We’ve reached a turning point where it is hard for any Global Warming Alarmist to claim (with a straight face) that the world as we know it is about to end in the coming decades unless we stop burning fossil fuels. Anyone deluded or foolish enough to make such a claim would be laughed at by many audiences.
GLOBAL WARMING IS REAL
Yes, the world has warmed 1°F to 1.5°F (0.6°C to 0.8°C) since 1880 when relatively good thermometers became available. Yes, part of that warming is due to human activities, mainly burning unprecedented quantities of fossil fuels that continue to drive an increase in carbon dioxide (CO2) levels. The Atmospheric “Greenhouse” Effect is a scientific fact!
BUT GLOBAL WARMING IS NOT A BIG DEAL
Alarmist Theory is Handcuffed to High Estimates of Climate Sensitivity
As the animated graphic clearly indicates, the theoretical climate models used by the Intergovernmental Panel on Climate Change (IPCC) are handcuffedto inordinately high estimates of climate sensitivity (how much temperatures are expected to rise given a doubling of CO2). Since the advent of good satellite-based global temperature data in 1979, observed temperatures have risen at a fraction of the IPCC predicted rate even as CO2 continues to rise.
Relax, there is not and never has been any near-term “tipping point”. The actual Earth Climate System is far less sensitive to CO2 than claimed the IPCC climate theory, as represented by their computer models. Global Warming since 1880 is mainly due to Natural Cycles and Processes not under human control. Yes, the same Natural Cycles and Processes that were responsible for the many Ice Age cycles that repeatedly occurred about every 100,000 years or so.
A GREAT TIME TO PUT ALARMISTS IN THEIR PLACE
Last week, by a stroke of good fortune, I happened to be scheduled to present“Visualizing the Atmospheric ‘Greenhouse’ Effect – Global warming is real, but how much is due to human activities and how big is the risk?” to the Philosophy Club in the Central Florida retirement community where I live.
Everyone in the highly interactive and supportive audience was aware of newspaper and TV reports of the drama of those ill-fated Global Warming “Research” activists whose Russian ship, the Academik Shokalskiy, got stuck in the summer ice of the Antarctic. (Fortunately, those people are safe, having been rescued by a helicopter from a Chinese icebreaker.) In addition to the Antarctic adventure gone wrong, in the week leading up to and following my talk, the media was overrun by stories of the “polar vortex” literally freezing large parts of the US and even causing Florida temperatures to drop below 30°F (0°C).
Of course, everyone knows that the cold wave is only anecdotal evidence and “weather is not climate”. However, photos and videos of researchers stuck in the Antarctic summer ice as well as scenes of American life frozen in place for days on end, when combined with clear and irrefutable evidence of a slowdown in warming since 1979 and no statistically significant warming since 1996 (as depicted in the graphic above), has considerable emotional impact. Audiences often react more to emotions than their reason.
My animated PowerPoint Show, which should run on any Windows PC, is available for download here. (NOTE: I knew that many members of the Philosophy Club audience, while highly intelligent and informed, are not particularly scientifically astute. Therefore, I kept to the basics and invited questions as I proceeded. Since most of them think in Fahrenheit, I was careful to give temperatures in that system. By contrast, my 2011 talk to the more scientifically astute members of our local Science and Technology ClubSkeptic Strategy for Talking about Global Warming was more technical. Both presentations make use of animated PowerPoint charts and you are free to download and use them as you wish.)
I explained how a real physical Greenhouse works and how that is both similar and different from the Atmospheric “Greenhouse” Effect. The Greenhouse descriptions I learned in high school, as well as those available on the Internet, consider only the RADIATIVE effect. The glass roof of the Greenhouse allows visible light to pass through freely, heating the soil, plants, and air, but is opaque to the resultant infrared radiation, which is partly re-radiated back down into the Greenhouse, warming it further. That part is true, but far from the whole story. The MAIN reason a Greenhouse stays warm is that it is airtight to restrict CONVECTION and it is insulated to restrict CONDUCTION. In fact, it is possible to construct a successful Greenhouse using a roof made from materials that allow both visible and infrared to pass freely, but is impossible to make a working Greenhouse that is not both airtight and insulated.
HOW THE ATMOSPHERIC “GREENHOUSE” EFFECT WORKS
All warm objects emit radiation at a wavelength dependent upon the temperature of the object. The Sun, at around 10,000 °F, emits “short-wavelength” infrared radiation, centered around 1/2 micron (one millionth of a meter). The soil, plants, and air in the Greenhouse, at around 60°F to 100°F (15°C to 40°C), emit “long wavelength” radiation, centered around 10 microns (with most of the energy between 4 and 25 microns).
The Atmospheric “Greenhouse” Effect works because:
Short-wavelength radiation from the Sun passes freely through the gases that make up the Atmosphere,
About a third of this Sunlight is reflected back by white clouds, dust, and light-colored objects on the Surface, and that energy is lost to Space,
The remaining two-thirds of the Sunlight energy is absorbed by the Sea and Land Surface and causes it to warm,
The warm Surface cools by emitting long-wavelength radiation at the Bottom of the Atmosphere, and this radiation passes towards the Top of the Atmosphere, where it is ultimately lost to Space,
On the way to the Top of the Atmosphere, much of this radiation is absorbed by so-called “Greenhouse” gases (mostly water vapor and carbon dioxide) which causes the Atmosphere to warm,
The warmed Atmosphere emits infrared radiation in all directions, some into Space where it is lost, and some back towards the Surface where it is once again absorbed and further warms the Surface.
