2006-11-06, Real Climate - How Much CO2 is Too Much

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How Much CO2 Emission Is Too Much ?David ARCHER

Real Climate, 06 Nov 2006

Filed under: Climate Science Greenhouse gases IPCC

This week, representatives from around the world will gather in Nairobi, Kenya for the latest Conference ofParties (COP) meeting of the Framework Convention of Climate Change (FCCC) which brought us theKyoto Protocol. The Kyoto Protocol expires in 2012, and the task facing the current delegates is to negotiatea further 5-year extension. This is a gradual, negotiated, no doubt frustrating process. By way of getting our

bearings, a reader asks the question, what should the ultimate goal be? How much CO2 emissions cuttingwould it take to truly avoid dangerous human interference in the climate system?

On the short term of the next few decades, the line between success and excess can be diagnosed fromcarbon fluxes on Earth today. Humankind is releasing CO2 at a rate of about 7Gton C per year from fossilfuel combustion, with a further 2Gton C per year from deforestation. Because the atmospheric CO2concentration is higher than normal, the natural world is absorbing CO 2 at a rate of about 2 or 2.5Gton C peryear into the land biosphere and into the oceans, for a total of about 5Gton C per year. The CO2concentration of the atmosphere is rising because of the 4Gton C imbalance. If we were to cut emissions by

about half, from a total of 9 down to about 4Gton C per year, the CO2 concentration of the atmosphere wouldstop rising for awhile. That would be a stunning success, but the emission cuts contemplated by Kyoto wereonly a small step in this direction.

Eventually, the chemistry of the ocean would equilibrate with this new atmospheric pCO2 concentration ofabout 380ppm (the current concentration), and its absorption of new CO2 would tail off. Presumably theland biosphere would also inhale its fill and stop absorbing more. How long can we expect to be able tocontinue our lessened emissions of 4Gton C per year? The answer can be diagnosed from carbon cyclemodels. A range of carbon cycle models have been run for longer than the single-century timescale that isthe focus of the IPCC and the FCCC negotiation process. The models include an ocean and often aterrestrial biosphere to absorb CO2, and sometimes chemical weathering (dissolution of rocks) on land and

deposition of sediments in the ocean. The models tend to predict a maximum atmospheric CO2 inventory ofabout 50-70% of the total fossil fuel emission slug. Lets call this quantity the peak airborne fraction, andassume it to be 60%.

The next piece of the equation is to define dangerous climate change. This is a bit of a guessing game,but 2C has been proposed as a reasonable danger limit. This would be decidedly warmer than the Earth hasbeen in millions of years, and warm enough to eventually raise sea level by tens of meters. A warming of2C could be accomplished by raising CO2 to 450 ppm and waiting a century or so, assuming a climatesensitivity of 3C for doubling CO2, a typical value from models and diagnosed from paleo-data. Of the 450

ppm, 170ppm would be from fossil fuels (given an original natural pCO2 of 280 ppm). 170 ppm equals340Gton C, which divided by the peak airborne fraction of 60% yields a total emission slug of about

570Gton C.

How much is 570Gton C? We have already released about 300Gton C, and the business-as-usual scenarioprojects 1600Gton C total release by the year 2100. Avoiding dangerous climate change requires very deep
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cuts in CO2 emissions in the long term, something like 85% of business-as-usual averaged over the comingcentury. Put it this way and it sounds impossible.

Another way to look at it, which doesnt seem quite as intractable, is to say that the 200Gton C that can stillbe safely emitted is roughly equivalent to the remaining traditional reserves of oil and natural gas. Wecould burn those until theyre gone, but declare an immediate moratorium on coal, and that would be OK,according to our defined danger limit of 2C.

A third perspective is that if we could limit emissions to 5Gton C per year starting now, we could continue

doing that for 250/5 = 50years.

One final note: most of the climate change community, steered by Kyoto and IPCC, limit the scope of theirconsideration to the year 2100. By setting up the problem in this way, the calculation of a safe CO2 emissiongoes up by about 40%, because it takes about a century for the climate to fully respond to rising CO2. If CO2emission continues up to the year 2100, then the warming in the year 2100 would only be about 60% of thecommitted warming from the CO2 concentration in 2100. This calculation seems rather callous, almostsneaky, given the inevitability of warming once the CO2 is released. I suspect that many in the communityare not aware of this sneaky implication of restricting our attention to a relatively short time horizon.

Note: responding to suggestions in the comments, some of the numbers in the text above have been revised.

7 November 2006, 2:31 pm. David

72 Comments 1. Can you please provide some indication of the degree of ocean acidity increase that these numbers involve?For example, what pH changes would arise from 500Gt C staying in the air.Have any of the stabilisation studies addressed the impact on marine life? ie. stabilised at 450ppm is a commonidea (though that ship may have already sailed), what would that mean for ocean acidification?[Response: I wrote a post on ocean acidificationhere, but it wont really answer your question about how bad itwould be, if pCO2 were stabilized at some level. I guess I feel that ocean acidification is analogous to ozonedepletion, in that it seems like a fairly frightening, fundamental change to a component of the Earth system, butits difficult to point to who exactly would suffer and how much. For ozone depletion, one could get a comparable

increase in UV by moving a few hundred kilometers closer to the equator, and yet it seemed a serious enoughproblem to ban freons, a decision I agree with. Would ocean acidification lead to some sort of biological collapsein the ocean, or extinctions, or would the biological effects even be measurable? Its hard to know. David]Comment byCoby 6 Nov 2006 @3:31 pm

2. RealClimate does an excellent job on reporting the facts about global warming. This piece on CO2 emissionsis one of the best, realistic, fact driven summary of the current state of affairs.Realclimate should be requiredreading for every member of the House and Senate.I believe that worldwide co2 emission levels should beimmediately reduced by 80%, right now, for us to have any viable chance at reducing the negative impacts of theglobal warming trends already in the pipeline.The latest conference. in Nairobi, of the parties to the UNFCCCmust extend Kyoto beyond 2012 and implement much greater restricions that those currently in effect.Once again,thanks to RealClimate for all the work that you do.Comment by Mark J. Fiore 6 Nov 2006 @3:35 pm

3. Could a 500Gton emission slug reasonably called safe given other likely impact besides atmospheric onesthe kinds of consequences of ocean acidification that some studies (e.g. The Royal Society, June 2005) point to?Comment byCaspar Henderson 6 Nov 2006 @ 4:05 pm

4. Given the environmental changes we are already seeing with less than 1C warming, the idea of 2C beingsafe may need some clarification. Is 2C the point at which some irreversible tipping points are thought tooccur (meridional overturning current disruption; clathrate release; ice-sheet loss; forest die-off; ...)? Putting itanother way, can we expect the climate and environment around us to be familiar and reasonably livable still at2C, for the long term?

[Response:Replying at once to this comment and the last (#3). The word safe seems a little weird to me in thiscontext also. A smaller CO2 slug would definitely be better. I think Hansen takes 1C as his safety limit. Iguess theyre also referred to as danger limits. Maybe thats a bit better word.
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And in response to just #4, its not as clear cut as that to predict when any sort of tipping point might be reachedand what it might be that tips. Who knows? We cant even figure out past tips, let alone predict future ones.David]Comment by Andrew Alcorn 6 Nov 2006 @ 4:23 pm

5. It is silly to say that a rise of up to 2C in global temperatures is not dangerous.A global increase of 2C means will mean an increase of at least 4C on the continents, because they heat muchmore than the oceans which provide 70% of the surface. Moreover, with polar amplification you will get 8C inmid latitude continental areas such as the USA and Europe, and up 20C in polar regions. That will means a rapidthaw of the Greenland ice sheet, which is already starting to melt, and so the flooding of New York, London, and

nearly every other port in the world.

