How much warming in the pipeline? Part II – it’s as tricky as ABC

Warming ‘in the pipeline’ is a term used to describe lags and inertia in the climate system. As explained in my previous post on this topic,  the planet is committed to further heating and sea level rise, irrespective of what choices we make now, or in the immediate future, to reduce carbon emissions. The global warming trend over the last 100 years (actually, from 1906 to 2005), of 0.56°C to 0.92°C, is not all that we would have expected. That is, there is a ‘missing’ quanta of  warming, which is being hidden by a number of poorly understood factors.

First, let’s consider 21st century carbon emissions mitigation scenarios. A range of possible future energy and economic development storylines have been developed by the Special Report on Emissions Scenarios (SRES), such as A1FI, A2, B1 etc. (based on global vs regional action, and different tech pathways). For details, see here. These scenarios were used as a basis for the IPCC 2007 AR4 projections of future climate change. Two important points with these SRES storylines: (i) there is no explicit preference given to any particular scenario, and (ii) they are not active mitigation scenarios (mitigation is a byproduct of economic, social and technology choices). As such, it can be confusing to work out what ‘is likely’, and indeed, whether any are particularly realistic. 

More usefully in terms of future predictions, a recent paper in PNAS by Van Vuuren and co-workers (including a friend of mine, Tom Wigley, who is an Adjunct Professor at the University of Adelaide), assessed the impact on climate change of some plausible real-world actions. Here is the abstract, with some bolding by me:

Estimates of 21st Century global-mean surface temperature increase have generally been based on scenarios that do not include climate policies. Newly developed multigas mitigation scenarios, based on a wide range of modeling approaches and socioeconomic assumptions, now allow the assessment of possible impacts of climate policies on projected warming ranges. This article assesses the atmospheric CO2 concentrations, radiative forcing, and temperature increase for these new scenarios using two reduced-complexity climate models. These scenarios result in temperature increase of 0.5-4.4°C over 1990 levels or 0.3-3.4°C less than the no-policy cases. The range results from differences in the assumed stringency of climate policy and uncertainty in our understanding of the climate system. Notably, an average minimum warming of ≈1.4°C (with a full range of 0.5-2.8°C) remains for even the most stringent stabilization scenarios analyzed here. This value is substantially above previously estimated committed warming based on climate system inertia alone. The results show that, although ambitious mitigation efforts can significantly reduce global warming, adaptation measures will be needed in addition to mitigation to reduce the impact of the residual warming.

Their conclusion? Even with a strong and concerted effort towards rapid carbon mitigation, we are committed to 0.5 to 2.8°C additional warming (on top of what has already been experienced), due to the combined effects of climate system, economic and technological inertia. 

This sobering view is supported by many climate scientists in this field; most prominently, by Prof V Ramanathan of University of California — San Diego. Ram is the scientific guru of the study of tropospheric aerosols (soot, dust, sulphates, nitrates and other chemicals that together constitute the low-lying ‘haze’ seen over polluted cities worldwide, and now, large parts of Asia). Aerosols can cool the climate by reflecting solar energy back out to space before it has a chance to be absorbed and re-emitted as infrared radition by the Earth’s surface, and also warm the climate by absorbing extra energy in the lower atmosphere (coming mostly from incompletely burnt carbon from coal-fired power stations and dung braziers). Collectively, it’s called the Atmospheric Brown Cloud (it used to be known as the Asian Brown Cloud, ’cause that is where most of it is). Also known as ABC.

