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« Lies, damned lies and statistics | Main | New peer reviewed study sinks claims of sea level rising »

Comments

R2D2

Haha good work Ian

CM

I've written a reasonably long response and have tried to post it 4 times but it won't accept it.

CM

Ian, it would be great if you could reference your graphs and charts, especially if you are wrapping an entire argument around them (pretty standard practice).

Also, you’ve provided a quote from Gareth, but then have immediately misquoted him (by replacing ‘inevitably’ with ‘invariably’). Could be argued that the mistake is meaningless, but it is very sloppy and imprecise (see your other post and my comment about being precise).

CM

I see the graph is used here:
http://tinyurl.com/yzwc7yt

(Australian Parliamentary Library website)

It is pointed out in response that “many other factors can also affect global temperature over long time period”

And:
“Moving to more recent geological times (the last one million years), Earth has shown regular glacial and interglacial periods. We have only recently, geologically speaking, emerged from an ice age (a glacial period). This occurred about 10,000 years ago, when our modern climate became established. Of course, during an even shorter period – those 10,000 years – there have also been small and more rapid variations in climate.

It is easy to forget, however, that these changes took place over thousands of years. Human civilisation of the last five thousand years has developed during a time of particular climate, and for the moment relies on retaining the characteristics of that climate. Humanity’s advanced civilisation and large population is now much more vulnerable to disturbance by climate change than were our cave-dwelling ancestors.”

The key would seem to be working out what might happen under the Earth’s conditions as they are most relevant to us now. Would you agree?

CM

In the last 400,000 years, when conditions were the most similar to today, temperature and C02 levels tracked closely.
See: http://www.geocraft.com/WVFossils/last_400k_yrs.html

In the last 50,000 years (when conditions were even closer than they are today) the correlation is closer.
http://www.geocraft.com/WVFossils/last_50k_yrs.html

And so on and so on (2,000 years, 500 years, etc)
http://www.geocraft.com/WVFossils/temp_vs_CO2.html

CM

This paper (referenced at that aph.gov page) partially explains how the processes were quite different: http://www.geocraft.com/WVFossils/Reference_Docs/Geocarb_III-Berner.pdf

As the aph.gov page notes:
“there is evidence that CO2 concentrations also varied, being much higher than today until the evolution of large land plants about 400 million years, which caused a considerable decline in the abundance of atmospheric CO2.”

When taking these differences into account, BERNER and KOTHAVALA mention in their conclusion:
“This means that over the long term there is indeed a correlation between CO2 and paleotemperature, as manifested by the atmospheric greenhouse effect.”)

Historic assessment is important. But it’s only partially helpful in explaining processes occurring on Earth as it is today.

Not only should we be precise, we should compare apples with apples. No?

Ian Wishart

Craig, I know a workman is not supposed to blame tools but my glasses broke and I've been relying on contacts for general use...unfortunately they're not great at closer work and fine print, particularly in the dark with the laptop perched on my lap close to midnight..so fair cop, I misread Gareth's 'inevitably'...but yeah, of no significant note in this case.

The graph, you will see in the lower corner, is sourced to the studies it is based on - well accepted studies I would add.

There may be a 'correlation' between CO2 and temp more recently, but even Real Climate admits all the cores show a lag of between 600 and 1000 years, where sun forces first, then CO2 is released around 800 years later.

RC argues this doesn't prove CO2 can't force first. At one level they're right. But nor does it disprove that aliens did it. I would be on a stronger ground than RC when I argue in Air COn that the current CO2 increases may be the result of warming a thousand years ago.

Based on past historical records, that is entirely consistent with the empirical data.

I'm not arguing that human CO2 emissions are not part of the mix now, of course they are. But if CO2 is primarily a lagger not a forcer, then we are all getting tremendously excited about something that may turn out to be an effect, not the cause. And if the cause is something else, perhaps we should look at that rather than obsess about CO2.

R2D2

CM:

Gareth has claimed that ice age temperatures can not exist with CO2 at concentrations of greater than 300ppm.

