Bob Irvine is touting his new paper at WUWT. He seems very happy with himself. He shouldn’t be: the paper comparing the efficacy of solar and greenhouse forcing is awful.
The first indication that the paper is going to be bad (other than it being recommended on WUWT), is where it is published: WIT Transactions on Engineering Sciences is not the obvious journal to publish a climate science paper in. Climate sceptic often publish in an off-topic journal, where the editor and the usual set of reviewers have little background in climate science and so cannot properly evaluate the manuscript. Not a good sign.
Of course it is possible to publish a good paper is an inappropriate journal, just as it is possible to publish a bad paper in a relevant journal.
The next indication that the paper is bad is in the second sentence of the abstract.
Most Coupled Model Intercomparison Project Phase 5 (CMIP5) climate models assume that the efficacy of a solar forcing is close to the efficacy of a similar sized greenhouse gas (GHG) forcing.
Irvine makes no attempt to substantiate the claim that the models make this assumption. He cannot, for this claim is simply wrong and demonstrates a profound misunderstanding of how coupled climate models work. Irvine could read the code of a climate model from end to end and he would not find the line that codes the relative efficacy of different forcings, nor of climate sensitivity, because they are not there. Climate sensitivity and the efficacy of different forcings are not inputs to the model, they are the properties that arise from the basic physics represented in the model.
Irvine argues that solar forcing has a much higher efficacy than greenhouse gas forcing, that is, one watt of solar forcing causes more heating than one watt of greenhouse gas forcing. Coupled climate models suggest that the different forcings have similar efficacies despite their different geographical and seasonal distribution, and physical mechanisms.
Irvine disputes this. Instead he argues that forcing with short and long wave (IR) radiation has very different effects on climate. IR re-emitted from CO2 in the atmosphere is absorbed by the top millimetre of the ocean. Irvine claims that this energy is “returned almost immediately to the atmosphere and space as latent heat of evaporation.”
Short wave radiation direct from the Sun penetrates the ocean more deeply.
For energy of 418nm, light drops to one thousandth of its original intensity after travelling about 1570 meters in pure water.
Irvine goes on to make a “crude forcings model” that matches the observed instrumental climate record much better than a CMIP5 model and performs a simple experiment aimed to show that downwelling IR has little impact in slowing the cooling of water.
So what are the problems.
First the depth which the 0.1% of blue photons reach in pure water is irrelevant and misleading. What matters is where the bulk of the short wave photons are absorbed and warm the ocean: the upper fifty metres in clear ocean, much less where the water is turbid. This is still much deeper than IR, but well over an order of magnitude shallower than the depth Irvine gave.
The “crude forcings model” is discussed at length, but bizarrely, the model is never specified. The results are apparently just too exciting to bother with tedious details like methods. This is a failure of the peer review process (if any) at the journal. From what is written, the model appears to be a curve-fitting exercise with the observed temperature being a linear function of solar, greenhouse gas and aerosol forcing plus internal variability. The internal variability is included as the sum of the Atlantic Multidecadal Oscillation and the Pacific Decadal Oscillation. This sum of two indices has little if any physical meaning, but gives Irvine’s model a help in matching the instrumental data. This means that the comparison with the CMIP5 model is not remotely fair as the model’s internal variability is unlikely to be in-phase with the internal variability in the real climate.
Further, Ivine’s model generates decadal mean results which are compared with decadal mean instrumental data, so short term variability such as the El Nino is removed. The CMIP5 model results are presented at an annual resolution and of course the timing of the El Nino in the model and real climate do not match. You would not expect them to even in a perfect model.
I’m not sure that it is possible to meaningfully compare the results of a CMIP5 model with a curve fitting exercise, but if it is, Irvine has done a bad job of it.
Irvine finds that solar forcing has a climate sensitivity of 1.4°C/wm-2 [Irvine's unit notation] and that greenhouse gas forcing has a climate sensitivity of 0.35°C/wm-2. In appendix B, the sensitivity for greenhouse gas forcing is given as 10 times higher but the units are wrong. If I fit a linear model to the numbers in appendix B, only greenhouse gas forcing is a statistically significant predictor of temperature. There is insufficient information to work out what Irvine has done here.
Next the experiment. Irvine takes two bowls of warm water, each beneath a shelter. One shelter is transparent to IR emitted by the water, the other reflects it, while computer fans provide a draft. Initially the water in the bowls is free to evaporate. The cooling rate is the same in both bowls. Then evaporation is stopped by placing cling film over the bowls. The bowl under the IR reflector now cools more slowly. Irvine argues that this experiment shows that the energy from the reflected IR immediately lost as latent heat by driving evaporation.
It is not a well designed experiment, at least not one that resembles reality. Blowing dry air over the water is bound to cause such a large amount of evaporation that the reflected IR will have minimal impact on the rate of cooling.
If Irvine was correct, and that incoming IR is immediately lost by the ocean, it is unclear how the natural greenhouse effect that warms the Earth 33 °C over what is expected for a blackbody this far from the Sun with the current albedo could arise.
So what really happens to downwelling long wave radiation? It warms up the top millimetre of the ocean. By adding energy at the surface it slows down the rate of energy loss by emission of long wave radiation and evaporation. As the net rate of energy loss is reduced, the equilibrium temperature is warmer. Simple. Irvine’s notion that the ocean can recognise the energy added to the surface of the ocean by IR and treat this energy differently from other energy, immediately directing it into evaporation or long wave emission, is simply absurd. An engineer should know better.