Last year, Ramanathan and co-author Y. Feng published a remarkable paper in PNAS called “On avoiding dangerous anthropogenic interference with the climate system: Formidable challenges ahead“). Here, once again, is the abstract:

The observed increase in the concentration of greenhouse gases (GHGs) since the preindustrial era has most likely committed the world to a warming of 2.4°C (1.4°C to 4.3°C) above the preindustrial surface temperatures. The committed warming is inferred from the most recent Intergovernmental Panel on Climate Change (IPCC) estimates of the greenhouse forcing and climate sensitivity. The estimated warming of 2.4°C is the equilibrium warming above preindustrial temperatures that the world will observe even if GHG concentrations are held fixed at their 2005 concentration levels but without any other anthropogenic forcing such as the cooling effect of aerosols. The range of 1.4°C to 4.3°C in the committed warming overlaps and surpasses the currently perceived threshold range of 1°C to 3°C for dangerous anthropogenic interference with many of the climate-tipping elements such as the summer arctic sea ice, Himalayan-Tibetan glaciers, and the Greenland Ice Sheet. IPCC models suggest that ≈25% (0.6°C) of the committed warming has been realized as of now. About 90% or more of the rest of the committed warming of 1.6°C will unfold during the 21st century, determined by the rate of the unmasking of the aerosol cooling effect by air pollution abatement laws and by the rate of release of the GHGs-forcing stored in the oceans. The accompanying sea-level rise can continue for more than several centuries. Lastly, even the most aggressive CO2 mitigation steps as envisioned now can only limit further additions to the committed warming, but not reduce the already committed GHGs warming of 2.4°C.

You can download the PDF of the full paper, for free, here. It’s an excellent piece that should, in the most part, be intelligible to the majority of interested readers.

The net climate-forcing effect of ABCs is much more poorly known than that of long-lived trace greenhouse gases, as explained here. Our best estimate is that in sum, ABCs cool the climate system — potentially offsetting more than half the warming we would have otherwise expected to date.  That is, the new industries and traditional stoves of Asia may have delayed the worst impacts of climate change. Here is a key point made by R&F (I removed the reference numbers for clarify of reading here — see the original paper for the links to the relevant peer-reviewed literature; GHG = greenhouse gases, CEWGA = committed equilibrium warming from greenhouse gases and aerosols, Wm2 = watts per metre squared, DAI = dangerous anthropogenic interference with the climate system):

First, we have to consider the effect of aerosols, which start off as urban haze or rural smoke and ultimately become transcontinental and transoceanic plumes o ABCs consisting of sulfate, nitrate, hundreds of organics, black carbon, soil dust, fly ash, and other aerosols. ABCs have masked GHG warming by enhancing the albedo (percent of incoming solar radiation re-flected back to space) of the planet. A recent review of available literature estimates the masking effect of ABCs to be 47% (1.4 Wm2) with a 90% confidence interval of 20-80%. The IPCC-AR4  value for the masking is 40%. Effectively, the forcing ‘‘felt” by the climate system is only 53%, i.e., 1.3°C, which is identical to CEWGA, the committed warming adapted by earlier studies. About 8% of the committe warming (0.2°C) is compensated by increases in the surface albedo because of land-use changes; 20% (0.5°C) is delayed by the thermal inertia of the oceans and it is only the balance of 25%, i.e., 0.6°C, that should by now have manifested as observed warming. This algebraic exercise demonstrates that the observed surface warming of 0.76°C (since the latter half of 1800s) is not inconsistent with the committed warming of 2.4°C.

The fundamental deduction (subject to the assumption of IPCC climate sensitivity) is that if we get rid of the ABCs today the Earth could warm another 1.6° (which includes the delayed warming caused by ocean thermal inertia) unless we act now to reduce GHG concentrations. As shown by couple ocean atmosphere models used in IPCC, 50% of this warming can happen in few decades, and most of the balance will manifest during the course of this century. The situation with respect to sea-level rise is considerably more complex. Sea-level rise caused by thermal expansion (in the range of 10 to 30 cm per century) is likely to continue for centuries (even if the warming asymptotes to values close to CEWG by 2100) because of the time required for mixing of the heating to deeper oceans. In addition, the range of CEWG (1.4-4.3°C) raises another major DAI-related issue. As suggested by the IPCC the Greenland Ice Sheet can disappear completely if surface warming is maintained in excess of 1.9-4.6°C for millennia and raise sea level by 7 m or more.

