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Happy 35th birthday, global warming!

Filed under: — stefan @ 28 July 2010 - (Deutsch) (Español) (Italian)

Global warming is turning 35! Not only has the current spate of global warming been going on for about 35 years now, but also the term “global warming” will have its 35th anniversary next week. On 8 August 1975, Wally Broecker published his paper “Are we on the brink of a pronounced global warming?” in the journal Science. That appears to be the first use of the term “global warming” in the scientific literature (at least it’s the first of over 10,000 papers for this search term according to the ISI database of journal articles).

In this paper, Broecker correctly predicted “that the present cooling trend will, within a decade or so, give way to a pronounced warming induced by carbon dioxide”, and that “by early in the next century [carbon dioxide] will have driven the mean planetary temperature beyond the limits experienced during the last 1000 years”. He predicted an overall 20th Century global warming of 0.8ºC due to CO2 and worried about the consequences for agriculture and sea level.

Global temperature up to June 2010 according to the NASA GISS data. Grey line is the 12-month running average, red dots are annual-mean values. The thick red line is a non-linear trend line. Broecker of course did not have these data available, not even up to 1975, since this global compilation was only put together in the late 1970s (Hansen et al. 1981). He had to rely on more limited meteorological data.

To those who even today claim that global warming is not predictable, the anniversary of Broecker’s paper is a reminder that global warming was actually predicted before it became evident in the global temperature records over a decade later (when Jim Hansen in 1988 famously stated that “global warming is here”).

Broecker is one of the great climatologists of the 20th Century: few would match his record of 400 scientific papers, a full sixty of which have over 100 citations each! Interestingly, his “global warming” paper is not amongst those highly-cited ones, with “only” 79 citations to date. Broecker is most famous for his extensive work on paleoclimate and ocean geochemistry.

It is very instructive to see how Broecker arrived at his predictions back in 1975 – not least because even today, many lay people incorrectly assume that we attribute global warming to CO2 basically because temperature and CO2 levels have both gone up and thus correlate. Broecker came to his prediction at a time when CO2 had been going up but temperatures had been going down for decades – but Broecker (like most other climate scientists at the time, and today) understood the basic physics of the issue.

Basically his prediction involved just three simple steps that in essence are still used today.

Step 1: Predict future emissions

Broecker simply assumed a growth in fossil fuel CO2 emissions of 3% per year from 1975 onwards. With that, he arrived at cumulative fossil CO2 emissions of 1.67 trillion tons by the year 2010 (see his Table 1). Not bad: the actual emissions turned out to be about 1.3 trillion tons (Canadell et al, PNAS 2007 – estimate extended to 2010 by me).

A shortcoming, from the modern point of view, is that Broecker did not include other anthropogenic greenhouse gases or aerosol particles in his calculations. He does however discuss aerosols, which he calls “dust”. In fact, the first sentence of the abstract (quoted above) in full starts with an if-statement:

If man-made dust is unimportant as a major cause of climate change, then a strong case can be made that the present cooling trend will, within a decade or so, give way to a pronounced warming induced by carbon dioxide.

That is a nod to the discussion about aerosol-induced cooling in the early 1970s. Broecker rightly writes:

It is difficult to determine the significance of the next most important climatic effect induced by man, “dust”, because of uncertainties with regard to the amount, the optical properties and the distribution of man-made particles,

citing a number of papers by Steve Schneider and others. Because he cannot quantify it, he leaves out this effect. Here luck was on Broecker’s side: the warming by other greenhouse gases and the cooling by aerosols largely cancel today, so considering only CO2 leads to almost the same radiative forcing as considering all anthropogenic effects on climate (see IPCC AR4, Fig. SPM.2).

Table 1 of Broecker (1975)

Step 2: Predict future concentrations

To go from the amount of CO2 emitted to the actual increase in the atmosphere, one needs to know what fraction of the emissions remains in the air: the “airborne fraction”. Broecker simply assumed, based on past data of emissions and CO2 concentrations (Keeling’s Mauna Loa curve), that the airborne fraction is a constant 50%. I.e., about half of our fossil fuel emissions accumulates in the atmosphere. That is still a good assumption today, if you look at the observed CO2 increase as fraction of fossil fuel emissions. Broecker calculated that about 35% of the emissions is taken up by the ocean and the other 15% by the biosphere (again not far from modern values, see Canadell et al.). On this basis he argued that if the ocean is the main sink, the airborne fraction would remain almost constant for the decades to come (his calculations extend to the year 2010).

Thus, with a 3% increase in emissions per year and 50% of that remaining airborne, it is easy to compute the increase in CO2 concentrations. He obtains an increase from 295 to 403 ppm from 1900 to 2010. The actual value in 2010 is 390 ppm, a little lower than Broecker estimated because his forecast cumulative emissions were a little too high.

