Stern report 2: the ABC

Stern report, comment 2 in a series: a capsule of the consensus about where we stand today.

Chapter 1 reviews the basic science. If you have as short attention span as some we won’t name, you can squash it into three of Stern’s graphs.

A. The earth is warming up fast.

Chart page 5, sorry for the poor quality:

Stern 1.3.jpg

The hockey stick is an irrelevance. What does it matter if it was as hot in 1206 as now? We know that 1206 and 2006 both offered liveable climates, unless you live in New Orleans. But they weren’t doing anything much in 1206 that could change their global environment for the worse, and we are.

B. Why? Greenhouse gases.

Chart page 4:


“The rising levels of greenhouse gases provide the only plausible explanation for the

observed trend for at least the past 50 years …. The causal link between greenhouse gases concentrations and global temperatures is well established, founded on principles established by scientists in the nineteenth century.” (Stern p.6)

C. There’s a smoking chimney: fossil fuels.

Chart p. 175:

Stern 7.1.jpg

Fossil fuels accounted for over 60% of the greenhouse gas emissions in 2000 (p.171). The growth rates in emissions from deforestation and other land use changes were roughly parallel to those in fossil fuels back to 1950, when the data for the former give out.

So much is common ground. Even George Bush accepted the reality of anthropogenic climate change in his Rose Garden speech in June 2001.

What I found most interesting in this part of the Stern report was its discussion on the origin of the science (Wikipedia links added):

Current understanding of the greenhouse effect has its roots in the simple calculations laid out in the nineteenth century by scientists such as Fourier, Tyndall and Arrhenius. Fourier realised in the 1820s that the atmosphere was more permeable to incoming solar radiation than outgoing infrared radiation and therefore trapped heat. Thirty years later, Tyndall identified the types of molecules (known as greenhouse gases), chiefly carbon dioxide and water vapour, which create the heat-trapping effect. Arrhenius took this a step further showing that doubling the concentration of carbon dioxide in the atmosphere would lead to significant changes in surface temperatures.

This underlying physics is rock-solid, unexciting stuff. (You can check out some of it yourself. I’ve built a toy model that does this, too childish for posting here, so it’s tucked away here on my personal website). It doesn’t fit the Romantic, Promethean story revived by Thomas Kuhn, of lonely geniuses struggling to overthrow an inferior paradigm embedded in a consensus conventional wisdom. There’s no equivalent here to phlogiston, the ether, heliocentrism, or special creation of species, strong explanatory accounts with wide support. It’s much more like the Baconian story of electricity: first there wasn’t any science, then Ampère, Faraday, Ohm etc. made some observations, and after a bit of to-ing and fro-ing knocked it into a perfectly sound theory. New bits are being added all the time, but there’s no fundamental debate as with cosmology or sociobiology.

There’s something else.

Climate models use the laws of nature to simulate the radiative balance and flows of energy and materials. These models are vastly different from those generally used in economic analyses, which rely predominantly on curve fitting. (Stern p.8)

Social scientists are used to models where the underlying theory is almost completely qualitative, as with microeconomics, and at best gives you the direction of a causal link. To build a quantitative model, you have to tweak the model parameters till they fit the data. There’s no deep reason why the elasticities in an economic model should be what they are. The basic laws in climate models, physical or chemical, are quantitative. Potentially, climate models can be far superior to economic ones, and Stern claims they already are. They are certainly much bigger. I’m one of 60,000 volunteering my PC to a distributed climate simulation; my run will be 1850 hours of CPU time when it’s finished, and that’s just one run of one component of one model.

Sceptics can’t challenge the basic science, as it’s secure textbook stuff. But since the interactions are numerous, a climate model gets forbiddingly complex and pushes against the frontiers of computability. The uncertainties arise in the way the models are put together.

In the next post I’ll have a look at the controversial science: predictions, sensitivities, and should we give the surviving sceptics air time?

If you found this too elementary, join the discussion at instead. I don’t propose to compete with climate scientists.

Author: James Wimberley

James Wimberley (b. 1946, an Englishman raised in the Channel Islands. three adult children) is a former career international bureaucrat with the Council of Europe in Strasbourg. His main achievements there were the Lisbon Convention on recognition of qualifications and the Kosovo law on school education. He retired in 2006 to a little white house in Andalucia, His first wife Patricia Morris died in 2009 after a long illness. He remarried in 2011. to the former Brazilian TV actress Lu Mendonça. The cat overlords are now three. I suppose I've been invited to join real scholars on the list because my skills, acquired in a decade of technical assistance work in eastern Europe, include being able to ask faux-naïf questions like the exotic Persians and Chinese of eighteenth-century philosophical fiction. So I'm quite comfortable in the role of country-cousin blogger with a European perspective. The other specialised skill I learnt was making toasts with a moral in the course of drunken Caucasian banquets. I'm open to expenses-paid offers to retell Noah the great Armenian and Columbus, the orange, and university reform in Georgia. James Wimberley's occasional publications on the web

