Average global temperature

Discussion in 'Earth Science' started by vhawk, Mar 2, 2009.

  1. vhawk Registered Member

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    is it true that there is no such thing as an average global temperature?
     
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  3. spidergoat Valued Senior Member

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    I think it's true that there are different ways to calculate it.
     
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  5. draqon Banned Banned

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    well there is average global temperature...but it always varies in accordance to the time frame this average global temp. is calculated. So I guess there is not one number for average global temp.
     
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  7. Enmos Staff Member

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    Which just means that there are different definitions.
     
  8. D H Some other guy Valued Senior Member

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    Spider pretty much nailed it. There is no such thing as the average global temperature because there are multiple definitions. There are averages for different time scales: yearly, monthly, weekly, daily, maybe others. Each time scale has different uses and different limitations. Different sets of meteorologists definitely use different data sets to compute the averages and probably use different averaging techniques as well. If they are diligent, they will describe what they mean by global mean temperature, identify their data sources and reference the averaging technique.
     
  9. Buffalo Roam Registered Senior Member

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    Then what is all the fuss about global warming?
     
  10. spidergoat Valued Senior Member

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    That's not to say the world isn't warming, only that one's frame of reference influences the results, as it does in many other aspects of science.
     
  11. vhawk Registered Member

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    does that not make a bit of a nonsense of global warming theories since average temperatures are used to evidence them?
     
  12. D H Some other guy Valued Senior Member

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    No. There is no climatology cabal that dictates "this is the global mean temperature". Good thing, that. We're talking about science here, not religion.

    There is nothing special or suspect about the use of different time scales. Many time-based averages (not just the concept of a global average temperature) use different averages computed over different time scales because there each has a value, but also limitation. Think of it this way: Where ever you live, there is a local yearly mean temperature for that locale. This yearly mean temperature won't tell you much at all about today's weather. You need a much shorter time scale average for that.

    If, on the other hand, you want to know whether your local climate is heating up, you need to look at 20 years or so of weather data. You would be overwhelmed if you had to look at 175,320 hourly temperature readings over the last 20 years. If you look at 7305 daily averages the main effect you will see are seasonal variations, with temperatures swinging 20 degrees celsius or so between summer and winter. Seeing a small warming (or cooling) trend on top of that huge seasonal variation is going to be tough. The yearly average gets rid of those seasonal variations, making the general trend much easier to see.

    Just because there are different ways to measure the global mean temperature and different data sets to use for those calculations does not invalidate the concept of global warming (note well: I said global warming, not anthropogenic global warming). To the contrary: That different techniques and different data sets all indicate that the climate has warmed over the last 100 years validates the claim. There is no doubt that the climate is warming. No honest AGW skeptic will make such a claim.
     
  13. nietzschefan Thread Killer Valued Senior Member

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    Well that's just it Buff, They gotta Fib a little to get everyone to pitch in and help.

    Some areas are affected more than others at first. It's really just "Local" warming now.

    I wish they would be more honest - they might get people on board more. It IS as serious as they say. Dry places getting drier, coastal areas flooding, places like China getting fucking hot.
     
  14. Fraggle Rocker Staff Member

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    Obviously not. Defining the statistical calculation is trivial. If you want the average temperature of the planet's surface at a particular instant, just measure the current temperature at every point on the planet and then use calculus to turn that into an average.

    Obviously you can't take this down to an infinite number of measurements of infinitesimally-sized plots of land. But you don't have to. The temperature gradient across a fairly large plot of land is satisfactorily continuous. If you only take measurements of every acre (or hectare) or even every square mile (or kilometer), your average isn't going to be off by a ten-thousandth of a degree Fahrenheit (or Celsius).

    If you want the average temperature of the planet's surface over a year, then just calculate the average at every moment in time using the methodology described above, and use simple arithmetic to turn that into an average.

    You actually can use sensors to get continuous readings, and they'll have built-in computers to do the averaging for you, so you don't have to worry about taking individual readings throughout the year. But even if you do, once again the temperature gradient between two instants half an hour apart will be satisfactorily continous so it won't destroy the precision of your statistic.

    Of course being able to describe this methodology is not the same thing as being able to put it into practice. The weather balloons used for global forecasting are something like 500 miles apart, which means they miss every one of the earth's mountain ranges, which have a profound effect on the weather. If you're measuring the temperature of the planet's surface you won't be able to place them close enough together to put my methodology into practice.

    But that's a problem in the application of the methodology, not the methodology itself.

    There is indeed "such a thing as an average global temperature," whether you want it for an instant, a day, a year, a decade or a century. You just may not be able to perform the measurement using today's technology, so you won't know what that average is. That's an engineering problem, not a science problem.
    The temperature measurements we have today are adequate to detect global warming. As far apart as our existing sensors are, there are thousands of them. In aggregate, the average temperature they provide for the planet is certainly precise to within a tenth of a degree.

    The skepticism directed at the global warming hypothesis is not based on criticism of the accuracy of measurement of the average temperature at any one time, or even the averages tracked over decades. It is based on the assertion that we don't know enough about the forces that influence the earth's weather patterns, in order to be confident that what we're experiencing is a long-term trend rather than short-term. For example, we only dimly understand the effect of sunspots and our predictive model of sunspot cycles has not been tested through enough cycles to earn everyone's trust.

