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Saturday, July 31, 2010

Conceptual Musings on CO2


Conceptual Musings on CO2

At first sight it seems that increases in CO2 lead to increases in temperature by trapping infrared radiation. And the higher temperature will lead to more water vapor, which will lead to higher temperatures and so on. If this were the whole story, any increase in CO2 would inevitably lead to a runaway greenhouse effect. If that were to happen the temperature of the Earth would be measured in the hundreds of degrees Celsius (as in Venus) and life would have long disappeared from the planet. But surely there have been fluctuations in the level of CO2. Indeed, it seems that in the past the level of CO2 has been much higher than it is now: 10 to 30 times higher in some eras, and also a bit lower than it is now (two thirds of today’s level during the last ice age).[1] Thus we should expect the Earth to be lifeless by now. But of course it is not.

We know, therefore, that the Earth itself must have mechanisms that regulate the level of CO2 and its effect on temperature. It is clear, then, that to understand the significance of the increase of CO2 we first need to understand those mechanisms.

Three mechanisms are particularly influential in the regulation of carbon and thus of temperature: plate tectonics, stone weathering, and terrestrial life.

Let us begin with life. As CO2 increases, plants and bacteria that thrive on it will displace others that do not. But as these life forms become very successful and proliferate, there will be more of them to remove CO2 from the atmosphere, and thus the temperature will begin to go down.[2]

It used to be thought that plants were by far the main biological sink of CO2 in the planet, even though as Lynn Margulis and James Lovelock argued many years ago, bacteria have a much greater influence on the composition of the atmosphere than plants do.[3] This particular controversy has been pretty much settled by the launching in 1997 of a satellite capable of keeping a close watch on the world’s populations of phytoplankton (Sea Wide Field Sensor). Whereas plankton remove as much as 45 billion to 50 billion metric tons of inorganic carbon, plants handled about 52 billion metric tons.[4] We should see this pattern repeated time and again: Firm knowledge about problems of the global climate seems more likely when we can investigate them with space science and technology.

Plants, however, contribute to the removal of CO2 not merely by photosynthesis, but also as part of the so-called “silicate-carbonate geochemical cycle,” which works by taking the calcium living beings produce and combining it with carbonic acid to make limestone. As astrobiologists Peter D. Ward and Donald Brownlee explain

Here we have a wonderful partnership. Animals such as coral are harnessing calcium. The roots of plants exude an acid that helps to break down rocks, accelerating weathering by the wind and rain generated by the atmosphere and oceans, creating the [carbonic] acid necessary to convert the calcium to limestone. All combined are working together to take excess carbon dioxide out of the atmosphere and bury it in “reservoirs” of rock within the Earth, and thus balance temperature.[5]

To understand the regulation of CO2 we also need to determine the ways in which CO2 is put back into the atmosphere. The oxygen produced by the organisms that remove CO2 is itself taken up by other organisms, which end up producing more CO2 as waste. Plankton stores carbon in the ocean, but much of that carbon is returned to the surface via upwelling and ocean currents in a few hundred years at the most.[6] Most of those carbonates that fall to the bottom of the ocean become part of the crust, and because of the spreading of the ocean floors, through plate tectonics, they are eventually pressed onto continental shells as plates collide (in subduction zones) and finally find their way into volcanic eruptions as CO2 again. Of course there is a long lag in this geologic cycle, perhaps in the millions of years.

Let us continue, then, with the scenario in which the planet begins to cool. As more water freezes in the polar caps, the level of the oceans drops, and more land is exposed to the wind and the rain. Phosphates and calcium in great abundance come to the oceans. The phosphates feed the plankton, which will then make more carbonates from atmospheric CO2. As a result, the temperature will decline even more (a case of positive feedback). Will the Earth finally become like Europa, the Jovian satellite, a beautiful ball of ice?

No (but see below). As the ocean surface is reduced, the ability of the planet to support plankton is also reduced. A saturation point is eventually reached, and the temperature becomes stable. After a long time the combination of plate tectonics and volcanism will begin to increase the level of CO2 and the temperature will begin to rise again (although big volcanic eruptions put up large amounts of dust that initially may cool the planet more instead).

