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.

Monday, May 08, 2006

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Active Threads

I have not yet found a way to get a real listing of recent comments, so thought I would ust post this because there are a couple of active threads from old posts.


The economic ones are my least competent subects, maybe others can contribute better material...

see here
and here as well

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  • At May 10, 2006 2:34 AM, Blogger Heiko said…

    You wouldn't by chance have a link handy explaining the importance of land use change for surface albedo as a climate forcing?

    I don't seem to be able to find much useful at real climate and a quick look at the IPCC report didn't give me much either.

    In short, I want to know how important roof tops and roads (mostly black) are in driving up temperatures (locally, globally, regionally).

  • At May 10, 2006 9:20 AM, Blogger coby said…

    Hi Heiko,

    You may find some good resources in the Wiki Urban Heat Island article.

    I think it is linked to here

    My impression is that it is a very local effect only.

  • At May 10, 2006 10:11 AM, Anonymous Anonymous said…

    Hi Coby,

    The other day I found this interesting article: http://www.junkscience.com/Greenhouse/

    Of course, being a junkscience article, it plays down the importance of CO2 in global climate. And of course, I wouldn’t expect you to sympathize much with the authors. But I do think that you could possibly refute its content, if you have the time. They are supposed to use very bad, distorted science, aren’t they?

    I read it quickly and couldn’t spot any obvious trick.



  • At May 10, 2006 1:20 PM, Blogger Heiko said…


    Firstly, thanks. Secondly, you wouldn't mind another try?

    Let me explain, the urban heat island effect is not what I was on about. I believe that that is supposedly about the fact that many land based stations were located close to urban areas 100 years ago, and are now in urban areas, that is the world average temperature is supposedly overstated because the weather stations aren't representative.

    The IPCC say the effect is minor and/or corrected for and I am perfectly happy with that.

    Let me restate the urban heat island theory in numbers (that's the way I think). The idea is that 1% of the Earth has warmed 5C and the rest hasn't warmed at all, but because 20% of stations are in the areas that have warmed by 5C, the actual increase of 0.05C is overstated by a factor 20 (numbers plugged out of thin air, merely for illustration).

    I am saying that maybe 20% of land area has cooled by a degree or two (see IPCC link above) and 10% has increased by a degree or two and maybe 5% has increased by 2-3C, giving an overall effect of maybe 0.1C, or that's the kind of thing that I expect from reading what's on the IPCC website.

    But isn't there a better discussion with greater detail somewhere, and in particular the effect of roads/pavements/roof tops.

    Notably in March/April I'd effect a significant effect in areas where 10-20% of land is in human use with snow being removed/molten through salt addition.

    So would you know some place discussing that in a bit of detail?

  • At May 10, 2006 2:45 PM, Blogger Heiko said…


    I am sure Coby doesn't mind if I jump in here.

    There's some good points in their presentation, that are helpful, but also much muddying of the waters that's not. I don't think proper context is provided for example when human carbon dioxide emissions are compared with natural exchanges (such as absorption by plants and respiration by animals).

    They obviously make that point to make anthropogenic carbon dioxide emissions appear small. But in that attempt they may leave some readers confused. Reading just that people might easily be led to believe that because human carbon dioxide emissions are so small, they won't be noticed against the background noise of natural exchanges, when that is patently untrue with CO2 concentrations stable within a few ppm around 280 ppm for the last few thousand years until mass fossil fuel burning started.

    They do correctly note (rounding generously though) that about a quarter of present day airborne CO2 is anthropogenic (about 100 ppm out of 380 ppm) and that about half of human emissions end up in sinks (the oceans, soil carbon from increased plant growth etc..). So a well informed reader will pick up the apparent discrepancy between near zero contribution of anthropogenic emissions and essentially 100% responsibility for the 100 ppm increase, but a well informed reader probably doesn't need their primer in the first place.

  • At May 10, 2006 2:56 PM, Blogger Heiko said…

    Oops, just noticed that my second attempt at asking the question is a bit deficient as well.

    The 0.1C (plugged out of thin air at any rate) is for land use change / albedo only!

    I don't know what uncertainty IPCC would put on that number (maybe, very maybe something like -0.2 C to + 0.3 within 99% confidence bands and -0.1 C to + 0.1 C with 90% confidence bands, but that's just an informed guess from reading what else they've got to say).

  • At May 10, 2006 8:18 PM, Blogger coby said…


    No, I didn't think you were on about the UHI effect, but I thought I remembered some specific comments about roads in that wiki article. I can't think of anywhere I've seen the specific effect you mean talked about.

