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Gary Novak
Why Global Warming Science is Nothing but Fraud Saturation, Proof of Climate Science Fraud Fudge Factor for Settled Science Fakery of the Primary CO2 Effect
Crunching the Numbers Absorption Spectra Explanations Simple Words Contrivance Communication Corruption
The Cause of Ice Ages and Present Climate |
Global Warming and Nature's Thermostat by Roy W. Spencer
This is text without graphics.
The original with graphics is here. (external) Introduction Warming Over the Last Century Fig. 1. Globally averaged surface temperature variations (deg. C) over the last century (through 2006) have shown warming until about 1940 (which must have been natural), then a slight cooling until the 1970's (either natural or the result of aerosol pollution), then steady warming since the 1970's (J. Hansen, NASA/GISS). The warming up until 1940 represents the end of the multi-century cool period known as the "Little Ice Age" which was, historically, a particularly harsh period for humanity. This warming must have been natural because mankind had not yet emitted substantial amounts of greenhouse gases. Then, the slight cooling between 1940 and the 1970's occurred in spite of rapid increases in manmade greenhouse gases. One theory is that this cooling is manmade -- from particulate pollution. Finally, fairly steady warming has occurred since the 1970's. It should be noted that there is still some controversy over whether the upward temperature trend seen in Fig. 1 still contains some spurious warming from the urban heat island effect, which is due to a replacement of natural vegetation with manmade structures (buildings, parking lots, etc.) around thermometer sites. Warming Over the Last Millenium Fig. 2. The Mann et al. (1998) proxy (mostly tree ring) reconstruction of global temperature over the last 1,000 years is believed to have erroneously minimized the warmth of the Medieval Warm Period (MWP). But it turns out we don't need to use "proxies" for temperature like tree ring measurements -- there are actual temperature 'measurements' that go back over 1,000 years. 'Borehole' temperatures are taken deep in the ground, where the seasonal cycle in surface temperature sends an annual temperature "pulse" down into the Earth. A measurement and dating of these pulses from Greenland (Fig. 3) reveals much warmer temperatures 1,000 years ago than today. Fig. 3. The GRIP (Greenland) borehole record is one of the best records because it is not a proxy, it is a DIRECT measure of temperature. Shown are the last 2000 years. (Dahl-Jensen et al. 1998, Science, 282, 268-271 "Past Temperatures Directly from the Greenland Ice Sheet"). A similar reconstruction occurs for the Ural Mountain borehole temperatures (i.e. warmer 1000 years ago, Bemeshko, D., V.A. Schapov, Global and Planetary Change, 2001. Note that such methods for dating temperatures cause a "smearing" of the signal in time. Because of this smearing effect, decadal-time scale temperature "spikes" probably occurred during the MWP which are smoothed out in Fig. 3. If we could see those temperature spikes that undoubtedly occurred during the MWP, our current warmth would seem even less significant. Thus, we see that substantial natural variations in temperature can, and do, occur -- which should be no surprise. So, is it possible that much of the warming we have seen since the 1970's is due to natural processes that we do not yet fully understand? I believe so. To believe that all of today's warmth can be blamed on manmade pollution is a statement of faith that assumes the role of natural variations in the climate system is small or nonexistent. If We Can't Explain It, It Must Be Human-Induced As a result, how worried we are about global warming is directly related to how much faith we have that natural climate variations (for instance, a small change in low-level cloudiness) are not substantially contributing to our current warmth. "When all you have is a hammer, everything looks like a nail." Global warming is our hammer, and so every change we see in the climate system that we can not otherwise explain tends to look like a nail. Climate Prediction and Weather Forecasting Are Not the Same In contrast to weather prediction models, the purpose of climate models is not to get a good 3 day or 10 day forecast. Climate models are instead run for much longer periods of simulated time - many years to centuries. Their purpose is to determine how the model's climate (average weather) is affected when one of the rules -- 'boundary conditions' -- by which the atmosphere operates is changed in the model. In the case of global warming, that rule change is mankind's addition of greenhouse gases, mainly carbon dioxide from the burning of fossil fuels, which then affects the model's 'greenhouse effect' -- the way in which the model atmosphere processes infrared (radiant heat) energy. The Earth's Natural Greenhouse Effect Fig. 4. The Earth's natural 'greenhouse' effect is due to the absorption of infrared (heat) radiation by water vapor, clouds, carbon dioxide, methane, and other greenhouse gases in the atmosphere. Mankind's Enhancement of the Greenhouse Effect Fig. 5. The Earth's radiative energy balance is fundamental to understanding global warming theory, which says that mankind's greenhouse gas emissions is disrupting the 235 W/m2 balance (solar input & infrared output). But mankind's emissions of greeenhouse gases is believed to have disrupted that balance. Since the beginning of the industrial revolution, it is estimated that the normal infrared cooling rate of 235 W/m2 has been reduced by about 1.6 W/m2. Taking into account the warming that has already occurred (supposedly) in response, one estimate is that a 0.8 W/m2 imbalance still exists today. That continuing imbalance represents further warming that must occur, even if we were to stop producing greenhouse gases immediately. Of course, since mankind continues to emit greenhouse gases, a radiative imbalance will continue to exist, and so warming will continue as well. Interestingly, the Earth-orbiting instruments for measuring the Earth's radiative components are not quite accurate to measure the small radiative imbalance that is presumed to