It would be a terrible mistake to conclude from these speculations that the planet's mechanisms are bound to take care of any and all environmental consequences of burning fossil fuels. As a first approximation we might say that all such mechanisms working together have served as if the Earth had a thermostat. But all the mechanisms guided by thermostats operate successfully only within limits. On a very hot summer day, the air conditioner may be stretched beyond its specifications and be unable to bring the temperature down anywhere near the thermostat setting. Likewise, if the energy that we receive from the sun were to increase continuously, as it presumably will – up to the apocalyptic end in a few billion years when the sun will become a red giant – the feedback mechanisms of the planet will moderate the temperature somewhat, but the heat from the sun will eventually overwhelm, and finally scorch into oblivion all: life, oceans, and air.

Short of that calamity, many changes in the environment can be disastrous enough. At first sight, however, we find reason for optimism in the work of some observers. In presenting his famous Gaia hypothesis, J. Lovelock has compared the totality of Earth's life, the biota, to a super-organism with a fierce instinct for self-preservation. As his “Gaia” metaphor is pressed to explain the natural history of our planet, it does become clear that life has always managed to adapt to profound changes in the environment. It also becomes clear that the biota is a very effective mechanism in the regulation of that environment.

Indeed, if a spaceship were exploring our solar system, it might be able to determine from a long distance that life was plentiful on Earth. The reason is that our atmosphere is not chemically stable. For example, oxygen forms 21% of the volume of the atmosphere. From a purely chemical point of view this high percentage is very surprising, for oxygen is a very reactive element (it combines easily to form compounds); thus it should be swept up in a rather short time. Life, however, replenishes the free molecular oxygen that is lost to chemical reactions. And given the large amount of oxygen, the percentage of other gases would be impossible except for the action of life. Methane, for instance, is 1029 times more abundant than it ought to be. According to Lovelock and Margulis, nitrogen is one billion times and nitrous oxide ten trillion times more abundant than they would be, given chemistry alone.[7]

Since nitrogen makes up nearly 75% of the atmosphere, the impact of life on the composition of the atmosphere cannot be underestimated. Although nitrogen would not be detectable in the Earth’s spectrum, the exploring spaceship might still be able to determine the existence of life on Earth, long before arriving, from the extremely high concentrations of trace gases such as methane and nitrous oxide.[viii]

The converse is also true. By spectral analysis, Lovelock determined in the early sixties that life on Mars would be very unlikely. His determination was confirmed when the two Viking spacecraft landed in 1975 and found that the chemistry in the Martian soil could not support life. Lovelock had played the role of the visiting spaceship scientist and drew the appropriate conclusions from the fact that Mars' atmosphere is in chemical equilibrium.[ix] As we will see later, however, our enthusiasm for this approach should be tempered by the realization that the atmosphere of Venus is not quite in equilibrium, even though Venus is lifeless.[x]

[1]. For an account see H.D. Holland, B. Lazar, and M. McCaffrey, "Evolution of the Atmosphere and Oceans," in Nature. Vol. 320, March 6, 1986. p. 33. For variations in CO2 levels throughout the history of the planet see E.T. Sundquist and W.S. Broecker, The Carbon Cycle and Atmospheric CO2: Natural Variations Archean to Present. American Geophysical Union, Washington, D.C. 1985.

[2]. The importance of life to the climate has been particularly emphasized by J. Lovelock and L. Margulis. See their "Atmospheres and Evolution," in J. Billingham, (ed.), Life in the Universe, MIT Press, 1981, pp 79-100. See also their "Atmospheric Homoestasis by and for the Biosphere: The Gaia Hypothesis," Tellus 26:2, 1973. Most of the scenarios described in the pages below are offered merely to illustrate the many factors that may play a role in the behavior of the climate. They should not be ascribed to any one particular investigator.

[3]. Lovelock and Margulis. Op.cit.

[4] P.G. Falkowski, “The Ocean’s invisible forest,” Scientific American, Vol. 287, No. 2, August 2002, pp. 56-57.

[5] Peter D. Ward and Donald Brownlee, The Life and Death of Planet Earth, Times Books, 2002, p. 61.

[6] Ibid., p. 57.

[7]. Lovelock and Margulis, "Atmospheres and Evolution." Op.cit. p.81.

[viii]. This is a recurring theme in Lovelock's work. See his article in Nature, London, No. 207, p.568.

[ix]. See Lovelock's analysis of J. and P. Connes (J. Opt. Soc. Am., 1966, No.9, p. 896) in Lovelock and A.J. Watson, "The Regulation of Carbon Dioxide and Climate: Gaia or Geochemistry," Planetary and Space Science, vol. 30, no. 8, p 795.