Step 3: Compute the global temperature response

Now we come to the temperature response to increased CO2 concentration. Broecker writes:

The response of the global temperature to the atmospheric CO2 content is not linear. As the CO2 content of the atmosphere rises, the absorption of infrared radiation will “saturate” over an ever greater portion of the band. Rasool and Schneider point out that the temperature increases as the logarithm of the atmospheric CO2 concentration.

Based on this logarithmic relationship (still valid today) Broecker assumes a climate sensitivity of 0.3ºC warming for each 10% increase in CO2 concentration, which amounts to 2.2ºC warming for CO2 doubling. This is based on early calculations by Manabe and Wetherald. Broecker writes:

Although surprises may yet be in store for us when larger computers and better knowledge of cloud physics allow the next stage of modeling to be accomplished, the magnitude of the CO2 effect has probably been pinned down to within a factor of 2 to 4.

The AR4 gives the uncertainty range of climate sensitivity as 2-4.5ºC warming for CO2 doubling, so there still is about a factor of 2 uncertainty and Broecker used a value near the very low end of this uncertainty range. Modern estimates are not only based on model calculations but also on paleoclimatic and modern data; the AR4 lists 13 studies that constrain climate sensitivity in its table 9.3.

In Broecker’s paper the warming calculated with the help of climate sensitivity happens instantaneously. Today we know that the climate system responds with a time lag due to ocean thermal inertia. By neglecting this, Broecker overestimated the warming at any given time; accounting for thermal inertia would have reduced his warming estimate by about a third (see AR4 Fig. SPM.5). But again he was lucky: picking ~2ºC rather than the more likely ~3ºC climate sensitivity compensates roughly for this, so his 20th-Century warming of 0.8ºC is almost spot on (the actual estimate being closer to 0.7ºC, see Fig. above). (A modern version of this back-of-envelope warming calculation is found e.g. in our book Our Threatened Oceans, p.82.)

Natural Variability

Broecker was not the first to predict CO2-induced warming. In 1965, an expert report to US President Lyndon B. Johnson had warned: “By the year 2000, the increase in carbon dioxide will be close to 25%. This may be sufficient to produce measurable and perhaps marked changes in climate.” And in 1972, a more specific prediction similar to Broecker’s was published by the eminent atmospheric scientist J.S. Sawyer in Nature (for a history in a nutshell, see my newspaper column here).

The innovation of Broecker’s article – apart from introducing the term “global warming” – was in combining estimates of CO2 warming with natural variability. His main thesis was that a natural climatic cooling

has, over the last three decades, more than compensated for the warming effect produced by the CO2 [….] The present natural cooling will, however, bottom out during the next decade or so. Once this happens, the CO2 effect will tend to become a significant factor and by the first decade of the next century we may experience global temperatures warmer than any in the last 1000 years.

The latter turned out to be correct. The idea that the small cooling from the 1940s to 1970s is due to natural variability still cannot be ruled out, although more likely this is a smaller part of the explanation and the cooling is primarily due to the “dust” neglected by Broecker, i.e. due to the rise of anthropogenic aerosol pollution (Taylor and Penner, 1994). However, the way Broecker estimated and even predicted natural variability has not stood the test of time. He used data from the Camp Century ice core in Greenland, arguing that these “may give a picture of the natural fluctuations in global temperature over the last 1000 years”. Ironically, Broecker’s own later work on Atlantic ocean circulation changes showed that Greenland is likely even less representative of global temperature changes than most other places on Earth, it being strongly affected by variability in ocean heat transport (see our recent post on the Younger Dryas, or Broecker’s latest book The Great Ocean Conveyor). However, Broecker was right to conclude that the buildup of CO2 would sooner or later overwhelm such natural climate variations.

Overall, Broecker’s paper (together with that of Sawyer) shows that valid predictions of global warming were published in the 1970s in the top journals Science and Nature, and warming has been proceeding almost exactly as predicted for at least 35 years now. Some important aspects were not understood back then, like the role of greenhouse gases other than CO2, of aerosol particles and of ocean heat storage. That the predictions were almost spot-on involved an element of luck, since the neglected processes do not all affect the result in the same direction but partly cancel. Nevertheless, the basic fact that rising CO2 would cause a “pronounced global warming”, as Broecker put it, was well understood in the 1970s. In a 1979 TV interview, Steve Schneider rightly described this as a consensus amongst experts, with controversy remaining about the exact magnitude and effects.

SCIENCE Volume 189, Pages 460-463.

183 Responses to “Happy 35th birthday, global warming!”

  1. 101
    catman306 says:

    Thanks Chris Ho-Stuart, from your figures I suppose that there could be 2-4 % extra energy available IF this factor has not been included in the models. Of course that energy is carried away with the melt water, but it is concentrated in the channels where the water flows, as it flows. This makes the fissures wider helps to weaken the structure of the ice. I suppose.