Prof HJ Schellnhuber, Director of the Potsdam Institute, commented formally in PNAS on the R&F paper here: “Global warming: Stop worrying, start panicking?“.  His conclusion was that R&F’s assessment is technically right, but, as Mark Twain once commented on a Wagner opera, it’s not as bad as it sounds. That is, there is still a fair chance that we can ‘hold the 2°C line’, if strong mitigation of greenhouse gases is combined with the following three actions: (i) a slow, rather than instant, elimination of aerosol cooling, (ii) a directed effort to first remove warming aerosols like black carbon, and (iii) a concerted and sustained programme,  over this century, to draw-down excessive CO2 (geo- and bio-engineering) and simultaneously reduce non-CO2 forcings, such that the final equilibrium temperature rise will be lower than would otherwise be expected on the basis of current concentrations.

His bottom line? “This requires an industrial revolution for sustainability starting now“.

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58 Comments

  1. The main implication I draw is that some form of aerosol geoengineering is really really likely; first, just to make up for the global cooling effect lost as polluted cities clean their air, and later to buy time for decarbonization (and, I suspect, air capture).

  2. willy Soon says it better than i can

    It’s the Sun, stupid!
    [Ed: Snip -- just provide the link, not 700 words of regurgitated text. The comments section are for your own thoughts]

  3. Maybe some of the ‘masking problem’ could be explained by the ‘discredited’ data that shows CO2 levels were on average higher during 1800-1960 period than the 280ppm so often quoted. The figure for that period could have been as high as 335ppm but this was disregarded by Callendar to achieve the lower figure. This might explain why some extreme hot weather events happened prior to 1940. If a higher CO2 level is assumed for last century, would this factor help in explaining the ‘missing quanta of warming’ for recent temperature ranges?

  4. “The global warming trend over the last 100 years (actually, from 1906 to 2005), of 0.56°C to 0.92°C, is not all that we would have expected. That is, there is a ‘missing’ quanta of warming, which is being hidden by a number of poorly understood factors.”

    In other words, the computer models would predict much more heating over the past century than has actually occurred. If we assume that the computer models are correct, then something we don’t understand well must account for the difference between the actual heating and what the computer models would expect.

    An alternative theory is that the computer models have over-projected the amount of heating that can be expected from an increase in CO2.

    I would be interested in any empirical evidence that suggests that the first alternative is more likely than the second.

  5. Roger Pielke Snr’s cites Levitus 2001 to claim there has been no ocean heating and little ice melting since mid-2003.

    First, I wonder how a 2001 paper can make any judgement on what happened since 2003. Second, the most recent publications on this topic, Levitus et al 2005 and Dominiques et al 2008, both show a large and ongoing gain in ocean heat content. See:

    http://bravenewclimate.com/2008/11/23/what-bob-carter-and-andrew-bolt-fail-to-grasp/

    As stated earlier, I agree with the point that tropospheric aerosols from fossil fuels are incredibly bad for human health and other environmental impacts (black carbon soot, acid rain, radioactive emissions, mercury poisoning), putting us in a situation of damned if we do, damned if we don’t.

  6. PaulD I looked over the figures for CO2 data (post 8 above) and ran them against NASA yearly global temps to check correlations.

    From 1880 – 1910 there was a CO2 increase of 9ppm which resulted in a 0.15C drop in temp.
    From 1910 -1940 there was a CO2 increase of 10ppm which resulted in an 0.5C increase in temp.
    From 1940 – 1975 there was an increase of around 25ppm which resulted in a drop of 1.0C in temp (aerosols, pollution?).
    From 1978 – 2008 there was an increase of around 50ppm which resulted in a rise of 0.45 in temp.

    We can say that CO2 levels are rising rapidly but something is holding back the temperatures as the correlation between CO2 and temps are not consistent. For instance 1910-40 had the same temp rise as 1978-2008 with a 1/5th CO2 rise. However, one could conclude that a 75ppm CO2 increase has lead to a 0.45C rise in temps (ie 1940-2008) or an 86ppm CO2 increase has led to 0.9C rise (1910-2008). So maybe the models are wrong in their predictions. CO2 may be just a passive insulator which could account for higher minimum temps occurring. There is also some evidence that CO2 can only absorb a certain amount of heat but I’m not sure if this is correct.

