Here’s an open thread for various climate science related discussions, to prevent more off-topic clutter everywhere else. We have some good posts coming up, but if you want to discuss something you read in the media, saw in a press release or just wanted to ask about, this is the time.
Some interesting things we’ve seen recently include discussions on the epistimology of climate modelling, Andy Dessler’s adventures in debate land and his new paper on water vapour trends, and a review of trends in the Columbia glacier. Have at it.
Addendum: Kevin McKinney has beaten us to the mention of this, but another recent article of importance is a thorough review of the state of knowledge of drought, past and future, by Dai. The article is open access here.
So, rainforest is probably oxygen neutral, but there some serious question-marks over the carbon budget.
My gut feeling is that new forests will be a carbon sink, but long-established forests ought to be relatively neutral, simply because there is nowhere for the carbon to hide. The biomass is in equilibrium. The soil layer is very thin. Hank, the study you linked mentions a “large biomass increment” accounting for the carbon sink. That doesn’t sound like a forest in balance, or at least implies the observation period was too short to properly account for tree death.
Lindroth et al (1998) studying a boreal forest, found it was a carbon source, and were very surprised by this. Tan et al (2010) can’t get their methods to converge. Other studies also find a wide range of values.
I don’t think the book has been fully written on this yet.
Before you finish that book, what level of management would be required to tilt “long-established forests” into functioning carbon sinks?
Didactylos @346
I agree that the “lungs of the planet” is a misleading metaphor.
I fear that what follows is too long and at the same time too short to do the subject justice. Many people have told me that they found my paper on climate and forests to be helpful (www.defenders.org/climatechange/forests).
It may help to think of forests as leaky buckets (credit for this metaphor to Mark Harmon and Olga Krankina at Oregon State University), with photosynthesis providing carbon inputs, and losses through respiration, decomposition and fire represented by holes in the buckets. The relative balance of input and leaks will change over time and space.
In the absence of disturbance, a given forest stand can achieve the sort of balance you describe, where the photosynthetic inputs are balanced by losses to decay. Here in the Pacific Northwest this stage can take several hundred years to develop, with 500 metric tons or more of biomass (living and dead) per hectare. Forests elsewhere typically reach this stage in less time and with less biomass. Depending on factors such as precipitation and temperature, whether a stand’s net is positive, negative or neutral may vary from one year to the next.
At the landscape (or larger) scale it gets more complicated, but the idea of balance can still apply. Some stands will be young, perhaps regenerating after a fire, and losing more carbon to decay than the young trees are taking up via photosynthesis. Others will be in a maturing stage (perhaps 50 to 250 years here in the PNW) where gains significantly exceed losses. With a given disturbance regime (average frequency and severity of fire, for instance) a dynamic landscape will have characteristic amounts of stands of different ages, and characteristic average (not constant) carbon stores.
Worldwide, humans have reduced carbon stores both by eliminating many forests and causing others to store less carbon as a result of activities such as industrial timber management that increase both the frequency and severity of disturbance (logging, in this case), greatly reducing average carbon stores across forested landscapes. There may still be a dynamic balance, but the average carbon stores are less than they were and less than they could be. (Stores in wood products fall well short of making up the difference.)
In human-disturbed landscapes, reforestation and reductions in the frequency and intensity of disturbance can move things toward higher average carbon stores. While that transition is underway, “balance” would be lost — replaced by a trend of increasing stores — for a while, until a new balance is reached at higher average storage levels. This what people mean when they say that while the potential for forests to draw down atmospheric CO2 is considerable, it’s limited, or that the forest sink will “saturate.”
Disruption of forest dynamics as a result of climate change will be a substantial source of uncertainty.
Tropical rainforest is very different than temperate forest; I recall original tropical rainforest has thin soil, while temperate forest can keep accumulating deeper soil indefinitely — a shaded canopy limits underbrush growth and fires.