  2. 102
    frflyer says:

    There is an absurd article at Forbes, titled “The Death Of The Global Warming Movement” by Shikha Dalmia that could use some informed comments.

  3. 103
    Edward Greisch says:

    102 frflyer: URL please.

  4. 104
    Thomas says:

    Gavin, a secondary question would be how much of the arctic seaice loss is due to black carbon? I would venture it is significantly more than 20%. For two reasons. Soot above a reflective surface absorbs moe than soot over say forest or ocean. And, soot deposited on snow/ice may absorb solar energy for the entire meltseason rather than the week or two it is resident in the atmosphere. My (not modeled) hunch is that BC has a lot to do with the delta between observed seaice loss and modeled loss.

    [Response: That’s possible – but not necessarily obviously true. Some work on this in Shindell’s recent papers, but note that discussions of ‘attribution’ when you have cooling and warming factors together can get a little murky (and aren’t always consistently described). – gavin]

  5. 105
    Chris Ho-Stuart says:

    catman306, there is point on the energy of falling ice OR melting ice which is well worth thinking about. It is different in kind from the energy input from a forcing, such as a greenhouse forcing.

    Adding a fixed amount of a greenhouse gas to the atmosphere, or changing the albedo by painting a roof white or clearing a forest, or coating an ice field with a thin layer of black carbon, is not providing a certain fixed amount of energy. All the “forcings”, by definition, work by modulating in some way the continuous flow of energy between the Sun and the Earth and back out to space again.

    Their effect, therefore, is ongoing.

    Dropping a block of ice, or melting it, takes a fixed amount of energy, which is dissipated once and then is finished with.

    Such considerations, therefore, are fundamentally different from the considerations of forcings upon climate. All they can do is work as a kind of “sink” to soak up (or supply) a bit of energy that delays or speeds up the time to equilibrium; they do not affect the state of equilibrium.

    The largest “sink”, by far, is the thermal heat sink of the ocean. The consequence of a “forcing” is to set up a new energy balance, and the effect of that forcing will be complete once all the ocean has warmed up to reach the new equilibrium. This is often called “warming in the pipeline”.

    Think of it this way. Suppose we have a forcing of 1 W/m^2. (This is what you get from about a 20% increase in CO2 concentrations.) That means additional energy to the surface of 1 W (1 J/sec) for every square meter.

    Now suppose you drop 1 ton of ice a distance of 1 kilometer, above every square meter of Earth’s surface. The energy added to the Earth is 10,000,000 joules on every square meter. That’s a lot… but adding that energy is the same as having that additional forcing for an extra 10,000,000 seconds, or about four months.

    You can thus think of the net effect as reaching equilibrium about four months sooner than otherwise. Which doesn’t actually make a big difference. Melting of ice does represent a much larger heat sink (which soaks up rather than supplies energy) and it is part of the delay in reaching equilibrium… warming in the pipeline. But it still falls behind the energy it takes to heat up the ocean to the new equilibrium state, and this an aspect of the climate system where there is a long way to go to model it accurately. It’s also a major open question for measurement of energy flows going on at present.

    This isn’t a direct answer to your question, but it is an interest aspect of the basic problem you are thinking about!

  6. 106
    Edward Greisch says:

    104 Gavin: Thanks for leading me to
    Where I can download real live Papers!

  7. 107
    Hank Roberts says:

    Another paper for the phenology/disruption file:
    Matches and mismatches: ocean climate, prey phenology and breeding success in a zooplanktivorous seabird

  8. 108
    Brian Dodge says:

    @ catman306 — 30 July 2010 @ 6:27 AM”Does anyone know whether the kinetic energy of a falling or disintegrating glacier or ice sheet is included in the equations for modeling melting ice?”

    “We find that more melting has occurred than can be explained by the release of potential energy from the drainage of surface meltwater during one melt season suggesting that these moulins are persistent for multiple years.”

    6.1 Energy balance equation
    The energy balance equation in the form suitable to calculate ice temperature within a glacier is the advection-diusion equation which in a spatially fixed (Eulerian) reference frame is given by….[equation]…
    The heat production (source term) P can be due to different processes:
    Dissipation In viscous flow the dissipation due to ice deformation (heat release due to internal friction) …[more equations]…
    Sliding friction The heat production is the rate of loss of potential energy as an
    ice column of thickness H moves down slope.

    “Ice-sheet models used to predict future sea-level rise typically do not include the impact of surface meltwater on ice dynamics.”

    I get the impression that this is, as they say, “an active area of research”.

  9. 109
    Harold Pierce Jr says:

    Here is a comment I just posted over at WUWT

    I ask you all this simple question: Since 1900, where have the hundreds of billions of pounds of rubber and asphalt dust gone?

    The short simple answer is: Anywhere and everywhere! Every year the amount of this dust released into the enviroment keeps increasing. Rubber particles do not degrade when exposed sunlight, air or microbes.