  7. Ian, check your arithmetic: -0.15+0.5-1.0+0.45 = +0.1C, yet the rise from 1880-1900 to 1990-2008 has been greater than +0.8C (NASA GISS or Hadley). Thus illustrates the problem with picking individual years as start-end points.

    That ‘something’ holding back temperature rise is aerosols and inertia, mixed with volcanic, solar forcing and multi-year ocean-atmosphere dynamics (e.g. ENSO, PDO), as explained above and in the previous post on this topic, and other places on this blog. Your speculation about CO2 being a passive insulator etc. is just that – speculation. There are more robust, parsimonious explanations which fit with the theories and empirical data of physical science. But have fun musing — that’s what the non-peer-reviewed blogosphere is for.

  8. Thanks Alan. An excellent write-up of this issue, including discussion of the Willis et al 2008 paper cited by Pielke, can be found here:

    http://www.skepticalscience.com/Mystery-of-the-vanishing-ocean-heat.html

    “However, upper ocean heat, like surface temperature, doesn’t follow a monotonically warming trend during global warming. Ocean temperatures experience interannual variability and over the past 3 decades of global warming have had several short periods of cooling… Argo takes measurements in the top 2000 metres of the ocean. Could the heat have moved to the deep ocean? This seems unlikely. Deep steric changes occur over time scales of decades or longer and aren’t expected to explain the discrepancy over the last 5 years (Antonov 2005)… Willis 2008 speculates that there is most likely a systematic error in at least one of the three observing systems which is introducing a linear trend. “

    See also here for further details:

    http://www.realclimate.org/index.php/archives/2008/06/ocean-heat-content-revisions

    “…But the big picture is that ocean heat content has indeed been increasing in recent decades, just like the models said it should.”

    Both are worth reading to get a better understanding of OHC and how our knowledge of this critical measurement continues to be refined.

  9. We are behaving on the A1FI Scenario or above, so this is what we are heading towards.

    The lower scenarios are hypothetical unless or until the global community changes its behaviour and there are no clear signs that humans are likely to change in the near future. When we do, additional feedback loops at very large scales may have already locked in.

    When planning our future in areas such as the Murray Darling Basin, I think that we first need to acknowledge that we are headed towards the AiFI outcome which by the 2100 is around double the dangerous 2 degree climate change outcome, possibly up to triple dangerous climate change. So I find it strange that so organisations start picking supposedly low middle and high emission scenarios for planning work (all below the AiFI output).

    The lower scenarios are not something that we are close to.

  10. Barry Thanks for pointing out the typo – 1940-1975 should read 0.1C cooling, not 1.0C (the missing +0.1C occurred between 75-78). The reason I chose those periods was because they showed noticeable warming or cooling patterns. I ‘cherrypicked’ 1978-2008 as a 30 year period to match against 1910-1940.

  11. Michael W — yes, we are following an A1FI pathway at present, but I cannot see that continuing. None of the SRES storylines are realistic. I suspect, realistically, that we’ll track above A1FI for another decade or so, and then fall well below it as we collectively get our act together (coupled with shortages in oil/gas and locally, coal, starting to bite). But in terms of impact management and risk aversion, we need to plan for the worst, because even if we don’t follow the A1FI path to hell, the impact side of the equation could turn out to be more sensitive the climate system disruption than the mid-range expectation.

    IG – no problem, I wasn’t accusing you of cherry picking, simply trying to work out where your maths went wrong. A difference between 1C and 0.1C is rather large in this context, after all :)

  12. Ian George (10, 14) — Regarding the ice core CO2 data, you could compare all the Antarctic ones to see the variations. I doubt there is any statistically noticable effect as the problems of collecting data from ice cores have been repeatedly and exhaustively studied. But whatever you do, be sure to test for statistical significance (ss); I doubt that your short time studies possess ss as it usually requires at least 30 years of data when doing climatological studies.

    The IR properties of carbon diioxide are rather complex. I’m quite satisfied with the empirical formula in

    http://en.wikipedia.org/wiki/Svante_Arrhenius#Greenhouse_effect

    rather than attempting the postgraduate texts in atmospheric physics.

