John Cook and the atomic bombs

John Cook, who writes the Skeptical Science blog, has been criticised – in a blog article called Media Fail: John Cook’s Atom Bombs – for comparing global warming to atomic bombs. This Media Fail post is actually referring to an article in the French Tribune called Climate Change likened to atom bomb by scientists.

In the French Tribune John Cook is quoted as saying

All these heat-trapping greenhouse gases in our atmosphere mean … our planet has been building up heat at the rate of about four Hiroshima bombs every second – consider that going continuously for several decades.

What the Media Fail article claims is that no scientist has claimed that humans are 100% responsible for current temperature trends and hence this comparison is flawed. Indeed, no scientist has claimed that we are 100% responsible for current temperature trends, so that part of the statement is correct. Other factors can and do play a role in changing globel surface temperatures. However, there is a difference between the temperature trends (for global surface temperatures for example) and the top-of-the-atmosphere energy imbalance. What John Cook is referring to is changes in the energy in the climate system, not simply changes in the global surface temperature.

Although humans are indeed not responsible for all changes to global surface temperatures, there is a perfectly good argument for why humans are almost 100% responsible for the top-of-the-atmosphere energy imbalance. The energy imbalance simply refers to the climate system receiving more energy from the Sun than we lose back into space. Normally, we’d expect the system to evolve into some kind of equilibrium in which the surface temperatures are such that – on average – the amount of energy re-radiated back into space matches the amount we’re receiving. Currently, however, global surface temperatures are higher than they’ve been for most of the last few thousand years. If so, the surface of the planet must be radiating at least as much energy – if not more – than it has done for the last few thousand years. The Sun is also not more luminous today than it has been for the last few thousand years, so we aren’t receiving more energy than we have done for the last few thousand years. Yet, we still have an energy imbalance such that we’re receiving more energy than we lose. How is this possible?

Well the current scientific consensus is that the CO2 that we’ve been adding to the atmosphere has been trapping more of the outgoing radiation and reducing the amount of energy reaching the top of the atmosphere. The net effect will be that surface temperatures will need to continue to rise so as to reduce this deficit. Therefore, humans may not be the only contributor to changes in global surface temperatures, but they are most likely the prime contributor to the existing top-of-the-atmosphere energy imbalance.

So, what is the estimate for the energy imbalance? Well, it’s about 0.5 Wm-2. If you multiply this by the surface area of the Earth and by the number of seconds in a year, you get 8 x 1021 J. So, the energy in the climate system is currently increasing at about 8 x 1021J per year. What was the energy of the Hiroshima bomb? Well, it was 6.7 x 1013 J. If you multiply this by 4 and then by the number of seconds in a year you get 8.4 x 1021 J.

There you have it. The energy in the climate system is increasing at the same rate as 4 Hiroshima bombs every second and this energy excess is almost entirely due to the continued increase of CO2 in our atmosphere driven by our use of fossil fuels. So, as far as I can tell, John Cook is entirely correct and this is another example of people assuming that the only indicator of global warming is changes to the global surface temperature and don’t realise that global warming actually refers to energy, not temperature.

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19 Responses to John Cook and the atomic bombs

  1. Layzej says:

    “What the Media Fail article claims is that no scientist has claimed that humans are 100% responsible for current temperature trends and hence this comparison is flawed.”

    None at all except for these guys:

    Tett et al. 2000

    and these guys:

    and these guys:

    And these guys:

    And these guys:

    And these guys:

    … At least according to the summary available here:


  2. John Cook is absolutely correct in his criticisms. Climate change is an existential threat.

  3. Tom Curtis says:

    Donna LaFramboise is spinning like crazy in that post. It is true that “No official document … has declared humans 100% responsible for current temperature trends”. What is more, no climate scientist asserts that. But it is true that net natural forcings are currently negative. Further, it is also true that net natural temperature influences other than forcings (ENSO, etc) are also currently negative or neutral. So at the moment, the positive influences on temperature trends are 100% anthropogenic. Absent natural influences, temperatures would be rising by about 0.17 C per decade, or more.