    Try this: Take Post-It note and dab it on the dust on the top of your car until it doesn’t stick anymore. Then examine the dirty sticky strip with viewer with about 30x magnificaton. Note the enormous amount of tiny black particles. Also note numerous highly reflective particles which are probaby mica from the rocks in concrete.

    Another source of light-absorbing particles is metallic dust from disk rotors and brake drums as well as the rust that falls off cars and is ground to tiny particles by tires.

    In southern Caifornia the rubber and asphalt dust could act as an accelerant for brush fires. Homeowners there should probably wash off the roofs of their houses before fire season.

    Since most major cities are located on the coasts of the continents, it would be of interest to determine concentration of these black particle in the ocean waters.

    Lastly, we city folks breath in the really tiny particles (5 microns<) of rubber and asplhalt dust, and these probably cause respiratory problems such as asthma in childern. Car tires contain about 40% natural latex to which many people are allergic.

    I googled "tire dust" and found one article that states that about 600,000 mectic tons of rubber dust is released into the enviroment every year in the US.

  10. 110
    pete best says:

    35 years on and although some countries have implemented some measures to mitigate carbon emissions, globally we are increasing emissions before the recent recession hit.

    35 years on and the USA and Europe have achieved nothing in terms of carbon mitigation.

  11. 111
    Geoff Beacon says:

    Harold (109) asks about tyre dust. I wonder about it too. It travels long distances. We had report years ago that in certain conditions it floated across from the continent of Europe to the UK. But what are its properties as a climate forcing agent?

  12. 112
    Daniel J. Andrews says:

    Thanks Chris, I seem to recall something about Arrhenius saying if humans increase CO2 it would be great because we don’t want to go into another ice age. It might have been from Spencers work, but I will have to dig around.

    John…one spot this is mentioned is in Naomi Oreskes’ talk on the denial of global warming. She mentions Arrhenius thought GW would be a good thing.

  13. 113

    #112 Daniel J. Andrews

    Yes, I have read that and heard it in several places. In context, the CO2 output of humans was much smaller then. So if a little CO2 could prevent the next ice age, then that probably didn’t sound to o bad.

    I don’t think anyone in that time period imagined that we would jack up our output to such amazing levels as we have.

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  14. 114
    Lars Rosenberg says:

    #112 Daniel J. Andrews: “…Arrhenius thought GW would be a good thing.”

    Even Bert Bolin, the founding father of the IPCC, thought GW might be a good thing for Scandinavia. At least he said so when I interviewed him in 1990. What scared him was the consequences for Africa and Asia.

  15. 115
    Brian Dodge says:

    Re tire dust

    ” Units of [soot} emission yield a global total of 12.6 TgC/y …” or 12.6 million metric tons”

    “It is estimated that over 600,000,000 passenger cars travel the streets and roads of the world today.
    In the United States alone, 247,421,120 “highway” registered vehicles were counted in 2005, of which 136,568,083 passenger cars. (Bureau of Transportation Statistics U.S. Department of Transportation)”

    600/136=4.4 times the US tire dust for the world as a whole, assuming the same vehicle usage – probably an overestimate, but dust from unpaved roads more common outside the US probably is significant.
    4.4*600k=2.6 million metric tons of tire dust worldwide, or ~20% of the total black carbon soot(partial combustion of fossil and biofuels) emissions. Not dominant in forcing, but certainly significant – maybe we need white tires and roads worldwide for indirect albedo geoengineering? Use white marble dust and silica fume instead of carbon black as rubber fillers, and use a wear layer of limestone + white portland cement on the roads.

    The residence time of dust in the atmosphere is short – the fine sulfates from Pinatubo were gone in a couple of years, and mechanical dusts will have a larger particle size distribution than the sulfate condensates from volcanic eruptions or combustion[1] – since they act as nucleation centers for precipitation, and the larger mechanically produced particles also sink gravitationally.[2]

    [1] “Small particles are products of combustion and from chemical reactions (gas-to-particle conversion) of sulfate, nitrate, ammonium and secondary organics. Coarse particles result from mechanical processes and are composed of dust, sea salt, fly ash, tire wear etc. (Seinfeld and Pandis, 1998). ”
    [2] “Coarse particles emitted by wind action are similarly removed by rainout. In addition they sediment at a significant rate, providing another pathway for removal.”

    “Humanity stands … before a great problem of finding new raw materials and new sources of energy that shall never become exhausted. In the meantime we must not waste what we have, but must leave as much as possible for coming generations.” — Svante Arrhenius
    He not only anticipated global warming, but peak oil(coal/uranium…)!

  16. 116
    catman306 says:

    Thanks again, Chris Ho-Stuart and thanks Brian Dodge. It appears that much more energetic and knowledgeable people than I are on to this ‘extra’ energy.