  13. I said locally PeterW. China, for instance, is already hitting shortages: mine output relative to domestic demand — it’s the world’s largest coal producer but now a net importer. Limitations will be how much can be shipped out from ports of countries with an abundance of the black stuff. Worldwide reserves of economically recoverable coal would last 80-125 years, depending on future levels of use. But that’s not a globally even supply.

  14. Slightly off the point of this blog but here goes.
    Regardless of AGW, CC, sea level change, etc – why the govt is not investing in sustainable, ‘green’ energy is beyond me. Surely it makes sense to access a free supply of energy (eg wind, tidal, solar, geothermal, etc) and to wean ourselves off depleting supplies of fossil fuels. The infrastructure will initially be costly – we may even have to increase our C)2 levels to create that infrastructure. But the savings down the track in lowering pollution levels, lessening land degradation and accessing free sources is the only sensible option.

  15. Barry, I was involved in a coal gas exploration project recently and as part of the project quite a number of large bore holes were drilled in VERY large prospective area.

    Every drill hole revealed layer upon layer of high grade black coal – that is EVERY hole over an area of thousands of hectares and hundreds of metres of depth.

    Further exploration showed these ‘reserves’ continued into other geological provinces to the north south, east and west.

    Unfortunately for the exploration company the gas in the seams was not economically viable – not enough water or pressure in the seams or something like that (at the moment) as were the coal seams themselves given the shallower deposits already being exploited nearby.

    The geologists on the job were not surprised at the extraordinary amount of coal revealed – they commented that every province they had explored for coal seam gas in Australia, the US, China and India had similar results ( as will Antarctica).

    I was astonished at the numerous thick layers of coal revealed by the drill cores – it was seemingly endless and the geos calculated the total coal reserve (reserve used inappropriately by me) revealed by this exploration effort contained many times the known documented reserve in Australia.

    The exploration company archived their drill results and moved on, but the resources they identified were reported to their investors and flagged for further attention – perhaps in 20 or 30 years was one comment.

    As a result of this and a number of similar experiences I have been exposed to many exploitable resources drilled, explored, mapped and marked in confidential company archives for later attention, so as far as I’m concerned the ‘local’ or otherwise shortage of coal is a myth.

    I might add this applies to gold, iron ore, nickel and many other minerals as well – especially gold though ;-P

  16. Two relevant articles in this week’s Science, one on coal supplies:

    http://www.sciencemag.org/cgi/content/summary/323/5920/1420

    and another on increased aerosol dimming:

    http://www.sciencemag.org/cgi/content/abstract/323/5920/1468

    PeterW — coal supply is ultimately all about economics of recovery and EROEI. I have no doubt you are right that there are many trillions of tonnes of coal still harvestable in the upper crust — it’s just a matter of whether anyone can be bothered. A carbon price would help dissuade them, for sure. More fundamentally, I agree with the principle that to depend on ‘peak coal’ as a saviour of future CO2 emissions is a bad, highly risky bet indeed. There’s plenty left to take us to unpleasant places in the future.

  17. Given that surface temperatures have levelled off / slightly dipped for the last decade, what would be your response to a discovery that that the oceans have also not warmed over that period – i.e. that actually there is no warming waiting in the ‘pipeline’? Would it then be necessary to start looking elsewhere for proof of GW?

  18. Warming in the pipeline refers to both ocean heat content (down to 700 m, not sea surface temperature) and tropospheric aerosol masking (which is what is discussed in the post above).

    Regarding your question, there is not, and cannot be, any proof of global warming. There is a deep literature on the basic theory developed from first principles, models, experiments and observations (in many areas of physics, chemistry, geology, biology), and a large published body of empirical geophysical and biological evidence from real world systems, the majority of which is consistent with this underpinning science. There are also inconsistencies, which can indicate problems with aspects of this theory (e.g., unanticipated interactions or feedbacks, +ve and -ve), poorly understood aspects of Earth systems science (e.g. ENSO drivers), or measurement error (e.g., insufficiently precise or well-scaled instrumentation).

