NOV. 28, 2015 gave his answers to 16 questions in the N.Y. Times regarding Climate Change. This Climate realist added his answer.
Justin Gillis answer to Question 9. Are the predictions reliable?
“They’re not perfect, but they’re grounded in solid science.
The idea that Earth is sensitive to greenhouse gases is confirmed by many lines of scientific evidence. For instance, the basic physics suggesting that an increase of carbon dioxide traps more heat was discovered in the 19th century, and has been verified in thousands of laboratory experiments.
Climate science does contain uncertainties, of course. The biggest is the degree to which global warming sets off feedback loops, such as a melting of sea ice that will darken the surface and cause more heat to be absorbed, melting more ice, and so forth. It is not clear exactly how much the feedbacks will intensify the warming; some of them could even partially offset it. This uncertainty means that computer forecasts can give only a range of future climate possibilities, not absolute predictions.
But even if those computer forecasts did not exist, a huge amount of evidence suggests that scientists have the basic story right. The most important evidence comes from the study of past climate conditions, a field known as paleoclimate research. The amount of carbon dioxide in the air has fluctuated naturally in the past, and every time it rises, the Earth warms up, ice melts, and the ocean rises. A hundred miles inland from today’s East Coast, seashells can be dug from ancient beaches that are three million years old, a blink of an eye in geologic time. These past conditions are not a perfect guide to the future, either, because humans are pumping carbon dioxide into the air far faster than nature has ever done.
My answer to Question 9. Are the predictions reliable?
They are not perfect, for sure, but are they even grounded in solid science? For a model to have credibility it must be tested with measurements, and pass the test. There is important evidence suggesting the basic story is wrong. All greenhouse gases work by affecting the lapse rate in the tropics. They thus create a “hot spot” in the tropical troposphere. The theorized “hot spot” is shown in the early IPCC publications. (Fig A)
The models all assume greenhouse gases are additive. This is true for low concentrations and over short distances, such as is done in laboratory environments. Yet there is one truth bout heat absorption. Once all the energy in one frequency band is absorbed, that is it. If the water vapor has already absorbed the energy, no matter of added CO2 will change that. This is largely true in the tropics, where water vapor is dominant. As CO2 levels increased, no hotspot formed in the tropics. Near the poles the situation is different, more CO2 will lead to higher temperatures, but always less than what would have been predicted by separately adding the effects of water vapor and CO2.
[The amount of carbon dioxide in the air has fluctuated naturally in the past, and every time it rises, the Earth warms up, ice melts, and the ocean rises.]
This statement should read: Every time temperature rose in the past, the ice melted, and the oceans warmed up, causing carbon dioxide to be released from ice and oceans and rise with a 300 to 800 years delay, the amount of water vapor rose, increasing the earth’s cloud cover, stopping the temperature rise, and after a time delay CO2 also stopped rising, and ocean levels stabilized.
So CO2 is an effect of, not a cause for the observed temperature rise.
Al Gore’s movie An Inconvenient Truth used this very argument to show CO2 causes temperature rise. A British court found that this was one of the 9 errors of fact that appear in the movie. The court ruled that any theater showing the movie would need to inform the audience of these 9 errors. http://www.telegraph.co.uk/news/earth/earthnews/3310137/Al-Gores-nine-Inconvenient-Untruths.html