  17. 117
    sidd says:

    I just finished reading an article by Boyce et al, Nature,v 466, p 591, 2010, estimating a global rate of decline of 1%/yr since 1899 until the present. A news release about the paper is at

    I have two questions:

    1)This is amazing data and of critical importance to Net Primary Production. This means that a large fraction of the CO2 uptake capacity of the oceans has been declining for over a century. Why was this not detected earlier in other studies of carbon balance ?

    2)I reproduce Fig 3b at

    showing the data for the entire period covered, as well as that since 1950. It seems to me that the rate of decline doubled in 50 years. If so, this is of even greater concern.

    Would a marine biologist or anyone else care to comment ?


  18. 118

    #112 & 113:

    From my Hub article on Arrhenius, here’s a quote from his grandson, Gustaf, an oceanographer who enjoyed a distinguished career at Scripps:

    Well, my grandfather rang a bell, indeed, and people became extremely interested in it at that time. There was a great flurry of interest in it, but not because of the menace but because it would be so great. He felt that it would be marvelous to have an improved climate in “the northern climes.” And in addition, the carbon dioxide would stimulate growth of crops—they would grow better. So he was–he and people at the time were–not unhappy about the prospects. They were only sad that in his calculations it would take about 300 years for it to have the marked effect that we now think would happen in something like thirty or forty years.

  19. 119
    NeilT says:

    We have konwn, for a long time, that the relationship between CO2 and a warming climate was known in the 1800’s.

    The issue is not how long it has been recognised in modern science or whether it is “settled science” today.

    The issue is the number of people and businesses who have a vested interest in “Settling” the “Science” 6 feet under, preferrably in an unmarked grave.

    Until that is resolved, then this argument will rage on and on and on.

    As an aside, reading the last dozen or so posts, I wonder if anyone has ever modelled the change over from Asbestos brake materials in motor vehicles? Given the very high levels of asbestos particles in the atmosphere up to the 1990’s and their well knownw insulating properties and reflective capacity.

  20. 120

    #119 NeilT

    Certain parts of the science can be safely called settled science.

    – We are warming
    – Humans are causing the warming trend due to increased GHG/forcing

    you can toss more than a few things in that bucket.

    The unsettled part is regional influence, ocean heat content overturn, intra and inter-decadal influences, time scales, and then a lot more things can be thrown in that bucket.

    So the settled part is we are doing it and its going to get warmer, and that will have more than a few negative impacts on modern infrastructure and therefore the plants, animals and humans that live here.

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  21. 121
    Snapple says:

    Radio Free Liberty has written an article about an unhelpful and highly-publicized Russian conspiracy theory about global warming. RL called the Russian author and got him to back-off his claim that US scientists are using “climate weapons”…”to provoke droughts, erase crops, and induce various anomalous phenomena in certain countries.”

    RL wrote:

    “Asked whether or not Russia was also experimenting with climate-control methods, Areshev said since he was not a member of the government, he did not have information about such projects.”

    Well, he’s not a member of the American government, either.

  22. 122
    llewelly says:

    NeilT 31 July 2010 at 9:23 PM:

    As an aside, reading the last dozen or so posts, I wonder if anyone has ever modelled the change over from Asbestos brake materials in motor vehicles? Given the very high levels of asbestos particles in the atmosphere up to the 1990’s and their well knownw insulating properties and reflective capacity.

    The insulating properties of asbestos are primarily due to air pockets between the fibers. Loose asbestos particles do not have any particular insulating properties. (Their reflective properties are still interesting.)

  23. 123
    Sekerob says:

    sidd said:31 July 2010 at 6:13 PM

    phytoplankton huh, well quite recently there was this finding of the missing megafauna and the mega-poop… each whale good for 2 tonnes of ferro injection annual. Seemingly 300 years ago there were an estimated 94,000 grey whales in the Atlantic… think there is/was one now somewhere in the Med (which is thought to have gotten there by swimming from the Pacific via the Arctic… the Suez is not probable, nor rounding the Cape.

  24. 124
    Greg Laden says:

    The “Carbon dioxide problem” was the subject of an internal white house memo in 1969, reproduced here:

  25. 125
    David B. Benson says:

    Somewhat off topic.

    Issue#16 (Special Issue 2010) of SciDAC Review (Scientifc Discovery thorugh Advanced Computing) is all about the roadmap to exacale computing, 10^18 operations/second. I found all the articles of interest; one is about climate modeling.

    Read online @
    or request cuurent or back issues from
    scidacreview AT

    [I see reCAPTCHA is back and doesn’t agree, entoning “plebeian abstraction”.]

  26. 126
    Hank Roberts says:

    ‘sidd’ writes above

    > This means that a large fraction of the CO2 uptake capacity
    > of the oceans has been declining for over a century.