  19. BJF Cricklewood: “Given that surface temperatures have levelled off / slightly dipped for the last decade..”

    Please spare us the nonsense. This is a serious issue.

  20. David (#29) and Gaz(#30):
    In another discussion Barry has said that global surface temperatures have indeed levelled out (while cautioning that this ignores factors such as warming in the pipeline).
    Do you deny this plateau in the temperature records for the last decade or so?

  21. Barry (#28)
    Yes I appreciate that
    * anthopogenic global warming has not been proven, there being unknowns that we know about but cannot quantify, eg ocean heat content and aerosol cooling, that may or may not act as a pipeline of future warming.
    * what we nevertheless do have is an array of circumstantial evidence, proxies and models that many in the climatology business put their faith in.

    But what I’m trying to establish – particularly in the light if the abovementioned temperature plateau – is what the response of such climatologists would be to a discovery that this pipeline effect is negligible. Just how important is the pipeline to the AGW hypothesis? Would it collapse without the pipeline, or would empirical support be sought elsehere?

  22. BJF Cricklewood: “Do you deny this plateau in the temperature records for the last decade or so?”

    There has been some variation around a rising trend. If you want to call it a “plateau”, go ahead. Just don’t expect anyone to take it seriously except the hard-core “LA LA LA I’M NOT LISTENING” types.

    Have a look at the graph referred to by David B. Benson at #29. There are dozens of occasions in recent decades when this variation could have been described as a “plateau”, and just as meaninglessly.

    Why would you think the pipeline effect might be negligible? Is there a magical trap-door at the bottom of the ocean that allows all that heat to escape to Narnia?

  23. So you do deny the plateau, contradicting what virtually everyone else – Barry included – is saying?

    I didn’t say the pipeline is negligible, I asked what the reaction would be if it was.
    Bear in mind the pipeline idea only seems to have brought in in the first place, to explain why the temperature plateau does not show that GW has stopped.

  24. Bear in mind that you are wrong. Warming in the pipeline is not associated with any perceived ‘plateau’ — ocean inertia and aerosol masking has been a scientific topic in the peer-reviewed literature for decades.

    And the ‘plateau’ does not exist if you look at the data climatologically — the 30 year trend is strongly +ve. And the trend is +ve even over the last 10 years:

    http://www.woodfortrees.org/plot/wti/from:1999/plot/wti/from:1999/trend

    Not for 11:

    http://www.woodfortrees.org/plot/wti/from:1998/plot/wti/from:1998/trend

    Is for 12:

    http://www.woodfortrees.org/plot/wti/from:1997/plot/wti/from:1997/trend

    Is for 13 (and so on…)

    http://www.woodfortrees.org/plot/wti/from:1996/plot/wti/from:1996/trend

  25. BFJ Cricklewood: “I didn’t say the pipeline is negligible, I asked what the reaction would be if it was.”

    There is a big difference between “is” and “might be”, which is why I asked “Why would you think the pipeline effect MIGHT BE negligible?”

    Unless you think it MIGHT BE negligible, there is no point speculating about what might happen if that’s how it turned out.

    Anyway, I think it’s pretty clear that the recent short term fluctuations in global temperatures don’t say anything of significance about how much warming’s in the pipeline.

  26. BFJ Cricklewood (31) — Carefully define what you mean by plateau and go through the enitre record to determine the number of times this has occurred. Nothing extraordinary about this one, methinks, except possibly the rather extended solar minimum just now. That does not happen very often.

  27. Sorry, must have messed up the markup there…

    You yourself though associated them in your discussion on what Bob Carter supposedly missed, ie that the theoretically ‘missing’ heat could have gone into the oceans.

  28. And I still haven’t any response to the hypothetical question of how much of a rethink, a discovery that the alleged pipeline is negligible, would prompt.

    And here’s another: how much longer would the current plateau need to continue before you would deem the AGW hypothesis to be failing?

