I need to know if the the heat of combustion X the amount of fossils fuels being consumed by humans through combustion will give a reasonable figure to use for predicting the heat being added to the earth by humans, and, is this significant globally. My economist frient says global warming is a myth and the global mean temperature since the last ice age fluctuates between 40 and 70 f and we currently are at about 60f so well inside historical means. Also, isn’t the historical rate of globar temperature change (dT/dt) a key in understanding whether we are headed for trouble?
This thread may be headed for GQ, or even GD, but I’ll leave that decision to Ahnold 
In a word, no. No one to my knowledge (who doesn’t wear a tinfoil hat, anyway) claims that the energy released by burning fossil fuels is contributing significantly to a global warming. The mechanism proposed is the trapping of long-wave IR by CO[sub]2[/sub].
How this compares with solar fluctations, what the historical situation is, and what, if anything, should be done about it, are definitely beyond the scope of the current forum.
thegooddoctor: Your friend is completely out-to-lunch. The basic theory of global warming now has widespread acceptance throughout the science community even if the details and magnitude and such are still in question.
If you look in peer-reviewed scientific journals like Science and Nature, you will see that all papers on the subject start with the common ground of agreeing with the basic views expressed by the IPCC report (see www.ipcc.ch ), the latest reports (so-called “TAR” of third assessment reports) from this panel set up by the UN which summarizes the state of the scientific literature. The U.S. National Academy of Sciences also weighed in with a report a year or so ago, broadly in agreement with the IPCC reports.
As has been pointed out, global warming has nothing to do with the heat that fossil fuel burning releases into the air which is no-doubt quite insignificant on the scale of solar radiation. It has to do with the fact that CO2 and other “greenhouse gases” released act as a blanket to keep heat in by absorbing some of the infrared radiation radiated by the earth. Of course, without this blanketting effect due to the CO2 and other greenhouse gases in the atmosphere naturally present, the earth would be an inhospitably cold place but with too much of it, it could become inhospitably hot (witness Venus, for example). Of course, the changes contemplated from burning fossil fuels aren’t that extreme but are likely to be enough to cause various problems for humans and ecosystems, rising sea levels flooding low-lying areas, etc.
On this you are right, it is the rate of warming that is unprecedented. It is true that the surface temperatures of the earth have, over millions of years, varied quite a bit. However, these variations were generally on much longer time scales. (Also, there probably were some pretty nasty impacts for the flora and fauna of the planet from these variations…You know, extinctions, …)
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Please include a link to Cecil’s column if it’s on the straight dope web site.
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I imagine that your question was prompted by this column:
However, since the question is really going beyond the scope of the column, I will move this thread to our General Questions forum.
moderator, «Comments on Cecil’s Columns»
No and no.
The heat produced by fossil fuel consumption is not significant in the world-wide heat balance.
But humans cause a much larger heat effect than that by releasing greenhouse gases into the atmosphere, which allow visible light from the white-hot Sun to continue to the surface of the Earth, but retard the escape of IR from the barely-warm Earth. Thus the temperature of the Earth will tend to rise until the increase in amount and reduction of wavelength of the escaping IR restores a dynamic equilibrium. The heat of the Greenhouse Effect comes from the Sun, not from fossil fuels.
Do not rely on economists to give your the good oil on physics. I tell you this even though I am an economist.
Regards,
Agback
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Why would you take the advice of an economist over the word of a scientist or environmentalist? That’s like asking a Christian about Judaism instead of asking a Jew.
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Keep in mind that a global drop of 2 degrees Celsius (about 5 fahrenheit) is enough to cause the world to go into an Ice Age. Over the last 30-50 years (I’ve forgotten the exact number) the global temperature has increased by approxminately a half degree Celsius. If we continue at this rate, or if it increases, we will potentially experience more violently changing weather, flooding, and worse droughts. I say “potentially” only because we truly have no way of knowing for certain what will happen, but these are indications of what could happen.
That, to me, is one of the scariest things about the whole issue. The science of global warming is a horrendously complex area. There are a lot of factors to consider, and who knows what we haven’t picked up on yet?
Just some of the things that have to be taken into consideration:
[ul]
[li]Temperature goes up ==> greenhouse gases are freed from oceans ==> problem intensifies[/li][li]Temperature goes up ==> more evaporation ==> greater cloud cover ==> albedo rises ==> problem is ameliorated[/li][li]Temperature goes up ==> polar ice melts ==> planet’s albedo decreases ==> problem intensifies[/li][li]Temperature goes up ==> global vegetation patterns change ==> problem may get worse or better[/li][li]Temperature goes up ==> weather patterns change ==> areas of the world become less (or more) habitable ==> problem may get worse or better[/li][/ul]
etc., etc., etc., and there are a lot more things to take into account. Some of these things are relatively easy to calculate and some aren’t. I think caution is the only way to go.
RR