The following are excerpts from a lecture presented by Dr. Richard Lindzen to the Global Warming Policy Foundation in October, 2018. Dr. Lindzen was Alfred P. Sloan Professor of Meteorology at the Massachusetts Institute of Technology until his retirement in 2013. He is the author of over 200 papers on meteorology and climatology and is a member of the US National Academy of Sciences and of the Academic Advisory Council of GWPF.
Each of the following sections has more to it. Read the entire lecture here:
The climate system
The following description of the climate system contains nothing that is in the least controversial, and I expect that anyone with a scientific background will readily follow the description. I will also try to make the description intelligible to the non-scientist.
The system we are looking at consists in two turbulent fluids (the atmosphere and the oceans) interacting with each other. By ‘turbulent,’ I simply mean that it is characterized by irregular circulations like those found in a gurgling brook or boiling water, but on the planetary scale of the oceans and the atmosphere. The opposite of turbulent is called laminar, but any fluid forced to move fast enough becomes turbulent, and turbulence obviously limits predictability. By interaction, I simply mean that they exert stress on each other and exchange heat with each other.
These fluids are on a rotating planet that is unevenly heated by the sun. The motions in the atmosphere (and to a lesser extent in the oceans) are generated by the uneven influence of the sun. The sun, itself, can be steady, but it shines directly on the tropics while barely skimming the Earth at the poles. The drivers of the oceans are more complex and include forcing by wind as well as the sinking of cold and salty water. The rotation of the Earth has many consequences too, but for the present, we may simply note that it leads to radiation being distributed around a latitude circle.
The oceans have circulations and currents operating on time scales ranging from years to millennia, and these systems carry heat to and from the surface. Because of the scale and density of the oceans, the flow speeds are generally much smaller than in the atmosphere and are associated with much longer time scales. The fact that these circulations carry heat to and from the surface means that the surface, itself, is never in equilibrium with space. That is to say, there is never an exact balance between incoming heat from the sun and outgoing radiation generated by the Earth because heat is always being stored in and released from the oceans and surface temperature is always, therefore, varying somewhat.
In addition to the oceans, the atmosphere is interacting with a hugely irregular land surface. As air passes over mountain ranges, the flow is greatly distorted. Topography therefore plays a major role in modifying regional climate. These distorted air-flows even generate fluid waves that can alter climate at distant locations. Computer simulations of the climate generally fail to adequately describe these effects.
A vital constituent of the atmospheric component is water in the liquid, solid and vapor phases, and the changes in phase have vast impacts on energy flows. Each component also has important radiative impacts. You all know that it takes heat to melt ice, and it takes further heat for the resulting water to become vapor or, as it is sometimes referred to, steam. The term humidity refers to the amount of vapor in the atmosphere. The flow of heat is reversed when the phase changes are reversed; that is, when vapor condenses into water, and when water freezes. The release of heat when water vapor condenses drives thunder clouds (known as cumulonimbus), and the energy in a thundercloud is comparable to that released in an H-bomb. I say this simply to illustrate that these energy transformations are very substantial. Clouds consist of water in the form of fine droplets and ice in the form of fine crystals. Normally, these fine droplets and crystals are suspended by rising air currents, but when these grow large enough they fall through the rising air as rain and snow. Not only are the energies involved in phase transformations important, so is the fact that both water vapor and clouds (both ice- and water-based) strongly affect radiation. Although I haven’t discussed the greenhouse effect yet, I’m sure all of you have heard that carbon dioxide is a greenhouse gas and that this explains its warming effect. You should, therefore, understand that the two most important greenhouse substances by far are water vapor and clouds. Clouds are also important reflectors of sunlight.
The unit for describing energy flows is watts per square meter. The energy budget of this system involves the absorption and re-emission of about 200 watts per square meter. Doubling CO2 involves a 2% perturbation to this budget. So do minor changes in clouds and other features, and such changes are common. The Earth receives about 340 watts per square meter from the sun, but about 140 watts per square meter is simply reflected back to space, by both the Earth’s surface and, more importantly, by clouds. This leaves about 200 watts per square meter that the Earth would have to emit in order to establish balance.
The sun radiates in the visible portion of the radiation spectrum because its temperature is about 6000K. ‘K’ refers to Kelvins, which are simply degrees Centigrade plus 273. Zero K is the lowest possible temperature (-273?C). Temperature determines the spectrum of the emitted radiation. If the Earth had no atmosphere at all (but for purposes of argument still was reflecting 140 watts per square meter), it would have to radiate at a temperature of about 255K, and, at this temperature, the radiation is mostly in the infrared.