Here I am emphasising the effects on the developed nations, not out of chauvism but because there is a myth that itis the developing nations who will suffer and we in the west will get off scot free.

It is obvious to me that with a 33% increase in CO2 above preindustrial levels, we have already reached the limitof a safe increase. The scientific commitment to higher temperatures from the one third increase will lead not onlyto sea levels that will flood our cities, but also to an increased number of hurricanes, drought and floods that weare already seeing. OTOH, the record wild fires that the USA has experienced this year can not continue toincrease, since eventually the lack of unburnt forests will set a limit!

But unless the scientists come down out of their dreaming spires, join the political debate, and tell the politicians it

is time to stop, we will continue to sleep walk towards the precipice, and eventually step over the edge. We do notknow the cause of rapid climate change, so we are running forward like a man wearing a blindfolded. What could

be more insane than that?

When are you scientists going to admit that you do not know all the facts? When are you going to have thecourage to admit that you are wrong, and that your hubris has led the world to the brink of disaster?

[Response:I apologize, I guess I used the wrong word, as I responded to the last comment. Im just thinking of aboundary in the continuum of the climate impacts. Greater than 2 degrees C is clearly dangerous, is what I meantto say. Just to have a number, to talk about. The best would be to not change climate at all, I absolutely agreewith you. David. ]Comment byAlastair McDonald 6 Nov 2006 @4:39 pm

6. Some earlier discussion in response to:Comment bydave- 3 Jul 2005 @ 9:39 pm(Click the timestamp to see the original)[Response:The ratio of dissolved CO2 to CO32- is about 1:10 preanthropogenic in tropical surface waters. Thetwo will remain about inversely proportionate as CO2 rises. So double CO2, and you halve CO32-. Id neverthought about this in this way, but it sounds like the ratio of the two would reach 1:1 when CO2 reached aboutthree times preanthropogenic, at which point the buffer is getting pretty weak. We should note that there are hugeuncertainties with regard to changes in the circulation and biology of the ocean. David.]Comment by Hank Roberts 6 Nov 2006 @ 4:41 pm

7. The Stern report focused on carbon dioxide equivalent, at least the portion Ive read, citing currentatmospheric levels of GHG of 430 ppm carbon dioxide equivalent and discussing stabilizing at 550 ppm or lower.How would you rewrite this article if the question were, How much GHG emission is too much?[Response:I hadnt thought of the other greenhouse gases. Putting them into the mix would definitely make thenot-quite-as-dangerous CO2 level go down. Im not sure we know what methane is going to do in the future (seemy other recent scholary work,Rasslin swamp gas). More like to go up than down, though, I expect. David]Comment byKaren Street 6 Nov 2006 @ 4:51 pm

8. Ive heard a few people say that we are really at 420 or 430 ppm CO2 equivalent already, once the increase inother greenhouse gases is taken into account. What is the figure for CO2 equivalent at present or where can I findit? Thanks![Response:I just calculated an equivalent CO2 of 465 ppm. I assumed a radiative forcing of 3.4W/m2 for

doubling CO2, and that CO2 accounts for 60% of the total greenhouse gas forcing (no aerosols or anything likethat). And that the real pCO2 is now 380 ppm. David]

[Response: 430 ppm CO2e comes from just taking the 6 Kyoto gases (CO2+CH4+N2O+SF6+HFCs+PFCs). Thatdoesnt include CFCs, nor O3, nor aerosols, nor land use etc. The argument was made in Stern that the
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uncertainties in the other components dont lead to them being easily incorporated into this definition (which istrue), and that CFCs (which are quite well known) are not likely to increase further given the Montreal Protocoland subsequent amendments. Our best estimate of the net effect of all known anthropogenic forcings is around380ppm (i.e. most everything else apart from CO2 cancels). PS. the most usual estimate for the adjusted forcingdue to 2xCO2 is 3.7 (not 3.4) W/m2. - gavin]Comment by Almuth Ernsting 6 Nov 2006 @ 5:04 pm

9. Dang, bad linkThe link to the July 2005 9:39 pm question and response should lead to: http://www.realclimate.org/index.php?

p=169#comment-2833

2 Jul 2005 The Acid Ocean the Other Problem with CO2 EmissionComment by Hank Roberts 6 Nov 2006 @ 5:07 pm

10. Once again it comes down to what the politicians can do in this regard whilst maintaining economic prosperity(seems to be a prerequisite for politicians all over the world apparantly). I still cannot see humankind reducing theCO2 levels by the amount required because we will burn all of the available natural GAS and Oil whilstcontinuing to burn coal through it all because even if we had an alternatibe to Oil/GAS/Coal it nould take 50 yearsfor a worldwide rollout anyways which will still give us potentially dangerous warming because levels of CO2

burning are going to rise worldwide by 50% by 2040.Its a nasty situation by all accounts.Comment by pete best 6 Nov 2006 @ 5:20 pm

11. Re #7. How do you get to 465 CO2equivalent exactly? Sorry, I couldnt follow the arithmetic. It seems animportant number many should understand...[Response:Gavin is an atmospheric modeler, Im a water guy, so I defer on 3.7. For what its worth heres how Idid it.Doublings = ln (380/280) / ln (2)CO2WattsPerM2 = 3.7 * DoublingsGHGWattsPerM2 = CO2WattsPerM2 / 60%CO2EquivalentDoublings = GHGWattsPerM2 / 3.7CO2EquivalentPPM = 280 * 2^(CO2EquivalentDoublings)corrections welcome. David]Comment by Andrew Alcorn 6 Nov 2006 @ 5:43 pm

12. The problem with emission cuts is that we wont be able to see the science get validated. That would be a realshame.[Response:The Montreal Protocol is a bummer for ocean thermocline tracer types. David]Comment by ninin 6 Nov 2006 @ 5:58 pm

13. A warming of 2 C could be accomplished by raising CO2 to 420 ppm and waiting a century or so, assuminga climate sensitivity of 3.5C for doubling CO2, a typical value from models and diagnosed from paleo-data.Does this warming estimate include the effect of the current earth energy imbalance which means that there isconsiderable heat stored in the sea which will come out over the coming decades regardless of CO2 concentrationin the atmosphere?[Response:Yes, the climate sensitivity parameter is defined as the equilibrium response, after the ocean has had a

chance to warm up. David]Comment by Paul Duignan 6 Nov 2006 @ 6:17 pm

14. I regard Realclimate.org and the work you guys do very highly. However, I feel that this post oversteps theboundaries of what the blog should be about -- communicating and commenting on climate _science_.

If we consider improvements in human welfare to be our ultimate goal, judgements on what constitutes adangerous or safe level of climate change should be based on careful economic analysis, itself ultimately basedon a consistent system of values (or a number of alternative value systems, if we find it difficult to agree on acommon one). Mitigation of climate change does carry costs, so the question is not trivial!

