Storms of My Grandchildren (10 page)

Lindzen’s second graph showed that there was a high correlation between sunspots and the number of Republicans in the Senate. He concluded that the IPCC analysis was hardly better than the sunspot-Republican analysis, indeed, “in some respects the climate analysis is more questionable, since the effect is so much smaller.”

Any levity from Lindzen’s presentation dissipates upon the realization that his presentations were taken seriously by the administration. There are reasons to believe that Bush, Cheney, and Rove all shared Lindzen’s perspective (consistent with evidence presented in chapter 7) and distrusted the scientific community. The answer that the National Academy of Sciences had delivered in response to the president’s request, the report that Lindzen “critiqued,” was not the answer the White House wanted to hear. The president did not ask the academy for advice about global warming again during the remainder of his eight years in power.

I
SAID THAT MY STORY WOULD cover only the past eight years. Sorry. In this chapter I’m going to have to take you with me for a moment into a backward time warp. If you are irascible by nature, easily angered by broken promises, you may wish to skip directly to the next chapter. But in so doing, you will miss a discussion of some potentially crucial information, key to understanding the task of restoring Earth’s energy balance—and restoring Earth’s energy balance is the fundamental requirement for stabilizing our climate.

It is Kathie Olsen, associate director of the Office of Science and Technology Policy, who is responsible for pulling us into this backward time warp, with a question she asked at the end of my presentation to the White House Council on Environmental Quality in June 2003. Her question was about atmospheric aerosols, the fine particles in the air: What aerosol measurements were needed to define the climate forcing by aerosols and why were the measurements not being obtained?

It was a good question. Another Richard Feynman story can help me explain the answer. The story involves giants in the world of physics, but it has relevance to us ordinary people. You can call it “When Speaking to Authority.”

The great Danish physicist Niels Bohr and his son Aage visited Los Alamos at the time when everyone there was working on the bomb. Niels Bohr had won a Nobel Prize in 1922 for his work on the structure of atoms (Aage won his own Nobel Prize, in 1975, for work on the structure of the nucleus). While they were visiting the secret Los Alamos project, Niels and Aage were given the aliases Nicholas Baker and Jim Baker, but everyone knew who they were—Niels Bohr was a god even to the other famous physicists. At a meeting held to talk about problems with the bomb, Feynman had to sit way in the back because everybody else had crowded close to the great Niels Bohr. The day before the Bohrs were to return for a second visit, Feynman got a call. “Hello, Feynman? This is Jim Baker, my father and I would like to meet with you.”

A surprised Feynman said, “Who, me? I’m just…” They met at eight A.M., while the other scientists were still in bed. The Bohrs had ideas about how to improve the bomb: “We have this idea, blah, blah, blah.” Feynman responded, “No, that won’t work because blah blah.” “Well, how about blah blah.” “That may be better, but it still has this damn fool idea in it…” The discussion went on for about two hours, until Niels Bohr lit his pipe and said, “I guess we can call in the big shots now.” Aage then explained to Feynman that after their first visit, his father had told him, “Remember that little fellow in the back? He’s the only one who’s not afraid of me and will say when I’ve got a crazy idea. So next time that we want to discuss ideas, we’ll talk with him first.”

Reticence exists in different forms. The reticence I’m concerned with in this chapter is the reluctance to contradict authority. A good scientist is interested in how things work and doesn’t want to worry about authority. Niels Bohr might have appreciated respect—but not to a degree that would inhibit discussion. Reticence does not fit the scientific method.

How the real world works is an almost infinitely complex puzzle. A scientist’s task is to try to figure out a valid description of some part of the puzzle. If he keeps two sets of books, one he believes and another to please authorities, it makes the problem much harder. So a scientist should be clear and blunt about what he thinks, even if the authorities don’t like it—otherwise he will not do very well in science.

Feynman spoke out without reticence. It worked for him. But Feynman had advantages we ordinary people do not have: He was a genius and a scintillating, entertaining communicator. Also, as Feynman frequently acknowledged, he was fortunate to work in places, mostly at universities, where speaking openly was expected and appreciated.

I have had more difficulty. I try to speak up if something seems important. But I have always been shy, a poor communicator, and lacking in tact. I decided that the best chance for me to communicate better was to learn to write better. So for years, after Anniek and I would go to bed, I would read out loud to her, usually English novels, marking words to study later. It improved my vocabulary, but not my tact.

“Get to the point!” you might be thinking. “What is the relevance of communications and tact?” Well, the answer to Kathie Olsen’s question about why we do not have the data we need—about climate forcing by aerosols, which requires measuring aerosols and their effect on clouds—turns out to be a story of failed communications.

One way for me to tell that story would be to give a detailed accounting of my efforts over several years, as a scientist, to promote the aerosol and cloud observations that I believe to be necessary. It is a sorrowful tale, but one that will need to wait until I have retired.

Instead, we can look at the science of planetary observations, which was clear before I became a government employee in 1972 and remains valid today.

If you want to make measurements of a planet to learn what its atmosphere is made of and, if the atmosphere is not too thick, learn something about its surface, how can you go about this? Well, unless you plan to fly to the planet, land on it, and start poking around, about the only thing you can do is measure the radiation coming from the planet. Then you have two choices: measure the sunlight reflected by the planet or measure the heat radiation emitted by the planet. You had better choose to measure both if you want to figure out much about the planet.

