A Few Things Ill Considered

A layman's take on the science of Global Warming featuring a guide on How to Talk to a Climate Sceptic.

Thursday, March 09, 2006

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What About Mid-Century Cooling?

(Part of the How to Talk to a Climate Sceptic guide)

This article has moved to ScienceBlogs

It has also been updated and this page is still here only to preserve the original comment thread. Please visit A Few Things Ill Considered there. You may also like to view Painting With Water, Coby Beck's original fine art photography.



  • At March 14, 2006 5:56 AM, Anonymous Anonymous said…

    you have not addressed the mid century cooling, you only addressed the 1992 cooling.

  • At March 14, 2006 10:20 AM, Blogger coby said…

    I led with Pinatuba because it is a very clear and non-contaversial illustration of a temporary reversal of GHG warming, but the second paragraph does deal with the mid-twentieth century.

    I'll consider ways to clarify, thanks for the comment.

  • At March 14, 2006 5:45 PM, Anonymous Anonymous said…

    "The situation is similar to the cooling seen in the 40's and 50's."

    Not it is not similar because one event injected sulfate aerosols into the stratosphere where they stayed for years and affected the globe while the other ("human particulates and aerosol pollution") were produced in the troposphere and have a residency time in the atmosphere of about 4 days and had only a regional effect.

    "During this period the CO2 warming (a smaller forcing at the time)"

    Are you sure? CO2 changes at lower concentrations have a larger effect on IR absorption than changes at higher concentrations.

    " was temporarily overwhelmed by an increase in human particulates and aerosol pollution."

    Except there are a few problems with this scenario. First, areas that were not affected by aerosols show the 1940-1975 cooling trend as well. You can see this in IPCC Southern hemisphere temperature charts for the last century. How did these regional processes affect areas so far away?

    Next, regions that today produce massive amounts of aerosols don't show cooling at all. They actually show warming. Look at this chart from the IPCC: http://www.ipcc.ch/present/graphics.htm . Note that the big red dots cover the places (Europe, China, and to a lesser extent N. America) where aerosols are produced. Where's the aerosol cooling effect?


  • At March 14, 2006 5:48 PM, Anonymous Anonymous said…

    Sorry, that image link should be:


  • At March 14, 2006 6:08 PM, Blogger coby said…

    Thanks for the comments, nanny. I will try to get some more specific answers for you and either correct or fill out this article, but I think the main gist of the argument is that there are other factors at play and the simple lack of a perfect correlation does not mean that CO2 is not the primary driver of the general warming seen since 1900. For instance, check this nice graphic an compare the evolution of some of the major forcing factors over the 20th century and how it effected temperatures.

  • At March 15, 2006 2:37 AM, Anonymous Anonymous said…

    And finally Europe and the USA saw a massive cleanup of sulfate aerosols, and indeed the temperature rose.
    In the USA so much that CO2 is not needed to explain the recent heating.
    If all of the cooling in the usa from 1950 to 1975 is caused by increasing aerosols (Schneider et al) then all of the warming since 1975 is caused by decreasing aerosols.
    (sulfate emission upside down for easy reference)

  • At March 16, 2006 6:03 AM, Anonymous Anonymous said…

    LOL Dano

  • At March 19, 2006 12:17 AM, Blogger Matt Burgess said…


    I've enjoyed reading your blog. The blog appears dedicated to rebutting climate change deniers, so perhaps my comment is off-topic. If so, I apologise.

    Before I get to my main point, I want to make the following clear:

    1. I accept climate change is occurring and that human emissions are causally related to warming.

    2. I accept changes in human behavior can reduce climate change.

    3. I will assume climate change imposes a net cost on society i.e. it is bad.

    With these assumptions in mind, my comment is this: it does not follow from these assumptions that any response to climate change is required. That you (and many or most of your anti-CC colleagues) appear to believe in such an axiom is in my view an indictment of the entire anti-CC movement.

