The Weekly Carboholic: David Evans' climate facts hardly factual


I’ve started to read a number of commentators around editorial pages, blogs, and letters to the editor that are quoting an Australian by the name of David Evans. In case you’re unfamiliar, Evans wrote an op-ed in The Australian titled “No smoking hot spot” where he raises a number of issues with the science of global heating. Evans used to work toward mitigating global heating but has since become a skeptic based on perceived weaknesses in the data and modeling of the effects of global heating. Because of his background as a former global heating analyst for the Australian government, he’s become something of a rock star in the denier movement, and his quoting of Lord Keynes (“When the facts change, I change my mind. What do you do, sir?”) in his op-ed has become almost a mantra for the global heating deniers and skeptics.

Unfortunately for Evans’ global heating skepticism, but fortunately for the advancement of understanding of the Earth’s climate and anthropogenic global heating, it appears that the facts have changed on him yet again.

Evans’ first “fact” is that scientists have been looking for tropical warming in the troposphere for decades and have never detected it. Since weather balloons (radiosondes) haven’t detected the hot spot, it must not be there. As reported previously in the Carboholic, a new method of measuring temperature by proxy from the velocity of radiosondes in the atmosphere has been developed. And the new proxy data is not only much less error prone (the original temperature data that supposedly failed to find heating in the troposphere actually found no such thing – it had so many errors and systemic biases that the temperature measurements were all meaningless, something that Evans fails to mention – see the introduction to this paper for some examples of the errors), but the proxy data reveals that the troposphere a) has warmed and b) has warmed as the climate models have predicted. Unfortunately, Evans engages in ad hominim against the scientists who have proposed this proxy measurement. He should have read the actual papers (the top three papers available here) instead of blithely rejecting them with a suggestion that they’re contaminated simply because the research was done by so-called “alarmists”.

Evans’ second “fact” is that we have no evidence that carbon emissions are responsible for global heating. There are a great many papers that contradict this assertion, starting with John Tyndall in 1861 and proceeding through Svante Arrhenius, G. S. Callendar, and others. Most of the original science on the greenhouse effect and the impact of carbon dioxide (CO2) was done before the 1950s. However, the actual facts of the matter are these – the greenhouse effect exists (there is no debate about this whatsoever), CO2 is responsible for between 9 and 26% of the observed greenhouse effect, so a 30% increase in CO2 concentrations will increase the greenhouse effect by 3-8%. This simple estimate is made more accurate by using ice core data, from which climatologists have estimated the sensitivity of the climate to changes in CO2 (sensitivity is calculated using stable temperature periods, so which came first, the interglacial transition or the rise in CO2, doesn’t matter) at varying levels, but observations of how CO2 absorbs radiation have given estimates that range from as low as 1 to as high as 14 degrees C per doubling of CO2 concentration. Most experts agree that the most likely range is from 2 to 4.5 degrees C per doubling of CO2 concentration, with a mean value of about 3 degrees C per doubling. Regardless, however, the actual fact remains that a massive body of evidence that CO2 is having an impact on global climate exists, not “none” as Evans claims.

Evans’ third “fact” is that we can only trust satellite temperature data, but since it only goes back to 1979, we don’t have a long enough span of data to make good conclusions. What’s remarkable is that Evans’ claims that nearly 30 years of satellite data isn’t enough to estimate climate trends, yet he points out that the planet has supposedly cooled since 2001. If 30 years of data isn’t enough to make good trend estimates, a mere 7 years certainly isn’t long enough. Not only that, but Evans also claims that the GISS uses only land data and that the other major global temperature sets (MET and RSS/University of Alabama are two of them, perhaps all three) use satellite only or satellite and lands measurements. This is false – GISS uses land and ocean measurements, MET uses land and radiosonde and satellite, while RSS and UoA use the RSS-operated satellites exclusively. That said, however, Evans’ concern over the impact of urban heat island effects on land-based is valid. But that’s the only part of this section that is.

Evans’ final “fact” is that ice cores show an 800 year difference between the start of a deglaciation (transition from an ice age to an interglacial period) and the rise in CO2. While this is certainly true, Evans’ statement that this “says something important about which was cause and which was effect” is fundamentally in error. A 2003 paper by Caillon et al in the journal Science pointed out that the 800 year lag appeared to be step two in a three-step process: southern hemisphere heats up, southern oceans release a lot of CO2 into the atmosphere, global heating driven by CO2 melts the northern hemisphere. I go into gory detail on this paper here.

Evans’ facts are hardly factual, yet he has the audacity to claim that he changed his mind because the facts changed. I can’t help but wonder if he’ll change his mind again now that the false nature of his claims is so readily apparent.