> what level of management would be required to tilt “long-established
> forests” into functioning carbon sinks?
A much lower final level of ‘management’ than currently being done, but a great deal of ‘management’ in removing brush and smaller trees, moving toward restoring the mature forest pattern of widely separated large trees and continuous shade that controls underbrush:
http://www.fs.fed.us/psw/programs/snrc/forest_health/plumas_lassen_study_veg.shtml
“One approach to restoring forests and reducing fire intensity is to use thinning and gap-creation to increase the proportion of large fire-resistant trees and encourage more shade-intolerant regeneration.”
Hank @ 354
I’m all for thinning and prescribed burning overly dense, dry, fire-prone forests to restore habitat, reduce drought stress and reduce fire risk. However, these activities also reduce forest carbon and the most reasonable general conclusion to draw from the research is that – in dry, fire-prone forests — they should be considered carbon-neutral. See for instance:
Mitchell, S.R., M.E. Harmon, and K.E.B. O’Connell, Forest fuel reduction alters fire severity and long-term carbon storage in three Pacific Northwest ecosystems. Ecological Applications, 2009. 19(3): p. 643-655.
http://www.fs.fed.us/pnw/pubs/journals/pnw_2009_mitchell001.pdf
284 Mike G
Sorry I missed your comment earlier.
You said, “Calcification is a source of CO2. The equation is 2HCO3 + Ca–> CaCO3 + CO2 + H2O”
To me it looks like 2HCO3 first exists due to combination of water and CO2 and oxygen. 2CO2 + H2O + O making your 2HCO3 would seem like a believable starting point. If this becomes 2HCO3 after combining with Ca, as you say, then it looks like we captured some CO2 and lost some CO2. In effect, this constitutes capture of CO2. And the longevity of limestone seems to suggest a good job of sequestering it gets done.
What would be the process for weathering of carbonates?
Rick, I agree — I’d assume the study area is a logging operation — they have the loggers leave either 50 or 30 percent canopy and then let their biologists compare. It’s not a study on how to maximize recovery of forest, it’s figuring out how many trees they can take out and what the longer term costs are. At least that’s something, to finally be looking at those costs.
284 Mike G.
They say at :
http://www.galleries.com/minerals/carbonat/calcite/calcite.htm
Calcite is intricately tied to carbon dioxide in another way. Since many sea organisms such as corals, algae and diatoms make their shells out of calcite, they pull carbon dioxide from the sea water to accomplish this in a near reverse of the reaction above. This is fortuitous for us, as carbon dioxide has been found to be a green house gas and contributes to the so called “green house gas effect”. Environmentally then, calcite is very important and may have been quite important to the successful development of our planet in the past. By pulling carbon dioxide out of the sea water, this biological activity allows more of the carbon dioxide in the air to dissolve in the sea water and thus acts as a carbon dioxide filter for he planet. Environmentalists are now actively engaged in determining if this activity can be increase by human intervention to the point of warding off the “green house gas effect”. A significant amount of calcite precipitation in sea water is undoubtedly inorganic, but the exact amount that this contributes is not well known. Calcite and other carbonate minerals are very important minerals in the ocean ecosystems of the world.
Is this wrong?
[Response: Completely: CO2(aq)+CaCO3 + H2O <--> 2HCO3^- + Ca^2+ Look up ‘carbonate pump’ on wikipedia. -gavin]
347 Hank Roberts,
You wish me to go off and talk about forests in the Sahara, because they are talking about ‘it’ there? The ‘idea’ so to speak has nothing to do with foresting the Sahara.
It is an old trick to try to reframe that which you don’t like in order to defeat it.
The key to the ‘idea’ is that we have a possibility of rearranging water distribution in North America. China does also have that option. I can not imagine anything in the area of the Sahara having any such possibility.
I realize it is awkward to think about some difficult environmental issues with regard to water distribution. But for those who see that global warming carries with it worse environmental problems, I suggest, maybe it is time for some new thinking.