[x] Although the Viking controversy is not entirely settled, as we will see in Ch. 6.

Friday, July 23, 2010

Global Problems: CO2 and the Climate

Chapter 4B

Global Problems: CO2 and the Climate

Carbon dioxide (CO2), water (H2O) and sunlight are the main ingredients used by plants and many bacteria to make the organic compounds they need to survive and prosper (in the process called photosynthesis). Carbon dioxide (CO2) is thus essential to life on Earth. But in excessive amounts it may lead to the undue warming of the atmosphere, the infamous “global warming.”

CO2 has been increasing at a rate that seems alarming: 25% since the industrial revolution and 10% since 1957. Many scientists attribute most of this increase to human action.[1]

According to several climate models, at this rate the CO2 will double sometime in this century, raising the average global temperature anywhere from 1 to 5 degrees Celsius.[2] That higher temperature may transform the Earth in undesirable ways. For example, the polar caps might melt, slowly raising ocean levels and flooding out of existence New York, Hong Kong, Rio de Janeiro and many of the other great coastal cities of the world. The loss of land would destroy the livelihood of a billion people, while the new climate may turn the great agricultural areas of the American and Canadian Midwest into deserts.[3]

Some react to this problem of “global warming” by advocating an end to the practices that increase the CO2 in the atmosphere. But that solution is far from easy, for we create CO2 every time we burn fossil fuels – that is, every time we operate a factory, fly a plane, drive an automobile, or run a tractor. Modern society runs largely on the burning of fossil fuels and changing this habit will require much sacrifice and thus encounter great resistance. Not surprisingly, dissenters demand to know just how bad the problem really is and what alternative solutions exist.

The problem does seem to be catastrophic if one listens to the judgment of the majority of professional climatologists. Until recently they based their pessimistic conclusions on three main factors: the theory of the green-house effect, the fact that the temperature has risen by one degree Celsius in the last hundred years, and the projections they derive from computer models of the climate. Let us take a brief look at each in turn, and then let us look again at the ensuing controversy in the context of the long-term future.

The theory of the greenhouse effect seems about as solid as we could wish. Sunlight is absorbed by the Earth’s surface and re-radiated in the infrared. CO2 does trap infrared radiation, as do other “greenhouse” gases, such as methane (CH4), nitrous oxide (N2O), and ordinary water vapor.[4] And when you trap energy in the atmosphere you make it warmer. Indeed, there is little question that the Earth does experience a very large greenhouse effect. The average air temperature on the surface of the Earth is 14°C (57°F), which is about 32°C higher than the radiant temperature of the Earth (what the Earth radiates). This means 32°C more than can be accounted by the combination of sunlight and internal heat. So we can see not only that the greenhouse effect exists on a large scale, but also that it is a good thing, otherwise the mean temperature of the Earth would be well below freezing.

CO2 is an important factor in this greenhouse effect, even though its percentage in the atmosphere is just 0.035 – its increase coincides with the rise of temperature in the last century. Until recently, however, dissenters have questioned this worry on two fronts. The first is whether there is a connection between the increase in CO2 and the rise in temperature, for most of the increase in temperature took place up to the 1940s, even though in the last twenty years CO2 has increased almost half as much as in the previous 200. Moreover, dissenters dispute even the modest increase in world temperature in the last twenty years on the basis of satellite readings of lower atmospheric temperature (up to a height of seven kilometers). These readings actually show a slight decrease. According to the dissenters, satellite data of the lower atmosphere should be considered far more reliable than inferences drawn from a collection of readings from highly localized weather stations around the world, especially those from cities, where concrete and pollution create “islands of heat.”[5]

In their second front, dissenters argue that changes in temperature result from natural fluctuations in the climate. Ninety million years ago a cold-blooded crocodile, Champosaur, lived only 600 miles from the North Pole. The climate in the Arctic then was like Florida’s today. It is also well known that many hundred years ago England used to enjoy wine from its own vineyards, for the whole of Europe was much warmer then. About the same time the Americas were suffering from devastating droughts. That warm climate gave way to the Little Ice Age, about 400 years ago. But now the Earth seems to be returning to the balmy days of English wine, a time long before the industrial revolution and its massive use of fossil fuels.[6]

