'Just-in-Case': How to Think About Uncertainty and Global Warming

TCS Daily ^ | 14 Feb 2007 | Arnold Kling

[jonno]

"Let's just say that global warming deniers are now on a par with Holocaust deniers, though one denies the past and the other denies the present and future." -- Ellen Goodman

"Global warming is a false myth and every serious person and scientist says so. It is not fair to refer to the U.N. panel. IPCC is not a scientific institution: it's a political body, a sort of non-government organization of green flavor. It's neither a forum of neutral scientists nor a balanced group of scientists. These people are politicized scientists who arrive there with a one-sided opinion and a one-sided assignment. Also, it's an undignified slapstick that people don't wait for the full report in May 2007 but instead respond, in such a serious way, to the summary for policymakers where all the "but's" are scratched, removed, and replaced by oversimplified theses. This is clearly such an incredible failure of so many people, from journalists to politicians." -- Czech President Vaclav Klaus

Pundits, politicians, and the public have a hard time coming to grips with uncertainty. This makes the atmosphere for debating global warming policy especially foul, because the key issues with global warming are the uncertainties involved. Those who would try to reduce the issue of global warming to a yes-or-no question ("do you believe or do you deny?") are not scientists.

Real scientists understand uncertainty. Real science deals with uncertainty through relentless, skeptical inquiry. Real science resolves arguments not with consensus, but with data.

My understanding of global warming is influenced by my background in applied statistics and economics. There certainly are scientists who have spent more time than I have analyzing the meteorological data. However, before you call me a "hack," make sure that you are capable ...

[spunkets]

Thanks for the link. I understand what he's got there, regarding CO₂ solubility, but it has nothing to do with global warming. See, the range of CO₂ concentrations he's got there(200-280ppmv) includes almost no change in heat retention by the gas. So, the temp can't possibly change much, because of atmospheric CO₂. He's got a 10^o temp change there, so all of that must be due to something else. That something is the Sun's output, because that's the only energy source that could possibly cause that temp change. ...if the temp change is real that is. I don't know how they measured that.

"But obviously temperature dependent increases in photosynthesis can't because the observed correlation is defintiely positive and quite high."

The ice core data is independant of that. It's been ignored, as far as I can see.

"That's part of his argument about why CO2 doesn't cause the observed warming."

Nothing he's got there addresses any heat retention mechanism. The paper's oblivious to that. The simple fact that they show the range change as 200-280 ppmv says there's no effect from CO₂

[edsheppa]

Thanks, that's interesting but not relevant to my question.

[edsheppa]

I think you must have misinterpreted what he is saying. His point has nothing to do with variations in CO2 concentration affecting temperature but rather the reverse. So heat retention etc. is irrelevant to his point.

As for how they infer %CO2 and temperature from the ice cores, depth correlates with age, CO2 can be measured directly from gas bubbles in the ice and temperature is inferred from ratios of isotopes. I don't know what the relevant error bars are or how this data matches other historical inferences.

The ice core data is independant of that

What do you mean? You said photosynthesis increases 10% for each 1°C increase. By this I assumed you meant that for each 1°C plants would increase their absorption of CO2 by 10%. Therefore, if this photosynthetic temperature dependence accounts for CO2 temperature dependence, I'd expect to see CO2 concentrations go down as temperatures rise. The Vostok data show the reverse so it seems quite relevant to me. Further, I don't see how to conclude anything other than that photosynthetic temperature dependence doesn't account for the CO2 variations with temperture.

Have I missed something?

Nothing he's got there addresses any heat retention mechanism.

As I've been at pains to make clear, he doesn't mention it because it's not material to his argument. However, as you're evidently using it as an argument *against* CO2 caused temp increases, let's discuss it. I don't think it's directly relevant to pro-GW arguments. As far as I know, no one says that heat being retained in the CO2 accounts for temperature increases. That would be ludicrous because the gas is not insulated from the rest of the atmosphere.

[ancient_geezer]

Thanks, that's interesting but not relevant to my question.

I guess I misunderstood what the question was about. I could have sworn the issue was about how fast CO2 concentrations were increasing as a consequence of anthropogenic additions to the atmosphere and how that may relate to projected changes in climate.

