
timescale we expect from changes in ocean circulation and the strength
of the "carbon pump" (i.e. marine biological photosynthesis) that transfers carbon from the atmosphere to the deep ocean.

Several recent papers have indeed established that there is lag of CO2
behind temperature. We don’t really know the magnitude of that lag as
well as Barton implies we do, because it is very challenging to put CO2
records from ice cores on the same timescale as temperature records
from those same ice cores, due to the time delay in trapping the
atmosphere as the snow is compressed into ice (the ice at any time will
always be younger older than the gas bubbles it
encloses, and the age difference is inherently uncertain). Still, the
best published calculations do show values similar to those quoted by
Barton (presumably, taken from this paper by Monnin et al. (2001), or this one
by Caillon et al. (2003)). But the calculations can only be done well
when the temperature change is large, notably at glacial terminations
(the gradual change from cold glacial climate to warm interglacial
climate). Importantly, it takes more than 5000 years for this change to
occur, of which the lag is only a small fraction (indeed, one recently submitted paper
I’m aware of suggests that the lag is even less than 200 years). So it
is not as if the temperature increase has already ended when CO2 starts to rise. Rather, they go very much hand in hand, with the temperature continuing to rise as the the CO2 goes up. In other words, CO2 acts as an amplifier, just as Lorius, Hansen and colleagues suggested.

Now, it there is a minor criticism one might level at Gore for his treatment of this subject in the film (as we previously pointed out in our review).
As it turns out though, correcting this would actually further
strengthen Gore’s case, rather than weakening it. Here’s why:

The record of temperature shown in the ice core is not a global
record. It is a record of local Antarctic temperature change. The rest
of the globe does indeed parallel the polar changes closely, but the
global mean temperature changes are smaller. While we don’t know
precisely why the CO2 changes occur on long timescales, (the
mechanisms are well understood; the details are not), we do know that
explaining the magnitude of global temperature change requires
including CO2. This is a critical point. We cannot explain the temperature observations without CO2. But CO2 does not explain all of the change, and the relationship between temperature and CO2 is therefore by no means linear. That is, a given amount of CO2
increase as measured in the ice cores need not necessarily correspond
with a certain amount of temperature increase. Gore shows the strong
parallel relationship between the temperature and CO2 data from the ice cores, and then illustrates where the CO2 is now (384 ppm), leaving the viewer’s eye to extrapolate the temperature curve upwards in parallel with the rising CO2.
Gore doesn’t actually make the mistake of drawing the temperature
curve, but the implication is obvious: temperatures are going to go up
a lot. But as illustrated in the figure below, simply extrapolating
this correlation forward in time puts the Antarctic temperature in the
near future somewhere upwards of 10 degrees Celsius warmer than present
— rather at the extreme end of the vast majority of projections (as we
have discussed here).

Global average temperature is lower during glacial periods for two primary reasons:
1) there was only about 190 ppm CO2 in the atmosphere, and other major greenhouse gases (CH4 and N2O) were also lower
2) the earth surface was more reflective, due to the presence of lots
of ice and snow on land, and lots more sea ice than today (that is, the
albedo was higher).
As very nicely discussed by Jim Hansen in his recent Scientific American article, the second of these two influences is the larger, accounting for about 2/3 of the total radiative forcing. CO2
and other greenhouse gases account for the other 1/3. Again, this was
all pretty well known in 1990, at the time of the Lorius et al. paper
cited above.

What Gore should have done is extrapolated the temperature curve according this the appropriate scaling — with CO2
accounting for about 1/3 of the total change — instead of letting the
audience do it by eye. Had he done so, he would have drawn a line that
went up only 1/3 of the distance implied by the simple correlation with
CO2 shown by the ice core record. This would have left the impression that equilibrium warming of Antarctica due to doubled CO2 concentrations should be about 3 °C, in very good agreement with what is predicted by the state-of-the-art climate models.
(It is to be noted that the same models predict a significant delay
until equilibrium is reached, due to the large heat capacity of the
Southern ocean. This is in very good agreement with the data, which
show very modest warming over Antarctica in the last 100 years).
Then, if you scale the Antarctic temperature change to a global
temperature change, then the global climate sensitivity to a doubling
of CO2 becomes 2-3 degrees C, perfectly in line with the
climate sensitivity given by IPCC (and known from Arrhenius’s
calculations more than 100 years ago).

In summary, the ice core data in no way contradict our understanding of the relationship between CO2
and temperature, and there is nothing fundamentally wrong with what
Gore says in the film. Indeed, Gore could have used the ice core data
to make an additional and stronger point, which is that these data
provide a nice independent test of climate sensitivity, which gives a
result in excellent agreement with results from models.

A final point. In Barton’s criticism of Gore he also points out that CO2 has sometimes been much higher than it is at present. That is true. CO2
may have reached levels of 1000 parts per million (ppm) — perhaps much
higher — at times in the distant geological past (e.g. the Eocene,
about 55 million years ago). What Barton doesn’t bother to mention is
that the earth was much much warmer at such times. In any case, more relevant is that CO2 has not gone above about 290 ppm any time in the last 650,000 years (at least), until the most recent increase, which is unequivocally due to human activities.

