PrintApril 12, 2010
A Justice Stevens Performance Review
The retirement of Justice Stevens from the Supreme Court opens the way for the Senate to perform its constitutional duty to provide advice and consent to a co-equal branch of government. The key qualification the Republicans ought to be looking for is literacy in math and science, a profound weakness of Justice Stevens. A matter of highest interest to the body politic, soon to be considered by Congress, is the concept of cap-and-trade. The SCOTUS issued its take on the matter in the majority opinion written by Justice Stevens in Massachusetts v. EPA.
Justice Stevens wrote:
A well-documented rise in global temperatures has coincided with a significant increase in the concentration of carbon dioxide in the atmosphere. Respected scientists believe the two trends are related. For when carbon dioxide is released into the atmosphere, it acts like the ceiling of a greenhouse, trapping solar energy and retarding the escape of reflected heat. It is therefore a species-the most important species-of a "greenhouse gas."
The assertion that carbon dioxide is "the most important species" of greenhouse gas (or that it acts like a ceiling) is nonsense, written in April 2007 just as Al Gore's movie An Inconvenient Truth was being awarded an Oscar by Hollywood. It has no basis in science. The "most important species" of greenhouse gas is water vapor. Time has certainly flown since then! The British High Court has declared the movie to be propaganda and forced the British schools to inform their students to that effect. (Are you listening, Ruth Bader Ginsburg?)
In rendering its decision, the Court accepted the Intergovernmental Panel on Climate Change's (IPCC) Fourth Assessment. The IPCC did make the assertion that carbon dioxide is the most important anthropogenic greenhouse gas as measured by the yardstick of its effect on radiative forcing, which it defines in footnote 4 as such:
4 Radiative forcing is a measure of the influence a factor has in altering the balance of incoming and outgoing energy in the Earth-atmosphere system and is an index of the importance of the factor as a potential climate change mechanism. In this report radiative forcing values are for changes relative to reindustrialize conditions defined at 1750 and are expressed in watts per square metre (W/m2).
The IPCC report states (Page 14) that
This Topic considers both natural and anthropogenic drivers of climate change, including the chain from greenhouse gas (GHG) emissions to atmospheric concentrations to radiative forcing4 to climate responses and effects.
The key to understanding the game is that the IPCC has chosen to understand and model only the changes to the natural greenhouse effect ("Climate Change"), not the natural effect itself ("Climate"). The Court should take notice that water vapor is conspicuously absent from the "long lived" greenhouse gases (GHGs) shown in Chart 2.1 and listed in footnote 5.
5 Includes only carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulphurhexafluoride (SF6), whose emissions are covered by the UNFCCC. These GHGs are weighted by their 100-year Global Warming Potentials (GWPs), using values consistent with reporting under the UNFCCC.
They choose to omit water vapor from their calculations only because the average life of a water molecule is very short in comparison to anthropogenic GHGs (Wikipedia puts it at ten days), not because it is unimportant to the natural greenhouse effect. The fact that water vapor is replaced by evaporation from the oceans which cover 70% of Earth's surface seems unimportant to the IPCC. They prefer to deal in what is known as the Global Warming Potential based on a hundred-year timeframe. However, if they based the global warming potential on a time period of ten days, CO2 would be insignificant compared to water vapor. The water content of the atmosphere does not decay with time, as it does with anthropogenic gases, because there is an overwhelming, large, natural source of replenishment from the oceans.
A simple analogy would be to set the average residence time for an atmospheric gas equal to its half-life. Water has an average life of ten days, so it would decay to less than 1% of its original value in less than 70 days. It should be obvious that the Earth's atmosphere does not dry out to nearly nothing in two months. Why the IPCC does not consider the balance between condensation and evaporation plus sublimation in the atmosphere, when it does consider the balance between incoming solar radiation and outgoing thermal radiation, is an amazing oversight. Didn't they read Al Gore's book Earth in the Balance? (Sorry, I couldn't resist.)