    What is more, climate scientists have been saying this. We need only look at Foster and Rahmstorf to see that. We can also look at papers summarized at the bottom of this page.

    So, yes. If you only look at official statements rather than the findings of scientists. And if you blur the distinction between “influence” and “postive influence”; then you to can thoroughly mislead in the manner of Donna Laframoise. But if you are interested in what the science says, then Cook is absolutely right (if unfortunate in his choice of yardstick).

  4. Indeed, thanks. I’ve changed the style of your first link as it seems that, by itself, it was too long and the embedding didn’t work.

  5. Yes, that’s true. However, something I was trying to get across in the post was that even though the surface temperatures can respond to various different factors (some anthropogenic, some natural), it’s difficult to explain the top-of-the atmosphere energy imbalance as anything other than anthropogenic. Hence the energy increase (which is what corresponds to 4 Hiroshima bombs per second) can be entirely ascribed to human influence. You seem quite well informed on the subject. Do you agree with this, or is there some non-anthropogenic influence on the TOA energy imbalance?

  6. I agree. I still find it amazing that there are so many that want to undermine anything that suggests we should act against climate change. The threat, indeed, seems severe and the longer we wait, the more we risk.

  7. Tom Curtis says:

    Taken over a decade or so, the only influences on TOA energy balance are various forcings, their feedbacks, and the trend increase in surface temperature. As it happens, the change in forcing over the last thirty years, and probably over the last fifty have been net negative for natural forcings, and net positive for anthropogenic forcings such that over the thirty year period, all of the increase in TOA energy imbalance is due to anthropogenic factors. Given that the feedbacks are responses to the forcing, and the trend in surface temperature is a response to the forcings, they therefore are also anthropogenic in nature.

    Just as with temperature, however, from year to year there are significant natural effects on the TOA energy balance. The most obvious of these are increases or decreases in GMST due to ENSO (or possibly the PDO and/or the AMO). An increase in temperature from these causes will decrease the TOA energy imbalance. At the same time, however, feedbacks from that temperature increase will reduce outgoing IR radiation ameliorating the direct effect of the warming. Further, because the more even the temperature of the Earth, the higher it must be for a given total emitted radiation, oceanic oscillations that have a strong latitudinal component (such as the AO) will also shift the TOA energy balance.

    So, all in all, TOA energy imbalance is like the trend in GMST in that the anthropogenic factors are currently the cause of the imbalance (trend) but natural factors can change the year to year values. Thus, in a given year it may not be true that anthropogenic factors are the sole net cause of the imbalance. Of course, Cook was talking about the mean increase rather than the year to year variation, so this technicality does not save Laframboise’ argument.

  8. Thanks. Yes, that’s seems to essentially be what I trying to say but without as much detail and I hadn’t considered short-term changes. Indeed, there will be shorter-term variations that can change the imbalance but the long-term trend is primarily anthropogenic.

  9. Pingback: Watt about John Cook and the atom bombs? | Wotts Up With That Blog

  10. Layzej says:


    Given that some energy is produced on/by the Earth, shouldn’t we radiate slightly more energy than we receive? Eg. the amount of energy re-radiated back into space matches the amount we’re receiving, plus geothermal energy from the Earth, plus the energy of 85 million barrels of oil/day + the energy from 21 million tons of coal/day, + nuclear power (and perhaps minus any energy that is sequestered in newly created fossil fuels)? If not, why not?


  11. I think the simple answer is no. If we ignore the continued emission of CO2 and assume that the Earth can reach some kind of equilibrium then the surface temperature would increase to a value such the the amount of energy radiated back into space matched the total amount of energy we receive (from the Sun, from geothermal, from our own energy generation). In principle the others sources of energy are quite small, so I have been ignoring them in my posts, but you are correct that they will play a role in setting the equilibrium surface temperature.