  29. Gaz (#36) questions the point of speculating on the scale of the alleged pipeline.

    It seems to me it is this : if pipeline heat is significant, so is AGW; and if it isn’t, nor is AGW.
    A corollary being that if we can’t comment meaningfully on the scale of the pipeline, we can’t comment meaningfully on the AGW hypothesis either, it remains mere speculation.

  30. BFJ#43: A negative temperature trend over 20 years? Starting in 2005 or 1998? If it did occur, plenty of scientists would be scratching their heads, not really because they would doubt (A)GW, but because they would be worried about their estimation of where the heat is going. We know that more energy is arriving than leaving, that much is comparatively simple and measurable (satellites).

    Where it is going is a tougher issue? Is it melting ice? Warming the oceans? Warming continental land masses? etc. If you look at some of the moves between ice ages and warm ages, there have been long periods, really long periods, which went against the trend.

    Consider the run of 5 heads in the following sample produced by R software:

    [1] “T” “H” “T” “T” “T” “T” “H” “T” “H” “H” “T” “H” “H” “H” “H” “T” “T” “H” “H”
    [20] “T” “H” “H” “H” “H” “H” “T” “H” “T” “H” “H” “T” “H” “T” “H” “T” “T” “T” “T”
    [39] “H” “T” “H” “H” “T” “T” “H” “H” “T” “H” “H” “H”

    Does it convince me that the R random number generator is biased? A run of 5 heads is outside a 95%CI for a 5 throw sample. If I had written a naive random number generator that produced this run, I would double check my code. But the R generator has had substantial testing, so I have plenty of other reasons to trust it, after all a run of 5 heads isn’t SO unlikely. But a 20 head run would have me contacting the R authors for a bug fix!

  31. Responding to my #42 above, Barry (#22 in the Do Scientists Really Believe in AGW thread) :
    We’ve had +0.74C global warming in the last 100 years and about 90 ppm CO2 rise. That’s +0.0082C/ppm. A doubling of CO2 on pre-industrial by mid-century would be +280ppm. Based on no further acceleration of temperature rise and nothing in the pipeline, this would imply a warming of +2.3C. So your statement is patently false, even if there was no aerosol masking or ocean inertia.

    I am essentially just following up on your response to that Bob Carter, where you argue that he wrong to say that GW has stopped, since he is only considering the for now levelled out surface temperatures of the last decade or so, ignoring the ‘pipeline’. This argument of yours thus places great store in the pipeline as a proof of GW – it says the GW and the pipeline theories stand or fall together.

    It does seems to me significant that your challenge to Carter was over the pipeline, not over the (perhaps temporary) halt in surface temperature increases.

  32. BFJC: You are confused. My challenge to Carter was that 10 years was meaningless because of the sensitivity of global weather to short-term fluctuations. My calculation above was over 100 years — a period where a 10 year fluctuation becomes irrelevant.

    Your “stand and fall” straw man is patently rubbish. Stop posting rubbish. I’ve already explained that proof is impossible and unscientific. So stop repeating that nonsense too.

  33. (#44 Geoff)
    You say “we know that more energy is arriving than leaving”, which looks to me like an effective proof that GW is occuring, beyond any reasonable scepticism.
    But do we really know this (1)? There is presumably no comparable (satellite?) data from pre-warming periods to compare to, to help us eliminate errors in what we think we are measuring.

    So we ‘know’ GW is happening, but) we just can’t show where the heat is going anymore (2. Until recently, surface temperatures sufficed to show us GW, but something has now changed. Do we (3) even have an idea of what that something is?
    Do (1), (2) & (3) together not suggest agnosticism is in order?

    If you look at some of the moves between ice ages and warm ages, there have been long periods, really long periods, which went against the trend

    Sure. But that to me merely says AGW could be happening, not that it is happening.

  34. (#46 Barry)
    My challenge to Carter was that 10 years was meaningless because of the sensitivity of global weather to short-term fluctuations.

    Yes, I acknowledged that argument of yours, but also note that the gist of your what-bob-carter-and-andrew-bolt-fail-to-grasp article, eg ->
    ..about 90% of this additional energy has been used to heat water and about 7% to melt ice. Only about 3% is left over to warm the air. So we shouldn’t be at all surprised if air temperatures show the weakest response to the enhanced greenhouse effect – at least in the short term.
    -> was that the apparent halt in GW seized on by Carter, was due to the extra heat going into the oceans rather than the atmosphere, and that other heat was being reflected by aerosols, and that Carter was overlooking these.

