Not surprisingly, Watts up With That (WUWT) has a post mocking John Cook’s recent quote that the increase in energy associated anthropogenic global warming (AGW) is the same as 4 Hiroshima bombs per second. As I showed in yesterdays’s post, this comparison is actually quite accurate.
So, what does Anthony say in this post? He quotes Willis Eschenbach who apparently has said
400,000 Hiroshima bombs per day works out to 0.6 watts per square metre … in other words, Hansen wants us to be very afraid because of a claimed imbalance of six tenths of a watt per square metre in a system where the downwelling radiation is half a kilowatt per square metre … we cannot even measure the radiation to that kind of accuracy.
The Hansen mentioned is James Hansen (who initially made the comparison with atom bombs) and, indeed, the energy imbalance is equivalent to 0.6 Wm-2. That’s what everyone is concerned about. So Willis has calculated the same energy excess as is observed (good for him) but decided it’s insignificant. Really? All these scientists are just being melodramatic? Just because Willis thinks this is a small number doesn’t mean that it isn’t going to lead to significant changes in our climate.
Anthony then goes on to say
So imagine the output of a 0.6 watt light bulb, 1/100th the power of a common household 60 watt light bulb.
Could you even see it?
So I think this analogy is wrong. The correct analogy would be a house full of 60 Watt lightbulbs, but in which 0.6 J of energy per square metre per second nevers leaves the house. So a typical house has a footprint of about 200 m-2. This means the house would gain 120 J of energy every second. If the house has a volume of 2000m-2, then the mass of the air in the house is about 2300 kg. From what I can find, the specific heat capacity of air is 1000 J kg-1 K-1. The temperature of the air in the house would therefore increase by 5.22 x 10-5 K every second. Sounds like a tiny amount doesn’t it? Well, in fact, this means the temperature in the house would increase by 4.5 degrees per day. Unless my calculation is wrong, the house would reach boiling point within a month. Maybe Anthony thinks this is insignificant. Personally, I would disagree.
Anthony then includes the figure below and says
Note the figure on the Earth that I highlighted in yellow: Surface imbalance 0.6 ± 17 Wm-2
So, Anthony highlights the surface energy imbalance and suggests that such a large uncertainty (2 orders of magnitude greater than the estimated imbalance) means that we can’t even be sure that such an imbalance exists or that it will lead to anything in the future. Well, that isn’t the energy imbalance that James Hansen or John Cook are talking about. They’re talking about the top-of-the-atmosphere (TOA) energy imbalance. This is the energy imbalance that tells us how much excess energy is entering the climate system. Have a look at the top of the figure above and you will see “TOA imbalance 0.6 +- 0.4″ Wm-2. Okay, so the error is still quite large but indicates that there is indeed a positive energy imbalance. So, Anthony’s argument that the large uncertainty in this imbalance means we can’t make claims about the future is based on highlighting the incorrect energy imbalance.
Anyway, Anthony thinks that the analogy with atom bombs suggests that the energy imbalance is insignificant simply because the number associated with this imbalance happens to be a small number. However, extending his lightbulb analogy suggests that he would be happy living in a house that reached boiling point in less than a month. He then goes on to say that on top of this, the energy imbalance is so uncertain that we shouldn’t be basing anything on this estimate, but bases this on the incorrect energy imbalance (surface rather than TOA). Don’t really know what else to say? I suspect those who read this can draw their own conclusions.