    That is an iteresting notion I hadn't thought about, the winter difference because of bare roofs and roads etc. that would have otherwise been pure white. Actually, your best bet would be information about land use changes, that should fall right into that area.

  • At May 10, 2006 8:48 PM, Blogger coby said…

    Hi Mikel,

    That article strikes me as a bit of a sugar coated poison pill! I have underestimated the PR skills they are using. The initial info is all quite correct, but they sure give the impression it is hidden or damaging to "gw alarmists". I have never seen an explanation of how the greenhouse effect works that did not say how it is misnamed. I think the underlying message is that is ashameful secret!

    Never mind...I think they used the following misinformation:
    Water vapor overwhelms CO2's effects
    Nature is almost all of the CO2
    Water vapor could be a negative effect.
    Because the error margin on absolute temperature is large, the trend can not be known.
    A ton of modeling FUD
    CPN's recent error shows their projections are exagerated.
    Warming is likely UHI effect
    Climate changed before
    CO2 is a necessary gas and therefore not pollution.
    The warming could be natural
    There's nothing worse about a warmer climate

    Some topics I need to cover!
    In the summary they claim climate sensitivity is 1oC, which is bunk.
    They ignore the lag of several decades in using the current rise vs CO2 to support their too low sensitivity.

  • At May 11, 2006 2:54 AM, Blogger Heiko said…

    Thanks, it seems it's surprisingly hard to find something on the topic.

  • At May 11, 2006 7:42 AM, Blogger coby said…


    I tried a google scholar search and at least the fourht hit from this looks promising...?

  • At May 12, 2006 11:04 AM, Anonymous Anonymous said…


    I think that their assumption is that most people have no clue of what the natural or anthropogenic atmospheric levels of CO2 are (note the general tone of the article) but are constantly bombarded with the idea that we are pumping tremendous amounts of a very dangerous gas into it.

    From that point of view, which is one I am very close to, explaining what the real figures are seems wholy appropriate.


  • At May 12, 2006 11:09 AM, Anonymous Anonymous said…


    Thanks for your reply. I wish some climate scientists were equally approachable, especially when they claim to be running a website to make science available to the general public.

    Although I appreciate some subjectivity in some of your comments, you've given me plenty of food for thought. I guess I'll be coming back when I digest it.

  • At May 12, 2006 1:32 PM, Blogger coby said…

    Thanks Mikel, I appreciate you your words here and your other thoughtful comments.

    Come back anytime!

  • At May 12, 2006 1:54 PM, Blogger Dano said…


    you recall, of course, that the atm trop. rise is in concert with the surface temp rise. This datum, of course, does not cover the same temporal scale as the sfc record, but is indicative.

    Secondly, Roger Pielke Sr often goes on about LU changes and forcings. Check his site for a few specifics and I think he might have an empirical paper on the topic. Urban LU changes affect local conditions, but are too localized and not widespread enough for global changes.

    Lastly, you ask a good question with roads and distribution of temp changes. To my knowledge there is nothing about the global distribution of roads and their effect on temps. Road coverage of the planet is quite scarce. However your supposition about temp distribution is quite correct - look at the arctic. And the SE US has periods where it has -cooled- recently.



  • At May 17, 2006 3:09 PM, Blogger Heiko said…

    Thanks Dano, Roger Pielke Senior does discuss land use / albedo at length.

    Having checked the IPCC summary for policy makers again, I am left somewhat confused. In the IPCC summary there's a figure indicating land use (albedo) is responsible for a net forcing of -0.25 W/m2, with an uncertainty range of 0 to -0.5 W/m2 (the figure also indicates that scientific understanding of albedo is very low).

    Yet, on Roger Pielke's page, a peer reviewed paper is quoted saying there are absolutely huge uncertainties (in excess of 3 W/m2, ie albedo would be similar to a doubling of CO2!).

    Google scholar was also helpful. A few papers came up discussing urban heat islands in the summer. It seems that the most significant effect is actually not albedo there, but reduced evaporative cooling. Apparently the albedo of a pine forest is not all that different from that of a typical city centre. What is different is that most surfaces are sealed and dry in the city, but the pine forest allows lots of water to evaporate.

    Nothing on snow in March/April. Maybe it's just not all that significant (or maybe people aren't too bothered to highlight it, because 2-3C more in March/April in urban environments would be positive, ie it's not a problem that screams out for a solution).


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