The analysis should, obviously, be as complete as possible, in the sense of considering uncertainties and insuringsufficiently for them, considering potential extreme outcomes, considering the effects the inequal global incomedistribution has on the analysis, and so on. However, ultimately, the question of what is a dangerous level ofclimate change is not a scientific question, but an economic and ethical one!
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I feel Realclimate.org would be stronger for sticking to its chosen mission and recognizing its limitations. Maybeyou should encourage a bunch of climate change economists to start a twin blog focusing on the economic /ethical issues?[Response: Well, this post was mainly about what the carbon cycle implies for policy decisions - and that isclearly a scientific issue that those designing such policy need to account for. That is a very different thing thansaying that we are in a position to decide what aim policy makers should have or what the cost-benefit analysisshows. David picked some numbers here (I assume) on the dangerous limits because they are prevalent indiscussions, not becuase we think that they are necessarily right. Another blog run by RealEconomists would begreat though! - gavin]Comment by Niko Jaakkola 6 Nov 2006 @6:39 pm

15. http://www.enviroliteracy.org/article.php/578.htmlEnjoy.Our young climate scientists not only claim to understand global climate, a very debatable claim, but they alsoclaim to be able to forecast the evolution of technology and the human condition 100 years from now.[Response: Your point being that no efforts to deal with horse-related pollution should have occured because theydidnt forsee the motor car? Good one...... -gavin]Comment by joel Hammer 6 Nov 2006 @ 7:00 pm

16. I would like to point out that some of the figures presented in this article are rather different than those givenby James Hansen (eg. in this summary).17.David says fossil fuel emissions are 5 Gton C per year from fossil fuel combustion, with a further 2 Gton C peryear from deforestation, while Hansen states that annual emissions are now 7.5 Gigatons. The 2 Gt/yr fordeforestation seems rather high, even if you count forest fires.

David says the natural world is absorbing CO2 at a rate of about 2 Gton C per year into the land biosphere andinto the oceans, for a total of about 4 Gton C per year, whereas Hansen says The ocean is thought to take upabout 20-35%, leaving 5-20% as the net sink in vegetation and soil. While a little uncertain, it suggests the oceantakes up quite a bit more than the land.

David assumes a climate sensitivity of 3.5 degrees C for doubling CO2, while Hansen works with 2.7 degrees C.

Finally, David says The models tend to predict a maximum atmospheric CO2 inventory of about 50-70% of thetotal fossil fuel emission slug. Given that about 60% of CO2 is being absorbed now, with little change in trendover the past few decades, what is going to change to reduce that amount substantially?[Response:The range of climate sensitivity from IPCC is 1.5 to 4.5 degrees C. Hansen also assumes 1 degree as adanger limit, if I remember correctly. According to him, were already over the line (1 degree is the equilibriumwarming to the CO2 already in the atmosphere. Sabine et al (Science 305: 367, 2004) estimates that the oceancontains 118 Gton C of the fossil fuel carbon, while the atmosphere contains about 200 Gton excess C. David. ]Comment by Blair Dowden 6 Nov 2006 @ 7:37 pm

18. Re 14I think the post actually could have gone much further toward policy without leaving the domain of science -theres an awful lot of science required to determine the impacts of a given level of CO2/warming on the

biosphere etc. before getting to the economics. Too many economic impact assessments start with the assumptionthat welfare=consumption and the global distribution of agriculture and capital is in equilibrium with climate, andneglect the physical world.Comment by Tom Fiddaman 6 Nov 2006 @ 7:46 pm

19. The figure of reducing CO2 emissions down to about 10% of current emmisions answers half of a questionIve had about AGW.

The other half is beyond the scope of this blog, but can anyone point me to a discussion of how much fossil fuel isused for various applications? With current technology any stationary uses of energy can be done with a mix ofnuclear, hydroelectric etc., but small mobile machinery like cars, bulldozers & farm tractors are hard to run onanything but fossil fuels.

Ive seen energy use broken down into categories like transportation etc, but we need more detail to determinehow low emmisions can go with current tech, since railways can be electrified & large ships can run on nuclear.
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Also, any practical cuts would have to be a few % a year continued over decades, as old equipment is replacedwith non-fossil or more efficient equipment. How does such a gradual decline in emmisions affect the calculatedclimate effects?Comment by Jim Baerg 6 Nov 2006 @ 7:54 pm

20. Worth reading:http://ncseonline.org/SciencePolicy/Testimony/Benedick.doc.Conclusion: Acting Under UncertaintyThe Montreal Protocol was by no means inevitable. Knowledgeable observers had long believed it would beimpossible to achieve. The ozone negotiators confronted formidable political, economic, and psychological

obstacles. The dangers of ozone depletion could touch every nation and all life on earth over periods far beyondpoliticians normal time horizons. But although the potential consequences were grave, they could neither bemeasured nor predicted with certitude when the diplomats began their work.

In the realm of international relations there will always be resistance to change, and there will always beuncertainties. Faced with global environmental threats, governments may need to act while some major questionsremain unresolved. In achieving the Montreal accord, consensus was forged and decisions were made on a

balancing of probabilities -- and the risks of waiting for more complete evidence were finally deemed to be toogreat.

Politics, stated Lord Kennet during ozone debates in the House of Lords, is the art of taking good decisions oninsufficient evidence.14 The success of the Montreal Protocol stands as a beacon of how science can help

decision makers to overcome conflicting political and economic interests and reach solutions. The ozone historydemonstrates that even in the real world of ambiguity and imperfect knowledge, the international community, withthe assistance of science, is capable of undertaking difficult and far-reaching actions for the common good.

---------------http://ozonewatch.gsfc.nasa.gov/Latest Information, October 20, 20062006 was a record-breaking year. The area of 29 million square kilometers (11.4 million square miles) onSeptember 24 tied the largest value (on September 9, 2000) and the value of 85 Dobson Units on October 8 wasthe second lowest ever recorded by satellite measurements. The year also saw the second largest sustained ozonehole. In September and October, temperatures in the middle stratosphere set many record lows.Comment by Hank Roberts 6 Nov 2006 @ 8:13 pm

21. The carbon flux numbers are quite dated. Its now over 8Gt per year from fossil fuels, and rising very fast.See this link for a graph through 2004.http://www.theoildrum.com/uploads/12/fossil_carbon_1850_2004.jpg(thats emissions data from ORNL through 2002, extrapolated by BP fuel production data after that).

Global coal production is increasing by 5-7% annually from 2001-2005 (see the numbers athttp://www.bp.com/productlanding.do?categoryId=6842&contentId=7021390

Its extremely hard to see how we can stabilize the climate change under 2 deg C on this trajectory, and yet 2deg Citself seems a dangerously high goal (given Eemian sea level 5m or so higher than present and the present lack of

quantitative understanding of how fast the ice sheets will equilibriate to give that sea level).

Theres also a Science paper this week arguing that maintaining concentration below 450 ppm (which they take tobe the threshold for 2 deg C) would require in the near future reaching an annual 3.2% reduction in carbonemissions.http://www.sciencemag.org/cgi/content/summary/314/5800/764Comment byStuart Staniford 6 Nov 2006 @ 8:27 pm

22. Re: Gavins response to #8. ...most everything else apart from CO2 cancels...but, if aerosols are a net negative and given that they have an atmospheric residence time of ~days-weekscompared to ~centuries-millenia for CO2, CFCs, then its a bit non-useful to cancel out some of the other non-CO2 forcings with aerosols.