    Which is why it still seems to me that for GW to be a reasonable hypothesis, we first need a reasonable take on OHC.
    (btw I acknowledged too your view that accurate measurements of OHC are not (yet) practical).

    Question:
    The notion of the oceans being a heat sink I can readily understand as being a ‘pipeline’, whose stored up heat will unavoidably be delivered up to us sooner or later.
    But not the reflectivity of aerosols. The heat they have reflected is gone forever, surely?

    Rather than having a pipeline effect, is the main issue with aerosols instead that they degrade/dissipate (far?) sooner than CO2, so that if we stop creating new aerosols, we will quite soon lose their cooling effect?

  35. A warming period usually follows an ice age (even a mini one) and that is part of the natural cycle. If CO2 has been below 300ppm for 600,000 years then CO2 is unlikely to be the primary driver of all the extreme warming and cooling periods during that time. In the last 100 years, there has been an increase in global temps of about 0.8C. What percentage has been caused by natural warming and what % has been caused by CO2 increases? Can anyone quantify?

  36. Barry Depends on the start year. If you change it to 1998, the trend is downward.

    If we contend that seas are warming, wouldn’t that lead to higher evaporation rates resulting in more cloud cover.
    This would have the effect of generally dampening daytime temps but increasing nighttime temps (increased water vapour and the released CO2 from the warming oceans, acting as an insulator). Is this too simplistic?

  37. It was your linked plot Ian, not mine — I just added the trendline. Oh, and try changing the year to 1997…

    Evaporation rates are increasing over the oceans, but it’s thought to be mostly due to greater windiness. Curiously, pan evaporation rates are steady or slightly down over land — something the models cannot generally replicate. As to your cloud effect, it depends if they are low (tends to reflect sunlight) or high (tends to trap heat).

  38. Barry Thanks for the explanation above. I’ve just been noticing that minimum/nighttime temps seem to have increased more than max/daytime temps which has resulted in higher av mean temps. Snow in the middle east over the past 2 years may also indicate higher evaporation levels.

    I took your link at post 51 (which I originally posted at 50 but with no trend line) and changed the start date to 1998. It shows a downward trend – I was just pointing out that it’s the start date that counts (in your post at 35 you have done the same with global temps at ‘not for 11′).
    I have also read, though it will probably be open to much conjecture, that there has been a slowing in CO2 level increases, a cooler ocean temp emerging and a slowing trend to sea level rises since 2006.

  39. “Warming ‘in the pipeline’ is a term used to describe lags and inertia in the climate system”.

    No, it’s a line of spin used by publicly-funded climate change spivs who are frantically trying to seem to know what they are doing while being wrong about virtually everything they do, and hoping to keep the gravy train going a bit longer. Saying there is warming in the pipeline is like saying there’s a buildup of electricity in the wires that hasn’t yet been delivered to your house. Warming doesn’t cower in the corner, waiting to pop up. If the warming has been offset by other factors then it’s already gone.

    “we are committed to 0.5 to 2.8°C additional warming”

    You mean 1.65 +/- 70%? A range of error which might as well have been generated by a monkey with a typewriter. Why does nobody question this sort of thing?

    “This requires an industrial revolution for sustainability starting now”

    Go on then. What are you waiting for? You’re the bloody climate scientists. Ring up Penny Wong, she agrees with you. One day climate scientists are going to have to wake up to the reality that the politicians that say they believe in all this stuff are doing nothing about it. Why do you think they’ve picked 2050 as a target? If you want to see action, you’re going to have to do it yourself. Sitting around firing off reports and asking for the government to act is about as worthless as the horrible denialists who say nothing should be done at all.

  40. Pingback: Climate change basics III – environmental impacts and tipping points « BraveNewClimate

  41. Pingback: This Means Extinction - Survival Acres Blog

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