exist. That imbalance is, instead, a theoretical calculation. You might also be surprised to find out that the direct effect of this imbalance (often called a 'radiative forcing') from the extra CO2, by itself, would have very little effect on the Earth's temperature. If everything else in the climate system remained the same, a doubling of the atmospheric carbon dioxide concentration (probably late in this century) would cause little more than 1 deg. F of surface warming. The effect is so small because, even at CO2 doubling, the fraction of our atmosphere that carbon dioxide occupies is still less than 1 part in 1,000. Obviously, a 1 deg. F warming would cause little concern - if that was the whole story. The problem is that everything else probably doesn't remain the same. Positive or Negative Feedbacks? Most computerized climate models behave in this second way, amplifying the initial warming by anywhere from a little bit, to a frightening amount (over 10 deg. F by 2100). So, you can see then that is very important to determine how sensitive the climate system is to the radiative forcing from the extra greenhouse gases we are putting into the atmosphere. To be able to predict how much warming there will be, what we really need to know then is the kind of negative and positive feedbacks that exist in the climate system. The net effect of all of the feedbacks together determines what is called the 'climate sensitivity', which as the name implies, expresses how much surface warming would result from a given amount of radiative forcing - say, a doubling of the concentration of carbon dioxide in the atmosphere. Estimating Climate Sensitivity If we can't do a laboratory experiment, another way to estimate climate sensitivity would be some previous example of climate change in response to radiative forcing. For instance, there are pretty good estimates of how much the Earth cooled after the major eruption of Mt. Pinatubo in the Philippines in June, 1991 (see Fig. 6). The millions of tons of sulfur dioxide that was injected into the stratosphere by Mt. Pinatubo spread around the Northern Hemisphere, and reduced the amount of incoming sunlight by as much as 2% to 4% The resulting cooling effects lasted two or three years, until the sulfuric acid aerosols finally dissipated. Fig. 6. The explosive 1991 eruption of Mt. Pinatubo in the Philippines injected millions of tons of sulfur dioxide into the stratosphere. The resulting 2%-4% reduction in sunlight offered a natural test of the Earth's climate sensitivity to changes in solar radiation. Unfortunately, an estimate of climate sensitivity from changes in sunlight is not necessarily the same as the sensitivity to changes in greenhouse gases, which affect infrared light. While sunlight is the source of energy for the climate system, greenhouse gases affect how that energy courses through the climate system. Very simply put, sunlight causes weather, but the greenhouse effect is the result of weather. So, are there any previous examples of infrared (greenhouse) climate forcings? There are ice core measurements from Antarctica which suggest that, hundreds of thousands of years ago, carbon dioxide levels and temperature did indeed go up and down together. But there is much debate over which was the cause, and which was the effect. Based upon the available evidence, the current consensus of opinion is that the temperature changes preceded the carbon dioxide changes by a century or more. Temperature changes causing carbon dioxide changes might be explained by the fact that warmer water can not hold as much carbon dioxide, so periods of climatic warming led to a slow release of oceanic CO2. Thus, in contrast to volcanic eruptions and their effect on solar heating, we are possibly left without a natural example of infrared radiative forcing, which is what global warming is all about. But the climate models suggest it does not really matter. They suggest the climate has about the same sensitivity to solar heating changes as to infrared cooling changes. If that is true, then natural events like the Pinatubo eruption could indeed be used to estimate manmade global warming. But I believe that the climate's sensitivity to solar forcing is not the same as its sensitivity to infrared forcing. And here's why.... What Determines the Earth's Natural Greenhouse Effect? This cause-versus-effect role of the Earth's natural greenhouse effect is an important distinction. I mentioned above the common explanation that the Earth's "energy balance results in a roughly constant globally-averaged temperature". But I believe that this has cause and effect turned around: It is more accurate to say that "the atmosphere generates a greenhouse effect and temperature that results in energy balance" with the incoming sunlight. But Don't Climate Models also "Generate" a Greenhouse Effect? As it is, even climate 'experts' give faulty physical explanations for how manmade global warming works. For instance, the largest and most consistent positive feedback exhibited by these models is positive water vapor feedback. The common explanation for this feedback is that the warming tendency from the extra carbon dioxide causes faster evaporation of water from the surface...and since water vapor is the atmosphere's dominant greenhouse gas, this faster evaporation leads to an amplification of the warming tendency from the extra CO2. This simple explanation has great appeal, and is widely repeated by climate modelers. But it is grossly misleading. The average amount of water vapor that resides in our atmosphere is not controlled by evaporation. Instead, it is controlled by precipitation (rain and snow) systems. Even though water is continuously evaporating from the surface of the Earth, the atmosphere never fills up with it because precipitation systems remove it long before saturation is reached. Precipitation Systems: Nature's Air Conditioner? Fig. 7. Most of the atmosphere gets continuously recycled through precipitation systems, which determine the moisture properties, and thus greenhouse effect, of the air. But here's the part that even climate researchers tend to forget: For all of the moist air flowing into the precipitation systems in the lower troposphere, an equal amount of