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Some climate scientists say the world is warming. Some deny that. My question is: How is the world's average temperature calculated?

The average as measured by one temperature measurement station could be the sum of the daily high and the daily low divided by 2. It could be the sum of 24 readings divided by 24. It could be some kind of mean. It could be interpolated from continuous readings.

The average of N stations could be the average of their averages, or it could be some kind of average of cumulative readings across stations.

If stations are dense in some areas and sparse in others, is there any kind of weighting given to more accurately reflect the overall average per unit of area?

Satellites don't have little thermometers attached by long pieces of string, so presumably they measure temperatures through some kind of proxy measurements. What are these? I gather they measure the temperature at different heights in the atmosphere. How are these measures incorporated into global averages measured on the ground?

Once we calculate an overall global average, presumably half the places on earth are colder and half warmer. If the average rises, how does anybody determine which places have warmed, which have cooled, and which have stayed the same?

Finally, climate models attempt to predict future averages. Thus far they haven't proven to be very accurate. How do scientists account for this inaccuracy, and what modifications are they making to their models?

I am a bit of a global warming skeptic, but that has nothing to do with my question. I genuinely don't know how global averages are calculated.


  • Apr 26 2011: http://www.appinsys.com/GlobalWarming/GW_Part2_GlobalTempMeasure.htm#averages

    There is one resource.

    I hope that you have really looked into global warming (should really be called global climate disruption) before you have decided to be skeptical.

    Personally I have no idea how one can be skeptical if they have thoroughly researched it.
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      Apr 26 2011: "(should really be called global climate disruption)" well put! but ya it should be looked at in two ways, what we add that hurts our climate, and what our planet is doing regardless.
      • Apr 26 2011: It is true that the planet goes through cycles regardless, but such a quick shift in greenhouse gas (ppm), plus the inadvertent then square wattage is absolutely unprecedented.Usually this kind of change happens over thousands of years. I can't find any so called expert outside of the popular media who doesn't see this as a real and pressing issue.
        The good news is that there are already large measures being undertaken and the thought is that the policy changes needed will happen in short -time. Also, of course the people working on solutions are intelligent so we are in good hands.
        The problem is that the longer we piddle around the idea and make no large commitment the harder it will get to solve.
        I am no hippie idealist who thinks if we all get a little more GREEN everything will be okay either. Policy change needs to occur especially in the United States and China since they represent such a large part of the problem.(Though President Obama seems keen on moving things forward.)
        I watched a lecture on MIT World a few months back which was pretty general and yet interesting by a professor who's name I forget on Climate Change, then especially Nuclear energy. He said that we need to remove 7-9Gt(billion tonnes) of Carbon Dioxide from the atmosphere and from yearly emission rates.
    • Apr 26 2011: Deaven: Thanks! That is a detailed and very informative explanation.

      But I am kind of surprised that you -- who say you are suprised how one can be skeptical if they have studied the subject -- included the link when it spends a great deal of time disputing the whole global warming theory! Although it does a good job of at least partially answering my question as to how global average temperatures are calculated, it seems to me that it raises some serious questions about whether there has been any temperature increase at all, let alone how much of it has been anthropogenic. It pretty much openly accuses the IPCC of fiddling the numbers through the use of 'adjustments', interpolations, and selective start points in trend graphs to suit their own preconceived ideas. The link also points out that what has happened in the southern hemisphere is quite different from what goes on in the northern half of the globe.

      I have never questioned climate change, just human-caused warming. And again, I don't actively dispute it, I am just skeptical. I certainly don't dispute the increase in atmospheric CO2 as that is a simple measurement that is easy to plot, but I do question how and to what degree it may or may not be affecting the climate.

      I now have a better understanding of how temperatures are measured, but little further enlightenment on the whole topic! I will further follow up on some of the links included in the link you gave. Thanks again.
      • Apr 26 2011: I have an interesting question for you then.
        Regardless of climate disruption being man made or natural the consequences are still real of course, so do you think that even if it is totally natural, man can somehow overcome nature?

        Here is a quick article that I think you will find quite interesting by the MIT technology review(for some reason I find myself partial to MIT.)http://www.technologyreview.com/Energy/18217/?a=f
        It describes technology for capturing CO2 from plant stacks in the same way a plant would from the atmosphere using a genetically engineered E.coli strain.[by the way it's also a Canadian technology;)]

        (by the way I also found that previous article very informative and that's why included it. I don't think it is so productive to try to hide facts that oppose my views any more than it is to bend information to suit my case. The most compelling statistic i found was actually the square(m) wattage over the earth's surface and how that changes due to greenhouse gases.)
        • Apr 26 2011: I think the reason for my skepticism is that I'm not sure we should even be trying to change the climate, as I really can't believe that would be possible whether we caused the changes or not, but rather we should be expending effort on adapting to whatever changes are occurring.

          But I honestly didn't intend for this conversation to be a debate about the merits or otherwise of climate change. I flat didn't understand how average temperatures were derived, and that link you provided told me that the answer is... many different ways!

          I'll check out the MIT link.

          Later: Interesting little article. Like so many potentially effective ways to 'scrub' CO2 out of industrial waste, time will tell whether it becomes economically and/or technologically feasible. Up here in oil country they are experimenting with liquefying the CO2 and pumping it underground where it is assumed to stay forever. Hmmm...
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    Apr 26 2011: there is enough evidence to prove the earth has gone through a warming to cooling stage in history before, so its a cycle we will very muc h be living with.