In addition to the RADIATIVE effects noted in points 1 through 6, the Surface is cooled by CONVECTION and CONDUCTION (thunderstorms, winds, rain, etc.)
THANK GOODNESS FOR THE ATMOSPHERIC “GREENHOUSE” EFFECT
If not for the warming effect of “Greenhouse” gases, the Surface of the Earth would average below 0°F (-18°C), which would prevent life as we know it. This effect is responsible for about 60°F (33°C) of warming. According to the Intergovernmental Panel on Climate Change (IPCC), the Earth Surface has warmed about 1.5°F (0.8°C) since good thermometer data became available around 1880. Some skeptics (including me) believe the actual warming is closer to 1°F, and that government agencies have adjusted the thermometer record to exaggerate the warming by 30% or more. However, it doesn’t really matter whether the actual warming is 1°F or 1.5°F (0.6°C or 0.8°C) because we are arguing about only 0.5°F (0.2°C), which is less than 1% of the total warming due to the Atmospheric “Greenhouse” Effect.
HOW SENSITIVE IS THE CLIMATE TO HUMAN ACTIVITIES?
The IPCC claims that the majority of the warming since 1880 is due to human activities. It is true that we are burning unprecedented amounts of fossil fuel (coal, oil, gas), and that we are making land use changes that may reduce the albedo (reflectiveness) of the Surface. Most of the increase in Atmospheric CO2 (a 40% rise from about 270 to nearly 400 parts per million by volume) is due to human activities.
The IPCC claims that Climate Sensitivity (the average increase in Surface temperatures due to a doubling of CO2) is between 3°F and 8°F (1.5°C and 4.5°C). Some skeptics (including me) believe they are off by at least a factor of two, and possibly a factor of three, and that Climate Sensitivity is closer to 1°F to 3°F (0.5°C to 1.5°C). As evidence for our conclusions, we point to the fact that virtually ALL of the IPCC climate models have consistently over-estimated future temperature predictions as compared to the actual temperature record. Indeed, for the past 17 years as CO2 levels continue their rapid climb, temperatures have leveled off, which is proof that Natural Cycles, not under human control or influence, have cancelled out warming due to CO2 increases. Thus, Natural Cycles must have a larger effect than CO2.
Answering Some Objections to the Atmospheric “Greenhouse”Effect
Some WUWT commenters seem to have been taken in by scientific-sounding objections to the basic science behind the Atmospheric “Greenhouse” Effect. Their objections seemed to add more heat than light to the discussion. This section is designed to get back to basics and perhaps transform our heated arguments into more enlightened understanding :^)
The main scientific question for me, is how much does the increase in human-caused CO2 and human-caused albedo reduction increase the mean temperature above what it would be with natural cycles and processes? My answer is “not much”, because perhaps 0.2ºC to 0.4ºC (0.1ºC to 0.2ºC) of the supposed 1.5ºF (0.8ºC) increase since 1880 is due to human activities. The rest is due to natural cycles and processes over which we humans have no control. The main public policy question for me, is how much should we (society) do about it? Again, my answer is “not much”, because the effect is small and a limited increase in temperatures and CO2 may turn out to have a net benefit.
So, my motivation for this Visualizing series was not to add to the Alarmist “the sky is falling” panic, but rather to help my fellow Skeptics avoid the natural temptation to fall into an “equal and opposite” falsehood, which some of those on my side, who I call “Disbelievers”, do when they fail to acknowledge the basic facts of the role of H2O and CO2 and other gases in helping to keep temperatures in a livable range.
Objection #1: Visual and near-visual radiation is merely “light” which lacks the “quality” or “oomph” to impart warmth to objects upon which it happens to fall.
Answer #1: A NASA webpage targeted at children is sometimes cited because they say the near-IR beam from a TV remote control is not warm to the touch. Of course, that isnot because it is near-visual radiation, but rather because it is very low power. All energy is fungible, and can be changed from one form to another. Thus, the 240 Watts/m^2 of visible and near-visible Solar energy that reaches and is absorbed by the Earth System, has the effect of warming the Earth System exactly as much as an equal number of Watts/m^2 of “thermal” mid- and far-IR radiation.
Objection #2: The Atmosphere, which is cooler than the Earth Surface, cannot warm the Earth Surface.
Answer #2: The Second law of Thermodynamics is often cited as the source of this falsehood. The correct interpretation is that the Second Law refers to net warming, which can only pass from the warmer to the cooler object. The back-radiation from the Atmosphere to the Earth Surface has been measured (see lower panel in the above illustration). All matter above absolute zero emits radiation and, once emitted, that radiation does not know if it is travelling from a warmer to a cooler surface or vice-versa. Once it arrives it will either be reflected or absorbed, according to its wavelength and the characteristics of the material it happens to impact.
Objection #3: The Atmospheric “Greenhouse” Effect is fictional. A glass greenhouse works mainly by preventing or reducing convection and the Atmosphere does not work that way at all.
Answer #3: I always try to put “scare quotes” around the word “greenhouse” unless referring to the glass variety because the term is misleading. Yes, a glass greenhouse works mainly by restricting convection, and the fact that glass passes shortwave radiation and not longwave makes only a minor contribution.
Thus, I agree it is unfortunate that the established term for the Atmospheric warming effect is a bit of a misnomer. However, we are stuck with it. But, enough of semantics. Notice that the Earth System mean temperature I had to use to provide 240 Watts/m^2 of radiation to Space to balance the input absorbed from by the Earth System from the Sun was 255 K. However, the actual mean temperature at the Surface is closer to 288 K. How to explain the extra 33 K (33ºC or 58ºF)? The only rational explanation is the back-radiation from the Atmosphere to the Surface.