The June 2008 issue of the journal Science published a “News of the Week” story about how the Earth’s deserts appear to be carbon dioxide sinks, roughly on par with temperate forests for their capacity to sequester CO2. What’s unknown, however, is whether the measurements performed in the Mojave desert of California and the Gubantonggut desert in western China are anomalous or representative of all deserts. If all deserts absorb CO2 at the same rate as the two measured deserts do, and if the results of the two deserts are confirmed, then deserts could represent a previously unknown part of the carbon cycle.

However, the story makes it clear that deserts aren’t expected to fully account for the CO2 missing from the carbon emission/absorption equations – the Earth is simply absorbing more than scientists can fully account for at the moment. And some scientists are understandably skeptical about whether or not the desert CO2 flux measurements (the difference between CO2 absorbed and emitted) are even accurate. There are too many unknowns yet to know what’s happening for certain, such as what form the sequestered carbon it taking, where it’s going, the annual carbon flux vs. the nightly flux that was calculated, and so on. Regardless, though, the data is interesting enough, and the potential impact great enough, that every scientist interviewed for the story, however skeptical of the methodology or data, recommended continuing and expanding research into how deserts influence the carbon cycle.


A couple of weeks ago, the Guardian newspaper online ran a story about how political cartoonists were addressing global heating. The paper titled their story “Cartoonists use humour to tackle climate change”. The problem with this title is that very few, if any, of the cartoons are funny in any classical sense. In fact, most of them are morbidly serious, and a few I just didn’t get. One of the many cartoons available for viewing from the Guardian is pictured at right. The others are all worth viewing here.



There’s a great deal of question whether or not hydrogen makes sense as a “clean” fuel. It’s difficult to store, difficult to transport, highly energy intensive to create in the first place, and dangerously reactive. All those things make hydrogen an unlikely, but not impossible, replacement for natural gas and/or petroleum for use in homes or transportation. Only a few die-hards at the National Renewable Energy Lab (NREL) in Golden, Colorado had suggested that hydrogen might be viable as energy storage for when renewable energy sources weren’t active, such as when the wind stopped blowing or the sun set. Now, however, a new development out of the Massachusetts Institute of Technology may change all that, and all because Professor Daniel Nocera discovered an inexpensive, non-toxic, natural catalyst to boost the efficiency of electrolysis of water (the splitting of water into gaseous hydrogen and oxygen).

According to the article, “Nocera hopes that within 10 years, homeowners will be able to power their homes in daylight through photovoltaic cells, while using excess solar energy to produce hydrogen and oxygen to power their own household fuel cell.” While possible, this vision of a distributed energy future rests not on the ability to split water into its components, but rather on solving technical problems that are unrelated to hydrogen, namely the photovoltaic energy conversion efficiency problem and the safe hydrogen storage problem. Current photovoltaic cells are inefficient, with the best cells converting about 40% of the incident solar energy into useful electricity. Most cells are much less efficient, especially when compared to the global average of 33% for coal plants, and we don’t really want to be using the most carbon-intensive fuel around to create otherwise clean hydrogen. Storing hydrogen presently required great pressure and thus a high risk of explosion, extremely cold temperatures and a correspondingly high risk of freezing, or chemical storage, all of which are inefficient uses of energy. And I don’t know about you, but unless I’m really confident that the explosion, cryogenic temperature, or toxic chemical risks are minimal to my children and pets, I wouldn’t want any of the above in my personal home.


It may well be inevitable that plug-in hybrids or fully electric cars replace today’s petroleum-powered behemoths. In many respects, the sooner this occurs, the better, since it’s much easier to control the emissions of CO2 from centralized power plants than it is from hundreds of millions of individual vehicles. But there’s a catch – electric utilities couldn’t provide all the necessary electricity, and even if they could, the present electricity transmission wires are simply incapable of carrying the required electricity to charge all those batteries at the same time.

The electric or plug-in hybrid future requires a great deal of public investment in the electricity infrastructure, and that will take time. But according to the Chicago Tribune article, some utilities are hoping that the electric car future arrive sooner rather than later. The reason is that, when those batteries are all plugged in to the power grid, they serve as electricity storage for when the power company needs extra electricity to balance supply with demand (something demanded by the laws of physics rather than the laws of man), reducing the costs to the utility, the cost to the owner of those electric vehicles, and the amount of carbon dioxide emitted into the atmosphere. Of course, that requires that drivers charge up overnight and also plug their car into the grid during the day so that the utility can charge, or drain, their car battery as necessary. And that requires charging stations for every parking lot in the country. That’s a lot of 240 volt outlets.

The next decade could be a great year to be a green electrician….