13 thoughts on “Stern report 2: the ABC”

  1. "The hockey stick is an irrelevance. What does it matter if it was as hot in 1206 as now? We know that 1206 and 2006 both offered liveable climates, unless you live in New Orleans. But they weren't doing anything much in 1206 that could change their global environment for the worse, and we are."
    It's very relevant. If it was as hot in 1206 as it is now, then it is clear that what we are doing now is not necessary for it to be so hot. That is, it is quite possible that it would still be just about as hot today even if there were no greenhouse gases. It undermines the correlation between emissions and warming.

  2. If you look near 1800 you see a sharp spike in near-surface temperature, this to me, as apparently in 1206, is an irrelevance as stated above. The Earth's climate varies and but seemingly around an equilibrium point at their relative zero.
    What concerns me most is if you look closely at the first graph you see a hot-cold oscillation running +/- until just around 1920. Continue on through time you see the oscillation continues on and damps out beyond 1980. Is there more data going back beyond 1850? Does the author state that the data pre-1850 looks like the data from 1850-1920?

  3. It is great to have over 150 years of data regarding surface temps, but I am still not sold on global warming being caused by man.
    Archeological studies have shown that the earth has gone through global warming cycles several times.

  4. If I recall right(I am only 38), many scientific articles were written during the 70's and early 80's about the earth cooling and heading towards an ice age.

  5. Here is the latest release "Not in our media of course" from NASA.;
    Ice Caps Growing not shrinking.
    Antarctic Sea Ice Increases over Past Two Decades By Staff 22
    August 2002 In a surprising departure from other findings that point to a
    warming planet, a NASA researcher has found that the amount of ice in the
    Antarctic increased from 1979 to 1999, as measured by satellites. Many recent
    findings have detailed the decline of the ice cap in the Arctic, at the top
    of the world. These new results from the Southern Hemisphere imply that
    global climate change involves regional variations. Changes in ice cover are
    important not only because they indicate temperature changes that have
    occurred; the changes can effect future temperatures. With more ice, more
    solar radiation is reflected away from Earth. The ice also insulates oceans
    from the atmosphere. Less ice has the opposite effects. In the new study,
    published in the Annals of Glaciology, Claire Parkinson of NASA"s Goddard
    Space Flight Center analyzed the length of the sea ice season throughout the
    Southern Ocean to obtain trends in sea ice coverage. On average, the area
    where sea ice seasons have lengthened by at least one day per year is roughly
    twice as large as the area where sea ice seasons have shortened by at least
    one day per year. "You can see with this dataset that what is happening in
    the Antarctic is not what would be expected from a straightforward global
    warming scenario, but a much more complicated set of events," Parkinson said.
    The length of the sea ice season in any particular region or area refers to
    the number of days per year when at least 15 percent of that area is covered
    by sea ice. Some areas close to the Antarctic continent have sea ice all year
    long, but a much larger region of the Southern Ocean has sea ice for a
    smaller portion of the year, and in those regions the length of the sea ice
    season can vary significantly from one year to another. Parkinson also looked
    at how various regions of the Antarctic compared to one another. Regionally,
    the Ross Sea, on average, had its sea ice seasons getting longer, while most
    of the Amundsen Sea and almost the entire Bellingshausen Sea had their sea
    ice seasons getting shorter. "The Antarctic sea ice changes match up well
    with regional temperature changes," Parkinson said. The study used data from
    NASA"s Nimbus 7 Scanning Multichannel Microwave Radiometer (SMMR) and the
    Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave
    Imagers (SSMIs).

  6. Ty
    PS you should be aware that we *will* move into a cooling cycle.
    This was documented by Milenkovich (sp?), and stems from the earth's peturbations in orbit around the sun. He documented this in the 1930s, but published in Serbo-Croat, so his work has only been appreciated since about 1980.
    However there is no evidence that this will occur in the next several thousand years, and certainly not in the next couple of centuries. The 'little Ice Age' of the late medieval period was tiny by comparison.
    Whereas our massive, uncontrolled, one way experiment in doubling or tripling global CO2 concentrations has been running since about 1750, and will be fully played out by 2150 (by which time most of the world's accessible carbon fuel will be burnt up).
    Of course, if we were faced with an ice age, sometime in the future, we would have burned through our ready supplies of CO2 increasing substances (oil, gas and coal). Which would leave us high and dry if that were to occur. Double irony.