354 Hank Roberts,
You seem ok to be talking about management of existing forests. And you offer thoughts about how to do this.
Though I do not see much likelihood that existing forests can be made into a greater sink than they are, it certainly would be an interesting part of a forest project to establish a cadre of trained people who could maintain the existing forests, and learn about forest management in the process.
This skill set would then be applicable to the new forests that we might establish, and with skilled management, this could lead to permanent holding of ‘carbon’, as organic compounds.
Cess et al
“Uncertainties in Carbon Dioxide Radiative Forcing in Atmospheric General Circulation Models”
http://www.gfdl.noaa.gov/bibliography/related_files/rdc9301.pdf
from 1993, does mention SW forcing by CO2 – apparently the model average SW forcing is a 6 % difference to forcing at the tropopause level; I only skimmed this so I don’t know if that’s before or after stratospheric adjustment.
Figs 4 and 5 from Kiehl and Trenberth 1997:
http://www.cgd.ucar.edu/ccr/aboutus/staff/kiehl/Kiehl-Trenberth.pdf
– I would infer from fig 5 that the SW forcing from an increase in CO2 at TOA (instantaneous) (it’s a positive forcing at TOA) would be about 3 or 5 times greater with global average clouds than without clouds … (?)
…Although fig 5 doesn’t cover all Solar IR…
Hank’s quote from Peck et al refers to 0.0035 GtC of annual productivity of which about 20% might be sequestrated. That temporary drawdown is a drop in the bucket. Forests could easily beat that. Peck et al speculates that 0.01 GtC/yr might be sequestrated “eventually” after ice retreats further. The effect might be significant over the “thousands to hundreds of thousands of years” that the abstract considers… but not over the timescales we’re concerned about.
Jim Bullis, the unsurmountable obstacle to forests as a “solution” (as you say) is that they don’t fix nearly enough carbon. The consecreated word, I belive, is “wedge”.
If you’re going to do science-fiction (or rather engineering-fiction), consider ways in which biomass could be buried that would sequestrate the carbon for a long time. Then consider how much work would be required to bury adequate amounts of biomass in that way (and how much CO2 would be emitted in the process). Work the numbers and I don’t think you’ll find that burning coal for elecricity is worth it.
Wisconsin logs that sank in the 1800s are perfectly good today, so burying wood may not be the only option:
http://timelesstimber.com/
I had thought about sinking logs in the oceans but not in the great lakes. Perhaps some other lakes would be suitable as well such as Baikal. There’s enough volume in the great lakes to sequestrate more carbon than we need but it couldn’t happen very fast and it would still require a huge amount of work.
Any forestry experts who could guess how fast the soils of the region might deplete if one were to systematically harvest lumber for burial/sinking? And how much of the region’s wood output would potentially be suitable for efficient transportation and sinking to begin with?
Jim, look at your many repetitions of the same text in multiple postings, e.g. here: http://www.economist.com/user/Jim%2BBullis/comments
The NAWAPA idea goes back to the 1950s, done in detail, it’s not new.
If you could point to a success in creating new forests on land that hasn’t supported them, you’d be adding something novel to the NAWAPA idea — but you’d have to justify taking the water, which they have other plans for.
Gavin: “Look up ‘carbonate pump’ on wikipedia.”
It looks like there used to be such an article since I found a link to it inside Wikipedia, but it’s no longer there.
[Response: Hmm… well it should be. Try this textbook instead. – gavin]
263, Anonymous Coward: The consecreated word, I belive, is “wedge”.
You misspelled “consecrated”, but more importantly: “wedge” is a “proposed” word (based on the visual appearance of a graph), and has not been “consecrated” by anyone. The most important concept is a plurality of solutions, each inadequate by itself, undertaken concurrently.
Meanwhile, I remember that I have an obligation to provide references for a few of my assertions. I am working on retrieving them.