From a scientific point of view [rather than a political/economic point of view] Im really worried that the 500-550ppm CO2-eq stabilisation level takes us far too close to the edge. There are a lot of thresholds at around thatballpark level: Greenland, permafrost melt; soil carbon feedback.
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It would seem to me that an emissions pathway that took us to 550 ppm, could easily end up being a lot higher[750+?] if we were unlucky.

From a politics/economics point of view, I still dont see any sign of concrete policies being proposed that wouldlimit CO2 emissions at all, let alone stabilise them at any level


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26. RE 21, Timothy wonders why nothing is really being seen on the ground. If there is sufficient ice hung upabove sea level to give us say 20 metres of sea level rise, then I wonder if the thing that is holding it all together atthe moment is the input of the anthropogenic forcings into the latent heat of fusion being absorbed by all that ice.Its a huge sink.

Ive noticed that if you put a pair of ice cubes in a box, then they both hold up until they are both ice at zero C,then they both melt with a rush when the trigger Joule is absorbed. If the same thing holds at a global scale, thenwhen it starts to happen we will definitely be living in interesting times!

I guess a measure of that issue would be the proportion of global ice that is currently at zero C. Do we have any

idea of that?Comment by Nigel Williams 6 Nov 2006 @ 9:43 pm

27. You mention a climate sensitivity of 3.5C for a doubling of CO2 and say that its a typical value. I was underthe impression (or wishful thinking) that 3.5C was more towards the high end of the range for climate sensitivity.Are there any estimates of the likelihood of different climate sensitivities? What range for climate sensitivity is theIPCC working on? Thank you.[Response:The range from IPCC was 1.5 - 4.5 degrees C. I dont know if the real climate sensitivity is higher orlower than 3.5 degrees C, I just chose a number for discussion. David. ]Comment by Katherine Cinq-Mars 6 Nov 2006 @ 10:17 pm

28. I was wondering if anyone was going to take on Steven Milloys latest challenge: Challenge issued toenvironmental journalists and advocates of catastrophic AGW (Anthropogenic Global Warming):

He says, We believe climate models are programmed with excessive climate sensitivity based on a flawedunderstanding of past ice ages. Moreover, climate models wrongly magnify potential warming to accommodate

positive feedback mechanisms while comparison with empirical measure shows negative feedback dominates,reducing warming experienced to about half theoretical values. The challenge is for you to actually check thenumbers -- see for yourselves whether we are wrong or not. Look up Stefans Constant or just use 5.67 x 10-8(close enough for our purpose but look it up to be sure). Now use it to check the assertion: Global climateforcing was about 6-1/2Wm2 less than in the current interglacial period. This forcing maintains a globaltemperature difference of 5 C, implying a climate sensitivity of 3/4 1/4 C per Wm2. Either consult your textsfor Earths temperature in Kelvin and any other numbers you need or see the numbers weve used here. Off you

go -- well wait.

Back so soon -- how did you go, prove us wrong yet? Well, were waiting. All you need to do is show us whereweve messed up the calculations and well publicly retract and correct. Weve left you plenty of opportunities inour analysis of models and climate sensitivity. While you are about it, see how the smoking gun for globalwarming turned out to be nothing but a clown gun, just another failure of global warming proof that didntmake it into mainstream media coverage. Why is that?

If its proving too hard following a moderately complex document, try this simple one where we find significantheating does not trigger self-perpetuating enhanced greenhouse from the most prolific and important greenhousegas -- water vapor. Same deal -- show us where were wrong and well retract and correct.

We believe estimations of dangerous climate interference are based on seriously flawed models producingpatently ridiculous projections. We find no evidence the world is conforming to the models and thereforeconclude it is the models that are wrong (arent we terrible?).

We see no evidence carbon constraint will have any measurable effect on global temperatures and concludedesperate measures to transform energy supply have vastly greater potential for harm than for good.

We place our calculations online where scrutiny is invited and expected. The only question now is whetherreporters still follow the science or simply follow the faith. Thank you

[Response: Hes a funny guy.... Weve dealt with the reasons why climate sensitivity is considered to be around 3deg C for 2xCo2 in many pieces, and MILLOYs arithmetical sleight-of-hand doesnt impact any of that.

(Clue: dividing any temperature by any energy flux one can get something in the same units as climate sensitivity,but it wont be the same thing). I note that MONCKTONs recent piece tries to pull the same trick. We may takethis on for a bit of target practice.... - gavin]Comment by Christopher Sargent 6 Nov 2006 @10:47 pm
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29. RE: Davids PostI have a few simple laymans questions. Rather then the data that David lays out we consider the data presentedon the Oak Ridge Nat. Lab. that the Global Carbon Cycle Balance on an average year between 1997 and 2002 oreven the NOAA data for 2004 we get very different numbers from what I think I read in this article.

In the later two examples we have values of between 205 and 210 CT C that goes into the atmosphere and between207 to 212 that comes out of the atmosphere. Also from these sites we get an average direct anthropogeniccontribution to the atmosphere of between 5 and 6.5 GT C where some tables indicate a value as greate as 7.5 GTC (It must be the difference in contribution from deforestation or forest fires).

Given this the total anthropogenic contribution to the atmosphere on an annual basis is approximately 3%, if I readthings correctly. Though David is likely correct that a reduction of 3-4 GT C would likely allow things to returnto a balanced level, it means we must halve the current contribution across the globe to get close to the correct

balance.

It really does not matter if you recharge your vehicle at the wall socket (Though under nuclear sources this is nottrue.) or run a methane/ethane/biodiesel converted fossil fuel engine or feed and water your burro your enginewill still emit high amounts of CO2 with any of these systems. The time necessary to move to a Carbon freeenergy system is likely a min. of 30 years away.

Which is the the preferred manner in which to deal with the problem now? Do you start today to cut back 1/2 of

the energy you use every day? Do you only drive 1/2 of the distance to work or school and walk the balance? (Iwould love to see the average worker in DC drive only 30 miles and attempt to walk the balance in 8 hours thereand 8 hours back.) Do you only light or heat your house and warm the water on average for 4 hours every day?(Even with R-40 insulation throughout you would average 1/2 the equilibrium between the daily high and lowwithin 8 hours. What do you do if the high is less then 68 degrees?) Do you not buy anything made of or covered

by plastic? Do we reduce the population of the globe by 1/2 in the next 5 years? (Even if you halfed the populationof the US you only get back 10% of its contrabution to GW, that leaves the other 80% to be dealt with.)

It simply makes much more sense to boost the natural processes 1.5% to sequester the 3 GT C that it currently isnot. Would it not make more sense to start the process of dealing with the immediate problem while working onthe other issues. It almost appears that the issues will not get dealt with in a timely manner, so why do we we haveto endure the knawing of the bone Ad Nauseum.

Apparently, if it truly was a big deal you would think a few scientists could put together a fully funded NSFresearch project that involved a research ship to be chartered to dump several tons of Ironite mixed with sargassoweed for 6 months for less then a million dollars per year. If each of the major industialized countries did thesame you would be at a balance in next to no time, wouldnt you?Dave Cooke[Response:There have been iron fertilization experiments in the ocean, many of them, and theres no evidencefrom the field or from models that this technique could make much of a dent in the rising atmospheric CO2concentration. The reason is the long equilibration time between the atmosphere and the ocean; if we could keepit up for 500 years, we might make some progress, but on shorter timescales, walking to work is more practical. Ido it every day. David. ]

Comment by L. David Cooke 6 Nov 2006 @10:54 pm

30. Again, an excellent post. We certainly do need to think beyond 100 years, since we are the ones causing theproblem for hundreds of years to come, perhaps millennia.