When it comes to aerosols (fine particles or droplets suspended in the air), climate models have historically modeled their effect on climate in a relatively simple manner – either the aerosol is a net absorber or a net reflector of radiation. Scientists at Arizona State University have been directly measuring the optical properties of a large number of so-called “brown aerosols” (aerosols that are usually pollution and aren’t soot or visually transparent) and have discovered that the simple models of brown aerosols doesn’t accurately represent their climate effects. Apparently, the properties of the aerosols are such that whether they’re absorbing or reflecting depends on where in the atmosphere they’re located, and most of them are partially absorbing. What this means for climate modelers is that they’ll need to update their models to incorporate a more complicated system for estimating aerosol radiative forcing. Without knowing the exact details of the various brown aerosols, however, the exact error in the estimates of aerosol forcing on the Earth’s climate is still an unknown.

Image credit: Guardian newspaper online

14 replies »

  1. Thanks, Brian, for puncturing David Evans’s delusions. Good to have the Carboholic back. Environmentally lost without it.

  2. Love the cartoon of the riot police beating back the sea and the lady getting fined for her dog’s mess in front of the industrial pollution.

  3. I think they ought to legislate water, as water vapor is the biggest greenhouse gas:)


  4. If scientists could do something about water, they’d probably suggest it (and, in fact, some of the geoengineering ideas I’ve read actually do try to control water vapor via precipitation changes or reducing evaporation).

    One of the more interesting links I came across a while back was over on, where one of the cobloggers ran a quick model to see how long the model said water vapor stayed in the atmosphere. The guy artificially set the water vapor to 0 and watched to see how long it took for it to get back to normal – it was 14 days to 90% of normal and 50 days to 99% of normal. Cool little simulation.

  5. Pingback:
  6. Brian,
    I’ve seen the models of the short duration of water in the atmosphere, but since water covers a majority of the earth’s surface, the duration of it in the atmosphere is moot. Water is the uncontrollable in this equation.


  7. Jeff, I totally agree, but I didn’t want to “educate” you on something that you almost certainly already knew. I just found the simulation interesting, nothing more.

    For our other readers, however, Jeff’s point that we can’t control water vapor is correct – there’s just too water in the world to control it directly, and so even though it’s the most important greenhouse gas, we have to work with what we actually can control. And that means carbon dioxide (the 2nd most important greenhouse gas), methane, ozone, CFCs, HCFCs, pollution aerosols, and all that good stuff.

    The advantage of this, though, is that if we can reduce those other greenhouse gases, they’ll get a fast feedback kick from water vapor, since it responds to climate changes within months instead of years, decades, or centuries as with most of the other greenhouse gases.

  8. You can educate me BUT if you cannot control the biggest greenhouse gas – water – which is natural I am left wondering a little about things…which is good.

    I shall go read some more. 🙂

    Glad you are posting the weekly carbo again. It is probably the best regular read on S & R.

  9. I was on a 2-week vacation and decided that, while I had my laptop along, I didn’t really want to force myself to Carbo on vacation.

    It was nice to have a break.

  10. Brian! I find your position arrogant. How dare you dismiss a scientific uncertainty with such naivety, ‘the greenhouse effect exist (there is no debate about this whatsoever). Well, apparently, the big debate IS about the perceived greenhouse effect, nicht wahr?

  11. Imre, there’s a huge difference between debating “climate sensitivity” and the existence of the greenhouse effect. The first is debatable because, as I mentioned, scientists don’t know all the variables that go into determining the number. Not only that, but climate sensitivity is itself a simplification of the base laws of physics, so there will always be debate as to whether the simplification is justified, how much simplification is valid, and so on.

    The existence of the greenhouse effect is not debated because if the greenhouse effect didn’t exist, neither would we. Venus is hot enough to melt lead because of the greenhouse effect. Earth would be frozen solid if it weren’t for the greenhouse effect. I can do the math for you if you’d like, but doing some Google searches on black body radiation, black body absorption, and energy absorption from the sun at the earth’s orbit should get you all the physics you need to do it yourself.

  12. Carbon dioxide IR absorption is not linear, so each time you double it’s concentration you don’t double the absorption. At present levels, a substantial portion of all the possible absorption is already taking place, so doubling would only cause a small increase. Doubling again would probably have negligible results.

    The important thing is: the science is not “settled”. And, yes, IR absorption or the greenhouse effect (an odd name, but now used by one and all), is a fact, since without it the surface of the earth would be around -27C – not very hospitable.

    The ice core data clearly shows that CO2 concentration follows temperature (about 800 or more years) and does not precede it. So, historically, CO2 cannot be tha cause of temperature change. This does not mean that modern conditions may complicate matters, but it is certainly true that in the past, CO2 did not cause climate change. Cause must occur before effect.