Climate sensitivity is defined as …
a measure of how responsive the temperature of the climate system is to a change in the radiative forcing.
Nova’s recent claim on this topic is the use of Sherwood Idso’s research from the 1980’s. Idso’s research was scientifically debunked because his calculation did not actually equate to that of climate sensitivity (see below). No climate scientist used Idso’s methods to determine climate sensitivity because, as we’ll examine, his mistakes were obvious, measuring the change in surface radiation rather than top of atmosphere, measuring the changes in one small location, then extrapolating that to the whole planet, measuring apparent changes in Mars and expecting the Earth to respond in a similar way, not allowing time for equilibrium to be reached.
The most obvious reason why Idso’s estimate of 0.4°C rise in temps for a doubling of CO2 is too low; the planet has warmed that much since he first published in 1984, whilst CO2 levels rose 15% from 350 to 390 ppm.
Despite this, Nova says Idso is correct and most climate sensitivity work done since then is incorrect, although she won’t actually tell you precisely why, or offer any peer-reviewed science that rebuts recent estimates.
Equilibrium and Transient Climate Sensitivity
So how much will the climate change? Well that depends on how long you leave it at the new “heat” setting. Like turning up the heat under a pot of cool water; it takes time for the water to absorb the additional radiation and come to the boil. So too our planet’s oceans will take significant amount of time to absorb the additional radiation to the point where the incoming and outgoing radiation equalises.
Because of that reason there are several “types” of climate sensitivity definitions. A Transient definition estimates the increase in temperature over a period of more than 20 years; an Equilibrium sensitivity requires hundreds of years in order to reach a new balanced state.
It is the Equilibrium sensitivity that is most often mentioned when talking about the IPCC’s 3 degrees of warming per doubling of CO2. Most of Idso’s “natural experiments” take place over a timeframe of days – obviously not nearly enough time for the planet to warm to a new equilibrium state.
Phoenix vs The Planet
Idso looks at localised, short term events in Phoenix, then suggests this works for the rest of the planet. Enough said.
Mars vs Earth
Idso looks at Mars and somehow calculates climate sensitivity – I’d like him to explain how Mars, with it’s radically different atmospheric composition and lack of oceans can compare to Earth when trying to calculate equilibrium sensitivity.
Timeline of Idso Research vs Rebuttals
1984 – Idso publishes eight “natural experiments”
1984 – Schneider, S. H.: ‘”Natural Experiments” and CO~-Induced Climate Change: The Controversy Drags On – An Editorial’, points out (as other also had done) that what Idso is calculating is NOT equilibrium climate sensitivity.
1984 – Cess, R. D. and Potter, G. L. : 1984, ‘A Commentary on the Recent CO~ -Climate Controversy’, point out that Idso’s workings are “either founded in various violations of the first law of thermodynamics, or that they are based upon misinterpretations of historical data.”
1987 – Idso, concedes what he did was not an “equilibrium” calculation and he can’t explain energy flows. Says it doesn’t because the elusive equilibrium value can be calculate using more non-equilibrium calculations – LOL.
1987 – Gets debunked once more – G. L. Potter, J. T. Kiehl and R. D. Cess, A clarification of certain issues related to the CO2—Climate problem
Abstract. In this paper we examine and clarify several arguments that have been put forth by Dr. S. B. Idso in an article appearing within this issue of Climatic Change.
1998 – Idso republishes the same “natural experiments” once more without consideration given to previous criticisms. *** insert sound of crickets chirping ***
Only denialist websites list his work. Nobody in the scientific community bothers to reference his work and build upon his “foundation”, nor do they bother spending time repeating what others have already told him. Idso’s research dies a lonely death except for the denialists wishing to grasp for the lowest available climate sensitivity figure in order to promote their own ideology.
Ramanathan helps Idso – or does he?
Nova says Idso found there were negative feedbacks, but in fact Idso doesn’t do any such thing. Idso assumes they are negative because if they weren’t his climate sensitivity figure would not be so low.
In Idso 1998 claims …
In addition, Ramanathan & Collins (1991), by the use of their own natural experiments, have shown how the warming-induced production of high-level clouds over the equatorial oceans totally nullifies the greenhouse effect of water vapor there…
… and the great thing about peer-reviewed science is that over time, theories are put to the test and our understanding becomes greater. This paper recaps several studies that suggest why suggest SST may be regulated by mechanisms other than clouds, none of which will cap warming as Idso suggests.
Looking at Ramanathan’s more recent work shows they do not share Idso’s lack of concern for increased CO2 levels. In their study of black carbon in soot they say …
… emissions of black carbon are the second strongest contribution to current global warming, after carbon dioxide emissions.
the effect of greenhouse gases on global warming is, in my opinion, the most important environmental issue facing the world today.
These are not the words of someone suggesting that negative feedback from clouds will prevent warmer temperatures.