The data clearly demonstrates that the trend in CO2 growth from anthropogenic sources is toward a linear increase as oppose to exponential as claimed.

 

As far as known sources and sinks are concerned the following table represents what little has been estimated:

 

Atmospheric content of CO2 750 billion tonnes (Gt) [Schimel et al. 1995], @359 ppm concentration [IPCC 1995]

 

Atmospheric CO2 Flux billion tonnes(Gt) per year, [Schimel et al., 1995]
	Ocean Surface	Land	Anthropogenic
Sources	90	60	7.1
Sinks	92	61.4	Unk

 

Unfortunately one of the big problems with the above is that recent studies are showing significant returns of CO2 back into the atmosphere above and beyond the above older studies in the form of microbial decay products of plant sequestered CO2 out of peat bogs and old growth plant detritus putting high levels of organic CO2 back into the atmosphere along with organic fossil fuel emissions.

http://www.silsoe.cranfield.ac.uk/nsri/research/carbonloss.htm

Bellamy P.H., Loveland P.J., Bradley R.I., Lark R.M. & Kirk G.J.D. (2005) Carbon losses from all soils across England and Wales 1978–2003. Nature, 437, 245-248.

Summary of the findings

We have found losses of carbon from soils across England and Wales that are on an enormous scale. Given the current debate on soil carbon stocks in relation to climate change and the potential for carbon sequestration in soils, these results are of huge international importance. They are the first of their kind at a regional scale anywhere in the world.

 

A separate and earlier study involving peat bogs appears to potentially have even greater impact arising from previously unsuspected sources of organic carbon release into the atmosphere:

 

http://www.newscientist.com/article.ns?id=dn6124

Peat bogs harbour carbon time bomb

• 18:22 07 July 2004
• NewScientist.com news service
• Fred Pearce

The world’s peat bogs are haemorrhaging carbon dioxide into the atmosphere, accelerating global warming, warns a UK researcher.

And worse still, the process appears to be feeding off itself, as rising atmospheric levels of carbon dioxide are triggering further releases from the bogs.

Billions of tonnes of carbon could pour into the air from peat bogs in the coming decades, says Chris Freeman of the University of Wales at Bangor, UK. “The world’s peatland stores of carbon are emptying at an alarming rate,” he says. “It’s a vicious circle. The problem gets worse and worse, faster and faster.”

Peat bogs are a vast natural reservoir of organic carbon. By one estimate, the bogs of Europe, Siberia and North America hold the equivalent of 70 years of global industrial emissions. But concern is growing that such bogs are releasing ever more of their carbon into rivers in the form of dissolved organic carbon (DOC).

“There seems to be an increase of DOC in rivers of about 6 per cent a year at present,” says Fred Worrall of the University of Durham in the UK, who collates global data on DOC levels in rivers. Worrall suspects the rise in DOC began about 40 years ago.

*** SNIP ***

Recent data from the Centre for Ecology and Hydrology in Lancaster, UK shows a 90 per cent increase in DOC levels in Welsh mountain rivers since 1988.

“The rate of acceleration suggests that we have disturbed something critical that controls the stability of the carbon cycle in our planet,” Freeman says. “On these trends, by the middle of the century, DOC emissions from peat bogs and rivers could be as big a source of CO2 to the atmosphere as burning fossil fuels.”

Journal reference: Nature (vol 430 , p 195)

 

However, the real issue as I pointed out it what is means in regards to climate change. The bottom line is actually not very much, as the direct radiative effect on surface temperature of doubling CO2 concentration in the atmosphere is only about 0.2^oC.

[edsheppa]

I could have sworn the issue was about how fast CO2 concentrations were increasing as a consequence of anthropogenic additions

No, I was questioning whether human activity accounts for the recent considerable increase in atmospheric CO2. All I was looking for was data in tabular form so I could do the correlation myself. I've got human CO2 emissions since 1751 and I'm still looking for the CO2 concentrations that include that time range.

That information about the bogs is interesting.

[spunkets]

His point is really irrelevant to GW, heat retention is not. His point has an insignificant efffect on GW.