365 AC, why not use some of the logs for log homes? They have excellent thermal mass though they’re hard to insulate. I’m sure we have plenty of long-lived uses for wood.
Dutch NGO Natuur en Milieu (Nature and Environment) opens CO2 market for everyone: buy emission rights and have them taken out of the market, effectively reducing the European emission cap: http://bit.ly/CO2mkt (Dutch)
http://www.nicholas.duke.edu/thegreengrok/winter2010reports
—excerpt follows—-
“… While it may have been cold in northern Europe and in parts of the United States last winter, on a global scale, the winter was actually the warmest on record…. those cold temperatures and record snowfalls were not all that unusual and are actually consistent with there being a global warming trend.
“That new insight comes courtesy of two recent reports: the Arctic Report Card … and a paper published last week in the journal Geophysical Research Letters by Julien Cattiaux of the French Laboratoire des Sciences du Climat et de l’Environnement and colleagues that focused on the anomalously cold temperatures in northern Europe during the winter of 2010.”
Just added “climate hawk” to my Twitter bio. Who’s next? http://www.climatehawks.com
http://www.newscientist.com/article/dn19658-arctic-narwhals-reveal-climatemodel-errors.html
Hank Roberts@366 And Jim Bullis,
NAWAPA–Ah, yes, they wanted to use nukes to reverse the flow of the Yukon. Bigger bombs for a brighter tomorrow.
While winter 2009-10 was much warmer that the two preceding winters, it was not significantly different that the prior six. You ar correct in that the past winter was not all that unusual.
http://www.climate4you.com/
DanH, got a cite to a paper as a source for your statement?
(other than Climate4U — which seems to be teaching the controversy)
Click the link I gave for the papers referenced there.
Off topic: The Economist has just come out with a review of Pielke Jr.’s new book on the climate-change issue. There is the (as usual) depressing comment list below the review. Maybe people should drop by …
http://www.economist.com/node/17358792/comments#comments
My favorite denialist came up with a mechanism (or maybe this mechanism circulates in the denial-o-sphere, dunno) that could potentially \disprove gw theory\. I thought it was kind of cool and did a little back of the envelope calculation to see if I could convince myself all was well and that RC should close up shop. The mechanism is a negative feedback between CO2 and water vapor which I believe is correct. Addition of CO2 to the oceans should reduce the vapor pressure of the oceans and subsequently reduce the flux of water vapor into the atmosphere. The idea is that you shoot a bolus of CO2 into the atmosphere and immediately put half of it into the upper ocean which will reduce the vapor pressure of the ocean by an amount and that this reduction will result in a decrease in radiative forcing that beats the increase due to the equal sized bolus in the atmosphere and that consequently CO2 gives cooling rather than warming. I thought this not a stupid idea.
The bad news is that my back of the envelope calculation says that it is pretty unlikely to help us. The fractional decrease to the radiative forcing, dRF_vp, due to a bolus of CO2, dC, added to a top layer of ocean containing \W=amount of water in the layer\ should be proportional to: dC/W so that dRF_vp = A_vp dC/W. The fractional increase in radiative forcing due to the addition of of a CO2 pulse of the same size *since the oceans are supposed to take up roughly half the CO2 each year) should be dRF_C = A_C dC/C where C is the amount of CO2 in the atmosphere. If my denialist’s mechanism is to succeed in disproving warming it must be the case that dRF_vp/dRF_C ~ 1. WHich implies that: C/W x A_vp/A_c ~=1. I’m not sure what value one might take for A_vp and A_c but I guess the ratio shouldn’t be bigger than 10. What about C/W ? C is the amount of carbon in the atmosphere. W is the amount of water in the layer in which we’ve assumed the CO2 to be uniformly mixed. I’m thinking somewhere between 1-10m might be reasonable for the first year. Take a meter as a lower bound. Then W = 55,000 mols/m^2 (mols per square meter). According to wikipedia there are 3 x 10^18 grams of CO2 in the atmosphere which works out to 7 x 10^16 Mols which works out to C=140 Mols/m^2 . So that C/W is about .0025 which from my perspective pretty much ends that mechanism. I guess this is sort of amusing in that we are frequently told that CO2 is a \trace gas\ and that it couldn’t possibly have an effect. Of course it is precisely because CO2 is a trace gas that we can affect its concentration in the atmosphere. Similarly It is because it is a trace gas that the warming caused by a bolus of CO2 in the atmosphere beats the cooling caused by an equal sized bolus dissolved in the top meter of the upper ocean. Do you folks buy this back of the envelope analysis? I can back it up a bit more than I have here.