air must be flowing out of those same systems, mostly in the middle and upper troposphere. (The exception is thunderstorm downdrafts, which you have likely experienced before). That air flowing out has moisture (water vapor and cloud) amounts that are controlled by precipitation processes within the systems. Thus, precipitation processes within clouds have a controlling influence on the greenhouse effect. At this point some scientists will protest, "But that's only in the vicinity of the precipitation systems!" No, not at all...precipitation systems exert control over the greenhouse effect -- at least the water vapor portion -- far beyond the immediate vicinity of those systems - in fact, over the entire Earth. For instance, the cloud-free, dry air that is slowly sinking over the world's deserts got its dryness from air flowing out the top of precipitation systems. Eventually, that air will leave the desert, pick up moisture evaporated from the land or ocean, and be cycled once again through a rain or snow system. Similarly, the cold air masses that form over continental areas in the wintertime are extremely dry because the air within them came from the upper troposphere after it had been exhausted out of a rain or snow system. It this were not the case, wintertime high pressure systems would become saturated with water vapor as the air radiatively cools to outer space. Thus, we begin to see that much of the Earth's natural greenhouse effect is under the control of these systems. It doesn't matter whether they are tropical thunderstorms, or high latitude snowstorms, it is still the air flowing out of them in the upper troposphere that determines the humidity characteristics of the cloud-free regions everywhere else. ...And There's More.... Fig. 8. Marine stratocumulus clouds, which cool the climate system by reflecting sunlight, are partly under the control of precipitation systems far away. It should be increasingly clear to you that we can not know how sensitive the climate system is to mankind's small enhancement (from extra greenhouse gases) of the Earth's natural greenhouse effect (mostly from water vapor and clouds) unless we understand precipitation systems. Unfortunately, precipitation is probably the least understood of all atmospheric processes. In a little-appreciated research publication, Renno, Emanuel, and Stone (1994, "Radiative-convective model with an explicit hydrologic cycle, 1: Formulation and sensitivity to model parameters", J. Geophys. Res., 99, 14429-14441) demonstrated that if precipitation systems were to become more efficient at converting atmospheric water vapor into precipitation, the result would be a cooler climate with less precipitation. Thus, precipitation systems have the potential to be, in effect, the Earth's 'air conditioner', switching on when things get too warm. The big question is, do they behave this way or not? Precipitation in Climate Models Unfortunately, relatively little testing of the climate models has been done in this regard. Most of the emphasis has been on getting the models to behave realistically in how they reproduce average rainfall, not how the model handles changes in rainfall efficiency with warming. Recent research with satellite observations (in review for publication as of 7 March 2007) suggests that when the tropics become unusually warm for a few days or weeks at a time, precipitation systems there produce less high-altitude ice clouds. This, in turn, reduces the natural greenhouse effect of the tropical atmosphere. This reduction in high-altitude cloudiness causes enhanced infrared cooling to outer space, which then results in falling tropical temperatures. This is a natural negative feedback process that is counter-intuitive for most climate scientists, who believe that more tropical rainfall activity would cause more high-level cloudiness, not less. Whether this process also operates on the long time scale involved with global warming is not yet known, and will surely be the subject of considerable debate. A Summary, and the Future Precipitation systems thus act as a thermostat, causing cooling when temperatures get too high (and warming when temperatures get too low). It is amazing to think that the ways in which tiny water droplets and ice particles combine in clouds to form rain and snow could determine the course of global warming, but this might well be the case. I believe that it is the inadequate handling of precipitation systems -- specifically, how they adjust atmospheric moisture contents during changes in temperature -- that is the reason for climate model predictions of excessive warming from increasing greenhouse gas emissions. I predict that further research will reveal some other cause for the warming we have experienced since the 1970's -- for instance, a change in some feature of the sun's activity. In the meantime, a high priority research effort should be the study of changes in precipitation systems with changes in temperature -- especially how they confer moisture charateristics to the atmosphere as air is continuously recycled through them. Fortunately, we now have several NASA satellites in Earth orbit that are gathering information that will be immensely valuable for determining how the Earth's climate system adjusts during natural temperature fluctuations. It is through these satellite measurements of temperature, solar and infrared radiation, clouds, and precipitation that we will be able to test and improve the climate models, which will then hopefully lead to more confident predictions of global warming. Roy W. Spencer received his PhD in meteorology at the University of Wisconsin-Madison in 1981. He has been a Principal Research Scientist at the University of Alabama in Huntsville since 2001, before which we was a Senior Scientist for Climate Studies at NASA's Marshall Space Flight Center where he received NASA's Exceptional Scientific Achievement Medal. Dr. Spencer is the U.S. Science Team leader for the Advanced Microwave Scanning Radiometer flying on NASA's Aqua satellite. His research has been entirely supported by U.S. government agencies: NASA, NOAA, and DOE. Original Source of This Summary with Graphics (external)
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