    The reasoning goes like this. The case for a CC policy response requires an examination of the costs and benefits of this response. Any response to climate change requires diverting resources (capital and labor) away from other activities that make us happy, be it education or health or private consumption, etc, which is costly.

    Among the list of policy responses to be assessed under a cost/benefit criterion should be "no response", because this acknowledges the possibility, however slight, that it will be advantageous to deal with climate change's consequences rather than prevent it in the first place.

    Before you dismiss the possibility out of hand, consider:
    1. The world which deals with CC's consequences, say, 50 years from now will be far wealthier and have access to more technologies than we.

    2. Diverting substantial resources now to prevention is costly because it delays the arrival of wealth and technology that will make prevention and delaing with the consequences cheaper.

    3. With current technology, policy responses are particularly ineffectual.

    I would like to see a response to this included in the Economics/Political aruments section. I actually think the key question in the entire climate change debate is whether climate change is something worth responding to, in view of limited effects of such policies on climate and he need to divert resources away from other pressing issues.

    Note that my reservations against policy response hold even when I assume, in effect, that human-induced climate change is real and the effects of policy are certain.

  • At March 19, 2006 6:44 PM, Blogger coby said…

    Hi Matt, thanks for the positive feedback!

    You are right that acceptance of negative and avoidable climate change consequences does not automatically imply action to avoid it given the non-zero costs of change. The main purpose of my articles is to help get us to that discussion.

    I will probably be adding something along the lines of what you are requesting anyway, but the main problem is it involves many purely value judgements. What is a coral reef worth? The tourism dollars plus its impact on fisheries? Or does it have some intrinsic value of its own. What about if there were no coral reefs left anywhere? Is that worth X% of world GDP? Economists also have a hard time understanding how we depend in many ways of biodiversity. Is a mass extinction event just an externality? How about 500 million human deaths by starvation from droughts if the economy can still grow, is this a cost?

    That said, I do believe that an honest and comprehensive purely economic cost-benefit analysis would conclude climate change will be devasting compared to shifting to alternative energy sources. But even here what time frame to look at is another value judgement. I don't think economists put much stock in costs that will not be incurred for 50, 100 or 500 years.

    I don't dismiss out of hand the choice to simply deal with whatever consequences climate change brings, but rather it is my considered opinion that this would be the most foolish decision ever seen in history. I will try to add some articles that lay out why, hopefully in a simple and straightforward way.

    Thanks again for the comments.

  • At March 19, 2006 11:10 PM, Blogger Matt Burgess said…


    Thanks for the quick response, I'll be checking for additions to the economics section.

    Can I suggest care be taken not to mischaracterize how economists in collaboration with climate scientists and biologists would go about evaluating the costs and benefits of various policies. I agree the intangible aspects of the environment's value is not amenable to being expressed in dollars, and economists do not propose to do that. Instead, I believe economists would evaluate the tangible costs and benefits of a policy, making explicit the things that were not included in the calculation (the value of a coral reef, of x% of species saved, etc). Presuming this calculation produces a net cost, economists, collaborating with other experts, would be in a position to say: policy x prevents a,b c at cost d, policy y prevents e,f,g at cost e, etc. This method isolates the value judgements from the tangible costs and benefits and, in my view, substantially un-muddies the waters.

    Of course, it is a tremendously complex calculation - lumping all the complexity of an economic cost and benefits calculation on top of the complexity of the climate - but to me this information is essential to work out priorities between competing policies, both among climate change policies and between CC and other sources of human happiness.

  • At June 21, 2006 4:03 PM, Anonymous Anonymous said…

    re anonymous's early comment :

    The short residency time of aerosols that are constantly replenished implies that the climate response to changes in their production will be quite rapid. That is, the rate of change is an important factor, not just base levels.

    I don't know how good the data is on regional particulate levels in the 40's and 50's, but I assume there's some. Ice-cores from the Andes, for instance. The disruptions in trade during the late-30's to early-40's caused a relatively high rate of industrial growth, with associated particulates, in the Southern Hemisphere. Which might explain a similar cooling-trend, despite the low base. Not that South America and Australasia didn't have significant industries before then.