As for economic tipping points, I keep thinking about how the stock market nearly crashed in the 80s bec of acomputer glitch (nothing to do with productivity). So, Id say the economic tipping point (the point at whicheconomic problems, increasing economic inequalities, econ & polit fears, frustrations, fighting, wars, social chaosthrow us into a really bad state) is probably well before the 2 degrees warming. Look at Katrina, and scientists tellus that wasnt caused by AGW (or they are unable to tell us), so whatll be like in 5-10 years when AGW harmsgreater than Katrina really start kicking in.

Also, another problem w/ neoclassical econ is that it mainly measures the monetization of the economy, not actualproductivity, and certainly not quality of life. (For instance they might find a severe hurricane year to be justgreat, due to all the rebuilding.) And they reduce everything to (or equate everything with) money. Whilediamonds may be more valuable than bread, we just cant eat them. Cost/benefit analyses are pretty useless whenyoure standed on a desert island. At least paper money can be used as toilet paper, though. I would suggest
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another measure, LIFE-YEARS, over money. So how many life-years is my driving to the coast going to costre earlier death for people due to GW harms.

What we need is a holistic view, including the hard sciences and the social (economic, political, etc), cultural(beliefs, values, ideologies), and psychological (craziness factor) dimensions of the human/world system to fullyunderstand climate change, its causes & consequences.

In anthro and sociol they have revitalization (or social) movement theory: people fairly suddenly change andconstruct a better culture/society. I think thats our only hope. The problem is large numbers of people have tosense something is really wrong, have some acurate assessment of it, come up with technical and structural

solutions, and implement things. I know we have the technical solutions (see rmi.org), we just need to have asocial movement to implement them. And it seems no matter how alarmist environmentalists become, peoplearent connecting the problems to their lives or those of their children, and they certainly arent connecting thecauses to their actions.Comment by Lynn Vincentnathan 6 Nov 2006 @ 11:14 pm

31. Forgot to add, life-years (measured in earlier death of people) for as long as the GHGs one emits today aredoing harm & causing death, part of which could be in the atmosphere for millennia (as David pointed out in a

previous article here re life time of CO2 in the atmosphere).

And we need to consider all the indirect effects (not just heat deaths), such as crop & potable water loss &destruction of the web of life from AGW, AND wars & fighting due to harms due to AGW. The suicides of

drought-stricken farmers in India, etc.Comment by Lynn Vincentnathan 6 Nov 2006 @ 11:21 pm

32. In response to comment 19, I think its important to recognise that the Montreal Protocol on substancesdepleting the ozone layer largely became possible when a substitute was found for CFCs in most applications.Essentially, pressure from consummers and the threat of a ban forced CFC companies to invest in R&D of asubstitute. When one was found, all of a sudden the lobby groups for these industries started recognising thescientific evidence that CFCs were depleting the ozone and the Montreal conference was held in a matter ofmonths. Finding a substitute dramatically reduced the losses that the CFC industries would suffer from a ban onCFCs (and thus, the political costs), not to mention that it also meant that the practical uses of CFCs would nothave to be given up.

Unfortunately, the ozone and climate change cases are so different that there really is no basis for hope for climatechange based on the success of the Montreal Protocol. In the ozone case, the ban is of one group of chemicalsused in fairly limited applications and by just a few major companies. The boycot of aerosols didnt require bigsacrifices on the part of consummers. The same couldnt be said of a boycot of cars or heating! Also, everybodyand all sectors of the economy emit GHGs, not just a handful of companies as in the ozone case.

I think its very important that further research into the science and economics of climate change help reduce theuncertainty on these issues, but I dont think that uncertainty is the main obstacle to decisive action. Many policydecisions involving huge investments of public money are made on the basis of far less information than what wehave on climate change. If policy makers were told that there was a 30% chance that there would be a terroristattack on a major city, do you think they would delay action until they knew how many people were likely to be

killed? or until studies showed whether the economic disruptions of the attack would be worth the investments inincreased precautionary security measures?

Changes in the status quo happen when it becomes possible to minimize the losses of the projected losers from achange in policy (or when there are bombs falling on your head). So, the best contribution scientists can do is notto join the political debate, as suggested in comment 5, but to work on technological solutions that will provide 1)low-carbon alternatives to consummers (so they can afford to put commercial pressure on companies to go low-carbon) and 2) technologies such as carbon-capture storage that will minimise the losses of the major GHGemitters who are also major economic actors and as such have significant political influence.Comment by Katherine Cinq-Mars 6 Nov 2006 @ 11:58 pm

33. There was an old lady who swallowed a fly .... Know that cautionary song?Youre putting too much water, too fast, into the bathtub and its going to overflow, because the drains notdesigned to remove that much water that fast. Whats your best response? Figure out how to turn down the taps?Or try to enlarge the drain?

You can look this stuff up, to find out if anyone has ever thought of it before. Google is your friend.
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... some researchers and entrepreneurs have proposed boosting phytoplankton growth by fertilizing oceanswith iron, a nutrient essential to the organisms growth. Preliminary tests in the equatorial Pacific Ocean andSouthern Ocean since 1995 have shown that seeding seawater with iron does increase phytoplankton populationsin the short run.

But the prospect horrifies some ecologists. They say the approach could backfire, increasing atmospheric carbondioxide levels by spurring the growth of the marine bacteria that feed on dead diatoms. I could see significantwarming happening even faster than anyones imagined, says Kay Bidle, a marine biologist at the Rutgers marineinstitute and an expert on diatom ecology. Beyond that, Bidle and others say no one can predict how dumpingiron into the ocean would affect marine life in the long run.

http://www.smithsonianmagazine.com/issues/2004/february/phenomena.htm

This may happen anyway, if we see a whole lot of desert dust blown into the oceans from China and the Sahara --whether we want it to happen or not.Comment by Hank Roberts 7 Nov 2006 @ 12:00 am

34. I wonder if everybody understands that the concentration of greenhouse gases in the atmosphere determinesthe excess of solar input compared to the longwave IR radiation to space. This determiones the RATE oftemperature rise. If the GHG concentration does not change, the temperature will keep rising.[Response: Only until equilibirum when the OLR will again match the INC SW. - gavin]Comment by Richard LaRosa 7 Nov 2006 @ 12:22 am

35. From Davids response to comment #5:The best would be to not change climate at allPerhaps it was just a throwaway comment that Im reading too much into, but I have to ask whether this assertionis simply axiomatic, or based on some scientific and/or moral judgement.[Response:Interesting philosophical question, thank you for raising it. I guess I look at climate change as anunintended consequence of our energy pursuits. If its unintended, I think of it as something to be absolutelyminimized, just almost by definition. If one wants to talk about intentional climate change, thats another thing.In that discussion, I feel that it would be unwise to undertake so momentous, irreversible, and unpredictable

project as changing the climate, without at least talking about it first, beyond oh well, maybe it wont be so bad,or well, but were addicted. Is changing climate something we would do even if it werent our link to cheapenergy? I think in our current circumstances, the ideal, the best, would be to not change climate at all. David]