  • Sat, Dec 27, 2008 - 06:27pm

    #3

    Stan Robertson

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    Re: Hot off the projector – new AGW data

It seems to me that the subject of global warming is not really appropriate for this site. The real environment problems that Chris has pointed out consist of our using the most concentrated resources of all kinds to the point of unsustainability. Worries about polar bears, rising sea levels and other hard green issues are adequately addressed in many other places. This site has dealt with issues of more immediate impact on our way of life. Global warming is an issue on which attitudes are pretty hardened and disclaimers and pejorative terms such as "deniers" aren’t likely to be changed by things written here.

 Nevertheless, with respect to global warming, I would like for someone to explain just what part of cause and effect should precede and then judge the CO2 records revealed in the antarctic ice cores accordingly. What accounts for the quasi-periodic increases and decreases of CO2 in the atmosphere? What caused them before the arrival of modern humans? Termites and flatulent wildebeests? 

The truth of the matter is that if a few of the millions spent on flawed computer models were spent on measuring the extent of saturation of the CO2 absorption bands in the atmosphere, we could know exactly what direct temperature increase to expect from additional CO2. If the bands are already saturated, it won’t matter how much more we add except for the increasing acidity of the oceans (which might be of considerable effect). If they are not saturated, we ought to be able to say how much additional infrared absorption might occur. The measurements would not be difficult with satellite and ground based tunable lasers and detectors, but for some reason no one seems interested in really knowing the answer.

Stan Robertson 

  • Sat, Dec 27, 2008 - 07:03pm

    #4
    switters

    switters

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    Re: Hot off the projector – new AGW data

[quote=stanrobertson]

It seems to me that the subject of global warming is not really appropriate for this site. The real environment problems that Chris has pointed out consist of our using the most concentrated resources of all kinds to the point of unsustainability. Worries about polar bears, rising sea levels and other hard green issues are adequately addressed in many other places. This site has dealt with issues of more immediate impact on our way of life. Global warming is an issue on which attitudes are pretty hardened and disclaimers and pejorative terms such as "deniers" aren’t likely to be changed by things written here.

[/quote]

If some of the more dire predictions of climate change are accurate, the impacts will be more immediate, severe and potentially catastrophic than anything we’d experience from resource depletion or economic instability.

I agree that most people here are entrenched in their views on climate change and that so far the dialogue on the issue has been insufficient to change anyone’s mind.  But that doesn’t mean we should stop having the dialog.  

 

  • Sat, Dec 27, 2008 - 07:34pm

    #5

    Peter Bartels

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    Re: Hot off the projector – new AGW data

Chris.

If you want to promote dialog, and not conflict,  then may I suggest perhaps offering to members to avoid loaded statements, assumptions of truth (where the assumption does indeed have an argument in the negative, albiet a minority) weasel words, and phrases that act as perjoratives? 

I am a huge econut, and I am also a scientist (physiology, physics, statistics, and engineering…what can I say? I was a professional student for 12 years. 😉 ). 

However, I presently remain unconvinced with respect to anthropogenic global warming. (please folks, note the adjective). But I will not engage in a "dialogue" where the opening thread is loaded with a perjorative slam like "deniars". 

I consider myself skeptical. That does not imply that I am having a traumatic psychological dissociation episode. Now, I have a very thick skin, but I have been down this road before. Not going there. 

Interested parties probably have already made up their minds. No sense trying to "win" if the goal isn’t trying to "convince". 

TRUST ME.  If this is a new messagboard, it WILL get out of control quickly. (IDK, is it new? LOL)

My opinion, of course.  A concensus of scientists means nothing. (Argumentum ad populum, argumentum ad verecundium)

Thanks. 

  • Sat, Dec 27, 2008 - 08:02pm

    #6

    Nichoman

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    Re: Hot off the projector – new AGW data

[quote=stanrobertson]

 Nevertheless, with respect to global warming, I would like for someone to explain just what part of cause and effect should precede and then judge the CO2 records revealed in the antarctic ice cores accordingly. What accounts for the quasi-periodic increases and decreases of CO2 in the atmosphere? What caused them before the arrival of modern humans? Termites and flatulent wildebeests? 

 [/quote]

All paleoclimatic data are indirect measurements.   This is an evolving, immature field.   My view (also vast majority of my colleagues), there are more questions than answers toward the process and methodology of calculations, assigning value and merit of this data.  Doesn’t eradicate further research, far from it…just are more effective means to address Climate Change questions than using this type data to prove or disprove any issue.   Ultimately, Climate Change is still a immature science w/r/t man-made and natural forcings…such as: Solar, E-M interactions, Oceans, Earth Geophysics, Solar System and Galaxy issues to name the primary players…all currently in various stages of research.   We humans are an impatient, compulsive bunch looking for easy and/or quick answers.

[quote=stanrobertson]

The truth of the matter is that if a few of the millions spent on flawed computer models were spent on measuring the extent of saturation of the CO2 absorption bands in the atmosphere, we could know exactly what direct temperature increase to expect from additional CO2. If the bands are already saturated, it won’t matter how much more we add except for the increasing acidity of the oceans (which might be of considerable effect). If they are not saturated, we ought to be able to say how much additional infrared absorption might occur. The measurements would not be difficult with satellite and ground based tunable lasers and detectors, but for some reason no one seems interested in really knowing the answer.