Hat tip to this small-family-forestry group http://www.nnrg.org/
for some references that may be useful to others:
“Mark Harmon … is a professor and chair of the forest science department at Oregon State University. His research has been referenced to both credit and discredit the idea of achieving carbon neutrality by using waste wood of forest management for energy….”
2009 Congressional Testimony on Forest Carbon Sequestration
http://resourcescommittee.house.gov/images/Documents/20090303/npfpl/oversight/testimony_harmon.pdf
Potential Upper Bounds of Carbon Stores in Forests of the Pacific Northwest
http://www.biol.wwu.edu/hooper/Smithwicketal2002EcolAppl_UpperBoundsofCstoresinPNWforests.pdf
Successional changes in live and dead wood carbon stores: implications for
net ecosystem productivity
http://treephys.oxfordjournals.org/cgi/reprint/22/2-3/77.pdf
Those interested in forests as a potential solution will, if they have not already read it, find this interesting:
http://caos.iisc.ernet.in/faculty/gbala/pdf_files/Bala_CS2009.pdf
From Zhang et al., new at AGU:
http://www.agu.org/pubs/crossref/2010/2010GL044988.shtml
“Summer ice volume may be more sensitive to warming while summer ice extent more sensitive to climate variability. The rate of annual mean ice volume decrease relaxes approaching 2050. This is because, while increasing SAT increases summer ice melt, a thinner ice cover increases winter ice growth. A thinner ice cover also results in a reduced ice export, which helps to further slow ice volume loss. Because of enhanced winter ice growth, arctic winter ice extent remains nearly stable and therefore appears to be a less sensitive climate indicator.”
From Comment 11 at
http://dotearth.blogs.nytimes.com/2010/10/30/distilling-the-human-element-in-the-climate-challenge/
National Research Council – Committee on the Human Dimensions of Global Change: http://www7.nationalacademies.org… are multiple publications by this committee. Perhaps the most relevant are the workshops that were held on climate change and the behavioral sciences: http://www7.nationalacademies.org/hdgc/Current_Projects.html
http://www7.nationalacademies.org/hdgc/Addressing_Challenges_of_Climate_Change_Through_Behavioral_and_Social_Sciences.html
Routledge Handbook of Climate Change and Society: http://www.taylorandfrancis.com/books/details/9780415544764/
Oxford Handbook of Climate Change and Society (forthcoming – see book preview here) http://www.cvap.polsci.ku.dk/nyheder/nyhedsliste/oxfordhandbook/paneldebat_-_invitation.pdf/
American Psychological Association – Psychology and Global Climate Change http://www.apa.org/science/about/publications/climate-change-booklet.pdf
Robert J. Brulle PhD
Professor of Sociology and Environmental Science
Drexel University
John Pearson @ 378 – I thought this not a stupid idea.
And of ocean acidification?. You don’t appear to understand how serious an issue that is.
John E. Pearson @378 — I prefer the more straightforward
https://www.realclimate.org/index.php/archives/2010/10/unforced-variations-3-2/comment-page-5/#comment-189329
383 Dappled Water babbled “You don’t appear to understand how serious an issue that is.”:
You appear to prefer not to have any idea about answers to questions such as the one I raised.