Comment byJames Annan 7 Nov 2006 @ 2:38 amPerhaps Davids thinking of precautionary folk wisdom, as in dont make waves, dont rock the boat?While abrupt climate changes have occurred throughout the Earths history, human civilization arose during a

period of relative climate stability. http://www.epa.gov/climatechange/science/pastcc.html,http://www.epa.gov/climatechange/science/images/co2-temp.gifImage from A. V. Fedorov et al. Science 312, 1485 (2006):http://www.sciencemag.org/cgi/content/abstract/312/5779/1485where the authors write: During the early Pliocene, 5 to 3 million years ago, globally averaged temperatures weresubstantially higher than they are today, even though the external factors that determine climate were essentiallythe same. In the tropics, El Nio was continual (or permanent) rather than intermittent......Comment by Hank Roberts 7 Nov 2006 @ 4:32 am

36. [Response: Your point being that no efforts to deal with horse-related pollution should have occured becausethey didnt forsee the motor car? Good one...... -gavin]

No. You missed my point.

The problem of horse pollution was solved by technological advances, not by limiting the growth of cities,limiting economic growth, or putting arteficial caps on horse manure production.

Nobody foresaw that the problem of horse pollution would be solved by the automobile.In like manner, the pessimists of an earlier day saw the end of civilization because the supply of whales wasrunning out and where would the oils come from which were used to light the cities of the day. Whale oil wascrucial as a source of kerosene. That black stuff oozing out of the ground in Pennsylvannia provided the answer.Then, when it looked like the oil industry was doomed by the invention of the light bulb (who needed all that

kerosene now) the automobile came along.

My point is that technological innovation is still going on. Projecting our current technology 100 years into thefuture is just not realistic.
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[Response:Strawman argument. First off, no-one has ever said that technological development is forseeable 100years ahead - thats one of the reasons why the scenarios have such a large divergence. Secondly, the reasonhorses were phased out as quickly as they were was because the costs associated with using horses (maunre, deadcarcasses, stabling etc.) were borne by the same entities that benefited from their services (i.e. cities and

businesses). Thus as soon as technology with larger benefits and smaller costs came in, they were adopted. Thiswas very simple. If you want to take a lesson from that, it is that the costs associated with GHG emissions should

be bourne by the producers of those emissions such that no new technology is handicapped by effective subsidiesto fossil fuel users. Right now, the benefits accrue to the producers, and the costs are likely to be bourne byothers. -gavin]Comment by joel Hammer 7 Nov 2006 @ 5:37 am

37. Re: 34, James..Certainly an interesting point - and unless you put an absolute premium on non-interference in nature, there is nospecific moral reason. After all - to play the cynic - Nature had the planet for 4.55 billion years before humansand will presumably have the planet for several billion years after humans [go extinct]/[migrate into space]/[undergo technological transendance]/[insert future here].

But from a purely practical/economic point of view.. our agriculture is built around a constant climate and anychange will be bad because a farmer needs to know the likely weather to know what to plant. Our cities need freshwater; if climate changes and rivers stop flowing then many cities will be written off; and the effect of sea levelrises on the large percentage of the worlds population that lives on the coast goes without saying.

So.. its not an axiom, but there are two angles - if we completely screw up the environment then its going to takelonger than human timescales to recover even if we clean up our act later, and its almost certainly going to hurt useconomically by more than the avoidance cost.Comment by Andrew Dodds 7 Nov 2006 @ 5:46 am

38. Re #33 It is obvious from Gavinss reply that he is not aware that the level of carbon dioxide determines therate of increase in temperature. However, the temperature does not keep rising, because higher tempertures meanmore water vapour and clouds which reflect more of the incoming solar energy away, and a balance is reached.Comment byAlastair McDonald 7 Nov 2006 @5:57 am

Re #34 I cant speak for David, but there is a logical reason why we should not change the climate. Modernsociety has tuned itself to exist on the planet as it is. Agriculture is arranged to match the local climate, and

buildings are designed for the climate in which they were built. For instance, in Europe the slope of roofs is set tomatch the winter snowfall. In a warming world, here in Britain the central heating boilers will need to be replacedwith air conditioning units, and the wall to wall carpets with tiled floors. Any change in climate will involve vastcosts of adaption.

More serious is the desertification of the Mid West of the USA, already under way, and the subsequent reductionin global grain supplies.

But a warming world will also mean that the Greenland ice sheet melts. A 20 foot rise in sea level, which nowseems inevitable, will have few advantages. Travelling through the streets of London and New York by gondola,are the only one I can think of!

Comment byAlastair McDonald 7 Nov 2006 @6:12 am

39. Re #22 Here is a rebuttal of Christopher Monktons piece that I wrote earlier.Here are replies to his ten propositions. You can see that I accept none of his conclusions. He is just a charlatanholding out false promises.

Proposition Conclusion1. That the debate is over and all credible climate scientists are agreed. - False

Wrong! All credible scientists do agree that global warming is mainly caused by greenhouse gases.However, the debate is not over anymore than the debate over evolution is over. Creationists and theirfellow travellers will ensure that!

2. That temperature has risen above millennial variability and is exceptional. - Very unlikelyWrong! All the available evidence points to the current global temperature being higher than at any time

during the last 1000 years. However, that is unimportant since it is the temperature rise in the future thatwill do the damage. At present we are surviving fairly well, except in New Orleans.

3. That changes in solar irradiance are an insignificant forcing mechanism. - FalseWrong! The main source of warmth on the Earth is solar flux. However, there has been little change overthe last 100 years, and especially the last ten when temperatures have been at record levels.

4. That the last centurys increases in temperature are correctly measured. - Unlikely
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Wrong! Extreme measures have been taken in order to correct any errors that may have occurred intemperature readings in order to ensure their accuracy. Examples are the corrections for the urban heatisland effect, and for the adiabatic temperature difference in water temperature caused by the height of deckof the ship when taking sea surface temperatures.

5. That greenhouse-gas increase is the main forcing agent of temperature. - Not provenWrong! The 1000 page IPCC report is enough evidence for me that greenhouse gas increase is the maincause of global warming. What proof would all Mr Monckton accept?

6. That temperature will rise far enough to do more harm than good. - Very unlikelyWrong! Humans have tuned their agriculture and housing to the climate as it is now. Any alteration inclimate will have severe costs, and the benefits such as gondolas in the streets of London will be trivial.

7. That continuing greenhouse-gas emissions will be very harmful to life. - UnlikelyWrong! The Paleocene-Eocene extinction and the Permian-Triassic mass extinction are both thought tohave been caused by release of methane hydrates. This could happen in the future if ocean temperatures risetoo much. Only last night on BBCs Planet Earth it showed that the polar bears are threatened, and will bedoomed if we do nothing to stop the Arctic ice melting.

8. That proposed carbon-emission limits would make a definite difference. - Very unlikelyWrong! The Kyoto limits would not make much of a difference but the were only intended as a pilotexperiment. The full limits cutting CO2 emissions to 40% of todays levels would have an effect.

9. That the environmental benefits of remediation will be cost-effective. - Very unlikelyWrong! If you do not ignore or downplay the costs of global warming, which should include a rise in sealevel of 7 meters, drowning London and all other British ports, then the costs of doing nothing soon escalate.