[/quote]

 

CO2 absorption banding is reasonably well measured and understood…broadly, its the potential H2O interaction which is key.  Satellite and other particle wave measurements (lidar, laser, microwave, etc.) use weighting functions that loosely can only approximate the value.  It can’t find an exact value (we describe as "deterministic") because based on Quantum Physics…or probabilities. Another way of thinking is its like having 7 variables and say only 5 or 6 equations…mathematically…were unable to find a unique solution…just approximations of which variables tend to have greater or less weight.

BTW…the added energy retained from increased CO2 ppm concentrations…actually decreases logarithmically.  Here’s a rough analogy to consider…say the first 150 ppm of CO2 absorbs and retains 90% of all possible energy at those absorptive wavelengths for CO2.  The next added 150 ppm (now at 300 ppm) will absorb and retain 90% of the remaining…so 9%…our total is now 90 + 9 = 99%.   The third 150 ppm…or total of 450 ppm would be 90% of the remaining 1%…just .9% or a total of now 99.9%.   So little added energy is trapped beyond 300 ppm and almost none by 450 ppm. Similar analogies can be used for other greenhouse gases. Hopefully this helps in understanding H2O is the key player and how AGW interacts where the issues and "action" is.

 A useful reference (I differ with this page on small stuff) with many to your questions that explains in educated layperson terms, to most of your questions is…

http://junkscience.com/Greenhouse/index.html

 

Nichoman (Atmospheric Physicist)    

   

  • Sat, Dec 27, 2008 - 08:28pm

    #7
    joemanc

    joemanc

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    Re: Hot off the projector – new AGW data

[quote=Damnthematrix]

And now for all you Climate Change Deniers/Skeptics:

[/quote]

For the record, I am a skeptic…getting that disclaimer out of the way, does it really matter if I or anyone else believe/don’t believe in man-made global warming/climate change? The bottom line is we are depleting our carbon based resources and the faster we can move to clean and renewable energy sources, we will all be better off, environment included.

Instead of arguing endlessly about whether you believe in GW or not, let’s talk instead about these types of ideas:

http://www.connpost.com/localnews/ci_11314569

  • Sat, Dec 27, 2008 - 10:15pm

    #8

    Stan Robertson

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    Re: Hot off the projector – new AGW data

Thanks, Nichoman, for the link. A lot of people will find some useful, if politically incorrect, information there. While folks are shedding misconceptions, they might also be interested in knowing that the oft repeated claim of consensus among scientists is not true. Some 31,000 scientists have signed a petition that states their belief that atmospheric CO2 is not likely to be a serious problem. (And for what it’s worth, I am one of the 9,021 signers who claim some expertise in reaching this judgement.) The petition can be found at

http://www.petitionproject.org/

Stan Robertson 

 

  • Sat, Dec 27, 2008 - 11:10pm

    #9

    Nichoman

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    Re: Hot off the projector – new AGW data

@stanrobertson…

 

Seldom respond to Climate Changes issues anymore (this site…or others) for obvious reasons…but you asked reasonable questions.  Will state my background on Climate Change is on par with anyone.   That’s not the issue…the bastardization of science by both sides is…we all lose.   My experience is overall quality of Science is lowest ever seen in 3 plus decades.  

Our abandonment of sound project/program management, decision-making and leadership principles is a cancer.   Just like what is happening with our evolving financial crisis…energy…governance.   Seldom are the key questions asked by elected officials from both sides…sad is is their nonobjective problem solving capacity to get right answers.  It’s getting worse…almost by the month.  History will not look kindly on how we’ve handled and addressed this subject past 15 plus years…probably next 5 plus years or more.  

 Reference consensus earth is flat…earth center of solar system…current views of physics.   Will we ever learn what science is?   Pursuit of the truth possibly.   Or is it group-think and/or opportunism.

 

 My 2 cents.

 

Aware of petition, thanks.   Key is how few folks know how IPCC reports are written…how many writers are "Climate Scientists"…editing process…the scientific balance and standards used or not used…leave it at that.   Use/misuse of metrics by both sides.

 

Nichoman  

  • Sun, Dec 28, 2008 - 03:21am

    #10

    Stan Robertson

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    Re: Hot off the projector – new AGW data

@nichoman. . .

I agree with your assessment that the quality of science in the AGW issue is horrid. That is why I suggested that the topic ought to be dropped here. In my opinion, the most enthusiastic people on both sides are those who have no ability to judge the relevant data, computations or probabilities. AGW detracts from the central themes of this site.

In my opinion it is urgent that we Americans begin to wean ourselves from imported oil. Conservation is the only decent short-term response that we have. Ironically, it may be that the only way the public will swallow hard conservation measures is by fearing global warming. The problem with that is that it won’t work if the earth continues to cool. Better to have honest science and reporting, including honesty about the consequences of the oil supply shortages to come.

Stan Robertson 

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