  12. One thing to bear in mind is that we’ve always been emitting geothermal energy and its been decreasing with time. There’s no evidence that it has suddenly changed, so can’t be used to explain the rise in energy in the climate system that has occurred since the mid 1800s. I also worked out in an earlier post that the total amount of geothermal energy released per year is about 1.4 x 1021J per year. We’re currently adding 8 x 1021J of energy per year to the climate system, much more than that released by geothermal energy. I’ve also worked out the total amount of energy we generate is about 5 x 1020J per year, again much smaller than the amount we’re adding to the climate system through global warming.

  13. Tom Curtis says:

    For what it is worth, Andy Skuce looked at geothermal energy on Skeptical Science. Using his figures, and a Upward IR Flux of 240 W/m^2 at the TOA, I calculate the extra energy from geothermal sources, anthropogenic energy production plus tidal energy increases the expected effective temperature of radiation to space from 255.07 K to 255.1 K, ie, a difference of 0.03 K.

  14. Layzej says:

    Many thanks!

  15. Layzej says:

    I have two further questions if you are willing to indulge me. First I want to make sure that I have understood your response to my previous question. If I understand correctly, when we measure top-of-the-atmosphere energy imbalance – the measurement for incoming energy includes any energy created on or by the Earth. Is this the case?

    The second question is: If we are sequestering energy on Earth, would we expect that less energy will radiate into space than we are receiving? We are sequestering some energy in lumber/buildings/etc. Does this account for some of the imbalance?

    Initially I had thought that on the whole we are liberating more energy (as we burn fossil fuels) than is sequestered, so if anything we have a bigger gap than what is measured. However if liberated energy is already included in the measurement for incoming energy then I suppose this is not the case.



  16. The answer to your first question about the top-of-the-atmosphere imbalance is – I think – yes. The measurements are simply measuring all the energy coming in and all the energy going out. To be fair, though, I think the satellite measurements have quite large errors and so the errors are somewhat constrained by our knowledge of how much energy is going into the ocean. But the estimates of the energy imbalance does include all sources of energy.

    The answers to the other questions are maybe a little trickier. What I think you may be asking is, could the energy imbalance be due to our sequestering energy on the Earth. I don’t think so. Firstly, the total amount of energy we generate per year (through power stations) is about 20 times less then the measured energy imbalance. Also, if we were to suddenly sequester lots of energy, if there was no change to the greenhouse gas forcing, then the surface temperature should adjust to a new equilibrium fairly quickly. The heat content of the atmosphere is not particularly large and so it can gain or lose energy quickly if a new equilibrium temperature is required. The reason its not doing that at the moment is that our continued addition of CO2 is causing the equilibrium temperature to continue rising.

    Also, I think that if we sequestering energy on earth (i.e., taking some of the incoming radiant energy and converting it to another form of energy) then I think the imbalance would be the other way around. The surface temperatures should be above equilibrium, rather than below.

  17. Layzej says:

    I didn’t quite get your last answer so I did some reading. I think I get it now.

    I had thought that the radiation from the sun of 1360 W/m^2 was what we were measuring for energy received by the climate system. If Phytoplankton (for instance) absorbed just 0.04% of that and then sank to the bottom of the ocean, this would account for the 0.5W/m^2 that isn’t radiating back out. It would have ended up at the bottom of the ocean.

    This site ( points out that “energy in” = “energy absorbed”, not “energy irradiated”. So I guess any energy sequestered by Phytoplankton does not enter into the top-of-the-atmosphere energy equation.

    Am I getting close?

  18. I think the answer depends on how its measured. I don’t know much about the role of Phytoplankton but if one determined the TOA excess by simply measuring the amount coming in and subtracting the amount going out, then the excess would include everything that has absorbed this excess energy. On the other hand, another way would be to measure the change in land and atmosphere temperature and the change in ocean heat content and then use this to determine the excess, in which case the excess would ignore the role of Phytoplankton. I’ve no idea what role Phytoplankton play here, although am aware that they play a role in the carbon cycle (by absorbing carbon) – wasn’t aware that they sequestered much energy, but maybe they do.

  19. Pingback: Regaining trust! | Wotts Up With That Blog

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