    Maybe so, seems likely, but what’s your source on this belief?
    Do you know which species are changing? phytoplankton? zooplankton?

    > Why was this not detected earlier in other studies of carbon balance ?
    What “this” do you think was not detected earlier?

    “This” decline in plankton counts worldwide? Data collected for other reasons are collected in this study. Why not earlier? Lack of funding?

    “This” change in the CO2 sink in the oceans? Why do you believe it wasn’t detected? Have you looked, or are you just assuming nobody detected a change? How would you find this out?

    One example of what you can find by looking–just a place to start, with links:
    Saturation of the Southern Ocean CO2 Sink Due to Recent Climate Change Corinne Le Quéré, et al. Science 316, 1735 (2007);
    DOI: 10.1126/science.1136188

  27. 127
    Hank Roberts says:

    More for Sidd (found by clicking the ‘related content’ and ‘articles by’ links provided at the 2007 paper):

    Trends in the land and ocean carbon uptake

    “… Relatively little attention had been given to the quantification of the trends in CO2 emissions and sinks until after the publication of the fourth assessment of the Intergovernmental Panel on Climate Change (IPCC-2007). At the close of IPCC-2007, many questions remained open, particularly regarding the response of the CO2 sinks to elevated CO2 and climate change [8]. This paper reviews the recent publications that analyse evidence of recent trends in the CO2 sinks published since IPCC-2007. It discusses the available evidence and the various interpretations of the underlying drivers, and recommends ways to improve our knowledge and understanding….


    It is only recently that sufficient observations exist to constrain the trends in various components of the global carbon cycle. The detection of trends is thus necessarily controversial, because we are at the detection limit of the information. Another decade of observations will certainly help clarify the significance and causes of the observed trends, but time can be gained by improving synergies between models and observations. Improved constraints on the CO2 sinks would put us in a far better position to project the expected changes this century, to assess the potential for large and/or abrupt changes in biogeochemical cycles with consequences for future climate, and possibly to even provide independent information to constrain the reported emissions of CO2 at the level of large regions [47]. Such information is important to sustain climate policies and monitor their implementation.

    To produce information relevant to climate policies however, there is an urgent need to reduce uncertainties in recent trends and to improve confidence in their attribution and in future projections. Progress can be made immediately on three fronts ….”

    Remember that when you see a flood of statements trying to convince you that “we don’t know, we can’t know”* — from people arguing that more science can’t help reduce uncertainty. Wrong; plenty of ways known to improve what we know.

  28. 128
    sidd says:

    Mr. Roberts wrote on the 1st of August, 2010 at 2:45 PM:

    “Do you know which species are changing?”

    I realize my earlier message was unclear, and I apologize. The paper estimates phytoplankton counts, specifically total chlorophyll pigment concentration as a proxy for phytoplankton biomass.

    “What “this” do you think was not detected earlier? ”

    The decline in CO2 uptake caused by a decline of 1%/yr in over the course of a century. The paper states that the current global median chrolohyll concentration is 0.56mg/m^3

    I am no competent to translate a chlorophyll concentration into a carbon uptake number, perhaps someone reading can assist.


  29. 129

    The link attached to the following phrase appears to be broken. Please fix!
    “Are we on the brink of a pronounced global warming?”

  30. 130
    sidd says:

    To amplify my last comment:

    The first sentence of the Boyce paper states that one half of primary production is phytoplankton. This is after 1%/yr decline for a hundred years, which means a hundred years ago, more than 1/(1-0.01)^100 = 2.7 times current primary production was phytoplankton. How can this be, unless a large carbon sink has appeared over that last century, and if so, where is it ?

    or is my math horribly wrong ?


  31. 131
    sidd says:

    and to correct that last one : my math was wrong, the calculation ought to be
    0.5/(1-0.01)^100 = 1.4 time current primary production by phytoplankton a century ago.

    but my question still stands, what is the new carbon sink that has appeared over the last century ?


  32. 132
    reddog says:

    This is a fascinating thread. The historical context illustrates an important point that is not made often enough. The deniers often refuse to give AGW credence because they say it is all based on questionable temperature data. However, the science is really based on physics. The temperature data simply confirms the physics and allows us to more accurately quantify the effect.

  33. 133
    Thomas says:

    I’m not at all sure that oceanic carbon sequestration correlates with phytoplankton levels. Sequestration will be the excess carbon taken up after decay and loss of CO2 to the atmosphere is taken into account. The same suppression of convection that causes the loss of nutrients might allow the organic carbon (dead animal/plant life and poop) to sink to the bottom. So it is possible that oceanic carbon sequestration could go either way as a result of a phytoplantion collapse. Some people think a phyto collapse means the end of Oxygen, or a deadly climate/CO2 feedback. I don’t think those effects are nearly strong enough. But, a serious reduction in the biological productivity of the sea would be a big deal.