"temperature is inferred from ratios of isotopes."

I don't know what that's about.

"Therefore, if this photosynthetic temperature dependence accounts for CO2 temperature dependence, I'd expect to see CO2 concentrations go down as temperatures rise. The Vostok data"

I'd really have to read much more about this. That link leaves much out.

'Further, I don't see how to conclude anything other than that photosynthetic temperature dependence doesn't account for the CO2 variations with temperature."

It does in real life. In the summer it goes down, and in the winter, it goes up. Forests are a major sink.

"As I've been at pains to make clear, he doesn't mention it because it's not material to his argument. However, as you're evidently using it as an argument *against* CO2 caused temp increases, let's discuss it."

Whatever he's got there is irrelevant to GW. It did not use any of it "against" temp increases from CO₂. I said the range of CO₂ there will not result in measurable temp changes. That's true.

"As far as I know, no one says that heat being retained in the CO2 accounts for temperature increases. That would be ludicrous because the gas is not insulated from the rest of the atmosphere."

Sure they are. That's the mechanism for atmospheric heat retention. All polar molecules absorb certain wavelengths of radiation. CO₂water and methane are polar. The diatomic elemental gases are not. Photons come in and get absorbed by the polar stuff. That causes them to vibrate and rotate. They bang into other stuff and there's an energy transfer. Those polars can reabsorb more photons coming in from the Sun. There's an equilibrium exchange all through the atmosphere, and it includes what eventually gets lost into space. The loss into space is due to the Earth being a black body radiator. The whole GW thing is about this process. The Sun emits, the Earth absorbs and reflects, andemits according to temperature. In order to get 2^o temp changes, the CO₂ concentration must triple, or more. Just moving by +/-17%, as in that link is nothing.

[ancient_geezer]

I've got human CO2 emissions since 1751 and I'm still looking for the CO2 concentrations that include that time range.

 

Here is the IPCC scenario data table for CO2, 1765-1990 historical plus IPCC's IS92 projected series 1990-2100

http://www.cgd.ucar.edu/vemap/supplemental/IS92a.html

Another source for historical data is the NOAA site:

With the Moana Loa site monthly series Mar 1958->Jan 2007
http://www.cmdl.noaa.gov/projects/web/trends/co2_mm_mlo.dat

 

Have a ball ;O)

[supercat]

That portion, as scaled from zero at the y-origin (roughly):

More like (roughly--I don't know how to make the top image transparent in HTML):

[ancient_geezer]

For all kinds of historical series You can also go to the CDIAC site. Check the subject areas to the right side of the page, the will lead you to more chart & tabular data on climate related information than you will ever have time to utilize.

[supercat]

I've yet to read how we cope with the tides, caused by the gravitational pull of the moon. There are mucho feet between high and low tide on a daily basis and we more than manage.

Out of curiosity, how much of the change in "sea level" is attributable to variation in distance between the ocean's surface and the center of the earth, and how much is attributable to variation in distance between land masses and the center of the earth?

[supercat]

Sinks. perhaps not. Recent sources, yes: CO2 from fossil fuels has a different distribution of carbon 13/14 than CO2 from other proposed sources, the he observed isotopic trends are very good fit to CO2 from fossil fuel.

My understanding is that C-12 in the atmosphere tends to get turned into C-14 as a result of solar radiation; Carbon-14 dating is predicated upon the assumption that while something is alive, the percentage of C-14 within it will be roughly equal to that of the atmosphere; after it dies, the percentage of C-14 will constantly decay.

Fossil fuels would have a lower percentage of C-14 in them than the atmosphere as a whole, but so would any other natural sources of "old" carbon.

[TigersEye]

Knowing the amount of water vapor in the atmosphere helps answer the question of whether or not recent CO2 increases are explained by human activity because ________________.

It doesn't answer that question. The amount of CO2 created by human activity is fairly well known and doesn't need further verification. It is too miniscule to be a factor of global warming.

[ancient_geezer]

"temperature is inferred from ratios of isotopes."
I don't know what that's about.