10. That taking precautions, just in case, would be the responsible course. - False

Wrong! Who does not take out house insurance against fire, flood etc. against the full value of their home?If you were to consider the odds of it burning down then it is only one in a hundred, so why not only insurefor 1% of its value. That is the false reasoning of the self proclaimed Monckton of Brenchley!

If he has a serious scientific contribution to make why does he not write to Nature or Science where his ideas canbe properly accessed? I would attack the Telegraph as a Tory rag, but in fact even they printed a rebuttal ofProfessor LINDZEN by their weather correspondent, a qualified meteorologist. See:http://www.telegraph.co.uk/news/main.jhtml?xml=/news/2006/10/29/nclimate229.xml

Here is a more sensible article from the Telegraph. See:http://www.telegraph.co.uk/opinion/main.jhtml?xml=/opinion/2006/11/04/do0404.xml

So you can see that in fact, as Sargent Frazer in Dads Army used to say Waur doomed!

Comment byAlastair McDonald 7 Nov 2006 @7:11 am

40. Would some of the climate scientists here care to comment on this article in todays New York Times:http://www.nytimes.com/2006/11/07/science/earth/07co2.htmlComment by Fernando Magyar 7 Nov 2006 @ 7:31 am

41. Is it possible to get the good amounts of fossil fuel CO2 and deforestation or land-use CO2?When I look at NASA-GISS, I dont find Davids amounts.http://www.giss.nasa.gov/data/simodel/ghgases/

[Response:Sabine et al (Science 305: 367, 2004) estimate 118Gton of fossil fuel C in the oceans, and that the landis near zero net (deforestation + greening or whatever the high-latitude sink is). The atmosphere contains about200Gton of fossil fuel C (100 ppm * 2Gton C / ppm). So I get about 300 for the total anthropogenic carbonemission. David]Comment by Pascal 7 Nov 2006 @ 8:00 am

42. Re #27 and If its proving too hard following a moderately complex document, try this simple one where wefind significant heating does not trigger self-perpetuating enhanced greenhouse from the most prolific andimportant greenhouse gas -- water vapor. Same deal -- show us where were wrong and well retract and correct.Do a Google search for Clausius-Clapeyron Law.Comment byBarton Paul Levenson 7 Nov 2006 @8:05 am

43. RE: #32(Prenote: If my laymans ignorance is showing my humble apologies.)Hey Hank;Is it not time to defrock ecologists, not that they do not have a point in that it is a good idea to reduce theanthropogenic footprint. We are simply talking a slight boost of 3% total oceanic population of phytoplankton inone year, while humans do the same on the land. (Believe me, I am well aware of alternatives, I have been
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studying them since 1967. Your ecologists seem to forget that in the case of failure all that is being returned to theatmosphere is the very same CO2 that the phytoplankton were supposedly reducing. Meaning if the experimentfails, the contribution is net zero, except for some a couple million dollars, some ships oil, a little iron re-disposition and a little shading of the GS from the redistribution of a little Sargasso.)

As to your tub issues, it depends, which can you do most economically, turn down the taps or make the drainlarger? If it takes thirty years to turn down the taps 3%, costing 4 trillion dollars and only takes one year to cut outa 3% larger drain costing 3 million dollars, which do you think is the likely action?

In the presence of the constant bombardment of de-empowering rhetoric coming out of the scientific community,

action appears to be taking the reciprocal. Is this true desire, to de-empower the people to the point that the onlysolution is political? Why cant a simple green funded test take place. Certainly someone realizes if youdistributed the iron contribution widely, the issue of anoxia should not be an issue. (Anoxia is likely to happenonly if the Ironite contribution is concentrated in one place; if you distributed the iron over a largearea where there is likely to be phytoplankton, you would likely reduce the tendency of anoxia from forming.Anchoring the research ship in the middle of the GS and simply taking advantage of the GS for distribution wouldeven save the use of ships oil. For that matter, simply anchoring out a few rusting old hulks in the GS may do thesame.)

In the meantime, government can address the increase towards the possible 15% anthropogenic contribution in 30years. (Note: You are unlikely to make the drain 15% larger.) The result is you can economically deal with yourcurrent issues and set in motion a economically responsible movement towards a solution with a deadline in the

future. (Of course if ecologists keep pushing as hard as they are now without taking action themselves the generalattitude of the population at large is likely to rebound in the opposite direction, (as was the apparent case in 1980,when economics ruled and the environment returned to the pre-1976 condition for 20 years.).Dave CookeComment by L. David Cooke 7 Nov 2006 @9:00 am

44. Re #25:Ive noticed that if you put a pair of ice cubes in a box, then they both hold up until they are both ice at zero C,then they both melt with a rush when the trigger Joule is absorbed. If the same thing holds at a global scale, thenwhen it starts to happen we will definitely be living in interesting times!

There is no such thing as a trigger joule. It takes an enormous amount of energy to melt ice from a 0C solid to a0C liquid (roughly enough energy to heat that liquid to 80C). Try it - take an ice cube thats at 0C and put it in asmall glass of lukewarm water. See if the water is still warm after the ice is melted (it should be just as warm ifice melts as you so describe).

PS: If ice did melt in this way, one could easily fashion a perpetual motion machine that also generates free cold asfollows:1 - Take a piston and fill it with water at 0C.2 - Have the water spontaneously freeze by removing 1 joule of heat to push it over the edge (pushing against the

piston will further cool the ice, pushing it somewhat below 0C) (the joule can be removed just by tugging on thepiston a bit - decompressing a solid does cool it down by some tiny amount).3 - Melt the ice using heat from the outside.

4 - Go to step 2.And voila, perpetual motion.Comment by yartrebo 7 Nov 2006 @ 9:01 am

45. Re 36See theMarland and Houghton datasets at CDIAC.Comment by Tom Fiddaman 7 Nov 2006 @ 9:44 am

46. Another view on CO2 emissions can be found on http://www.1ocean-1climate.com/climate_changes_today.php.You can find there a nice graph about the emissions of CO2 in 1990,ordered by states. Also, there are some elements highlighted regarding the impact that the ocean and naval warhas on climate change.

Comment byAngi 7 Nov 2006 @ 10:37 am

47. Looking at the CO2 graph mentioned above, it looks as if we produced around 5Gt in 1980, 8Gt in 2000.Very round figures.
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The Mauna Loa graphs suggest that if I cut my CO2 production next year to 1980 levels, the increase inatmospheric CO2 will still be around 1.5/1.7ppm, the same as this year, the same as 1980.What am I missing here?JF[incidentally, for the site admin: clicking on comment policy after youve typed but not sent a comment leaves noway back and the post is lost. Unless, of course, you know different and you are reading my question twice.]Comment by Julian Flood 7 Nov 2006 @ 11:01 am

48. David Cooke -- I cant come up with sensible responses to your postings, sorry. They dont make sense to me,from what I know of the science. It seems to me youre making up fanciful speculation about what might be the

case with both CO2 absorbtion and primary production/ecology and saying why cant this be true. Look tonature for your basic facts before you speculate about how nature ought to or might most conveniently work.Comment by Hank Roberts 7 Nov 2006 @ 12:02 pm