  34. 134
    sidd says:

    Mr. Thomas wrote on the 1st of August, 2010 at 8:35 PM:

    “The same suppression of convection that causes the loss of nutrients might allow the organic carbon (dead animal/plant life and poop) to sink to the bottom”

    So the new carbon sink is the unimpeded flow of organic carbon to the abyssal silt. Can we put some numbers on this ?


  35. 135
    Dappled Water says:

    Sidd @131 – “but my question still stands, what is the new carbon sink that has appeared over the last century ?”

    Perhaps there isn’t one?. I take it you’re assuming a corresponding decrease in the oceans uptake of atmospheric CO2 to match that of the decline in phytoplankton abundance. Not sure that that such a simple relationship exists, as some earlier coupled climate model runs, which include carbon cycle feedbacks, predicted only minor changes to the oceanic carbon sink.

    “In our experiment, increased thermal stratification due to warming of the sea surface suppresses upwelling, which reduces nutrient availability and lowers primary production by about 5%. However, ocean-only tests suggest a small effect of climate change on oceanic carbon uptake, as this reduction in the biological pump is compensated by reduced upwelling of deep waters which have high concentrations of total carbon.”

    Pretty much what Thomas has pointed out @133.

  36. 136
    Joe Earth says:

    My memory of studying science in the 1970s was that the focus was on the environmental effects of the dropping of an atomic bomb(s). (Remember the “nuclear winter”.)

    Remember, we are talking about the Cold War Period.

    While we learned about the greenhouse effect on Venus and we started to worry about aerosols affecting the Earth’s ozone layer, carbon emissions on Earth just weren’t a priority.

  37. 137
    Ray Ladbury says:

    To assume that phytoplankton are the only sink for CO2 seems rather bizarre to me. As the oceans become less hospitable to phytoplankton, those niches will open to other species–probably species which don’t benefit us by producing oxygen.

    What is more, much of the ocean carbon sink is explainable in terms of simple physical chemistry.

  38. 138
    Nagraj Adve says:

    Professor Stefan,
    Re step 3 (predicting the temperature response), in a paper in PNAS, Ramanathan and Feng suggested that the warming we are already committed to is 2.4 deg C, and that this is being masked chiefly by aerosols and to a
    lesser degree delayed by ocean thermal inertia. Their argument is that
    once societies clean up their act, a good part of this warming will
    kick in. And that it is unavoidable. (V.Ramanathan and Y. Feng, ‘On Avoiding Dangerous Anthropogenic Interference with the Climate System: Formidable Challenges Ahead’, PNAS, vol. 105, no. 38, pp. 14245-50).

    Prof James Hansen, and doubtless others, have made the point that data for the last 7,00,000 years shows that a forcing of 1W/m2 yields a temperature increase of 0.75 C. Now, IPCC AR4 suggests a GHG forcing so far of roughly 3 W/m2 since the Indus Rev (the large negative aerosol forcing takes it much lower), hence it would yield a committed warming of over 2 deg C (even assuming dangerous warming is 2 deg C, likely lower).

    So does that suggest a larger temperature increase from emissions already made than is commonly understood?

    Nagraj Adve

  39. 139
    Hank Roberts says:

    sidd, if there’s an expert reading here who works in the field of ocean plankton and climate, perhaps we can tempt that person to speak up. So far it’s all just us readers here poking at a huge new field of research.

    You need to distinguish
    — CO2 going into solution in seawater (mixing into the upper layer depending on temperature and wind/wave mixing, then mixing into deeper water over time, changing the pH as it does)
    — CO2 available in the photic zone that is used for photosynthesis
    (for a start into the paleo work, try:
    Global change: Plankton cooled a greenhouse
    Birger Schmitz
    “Scientists who can perform laboratory experiments are lucky — a megalomaniac climatologist can only dream of putting an Earth-like planet in a giant test tube, pumping billions of tonnes of CO2 into its atmosphere, and registering the effects on life and climate. Fortunately, there are other approaches….”

    — what happens to that ‘primary production’ of carbon compounds?

    More CO2 in the air; more CO2 going into the oceans far faster than in paleo events, too fast for the biological recycling found in the paleo record. So ocean pH changes far faster than in the paleo record. So the biology changes under new pressures.

    Want a funny irony? People in the US are urged to eat more of the ocean fish (salmon/sardines/anchovies) for omega-3 fats, otherwise scarce in the US diet (removed from processed food to extend shelf life). (Aside: see . Be warned, nutrition science has vested interests, this is a hot topic; the ‘blog science’ about nutrition gets wackaloonier even than climate blogs).

    That form comes mostly from primary production in the ocean (plankton float, so don’t invest energy making roots, stems and seeds with the stiffer omega-6 form we get too much of, eating land plants).

