Guest essay by Richard J. Petschauer
A skeptic that believes in global warming? How can that be? We have been told that climate skeptics, sometime incorrectly called “deniers”, still believe the earth is flat and disagree with 97% of scientists. Well, first of all, most of us have seen a globe and know what it represents. Second, do you know on what these scientists agree? If not, don’t feel bad. Those making these claims, mostly politicians, probably don’t know either. Actually, a rather poor survey was done looking at a summary of many technical papers. If any one of many climate related points were made, they were put in the 97% camp. This article would probably have qualified too.
But the real question, not covered in the survey: How fast will the earth warm if we do nothing to curtail the growth of man made carbon dioxide emissions? And how much can we reduce the warming if we cut world emissions by some factor? The impact and costs of doing nothing or something will not be covered here, but it is obvious they would depend on how fast warming will occur. This we will discuss.
So what are the skeptics skeptical about? It is the amount and rate of the man made warming estimated by the United Nations Intergovernmental Panel on Climate Change (IPCC) and the claims of some spokespeople, many in government, who go much beyond what the IPCC says, like “the planet is having a fever” or “things are getting worse than expected”. But data shows global temperatures have increased much less than models predicted. In fact, unknown to many, accurate satellite data shows very little if any warming in the last 18 years.
Where there is general agreement
There are many areas where most skeptics and the “alarmists”, as they are called, agree. First is the idea of “climate sensitivity”, a useful benchmark for making estimates. It is the final average global temperature rise that would be caused by a doubling of the carbon dioxide (CO2) in the atmosphere, assuming there are no natural changes. Second, most agree on well established methods to estimate how greenhouse gases absorb and emit heat, and that doubling of CO2 will reduce the heat leaving the planet by a little more than 3.5 watts per square meter. This compares to both estimates and satellite measurements of the total now leaving of about 235 watts per square meter. If the value of 3.5 watts out of 235 seems low, it is because CO2 only absorbs the infrared wavelengths that involve about 20% of the heat leaving the surface, and in this region its action is partially saturated and the second doubling will reduce heat loss by about another 3.5, not 7 watts. A 1% change in energy from the sun or a 7% change in cloud cover would cause about the same change as doubling CO2. Third, there is general agreement on how much the average surface will warm to make up for this heat loss: about 1 C (1.8 F). But here is the rub: this estimate is before the atmosphere and the surface, including oceans, react to this temperature change.
Where there is not agreement
How the climate reacts to the initial warming is the main area where most skeptics have problems with the IPCC and others. These reactions are called “feedbacks”. Positive ones amplify any temperature change (warming or cooling from any cause, not just from CO2). Negative ones diminish a change. There are general agreements on the equations used to define the feedback strengths and how they are combined into one net temperature change multiplier that can be either greater or less than one. The major disagreements are the magnitudes of the feedback values and for clouds, even if it is positive or negative. The final IPCC warming estimates for doubling CO2 range from 1.5 to 4.5 C. The skeptics have no common voice, but their values range from about 0.5 to 1.2 C, a significant reduction. IPCC also uses a 1% annual growth of the CO2 content in the atmosphere, while data shows only about 0.55%. This increases CO2 doubling time from about 70 years to 140.
Two different approaches
One primary complaint is the IPCC and most government funding research have abandoned improving the simple energy balance model and the feedback concept and gone to complex climate models that try to estimate many conditions across the globe and layers in the atmosphere over many years and then a temperature change. Small errors can propagate into unknown large ones. There are over 100 of these models written by different teams and their results differ by a range to 3 to 1. And nearly all overestimate warming compared to observed data. This is settled science? No! And it is bad engineering practice, which some scientists apparently don’t understand, to try to solve such a complex problem without breaking it down into smaller steps that each can be verified and corrected. What is causing the errors in the climate models that cause them to overestimate global warming? How will any proposed correction be tested without waiting about 10 to 30 years?