49. Re: original post, #16, #20. 5 Gt of fossil fuel emission is not correct. According to the EIA (DOE), worldcarbon dioxide emissions from fossil fuels in 2004 was 27,044 Mt CO2 or 7.4 Gt C. The data is available here:http://www.eia.doe.gov/environment.htmlComment by David Lea 7 Nov 2006 @12:24 pm

50. Re original, 36, 48, 50 etc.The last common data point in the Marland and Houghton datasets I linked in 37 above was year 2000, with7.3GtC fossil/cement and 2.1GtC land use for a total of 9.4GtC emissions. Mauna Loa CO2 jumps around a bit,

but if you average a few years of data +/- from 2000 using 2.13 GtC/ppm, the net increase is around 4GtC whichputs uptake at about 5GtC or about 60% of emissions. Id guess that the majority of that 5GtC is rapidly mixinginto the surface ocean, with a smaller portion taken up by biomass or transported into the deep ocean.[Response:Thanks all for correcting my sorely out-of-date emission figures. This summary looks good, exceptthat the ocean is only taking up 2 or 2.5 Gton C per year, the rest seems to be going into the high-latitudeterrestrial biosphere someplace. The part Im still having trouble with, which made more sense with my oldernumbers, is the airborne fraction, which Hansen in this summary cited above shows as consistently 60%. In anyevent, the bottom line conclusion is that cuts of more-or-less 50% (maybe 60% according to Hansen) would berequired to stabilize atmospheric CO2. David]Comment by Tom Fiddaman 7 Nov 2006 @ 1:48 pm

51. Well, apparently the fishing industry is doing its own iron fertilization experiment -- perhaps well see whichof the many organisms benefits most and whether this causes the problems the plankton experts have beenworrying about.Found here: http://www.lbl.gov/Publications/Currents/Archive/Feb-23-2001.html----- excerpt follows -------... Already commercial outfits are dropping iron filings overboard, hoping to increase fisheries - meanwhileclaiming they are helping to prevent global warming.

In fact, Bishop explains, if the excess fixed carbon in plants is eaten by fish near the ocean surface, the net effectis no gain. And in every part of the ocean there are open mouths.

No one really knows where the carbon trapped by fertilization ends up. In one iron-fertilization experiment in

warm equatorial waters, chlorophyll increased 30-fold in a week, and there was increased carbon sedimentationdown through 100 meters. But the bloom shortly dissipated, the fate of the carbon in deeper waters wasntfollowed, and long-term effects werent measured.

In a more recent experiment in cold Antarctic Ocean waters the plankton bloom persisted much longer. Sevenweeks after the experiment ended a distinct pattern of iron-fertilized plankton was still visible from space - whichmeans the fixed carbon was still at the surface.

Bishop says that people who want to add iron think the particulate matter will fall straight to the bottom; I havesampled natural plankton blooms, and I have not seen that happen.....Comment by Hank Roberts 7 Nov 2006 @ 2:39 pm

52. Re 51 (Davids comment)Comparing Hansens charts 4 and 5, it looks like hes including only fossil emissions in the airbrone fractioncalculation. 4GtC/yr atmospheric increase divided by 7.3GtC/yr fossil/cement emissions equals about 55% -consistent with Hansens 58% long run average. Neglecting land use emissions in the calculation of the AF seems
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a bit odd, but its consistently done that way in my experience. As you say, the bottom line is about right eitherway.Comment by Tom Fiddaman 7 Nov 2006 @ 2:40 pm

53. Great articles on this site...Thank you for them all. One request I would make is to do an article that analyzesthe front page ofwww.junkscience.com and highlights the errors/misconceptions (Im pretty sure there are,unfortunately I cannot tell what they are because of my lack of background on the subject).Comment by Karan 7 Nov 2006 @2:45 pm

54. Karan, use the Search box, it will find what youre asking for.

For example: http://www.realclimate.org/index.php?p=299#comment-13279Comment by Hank Roberts 7 Nov 2006 @ 4:44 pm

55. I have enjoyed this blog very much. But the papers I have been reading recently eg (http://www.uni-leipzig.de/~meteo/MUDELSEE/publ/pdf/lag.pdf) seem to make it clear that there is no proven causal link betweenCO2 and temperature in the paleoclimate data. Why do we assume that the present warming ( which does seem to

be a fact ) is caused by our CO2 emissions?[Response: We dont assume it; nor is it to be proven from the palaeo data. There is a good theory to say thatincreasing CO2 should cause warming; simple and complex models built from the theory demonstrate this.Although the lags complicate things, there is no current way to explain the glacial/interglacial temperature changeswithout including CO2 feedback -William]Comment byDavid Askelon 7 Nov 2006 @ 5:00 pm

56. Re #36: You say My point is that technological innovation is still going on. Projecting our currenttechnology 100 years into the future is just not realistic.

Which is true enough. The point you seem to have missed is that not much technical innovation is needed, sincethe technology needed to significantly reduce CO2 emissions already exists, and could be brought on lineeconomically. The problem, if I may continue your horse manure analogy, is that the horse breeders and haydealers have managed to convince the public that their status depends on owning the biggest pair of Percherons orClydesdales on the blockComment by James 7 Nov 2006 @ 5:01 pm

57. Re:33,38. I just want to emphasize that present GHG concentrations influence the present rate of temperaturerise. I dont think most people understand this simple point. Im only talking about the present slope of thetemperature vs. time plot. It predicts temperature in the near future. Understand, savor, enjoy this simple fact

before attempting to predict further into the future.Comment by Richard LaRosa 7 Nov 2006 @ 5:34 pm

58. Gavin, you said: the reason horses were phased out as quickly as they were was because the costs associatedwith using horses (maunre, dead carcasses, stabling etc.) were bourne by the same entities that benefited from theirservices (i.e. cities and businesses). and If you want to take a lesson from that, it is that the costs associated withGHG emissions should be bourne by the producers of those emissions such that no new technology is handicapped

by effective subsidies to fossil fuel users.

Your history lesson on horses is new to me. I am also curious which technology you believe is handicapped bysubsidies to fossil fuel users? To which subsidy are you referring? Are you saying that the producers are sellingthe consumers their product too cheaply (passing on some kind of hidden subsidy so consumers will keep usingtheir product)? I will have to say that your complete comment is lost on me.[Response: This is normally discussed using the term externalities and often comes up in environmentaldiscussions. If a factory makes a product that creates waste, and that waste is simply thrown into the river, thenthe communities downstream are affected. If they have to pay to clean it up, that cost is not bourne by the

polluters and is not reflected in the price of the widget the factory makes - the costs of pollution are externalisedin the budget of the factory. If the factory was made to clean up the waste ahead of time, that cost would bereflected in the price of the widget - it would be internalised and thus figure more prominently in discussions overwhether the widget was good value for money. This is a reasonably easy case since most effects are local/regional

and so laws and regulations can be easily enacted to internalise most of the pollution-related costs. The same wastrue for horses. The greenhouse gas situation is very different since the costs of GHG emissions are likely to fallon communities that have no connection to the source of the pollution. For the sake of argument, lets assume thatGHGs increase sufficiently to melt a big chunk of Greenland. The people who will end up with all the costs are

people in low-lying coastal areas like millions of Bangladeshis - hardly the world worst polluters. If the costsassociated with flooding Bangladesh were internalised, then the cost of emitting CO2 would be higher and a fair
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2006-11-06, Real Climate - How Much CO2 is Too Much