Planetary Thermodynamics
The basic thermodynamic principle is that heat flows from hot to cold. The sun is hotter than the Earth, so heat flows from the sun to Earth in the form of sunlight. The Earth is hotter than deep space, so heat flows out to deep space as infrared thermal radiation. The peak wavelength is dependent on the temperature of the source, as shown by Wien's Displacement Law. The Sun, being much hotter, radiates at higher energy and shorter wavelengths than does the Earth. Over the millennia, the Earth has achieved an equilibrium temperature at which incoming sunlight is balanced by outgoing infrared radiation. The issue is whether mankind has upset that equilibrium by injecting anthropomorphic greenhouse gases into the atmosphere. While the IPCC loves to call the effect of CO2 a "forcing," the thing that forces the heat flow is the temperature difference between source and sink. A more accurate way of describing GHG's effect is to compare it to an impedance. The presence of GHG impedes the radiant flow of heat in the thermal wavelength range, where it scatters or absorbs it, but it does not impede it in the solar radiation wavelength range, where it transmits it. Water is unique among GHGs in that it can also impede sunlight. We call them clouds, which are an aerosol of water vapor and water ice or liquid droplets.
In an oversimplified radiation model (which ignores convection -- see The Thermostat Hypothesis), by letting the same amount of heat in from the sun while impeding the flow outward, an increase in a greenhouse gas would cause the Earth's temperature to rise until there was a new equilibrium where the now-reduced solar radiation due to a decrease in temperature difference between the sun and Earth would once again equal the new outgoing thermal radiation. That now is lower due to the impedance, but the decrease is somewhat mitigated due to the increased temperature difference between Earth and space. That increase in outbound thermal radiation rises quite quickly, as it is proportional to the fourth power of the absolute temperature as described by the Stefan-Boltzmann Law. The Earth's average temperature is usually given as 15 °C (59F), which equates to an absolute temperature of 288°K (degrees Kelvin). So a one-degree Celsius temperature rise would increase the average temperature from 288°K to 289°K, which means that the outgoing thermal radiation would increase 1.4%. A ten-degree Celsius rise would increase the thermal radiation by 14.6%. The steepness of this response is a major factor in explaining why the Earth's average temperature stays so stable.
Earth's Natural Greenhouse Effect
Now that we have some background on the thermodynamics, we can start to look at the solar system. We know that the Earth has a significant natural greenhouse effect because it is much hotter than the moon, though both are at essentially the same distance from the sun and therefore receive comparable isolation. Actually, the moon's incoming solar radiation is somewhat higher because the temperature difference between the source (the sun) and it is higher than that between the sun and the Earth. The moon also has a lower albedo and absorbs more solar radiation than the Earth, which reflects sunlight, particularly off the clouds. The moon obviously has no atmosphere or clouds and therefore no greenhouse effect.
At this point, it makes sense to compare the ability of various atmospheric gases to impede the flow of thermal radiation outward. Here is a link to the best representation I have found of the atmospheric transmission of gases in Earth's atmosphere.
Even a cursory visual inspection shows that the absorption and scattering caused by water vapor is much greater than any other gas, including CO2. It has multiple absorption bands from the high energy near-infrared range through the mid-infrared and to the far infrared (thermal radiation) range. That is why in its Inventory of U. S. Greenhouse Gas Emissions and Sinks: 1990-2006 (page 46 of the 394 pg PDF), the EPA admits the following:
Water Vapor (H2O). Overall, the most abundant and dominant greenhouse gas in the atmosphere is water vapor (emphasis added). Water vapor is neither long-lived nor well mixed in the atmosphere, varying spatially from 0 to 2 percent (IPCC 1996). In addition, atmospheric water can exist in several physical states including gaseous, liquid, and solid. Human activities are not believed to affect directly the average global concentration of water vapor, but the radiative forcing produced by the increased concentrations of other greenhouse gases may indirectly affect the hydrologic cycle. While a warmer atmosphere has an increased water holding capacity, increased concentrations of water vapor affects the formation of clouds, which can both absorb and reflect solar and terrestrial radiation. Aircraft contrails, which consist of water vapor and other aircraft emittants, are similar to clouds in their radiative forcing effects (IPCC 1999).
So there you have it from the United States EPA itself, the SCOTUS's most respected source of data on pollutants: Water is "the most important species" of greenhouse gas, and Justice Stevens was mistaken in his opinion. We need a new justice to replace him who understands math and science. Who knows -- maybe we'll get one who understands the concept of least significant digit. There was a time when we taught such concepts in grade school, when we asked, What is the decimal equivalent of one-third? Does anyone think that President Obama's new choice for the SCOTUS (or his "wise Latina," for that matter) will know some simple grade-school Boolean algebra?
Let's hope he nominates someone who does.