Corrections to the complex computer models
We believe the complex computer models overestimation of warming is mostly based on a combinations of three factors: overestimating positive water vapor feedback, underestimating negative feedback from increased sea surface evaporation and treating cloud feedback as positive feedback while it is very likely negative. For water vapor (a major greenhouse gas) the climate models show it increases about 7% per degree C of warming. But extensive data over 30 years from 15,000 stations at many latitudes over land and sea show an increase of only about 5% at the surface, the atmosphere’s main water vapor source. (Dia, “Recent Climatology and Trends in Global Surface Humidity”, American Meteorological Society, August, 1997). Water vapor is also an absorber of incoming solar energy, reducing what reaches the surface. Reduced greenhouse action and increased solar absorption cut the computer models positive water vapor feedback in about half. Regarding the cooling effects of increased evaporation, mostly over the oceans, both data (Wentz, et al, “How Much More Rain Will Global Warming Bring?, Science, 13 July, 2007) and basic physics indicate an increase of about 6% per degree C of warming, over double what the climate models average. Finally, the models estimate a value of positive feedback for clouds only because this amount is needed to boost the initial 1 C prefeedback warming up to the models final average estimate. It is more likely that more evaporation and water vapor will increase cloud content, a net cooling effect. Using simple energy balance models with proven greenhouse gas absorption/radiation tools, the result of these changes indicates a warming from double CO2 in a range of 0.6 to 0.9 C, much less than IPCC’s value of 1.5 to 4.5 C. Note the uncertainty range drops by a factor of 10, from of 3 degrees C to 0.3 C, because of the elimination of unreliable complex computer models and their net positive feedback.
A skeptics summary
About 1 C warming in the next 140 years does not seem to be a problem. (It will actually take longer because the ocean heat storage will delay the warming). Furthermore, both simple models and data show that most of the warming will be in winter nights in the colder latitudes. Less water vapor here reduces its competition with CO2. An example is in Minneapolis, Minnesota at 45 degrees latitude. About half of July record highs were set in the 1930s, with only 3 since 2000. However 80% of the record January lows were from 1875 to 1950. This winter warming is a benefit. And what makes people think the climate around 1900 represents the ideal? In 2014 we just saw a very cold winter, typical of that era. Finally, warmer temperatures increase evaporation and precipitation and since CO2 is a plant food, food crop production will increase, contrary to some other estimates. And any climate model that estimates a small, slowly increasing temperature will “disrupt” the climate should be looked at with great skepticism.
Digging deeper – does carbon dioxide really trap heat?
We have heard that carbon dioxide “traps” heat high in the atmosphere somewhat like a blanket that covers everything and is getting thicker as emissions increase, trapping more heat. Well, it’s not so simple and fortunately not that bad. Let us explain what happens.
The above figure is taken from an often cited paper, including by the IPCC, titled “Earth’s Annual Global Energy Budget” by Kiehl and Trenberth from the Bulletin of the American Meteorological Society, 1997, with notations that we added. The top curve shows how the intensity of the average heat leaving the earth’s surface varies with infrared wavelength. The lower jagged curve is that leaving at the top of the atmosphere under average cloudy conditions. The area under a curve is its total heat in watts per square meter. Note the large downward notch leaving the atmosphere in the 12 to 18 microns range caused by CO2. It is such a strong absorber here that it cannot release its heat outward until the density of its molecules drops significantly at high altitudes where the temperature is about –60 F. Hence the low radiation rate. If the amount of CO2 increases, the escape altitude moves up causing both the temperature and heat loss to drop further. The area of the CO2 notch below the dashed line is about 22 watts per square meter and represents the impact of the total CO2 given the existing clouds and water vapor. Doubling CO2, taking over 100 years at the current growth rate, would move the notch downward and increase the area by about 3.5 watts per square meter, or 16%. When the heat loss drops, since the net heat from the sun remains at 235, the atmosphere gains heat and warms about 1 degree C until its emissions rise back to 235, restoring balance. A warmer atmosphere reduces the heat loss from the surface, and it also warms about 1 C. This is all that CO2 does. And very slowly. The feedback processes can increase or decrease this warming, as they do for any other temperature change.
Correction: The 140 years cited in two places as the time for CO2 doubling for the compound annual increase of 0.55 % of the last 20 years should be 126 years (1.0055 ^126.4 = 2.0003). The 140-year value is for 0.50 %, consistent with the last 35 years.