For John Pearson — that sounds vaguely like Kasting and Ackerman’s paper (1986), http://www.geosc.psu.edu/~jfk4/PersonalPage/Pdf/Science_86.pdf
The tradeoff between surface pressure and vapor pressure as they described it came from arbitrary assumptions made in modeling, and goes away with other assumptions, as he says in that paper. Got anything more recent?
David at 384: I don’t know which is more straightforward, physical or statistical arguments. I prefer arguments that are rooted in physics. Statistical arguments are fine but as you know it is imaginable that we’re in a statistically weird warming period and that CO2 has nothing to do with it. That (plus uncertainties associated with water vapor and clouds) is why the IPCC gives only a 90% chance that the current warming trend is anthropic rather than something closer to certainty. From a typical physicist’s perspective I would think that the IPCC kind of understated the odds. I do find the fact that there are a hell of a lot more water molecules in one meter of ocean than there are CO2 molecules in the entire atmosphere to be pretty straightforward. I certainly didn’t mean to imply that this accounts for the warming. It does, I believe, shoot down the proposed mechanism.
386 Hank asked if I had anything more recent. No. Less recent. It’s been known since the 19th century that adding solute to a solution decreases the vapor pressure. That is clearly a negative feedback of CO2 on radiative forcing. My point was that negative or not it is inconsequential. I claim that the key figure of merit is the ratio of the number of CO2 molecules in the atmosphere to the number of H2O molecules in the upper ocean layers and that this is too small for the proposed mechanism to matter.
[Response: Furthermore, the oceans don’t take up half the emitted CO2, rather only about 1/4 of it. The rest goes terrestrial.–Jim
For John Pearson
Did you read the paper I linked? Do you see where they compare the tradeoff between the two consequences?
Theory from the 19th century — or the 20th before computer modeling–is not the most reliable source for details of radiation physics, as Weart points out; many details that made a difference weren’t understood until the 1960s, simply because nobody could do the math without machine help.
I’m just trying to figure out where your unnamed friend got this idea, and whether there’s anything published that talks about it.
I pointed to the one paper I could find mention of. It may or may not support your idea, I can’t tell.
That link goes to an old PDF (image file) so I can’t paste in the relevant text for you, but look around the paragraph on p1384 where it says “… little physical significance; a different choice of parameterization could either shift the increase to a different CO2 pressure or eliminate it entirely …. CO2 is not that efficient as a greenhouse gas; thus, the increase in surface pressure caused by the addition of CO2 outstrips the increase in H2O vapor pressure caused by higher [temperature]….”
If there’s something to your friend’s idea, probably someone has published about it.
Or else it’s time to throw out physics and start over, of course.
Anything, as the man says, is possible.
http://xkcd.com/812/
http://imgs.xkcd.com/comics/glass.png
You appear to prefer not to have any idea about answers to questions such as the one I raised.
Pointless is how I would characterize it. But having re-read your initial comment I realize it was a misinterpretation on my part. Guess I was incensed by Jim Bullis’ remarks on ocean acidification.
Re 387 John E. Pearson “why the IPCC gives only a 90%” – I thought it was at least 90 %; don’t have time to look it up right now…
Hank,
I was just posting the HadCRU values. Does that require a peer-reviewed research article? Many scientists reference these measurements. If you are claiming that this past winter was the warmest on record, should it not appear in Phil Jones’ database? Where are you getting your measurements?
> Dan H.
> where are you getting your measurements
See above, I posted the link:
29 October 2010 at 2:36 PM
JEP 387: it is imaginable that we’re in a statistically weird warming period and that CO2 has nothing to do with it.
BPL: But only if you don’t know very much about atmosphere physics.