  7. I know this issue is always up for debate and each argument supported by it's own scientist. I feel the best way to satisfy all is to have leadership in this country that will stand up and make a Kennedyesque pledge to be off off of fossil fuels in ten years and turn to more environment friendlier energy.
    Holistically, everyone wins from the environment to geo-political issues.

  8. Ty
    Blair has gone for a declaration we will emit 60% less carbon in 2050 than we do now.
    But even that is, so far, empty rhetoric, not matched with real policy.
    Carbon Free for the US in 10 years is completely impossible without economic collapse.
    With new technology, and a lot of hard work, mostly carbon free is possible by 2050.
    What the US needs is a JFK like figure, or better an FDR like figure, who says that the US will emit only 30% of the carbon, in 2050, it does now, and pledges whatever sacrifices are necessary to make that so.
    The problem is, that 70%, which is *possible* under current technology, may not be enough.
    But still, what you need, and we need, is a Churchill. Who says simply:
    I say to the House as I said to ministers who have joined this government, I have nothing to offer but blood, toil, tears, and sweat. We have before us an ordeal of the most grievous kind. We have before us many, many months of struggle and suffering.
    You ask, what is our aim? I can answer in one word. It is victory. Victory at all costs – Victory in spite of all terrors – Victory, however long and hard the road may be, for without victory there is no survival.
    I take up my task in buoyancy and hope. I feel sure that our cause will not be suffered to fail among men. I feel entitled at this juncture, at this time, to claim the aid of all and to say, "Come then, let us go forward together with our united strength."
    We are not yet to the crisis that will create an opportunity for such a man, nor does such a man or woman yet appear on the political radar screen. John McCain has the gumption, apparently, but I don't know that he has the political will to go against his own party like that.
    I am reminded that people thought little of FDR as an intellect or politician, at least before the Great Depression, and even less of Harry S. Truman. John Kennedy was seen as a young and unimpressive senator.

  9. The hockey stick is relevant because the graphs show that it is now warmer than it was in 1206. The graphs indicated that it is warmer now than during the last millenium by about .5 degrees Celsius, and that the increase in temperature pretty much correlates to the increase in CO2 in the atmosphere over the same time period.

  10. Curbing of Global Warming?
    "The researchers, who reported their findings in the Nov. 2 online edition of the journal Science, suggest the study could point toward new ways to curb global warming."
    Plankton's Influence on Clouds
    Phytoplankton, microscopic plants that live in the ocean in vast quantities, may play a role in cloud formation, which in turn may have an effect on how much sunlight reaches and warms Earth's surface, a surprising study has found.
    Researchers from the Georgia Institute of Technology and North Carolina State University discovered the link between clouds and the biosphere as they were examining increases in cloud cover over part of the Southern Ocean that encircles Antarctica. Using satellite observations, they found that the increased cloudiness coincided with a large phytoplankton bloom.
    The scientists theorize that oxidation of the chemical isoprene, which phytoplankton emit, produced airborne particles that helped double concentrations of cloud droplets in the region.
    The team calculated that the increased cloudiness reduced the absorption of sunlight by the same amount that has been observed in the more polluted areas of Earth. The researchers, who reported their findings in the Nov. 2 online edition of the journal Science, suggest the study could point toward new ways to curb global warming.
    "Studies like this one may help reshape the way we think about how the biosphere interacts with clouds and climate," said Georgia Tech assistant professor Athanasios Nenes, who co-authored the paper. "We can now see very strongly the influence of marine biology on oceanic clouds."
    — Juliet Eilperin (Washington Post 11-13-06 page A12)

  11. Ty
    If it does work like that, then why has the world temperature been moving up, in line with increased CO2 concentrations?

  12. I do not think the reports posted need to be automatically dismissed because they do not feed the narrow parameter of "increased CO2 = increased temperatures"
    All data should be considered holistically. Do I believe that man is contributor to increased temperatures? Yes, but not the single contributor. One has to consider history, cycles, and planetary placement within our solar system and galaxy as it moves through space.
    The earth is a very dynamic, multi-variabled planet. If we knew precisely how the planet worked, we would be able to duplicate it in a biosphere. To date, I am unaware that this has been done successfully.

  13. Ty at November 15, 2006 06:40 AM
    I do not think the reports posted need to be automatically dismissed because they do not feed the narrow parameter of "increased CO2 = increased temperatures"
    Increased levels of atmospheric CO2 does indeed correlate to increases in temperature. Increases in temperature also leads to increase levels of atmospheric water vapor, which is also a greenhouse gas. Increased levels of atmospheric CO2 can also lead to increased levels of plant life, of which phytoplankton is only one. If increased levels of phytoplankton does, indeed, lead to increases in cloud formation, that may lead to a decrease in a projected increase in temperature, but it does not negate the increase. If it did, it would have shown up in the temperature graphs.

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