Here's some articles on the subject that can help in understanding what they do:

Proxy (climate) - Wikipedia, the free encyclopedia

Since molecules made up of differing isotopes of the same elements have different masses, natural processes tend to favor some molecules over others in depositing them in snow, rain, incorporating them into plant tissues etc.

The ratios of these Oxygen isotopes can be used as an indirect measure of temperature and humidity/precipitation for example, as the rate such is deposited is dependent on these factors.

Other isotopes such as ¹⁰Be & ¹⁴C are created in nuclear interactions between cosmic rays and atmospheric nitrogen, since the geomagnetic field shielding the earth from cosmic rays is modulated by solar magnetic fields such isotope concentrations vary with the solar activity cycle and thus are indicators of solar factors on the climate such as solar brightness & other impacts on the atmosphere through ionization like cloud formation.

Using mass spectrometers, vary small concentrations can be measured and used to create proxies for the variables involved with creation and depositing of these isotopes in the geological record.

[edsheppa]

Forests are a major sink.

I don't doubt it. But they cannot be a dominant contributor globally unless the Vostok data are wrong. The fellow is saying that the oceans are the dominant sink, that their efficiency is temperature dependent and that variation accounts for the historical CO2 concentration record.

Sure [CO2] [is not insulated from the rest of the atmosphere]

No it isn't as you yourself note: they bang into other stuff and there's an energy transfer. Consequently heat will flow from the CO2 to the other atmospheric gases. By my calculation, the N2 and O2 in the atmosphere will take up about 2000 times the amount of heat as the CO2 given the relatively minute amount of CO2.

[edsheppa]

Thanks, I'll take a look.

[E. Pluribus Unum]

I seen no direct correlation between atmospheric CO₂ levels and average global temperatures over the past 600 million years, do you?

Why are we now going to be baked by atmospheric CO₂ levels that are at least an order of magnitude lower than historic highs, when the earth was not baked?

[spunkets]

Thanks. I was more the details and particulars I was referring to. I'd have to read more about the ice core work to know and understand it.

[spunkets]

"they cannot be a dominant contributor globally unless the Vostok data are wrong. The fellow is saying that the oceans are the dominant sink, that their efficiency is temperature dependent and that variation accounts for the historical CO2 concentration record.

The Oceans are essentially saturated. I'd have to read more about Vostok ice cores to know exactly what they're about. Still, the change is small and is irrelevant for GW concerns.

"Consequently heat will flow from the CO2 to the other atmospheric gases. By my calculation, the N2 and O2 in the atmosphere will take up about 2000 times the amount of heat as the CO2 given the relatively minute amount of CO2."

I'm not sure you understand how this works. Polar molecules are the only absorbers. If there were none, only the surface stuff would absorb radiation. Since there are polar molecules in the atmosphere, it too absorbs. The amount of energy absorbed is proportional to the concentration of polar molecules. Even though CO₂ is at a low concentration, it is responsible for a fixed definite amount of solar absorption. Doubling the concentration, doubles the value of it's term for the total energy absorption. The retention depends on the polar gases, because the other gases don't absorb and are fixed. Maybe this link and the calc and discussion with JasonC in #7 will help. Granted I don't know the details about Vostok yet, there temp numbers says the Sun's output varied ~10% over those cycles. So the sun's radiation varied from say, 1235W/M² to 1365 W/M². The apparent concentration of polar only changed +/-17%, that's too small to effect a significant temp change.

[ancient_geezer]

Doubling the concentration, doubles the value of it's term for the total energy absorption.

Actually doubling the concentration increments absorption of CO2 by a fixed increment due to the fact that CO2 spectal lines are saturated (i.e. not enough IR at the right wavelengths to go around for the density of CO2 molecules in the atmosphere).

The only additional absorption that can occur by increasing CO2 concentration is in those areas of the spectrum at the tails of strong line responses and in the weak spectral lines of CO2 thus the absorption of IR is logarithmic as opposed to linear increasing at something less than 5.35*ln(C/Co) w/m², how much less depending on amount of water vapor in the atmosphere overlapping CO2 spectral lines reducing the amount of IR available to CO2.

[spunkets]

good link.