Re: #387
I agree with the pro-physics drift of your comment but am far less sure about its apparent attempt to absorb different types of uncertainty into one concept and one probability of 90%. The cloud difficulty may help to determine the range of climate sensitivity but that does not mean that it contributes to the 10% probability that recent warming is down to natural variability. And why are water vapour included and aerosols excluded from your list?
[Apologies for not re-checking the AR4 first]
Hi John, I’ve been giving some consideration to your favorite denialist’s mechanism. One fault I see is that the water content of the atmosphere is not driven by the equilibrium between ocean surface and atmosphere, but rather by the capacity of the atmosphere to hold the water–i.e. relative humidity. The boundary layer is not a closed system, and so not in equilibrium. It is disrupted continually by wind. So, even if there were a significant effect, it still wouldn’t have an effect on RH. And indeed, it appears that RH has not changed appreciably. So, while clever, it’s wrong.
Dan H, where did you find that “Jones” / “Hadley CRU” info you posted?
I’ve looked there and haven’t found what you described.
While looking for your source, I did find this:
http://pubs.giss.nasa.gov/cgi-bin/abstract.cgi?id=ha00510u
described here: http://data.giss.nasa.gov/gistemp/2010summer/
“… it is not possible to say yet whether 2005 or 2010 will be the warmest calendar year in the GISS analysis. It is likely that the 2005 and 2010 calendar year means will turn out to be sufficiently close that it will be difficult to say which year was warmer, and results of our analysis may differ from those of other groups. What is clear, though, is that the warmest 12-month period in the GISS analysis was reached in mid- 2010, as shown in the Rev. Geophys. preprint….”
Hank asked at 389 if I read the paper. I scanned it a bit too quickly. Certainly I didn’t read it. And I missed the paragraph in question. I don’t know where he got that mechanism from. When he told me about it he presented it as if it were his own idea but he spends a lot of time posting on right wing blogs so it wouldn’t surprise me to learn that it is circulating in the denial-o-sphere. I’ll read the article a bit more carefully to see if their arguments jibe with mine.
I got a little bit of pleasure out of considering the areal mass density of atmospheric CO2 which is about 6 Kg/m^2. Each year we’re adding almost 60 grams/m^2 of which half stays in the atmosphere. Convert the mass to weight and give it in pounds, ounces, and the area in square yards cause Americans don’t know from metric and maybe someone who otherwise wouldn’t believe it will appreciate that it can easily have a non-trivial effect. I guess that during the industrial area the CO2 partial pressure has gone from 9 pounds per square yard to about 12.
Oh, for Dan H again: you asked
> this past winter … should it not appear in Phil Jones’ database?
Possibly you mean this database?
http://www.cru.uea.ac.uk/cru/info/warming/
It doesn’t include winter 2010 (yet). As of now, it’s a:
“… temperature record from 1850 to 2009….”
Where did you get your information, Dan H?
Patrick in 291, Barton in 394 and Geoff in 397.
The 90% confidence level is on page 11 of the IPCC summary for policy makers. (AR4). It says: Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.12 This is an advance since the TAR’s conclusion that “most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations”.
Very likely means 90% in IPCC-speak. For me that means that it is statistically imaginable that CO2 has nothing to do with the current warming. From the physics perspective I don’t see a way around it but when the experts tell me there is a 1 in 10 chance that the current warming isn’t CO2 driven and I’m presented with a mechanism such as the one my denailist proposed I feel obligated to consider it.
[Response: You are over-stating the converse. The 10% uncertainty is mostly related to a) the possibility that the IPCC assessment of internal variability on multi-decadal timescales is 3 or 4 times larger than any model has been able to produce, or any analysis has concluded, b) the possibility that the specifications of natural forcings are completely wrong, or c) the temperature record is completely wrong. Of these, a) is probably the most likely relative to the others, but I would not say it was likely at all. The statement’s converse has nothing to do with the expected effect of CO2 all other things being equal, which had that been asked of the IPCC authors, would have almost certainly been described as an ‘unequivocal’ warming. – gavin]