In the last few years, the pessimists have challenged the interpretation of the satellite data, largely to their own satisfaction, although the dissenters remain unconvinced. “A stubborn argument against global warming may be discredited by a reanalysis of the data central to its claims,” announces a Science commentary on a crucial report. But the authors of the report themselves point out that the relevant models cannot be used “to determine which of the two satellite data sets is closer to reality.”[7] The pessimists then announce that their “newest global-warming forecast is backed by data from myriad satellites, weather balloons, ships at sea, and weather stations…”[8] as well as by ice-core, animal and plant studies. But, according to S.F. Singer, former director of the U.S. Weather Satellite Service, a report from the National Research Council “confirms that the atmosphere has not warmed appreciably for the past 20-odd years.”[9] (See Figure 4.1) Singer does acknowledge that we are in a period of warming, but he claims this is just part of a natural cycle induced by changes in solar radiation. We can see this rough 1470-year cycle, he adds, superimposed on both glaciation and inter-glacial periods of the last 400,000 years, and perhaps of the last million years.[10]

The third basis for the pessimistic conclusions is the use of computer models of the climate. The computer models attempt to simulate the behavior of the climate some years from now by considering how a relatively few factors affect it. Dissenters point out that these models are gross simplifications of the real climate and the myriad of factors that do affect it (which in many cases are themselves not well understood, as we will see below). Pessimists cannot point to significant forecasts of climate change, which is the acid test required by dissenters.

In fairness, though, we must keep in mind that the climatologists are warning us about the probable effects of the accumulation of greenhouse gases over a period of several decades. They also worry that by the time those disastrous effects are large enough to convince the skeptics, it will be too late to reverse the trend and prevent a catastrophe.

Furthermore, their computer models have been tested somewhat successfully by the retrodiction of significant climatic changes in our distant history (a retrodiction is a prediction concerning what we will find out about the past). That is, in some instances when scientists have applied their climate models to determine what should have happened at, say, the time of the dinosaurs, they have gotten some rough agreement with what we believe really happened (given our knowledge of the geological record). But as climatologist Stephen Schneider puts it, this is valuable circumstantial evidence, but it cannot confirm or deny the model’s detailed regional projections.[11]

As of this writing, a bitter controversy rages on between the two sides, complete with name-calling, accusations of biased reporting,[12] and charges of fraud.[13] This controversy, to make matters worse, has been drawn along political lines, with the Left generally taking the side of strict regulation and the Right that of industry. The left tends to say that there are no two sides, but that would be rather unusual in the history of science.

It is not my purpose to settle this political controversy. My intent is rather to examine the matter philosophically and to argue that we face a condition of uncertainty in which we have a duty to act wisely, and that we will not be able to do so unless we make liberal used of space technology in the context of investigating the Earth as a planet. And to do the latter well, as I have already suggested, requires a vigorous exploration of the solar system.

[1]. Schneider, S. H., Laboratory Earth, Basic Books, 1997, p. 66.

[2]. Ibid, p. 50.

[3]. These are, of course, only educated guesses. Melting of icebergs floating in water would not raise the water levels, but melting of glaciers over land, as in Antarctica, would.

[4] They have that name because they work in the manner of a greenhouse: they let the sunlight through but trap the heat in.

[5]. The two sides agree that there was a substantial increase in global surface temperatures in 1998 (0.58EC above the baseline of the 1961-1990 period). But skeptics blame El NiƱo and point out that later in the year the atmospheric temperatures decreased to the baseline average. Science News, Vol. 155, January 2, 1999, p. 6. I expect that this debate will continue for years.

[6]. Recently some researches have argued that on the basis of such evidence we cannot prove that the global temperature was higher then.

[7] J.R. Christy and R.W. Spencer, Science, Vol. 301, 22 August 2003, pp. 1046-1047.

[8] “The Weather Turns Wild,” U.S. News and World Report, February 5, 2001, p. 47. This article was based on a report from the United Nations’ Intergovernmental Panel on Climate Change. See also Harries, J.E., et al, “Increases in Greenhouse Forcing Inferred from the Outgoing Longwave Radiation Spectra of the Earth in 1970 and 1997,” Nature, Vol. 405, March 15, 2001.

[9] See his letter to Science, Vol. 301, 1 August 2003, p. 595. The report in question is Reconciling Observations of Global Temperature Change, National Academy Press, 2000. See also Donald Kennedy’s response, Ibid. I must confess that I am very puzzled by those who claim that the last twenty years were the hottest in the last thousand, while at the same time all sides agree that the rise in temperature since 1900 to now is 0.6C and that the rise in temperature from 1900 up to 1979 was also 0.6C.