Regardless of what correlation may or may not exist, I think this claim is based on his own fantasies and not the real world data shown in this graph.

Its a little hard for me to read (as it is on a large scale), but it appears that an ice age much longer than the current existed 300 million years ago with CO2 levels (that appear to me to be) higher than 300ppm.

There is also an ice age 450 million years ago that occurred during a period where CO2 was at 4000+ ppm.

Looking at the abruptness it may well have been caused by an external/internal shock (such as an asteroid / super volcano).

However it can not be denied that this is evidence of Gareth's fantasy being categorically incorrect!

CM

R2D2, did you read what I posted above? If we compare the processes at work now, with those at work WAY back then, are we comparing apples with apples?

"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."

http://www.realclimate.org/index.php/archives/2007/04/the-lag-between-temp-and-co2/

So I don't see the issue.

CM

"The next glacial seemed rapidly approaching, when paleoclimatologists met in 1972 to discuss this issue (a period of so-called global cooling).[23][22] The previous interglacial periods seemed to have lasted about 10,000 years each.[22] Assuming that the present interglacial period would be just as long, they concluded, "it is likely that the present-day warm epoch will terminate relatively soon if man does not intervene."[24] Since 1972, our understanding of the climate system has improved. It is known that not all interglacial periods are of the same length and that solar heating varies in a non-linear fashion forced by the Milankovitch orbital cycles (see Causes section above). At the same time, it is also known that greenhouse gases are increasing in concentration with each passing year. Based on the variations in solar heating and on the amount of CO2 in the atmosphere, some calculations of future temperatures have been made. According to these estimates, the interglacial period the earth is in now may persist for another 50,000 years. That is, if CO2 levels increase to 750 parts per million (ppm). (The present atmospheric concentration of CO2 is about 385 ppm by volume,[25] but is rising rapidly as humans continue to burn fossil fuels.) If CO2 drops instead (to 210 ppm), then the next glacial period may only be 15,000 years away."

http://en.wikipedia.org/wiki/Quaternary_glaciation

CM

>>>>The graph, you will see in the lower corner, is sourced to the studies it is based on - well accepted studies I would add.<<<<

Ha, looks like while you need to get glasses fixed, I need to get some.
Although it would be good to get a link (often when people directly post graphs from websites etc simply right-clicking and choosing ‘Properties’ gives the location, but not in this case which is why I asked).

>>>>There may be a 'correlation' between CO2 and temp more recently, but even Real Climate admits all the cores show a lag of between 600 and 1000 years, where sun forces first, then CO2 is released around 800 years later.<<<<

Nobody has to ‘admit’ it, as that would suggest that it contradicted a theory. The lag makes sense and as far as I can see is scientifically well understood.

>>>>I'm not arguing that human CO2 emissions are not part of the mix now, of course they are. But if CO2 is primarily a lagger not a forcer, then we are all getting tremendously excited about something that may turn out to be an effect, not the cause. And if the cause is something else, perhaps we should look at that rather than obsess about CO2.<<<<

That implies that we’re not continually improving our understanding of the Earth’s climate, and the forcings and feedbacks, in a general sense.
C02 as a forcer is fairly basic physics, is it not?

R2D2

CM:

Yes I know it was a long time ago - but CO2 is CO2 is CO2 is it not?

Gareth has claimed that ice ages can not exist when CO2 is above 300ppm.

It seems pretty convenient to now claim, "Oh, we only mean they can't exist now. Things may have been different all that time ago when there actually were ice ages during periods of higher than 300ppm". I would reply, “Models say they can’t exist now, yet history shows it could occur in the past. What makes you trust a model more than history???”

Ian Wishart

Craig, CO2 has been shown in the lab to have all the properties we think it has, in enclosed containers.

We also know that those radiative properties will exist in the atmosphere too, but the issue is whether their effect is strong enough in a non-enclosed complex system to override other climate drivers, especially as individual molecules (which is what we are really talking about in terms of radiative absorbtion) only remain in the air for between 8 and 15 years, meaning the warming of new molecules has to begin anew.