Of course, the Earth does have an atmosphere and oceans, and this introduces a host of complications. So be warned, what follows will require a certain amount of concentration. Evaporation from the oceans gives rise to water vapor in the atmosphere, and water vapor very strongly absorbs and emits radiation in the infrared. This is what we mean when we call water vapor a greenhouse gas. The water vapor essentially blocks infrared radiation from leaving the surface, causing the surface and (via conduction) the air adjacent to the surface to heat, and, as in a heated pot of water, convection sets on. Because the density of air decreases with height, the buoyant elements expand as they rise. This causes the buoyant elements to cool as they rise, and the mixing results in decreasing temperature with height rather than a constant temperature. To make matters more complicated, the amount of water vapor that the air can hold decreases rapidly as the temperature decreases. At some height there is so little water vapor above this height that radiation from this level can now escape to space. It is at this elevated level (around 5 km) that the temperature must be about 255K in order to balance incoming radiation. However, because convection causes temperature to decrease with height, the surface now has to actually be warmer than 255K. It turns out that it has to be about 288K (which is the average temperature of the Earth’s surface).
This is what is known as the greenhouse effect. It is an interesting curiosity that had convection produced a uniform temperature, there wouldn’t be a greenhouse effect. In reality, the situation is still more complicated. Among other things, the existence of upper-level cirrus clouds, which are very strong absorbers and emitters of infrared radiation, effectively block infrared radiation from below. Thus, when such clouds are present above about 5 km, their tops rather than the height of 5 km determine the level from which infrared reaches space. Now the addition of other greenhouse gases (like carbon dioxide) elevates the emission level, and because of the convective mixing, the new level will be colder. This reduces the outgoing infrared flux, and, in order to restore balance, the atmosphere would have to warm. Doubling carbon dioxide concentration is estimated to be equivalent to a forcing of about 3.7 watts per square meter, which is little less than 2% of the net incoming 200 watts per square meter. Many factors, including cloud area and height, snow cover, and ocean circulations, commonly cause changes of comparable magnitude.
It is important to note that such a system will fluctuate with time scales ranging from seconds to millennia, even in the absence of an explicit forcing other than a steady sun. Much of the popular literature (on both sides of the climate debate) assumes that all changes must be driven by some external factor. Of course, the climate system is driven by the sun, but even if the solar forcing were constant, the climate would still vary. This is actually something that all of you have long known – even if you don’t realize it. After all, you have no difficulty recognizing that the steady stroking of a violin string by a bow causes the string to vibrate and generate sound waves. In a similar way, the atmosphere–ocean system responds to steady forcing with its own modes of variation (which, admittedly, are often more complex than the modes of a violin string). Moreover, given the massive nature of the oceans, such variations can involve time scales of millennia rather than milliseconds. El Niño is a relatively short example, involving years, but most of these internal time variations are too long to even be identified in our relatively short instrumental record. Nature has numerous examples of autonomous variability, including the approximately 11-year sunspot cycle and the reversals of the Earth’s magnetic field every couple of hundred thousand years or so. In this respect, the climate system is no different from other natural systems.
Of course, such systems also do respond to external forcing, but such a forcing is not needed for them to exhibit variability. While the above is totally uncontroversial, please think about it for a moment. Consider the massive heterogeneity and complexity of the system, and the variety of mechanisms of variability as we consider the current narrative that is commonly presented as ‘settled science.’
The popular narrative and its political origins
Now here is the currently popular narrative concerning this system. The climate, a complex multifactor system, can be summarized in just one variable, the globally averaged temperature
change, and is primarily controlled by the 1-2% perturbation in the energy budget due to a single variable – carbon dioxide – among many variables of comparable importance. This is an extraordinary claim based on reasoning that borders on magical thinking. It is, however, the narrative that has been widely accepted, even among many sceptics.
Many politicians and learned societies go even further: They endorse carbon dioxide as
the controlling variable, and although mankind’s CO2 contributions are small compared to the much larger but uncertain natural exchanges with both the oceans and the biosphere, they are confident that they know precisely what policies to implement in order to control carbon dioxide levels.
At this point, some of you might be wondering about all the so-called evidence for dangerous climate change. What about the disappearing Arctic ice, the rising sea level, the weather extremes, starving polar bears, the Syrian Civil War, and all the rest of it? The vast variety of the claims makes it impossible to point to any particular fault that applies to all of them. Of course, citing the existence of changes – even if these observations are correct (although surprisingly often they are not) – would not implicate greenhouse warming per se. Nor would it point to danger. Note that most of the so-called evidence refers to matters of which you have no personal experience. Some of the claims, such as those relating to weather extremes, contradict what both physical theory and empirical data show. The purpose of these claims is obviously to frighten and befuddle the public, and to make it seem like there is evidence where, in fact, there is none.
So there you have it. An implausible conjecture backed by false evidence and repeated incessantly has become politically correct ‘knowledge,’ and is used to promote the overturn of industrial civilization. What we will be leaving our grandchildren is not a planet damaged by industrial progress, but a record of unfathomable silliness as well as a landscape degraded by rusting wind farms and decaying solar panel arrays. False claims about 97% agreement will not spare us, but the willingness of scientists to keep mum is likely to much reduce trust in and support for science. Perhaps this won’t be such a bad thing after all – certainly as concerns ‘official’ science.
There is at least one positive aspect to the present situation. None of the proposed policies will have much impact on greenhouse gases. Thus we will continue to benefit from the one thing that can be clearly attributed to elevated carbon dioxide: namely, its effective role as a plant fertilizer, and reducer of the drought vulnerability of plants.