[10] S.F. Singer and D.T. Avery (2007). Unstoppable Global Warming: Every 1500 years. Rowman and Littlefield.

[11]. Op. cit., p. 51.

[12] The battle is often fought through the most prestigious organs of the press, which tend to favor the doomsday scenarios. For example, on March 5, 1999, the Washington Post ran the headline Shrinkage Detected in Greenland’s Ice. According to the World Climate Report, the “real” story is that even though Greenlands southern glaciers are receding, that recession is more than compensated for by a thickening of the ice sheet in West Greenland, the largest ice mass in the Northern Hemisphere (March 15, 1999). Indeed, satellite data indicate that there had been a cooling trend around Greenland for the previous twenty years.

[13] According to Singer, the claim that scientists had found a “human fingerprint” in the current warming was inserted into the executive summary of the United Nations’ Intergovernmental Panel on Climate Change (IPCC) “for political, not scientific reasons. Then the ‘science volume’ was edited to take out five different statements – all of which had been approved by the panel’s scientific consultants – specifically saying no such ‘human fingerprint’ had been found.” The editor, a U.S. government employee, later admitted his “indefensible action,” claiming he had been under pressure from higher U.S. government officials. Singer and Avery, op. cit., p. 10. Singer’s source is Frederick Seitz, former president of the National Academy of Sciences, in “A Major Deception on Global Warming,” Wall Street Journal, 12 June 1996, editorial page. Also, S.F. Singer, Climate Policy from Rio to Kyoto: A Political Issue for 2000 and Beyond (Palo Alto, CA: Hoover Institution, Stanford University, 2000), p. 19.

Wednesday, July 14, 2010

The Immediate Future of Exploration

The NASA Budget

For those of you who are interested in supporting exploration, I thought I would pass on this urgent message I received from the Planetary Society:

The NASA budget is coming to a critical vote tomorrow -- July 15 -- by the U.S. Senate Committee on Commerce Science and Transportation. This is the Committee that authorizes the NASA program. The planned authorization bill has some good features -- fully funding the President’s request for an increased budget for NASA, strong space and Earth science programs, and redirecting human space flight towards exploration into the solar system. It also increases support for the deep-space rocket and spacecraft necessary to take astronauts there.

But it has two big drawbacks:

It stops the rapid development of commercial rockets for Earth orbit crew transportation, while authorizing no new government program to replace the shuttle.
It cuts out most of the technology development (90%!) and robotic precursor missions related to the future of exploration, two of the brightest lights in the new exploration strategy.

Two amendments are being introduced tomorrow to correct these problems: one by Senator Mark Warner of Virginia and the other by Senator Barbara Boxer of California. Together they will restore much of the technology program (increasing it by $356 million) and permit commercial launch vehicles to be developed to allow astronaut flights to the International Space Station sooner.

We urge you to call your Senators today and ask them to support the Warner and Boxer NASA Authorization Amendments -- especially if one of them is on the Senate Committee. A phone call is necessary -- there's no time for a written letter (these amendments just were announced late yesterday). These are the Committee members:

Jay Rockefeller, West Virginia, Chairman
Daniel Inouye, Hawaii
John Kerry, Massachusetts
Byron Dorgan, North Dakota
Barbara Boxer, California
Bill Nelson, Florida
Maria Cantwell, Washington
Frank Lautenberg, New Jersey
Mark Pryor, Arkansas
Claire McCaskill, Missouri
Amy Klobuchar, Minnesota
Tom Udall, New Mexico
Mark Warner, Virginia
Mark Begich, Alaska

Kay Bailey Hutchison, Texas, Ranking Member
Olympia Snowe, Maine
John Ensign, Nevada
Jim DeMint, South Carolina
John Thune, South Dakota
Roger Wicker, Mississippi
Johnny Isakson, Georgia
David Vitter, Louisiana
Sam Brownback, Kansas
Mike Johanns, Nebraska
George LeMieux, Florida

You may call your Senator directly in Washington by calling the U.S. Capitol main number 202-224-3121 or find their office numbers through The Planetary Society Legislative Action site. Please call today; the vote is tomorrow morning.

Thank you for your consideration and prompt action -- no one is more devoted to the future of human and robotic space exploration than Members of The Planetary Society.


Louis Friedman
Executive Director