Without scampering through my papers or scouring the net, I'm struggling to recall a paper that definitively and unequivocally proves via empirical testing (not modelling) that CO2 in the wild is having the predominant effect on climate that is claimed in theory.

By the way, never cite Wikipedia on controversial issues if you wish to impress. It is widely and deservedly regarded as unreliable on all but uncontested information.

Ian Wishart

Hear, hear, R2.

My point in the book has always been that CO2's properties remain constant throughout the universe and through history. You can't appeal, as HT constantly does, to "it's different now".

What the historical record shows is that whatever power CO2 had it could be overridden, and was, by other climate factors that lasted far longer than mere orbital variations or continental shifts.

If anything, CO2 appears to be quite a fragile flower and I am far from convinced that it has a major forcing role.

CM

R2D2, C02 is C02 but how it effects the earth's balance is determined by a whole lot of other factors, many of which are different today than a million years ago (lithosphere). No scientists is claiming the mere presence of C02 does anything. It's how it acts today that matters.

I'm not going to defend a claim that "ice ages can not exist when CO2 is above 300ppm", as I haven't seen any evidence (strong or weak which says that).

'Trusting history' is pointless unless you understand that 'history' and relate it to today in a meaningful way. Just because you didn't get hit by a car crossing a road one day, doesn't mean you won't get hit the next.
Models suggest what might happen in the not-to-distant future because they have a decent understanding of Earth's current processes and systems.

R2D2

"'Trusting history' is pointless unless you understand that 'history' and relate it to today in a meaningful way. "

OK. I agree with what you are saying here (the logic of it).

But I do not see how we can not apply this history to the present. The theory goes that if CO2 increases by a certain magnitude it will drive temperature increases by a certain magnitude.

If we look at history this is not the case. What am I missing? Why has CO2 become the dominant driver now when it wasn’t in the past?

I’m listening, please explain.

Thomas Everth

Ian, this (CO2 vers Temp / lead or lag) is really a very old hat and was trashed around well and truly for a few years now.
I refer to this:

http://tinyurl.com/33enej

as not to have to waste my time typing the argument down here.

As far as CO2 and temps in distant history goes:
It would seem that some mechanism holds Earth temp at round 22 Deg (about ten more than now) for times in which CO2 has been significantly higher than 200 - 300 ppm. And I guess that is consistent with the view that CO2 increase to a range above 500ppm will see us drifting there again.

Of cause Earth and the biosphere will adapt over time. The argument however is how civilization will adapt in a short time to such changes. It has been aptly shown that mitigating CO2 is by far less costly than taking the effects of 4 or more Deg warming on the chin within the next century. And this is the essence of the entire debate.

Thomas Everth

This article on CO2 versus Temp time lag from back in 2004 is probably most clear:

http://tinyurl.com/2ssxek

CM

R2D2, BERNER and KOTHAVALA mention in their conclusion:
“This means that over the long term there is indeed a correlation between CO2 and paleotemperature, as manifested by the atmospheric greenhouse effect.”
Simply looking at a graph with raw data is meaningless if it doesn't compare apples to apples.
Past reconstructions and everything else we can determine from ice cores etc are interesting and certainly increase our understanding, but are only of minor relevance in terms of modelling how the Earth acts now. We're not trying to work out how to survive when we didn't exist.
Timescales are certainly very important in terms of the speed of change though, and this is a central problem that deniers/skeptics struggle to explain - how to explain the current RATE of change. History doesn't help much.

I've never seen an argument that C02 'acts differently'. Only that the planet does (over millions of years). We know in the next few centuries the atmospheric and land/water processes are going to be the same as they have been over the last few. Which is why modelling and explaining the very recent past is considerably more important that knowing exactly what happened 2 million years ago.

CM

Ian said:
>>>>What the historical record shows is that whatever power CO2 had it could be overridden, and was, by other climate factors that lasted far longer than mere orbital variations or continental shifts.<<<<

So what current 'climate factor' has been shown to kick C02's ass in terms of effects on temperature? And if none has been shown, why/how is it hiding? Mass/gross scientific incompetence and/or conspiracy?

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