    The warming-trend in regions that produce a lot of aerosols may be more to do with the rate of change rather than the absolute amounts. The shift from coal to natural gas over the last few decades has had more influence than any clean-air legislation.

  • At June 27, 2006 10:08 AM, Anonymous Anonymous said…

    According to Tim Flannery, industry habitually exaggerates the costs to them of legislative changes proposed for environmental or safety reason, which, when enacted, turn out to have costs a factor of ten lower than stated.

    It may even be that the necessary changes will lead to purely economic benefits as well, as waste and excess is eliminated, freeing up energy stocks for productive use, and new technologies and production methods supplant old. The German and Japanese post-war economic miracle was in part due to this effect, as modern plant was installed (with generous US and other investment) to replace that destroyed in war.

    I heard rumours of studies during the Californian electricity crisis that showed it was cheaper per watt to subsidise or give away energy efficient appliances to homeowners and businesses, than to build new generation capacity, I apologise for having nothing more concrete on this, but perhaps another commenter is aware of this or similar research.

    Hi Arthur.

  • At June 30, 2006 9:35 PM, Anonymous Anonymous said…

    i have seen no temperature chart for anywhere on earth during the 20th century that shows a cooling trend. since 1950 it is very clear that a warming trend has begun, one that does not appear in the historical temperature data for at least 100 years. clearly, the warming trend was stepped up in the 1950s. is this mother natures reaction to the cold war?

  • At October 04, 2006 5:00 AM, Anonymous Anonymous said…

    The only good correlation with temperature have volcanism but even better the activity of sun.

    Co2 have influence, but it's surely the most important. Then we have clouds. There are more clouds than 100 years ago and more than in 1930's.

    And what's more. Temperature rise in last few decades is mostly because higher night temperatures in winter time. So coldest peaks have "warmed". But temperatures in day time have not increased so much.

    I found this current warming period mostly just natural based on high solar cycles and with low level volcano and co2 increasing. With lower solar activity and with current volcano we will see cooling. If volcano activity is high the cooling will be stronger.

    Next 6-8 years will be mostly quite warm. Cooling will propably begin in mid 2010's. Cause Cycle 25 will be not just week, it's supposed to be very week. And that means cooling.

  • At October 07, 2006 6:30 PM, Blogger coby said…

    -----Original Message-----
    From: Anonymous [mailto:anonymous-comment@blogger.com]
    Sent: Wednesday, 4 October 2006 9:22 AM
    To: coby101@telus.net
    Subject: [A Few Things Ill Considered] 10/04/2006 05:00:23 AM

    The only good correlation with temperature have volcanism but even better the activity of sun.

    No, there isn't good correlation between 20th century temperature and 20th century soalr activity.

    Co2 have influence, but it's surely the most important. Then we have clouds. There are more clouds than 100 years ago and more than in 1930's.

    Oh. What type of clouds? And what is the cumulative radiative effect? Clouds can both warm and cool the surface.

    And what's more. Temperature rise in last few decades is mostly because higher night temperatures in winter time. So coldest peaks have "warmed". But temperatures in day time have not increased so much.

    Not *as* much, but daytime temperatures have indeed increased significantly.

    I found this current warming period mostly just natural based on high solar cycles and with low level volcano and co2 increasing. With lower solar activity and with current volcano we will see cooling. If volcano activity is high the cooling will be stronger.

    Unfortunately in science not all opinions are created equal. Have a look here for a more realistic attribution of the 20th century temperature trends based on more than just hot air.

    Next 6-8 years will be mostly quite warm. Cooling will propably begin in mid 2010's. Cause Cycle 25 will be not just week, it's supposed to be very week. And that means cooling.

    Care to put your money where your mouth is?