The reflected sunlight is what you see with your eyes when you look at the planet. The heat radiation needs to be measured with an instrument. In fact, you had better use instruments to measure both the reflected sunlight and the planetary heat radiation if you want to obtain detailed information about the planet.

The left graph has two jagged curves. The top curve is the sunlight (solar radiation) that hits Earth, and the lower curve is the amount of sunlight that gets to the ground on a cloudless day. Not all the sunlight reaching the planet gets to the ground—some is absorbed by gases such as water vapor and ozone, and some is reflected back to space by aerosols and air molecules.

The jagged curve in the right graph represents the heat (thermal radiation, or terrestrial radiation) emitted by Earth. This measurement was made by an instrument called IRIS (Infrared Interferometer Spectrometer), which was developed by Rudy Hanel, a NASA scientist, for planetary studies. The measurements shown in figure 5 were made in 1970 above the Sahara Desert, when the instrument was on a satellite orbiting Earth.

Sunlight and Earth’s heat radiation bear many similarities. They are both thermal (heat) radiation. It’s just that sunlight is coming from a much hotter body. The temperature of the sun’s surface is almost 6,000 degrees Kelvin (about 5,700 degrees Celsius). The average temperature of Earth’s surface is about 288 degrees Kelvin (15 degrees Celsius), which means it is cooler than the sun by a factor of about 20.

An aside: A Kelvin degree is the same as a Celsius degree, except that zero degrees Kelvin is defined as the temperature at which all molecular motion ceases. That is really “stone cold.” Zero degrees Kelvin is about −273 degrees Celsius. That is the coldest anything can be, so zero degrees Kelvin is absolute zero, and temperature in Kelvin is also called absolute temperature. The Kelvin scale might have been chosen “at the beginning” if this had all been understood then. But it is useful to also keep Celsius, which is almost the same as Kelvin except for a constant offset, because who would want to say, “The temperature today will be 288 degrees”; better to have small, more manageable numbers. (The Fahrenheit temperature scale used in the United States, like inches, feet, yards, and miles for distance, instead of centimeters, meters, and kilometers, perhaps should be abandoned, but such decisions are made in Washington. Maybe that’s the way it should be in a democracy. But our grandchildren are being handicapped a bit—science would be easier for them if they could use the more logical scales that are used in most other countries.)

The amount of radiation emitted by a body is, approximately, a simple function of its temperature. We have a name for the equation that describes the amount of radiation as a function of temperature and wavelength: the Planck function. It accurately describes the radiation from a perfect absorber, or blackbody, material that completely absorbs all wavelengths of incident radiation, that is, all the energy shining upon it. Black carbon (black soot) is a good approximation of a perfect absorber.

The dashed lines in figure 5 represent the amount of radiation that would be emitted by blackbodies at the temperature of the sun’s surface (left graph) and Earth’s surface (right graph). The jagged curves for actual radiation measured differ from the ideal blackbody curves because of the absorption of the radiation by gases in either the sun’s upper atmosphere or Earth’s atmosphere.

Gas absorption occurs at specific wavelengths that depend on the type of gas—so the absorption lines serve as spectral fingerprints that identify gas species. For example, the broad feature at wavelength 15 microns (a micron is a micrometer, one millionth of a meter) in Earth’s thermal emission is due to absorption by carbon dioxide. The narrower absorption near 10 microns is absorption by ozone.

Energy absorbed by these gases is promptly reemitted in all directions, but the amount and spectral (wavelength) distribution of the emitted radiation depends on the temperature at the location of the absorbing gas molecules. Because Earth’s temperature gets colder the higher we go in the lower atmosphere, absorption by the greenhouse gases reduces the amount of heat radiation to space. Therefore, if the amount of these gases increases, terrestrial radiation to space is reduced. This change causes a temporary planetary energy imbalance, with Earth emitting less energy to space than it absorbs from the sun. So Earth warms up until energy balance is restored. Thus figure 5 gives a realistic “picture” of the greenhouse effect, which we’ve already discussed in words.

Our interest here is the information about Earth’s atmosphere that we can extract from the planet’s thermal spectrum and reflected sunlight. Clearly, the thermal spectrum tells us what gases are in the planet’s atmosphere, because each gas has its own spectral absorption signature, as we noted for carbon dioxide and ozone. In addition, we can use this spectrum to measure the vertical temperature profile—how the temperature varies at different altitudes in the atmosphere. Careful measurement of the thermal spectrum reveals many narrow absorption lines. The depth of an absorption line depends on the temperature profile in the atmosphere. If we measure the depth of many lines, very accurately, and compare them, we can deduce the atmosphere’s temperature profile.

The amount and accuracy of information that can be extracted from the thermal spectrum depend primarily on the precision with which the radiation intensity is measured at one wavelength relative to the intensity at other wavelengths. It is for this reason that an interferometer measurement, such as those taken by the IRIS instrument and shown in figure 5, is required for the most precise results. In such an instrument a wide range of wavelengths is recorded on the same detector, which allows greater precision than is possible with an instrument that uses separate detectors to record different wavelengths, because the detectors must be calibrated against each other—and calibrations are always imperfect.

Newton had the picture basically right, even though he lived long before there was knowledge of the structure of atoms or the nature of electromagnetic radiation. Oscillating charged particles in any molecule eventually emit a packet of electromagnetic radiation—so-called because it radiates from electrically charged particles. The radiation has the form of self-propagating waves with electric and magnetic components that oscillate perpendicular to the direction of energy propagation. True for sunlight. True for any thermal emission.