    The food produced by the plankton is changing. Look up “junk food” +seabirds for some of the work. It’s new science, the work is scattered, and there’s plenty to read. One example:

    “These diving seabirds were having a terrible breeding season in the United Kingdom, and some colonies hatched no chicks at all. But Wanless could see that parent birds were catching as many fish as ever, if not more. “We couldn’t work out what was going wrong,” she said. The light dawned when she and her colleagues measured the fat and protein in the fish being caught, mostly sprat, a member of the herring family. Compared with previous years, the amount of energy a hungry guillemot received from a 10-centimeter sprat plunged in 2004, dropping from 55 kilojoules to 12 kilojoules. “They were largely water,” Wanless says.
    Wanless concludes that the guillemots (Uria aalge) were suffering from a diet of what some ecologists have called marine “junk food.” They hypothesize that in some cases, marine predators’ prey is being replaced by less nutritious species ….
    … This summer, the U.K.’s Royal Society for the Protection of Birds reported that “virtually no” chicks fledged from some kittiwake and tern colonies. The main cause is thought to be changes to fish populations due to fishing and the effects of global warming on fishes’ planktonic food species, because the North Sea is now 1.5°C warmer than it was 40 years ago. The warming has resulted in a 70% drop in the populations of a tiny crustacean called Calanus finmarchicus, thought to be the main food of sprat and sand eels, as well as a rise in the numbers of a warm-water relative, C. helgolandicus, which contains much less fat and so is junk food for the fish….

  40. 140

    Are there any essays planned about the recent collapse of climate change legislation in the US congress?

    [Response: Not a scientific issue, and so not something we can usefully comment on. Try for that kind of thing. – gavin]

  41. 141
    CM says:

    Another blast from the past: The post sent me back to some dusty bookshelves for an old popular science work, a 1964 translation of a 1962 Time-LIFE book by Arthur Beiser, The Earth. (Perhaps some other reader has the English original? Google Books displays a snippet with the relevant quote on p. 163, but gives the date as 1980, so it may be a later edition.)

    Beiser noted that humanity may be able to influence climate and glaciations. Growth in industrial activity, as well as deforestation, had led to huge CO2 emissions. Half of the emitted CO2 had been quickly removed by various chemical processes, while the rest remained in the atmosphere, raising its CO2 content by 13%. CO2 prevented long-wave heat radiation from the earth from escaping, and therefore, this change in the composition of the air had led to a mean temperature rise of perhaps 0.5ºC. The CO2 concentration was set to grow over the coming centuries, leading to a gradual increase of the earth’s mean temperature.

    Beiser at the time had his doubts about Wegener’s continental drift theory, but seems to have taken anthropogenic global warming as pretty much cut and dried.

  42. 142
    pete best says:

    Re #50; Why yes the deniers have many listeners, its only human nature to decry its scientific merit.

    Another excellent article – I doubt in fact the libertarians actualy mean it in any meaningful way, they just have a dark idelology so to speak.

  43. 143

    Happy Birthday to AGW awareness. To bad people are still so unaware & that unawareness seems to be getting stronger and more vicious, as the proof in the pudding gets stronger and stronger, and great sites like RC debunk the falsehoods as fast as they come out. Thanks, RC!

    Can anyone give my a good and short response to this article which a blogger, who claims he’s a Harvard educated scientist, says disproves AGW —

    (At least it is not denying the natural greenhouse effect.)

  44. 144
    Silk says:

    Lynn – See comment on that thread by Posted by: findor
    Feb 23, 10:37 PM

  45. 145
    Doug Bostrom says:

    Lynn Vincentnathan says: 2 August 2010 at 3:40 PM

    Can anyone give my a good and short response to this article…

    Yet another “smoking gun” (gub?).

    Skeptical Science did a piece on Thompson’s article. Thompson (the author of the article in question) weighed in to defend his piece, eventually ended up modifying the article in response to the dialog there. Science of Doom also did a treatment.

  46. 146
    Thomas says:

    Sidd @134. I’m not an expert, and so I won’t attempt to do more than throw out ideas. I’ll await the real experts. Thats why I come to RC.
    I suggest we wait for a RC post on the phytoplanton issue. Seems like if confirmed it should be of great concern.

  47. 147

    Medvedev, 30 July: “What’s happening with the planet’s climate right now needs to be a wake-up call to all of us, meaning all heads of state, all heads of social organizations, in order to take a more energetic approach to countering the global changes to the climate”

  48. 148
    Edward Greisch says:

    I’m not using my real name on, but more good comments are needed there on a continuing basis.

  49. 149
    Doug Bostrom says:

    Speaking of Science of Doom it’s a prime candidate for the blog roll here.

    Oracular captcha: phenomenal plank.

  50. 150

    #118 Kevin McKinney

    Thanks for that. It does give good perspective that global warming was really recognized at that time as human related and from that perspective, not a bad thing. As I pointed out before, the emission rates were so much lower, I don’t think they could imagine the burn rates of today.

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