  • At January 30, 2007 3:35 PM, Anonymous Anonymous said…


    The first couple topics I read and shot back some critical points. You deal with a lot of them as I read on. I still am not convinced on a lot of them, but they are interesting. This one is really interesting since the "Next Ice Age" debate was at it's hottest around the time I started watching the news. It seems to me that there was a warming trend (how far back it goes we'll agree to disagree on) and then it really ramps up around the 1970's about the time industry really started dealing with acid rain. Now, I don't like two-headed newts and appreciate marble sculptures so I'm not advocating going back to acid rain. But, what if there is a middle ground where there was a natural increase in climate and CO2 and sulfates cancelled each other out? We basically accelerated the climate increase by cutting aerosol emissions - ironic.

    Just as a note: There wasn't a big push from the scientific community because the idea anthro-whatever-human emissions affecting climate were new and unsupported. But the fear that it caused in the public (aided by the other adverse affects of the resulting rain) gave it just as much momentum and significantly changed industry in the US (And those whiney Canadiens in Quebec also helped).

  • At January 30, 2007 4:22 PM, Blogger coby said…

    Hi agian, and thanks for the comments.

    I would say that you have it summed up prety well. The early 20th saw a relative balance of anthro forcings, CO2 up and aerosol pollution down, natural (volcanic) aerosols decreased (up) and solar increased (up). So a net warming. Mid century anthro aerosols dominated CO2 and solar stopped increasing, so down a bit. Then CO2 continued to pick up steam as anthro aerosols were much reduced causing a steeper warming. Which is where we are today.

    No one serious about the science ever thinks that CO2 is the only game in town, the GISS Model E for example runs with 12 major forcing components. The Perfect Model(tm) would probably have humdreds but 12 seems good enough to reconstruct the 20th century so probably has all the significant factors.

  • At February 20, 2007 5:09 PM, Anonymous Anonymous said…

    Sadly, CO2 forcing is not the all or nothing proposition this argument depends on. Try to be patient, make that point and present the current understanding of the 20th century temperature trends.


    "Oh no, if we are too patient it will be too late, and we will all be dead, and the world will end, the sun will turn as black as sackloth and the moon red, and the stars will fold up like a scroll in a really bad attempt to plageurize Saint John." Coby.

  • At April 06, 2007 8:34 AM, Anonymous Anonymous said…

    I am from jungle. Can you tell me what is global warming?

  • At July 28, 2007 3:30 PM, Anonymous Anonymous said…

    Couldn't the very large numbers of atomic tests from the early 50s onward until the 70s play a factor in the cooling of that period? It seems that the trend levelled off right when we started detonating them and continued until the moratorium on nuclear testing.


  • At July 29, 2007 11:30 AM, Blogger coby said…

    Hi David,

    I think that question has been investigated, it is a tempting correlation, but the expected effects are too small. IIRC, RealClimate has discussed this...

  • At March 10, 2008 1:11 AM, Blogger jpbenney said…

    In Australia, where I live, it cooled only from 1943 to 1956 (though 1949 and 1956 were the two coolest of the last 80 years) and has warmed up constantly since 1957.

    Whilst I am sure some will say it's due to the absence of sulfate aerosols in large enough quantities), my own gut instinct says that because Australia does not have large mountain ranges to block heating from the land, temperatures will warm (or cool) there before they warm (or cool) anywhere else on the globe as air circulate to the edges of the continent freely.

    Thus, I suspect that had people known Australia's temperature pattern during the 1970s, they would have been aware global warming was coming long before it actually did. Even Australia's 1970s "pluvial" was itself a curious coincidence of global warming beginning to strengthen the monsoon before it could (as it has done since 1997) virtually eliminate the southern winter rainfall systems.

    I also suspect Australia's 1970s "pluvial" was influenced by stratospheric ozone depletion pulling the monsoon and other moist air systems far into the continent.

    By recognising global warming much earlier, we would have been saved a great deal judging by the forecast of a week of 35 degree weather in Melbourne and no sign of a cool change.

  • At July 11, 2008 11:04 PM, Anonymous Anonymous said…

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