    There have been short-term warming-cooling cycles (cycling over a couple of centuries or longer) during historical times. Within the past millennium, there was once a huge network of navigable, liquid-state inland waterways in Scandinavia, and a flourishing vineyard and winemaking industry in England, both of which take more than a few decades of consistent weather to establish.

    The most reputable critics of the global warming hypothesis are concerned that we've based a model on observations that have only been collected for a relatively short time, and are using it to predict conditions over a much longer time. Their assertion is that this makes it a very weak hypothesis. Its supporters counter with, "Yeah sure, but what if it's right? We won't have enough time to wait."

    Again, this sounds more like a question for engineers than forscientists. It's engineers who figured out how to build airplanes when scientists thought they were impossible with the existing technology.
     
  15. DwayneD.L.Rabon Registered Senior Member

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    Earths Average Global Tempiture, 288 Kelvins (thats like 58.73 degrees Fahrenhiet or 14.84 Celsius).

    Is there a solar space Average Tempiture

    Dwayne D. L. Rabon
     
  16. Buffalo Roam Registered Senior Member

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    But is it global warming? or natural cycles, local, global, cosmic?

    And do we really know if anything they propose is going to help, hurt, or make no difference at all, and just be a tremendous waste of money and resources, for no benefit.
     
  17. nietzschefan Thread Killer Valued Senior Member

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    It's NOT global warming! China is fucking cooking...some bean counters get out their calculators and adding all the temps across the board and call it "global". THEY SHOULD NOT LIE IT HURTS THEIR CAUSE.

    Talk about another billion pounds of ice falling off an Glacier into the Ocean, Talk about people not able to breathe in some cities, talk about massive damage done to soil, ground water...etc ETC ETC!!! Global WARMING...REALLY this is what we are worried about??? I suspect it's a ploy to DUMB IT DOWN FOR THE STUPID FUCKING MASSES, cause too many problems at once gives them a headache. Pointing to a raise in the AVERAGE of temps across the globe(make sure you DON'T MISS CHINA), and going "sky is falling" seems to actually work and get fucktards put garbage in the garbage can.

    We are most assuredly fucking up the environment. Buying a brand new hybrid probably does more harm than good. The only way to solve it is for nearly EVERYONE to LIVE SMALLER AND REQUIRE LESS GOODIES. Not get a nice new car that emits less CO2 emissions. That car is made out of all kinds of plastic and shit that might have been made with massive CO2 emissions.

    Buying up new vehicles for everyone is a fucking pipe dream. Driving a good older car(passing emissions tests) into the ground is a far better thing for the environment. BUT NO ONE WANTS TO HEAR THAT. That means less money, less prestige, less plastic shit in their pockets.

    Finding a pure clean technology right fucking now like Obama wants to do is a pipe dream too. You can't "Tech" your way out of this coming disaster. Wind Power, solar power, etc, these are good to use and improve on, even nuclear power, HOWEVER ALL REQUIRE THE "CONSUMER" TO DEAL WITH HAVING LESS CONSUMING LESS BULLSHIT PLASTIC SHIT IN THEIR HOMES, IN THEIR PANTS IN THEIR DRIVEWAYS.

    CONSUMER Capitalism must die.
     
  18. Fraggle Rocker Staff Member

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    None of those things are mutually exclusive. But it's not likely to be "cosmic." Not enough radiation reaches us from other stars to have a measurable effect on the temperature of our planet.

    But sunspots have been implicated, and there's intriguing (but not yet convincing) evidence that sunspots have cycles.
    The greenhouse effect is real; the effect of increased atmospheric carbon dioxide on surface temperature is a no-brainer. Reducing our carbon emissions will incontrovertibly result in a lower average global temperature than would prevail without that reduction. However the precise amount of that reduction in degrees per petaton (1000 gigatons) of carbon is controversial. Even more controversial is the question of what other (natural) forces are also at work, and therefore whether anything we do will be enough to make the difference we want to make.

    But on a local scale your question is significant. We three hundred million Americans can bicycle to work and shut off our air conditioners... and what difference will it make when two billion people in China and India all intend to get cars?
    One fourth of America's petroleum consumption is expended directly on commuting. That doesn't count the energy spent on building and maintaining cars and trains, highways and tracks, and it doesn't include the second-order effects of the commuter economy, such as fast food joints for people with no time to cook and nannies driving around to take care of kids whose parents are both at work.

    As I've pointed out many times, the post-industrial economy does not require the majority of people to "go to work," since they all have computers and telephones at home. The only reason most of us drive to the office every day is that we have dinosaur managers of my generation who are too incompetent to figure out a way to manage people they can't see.

    This will change when the generation that grew up with cell phones, chat rooms and MMORPGs takes charge.

    In the meantime, if you want to cut back on America's carbon footprint (not to mention our dependence on oil from countries that hate us), get your municipal government to mandate telecommuting for businesses in its jurisdiction. Doctors, chefs, diplomats, gardeners, janitors, bulldozer operators, etc. need to work on site. Most of the rest of us don't.
     
  19. D H Some other guy Valued Senior Member

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    There is extremely convincing evidence that the number of sunspots is cyclical. Astronomers have been burning out their retinas for 400+ years counting sunspots. The data are a bit spotty for the first 150 years, but are very solid for the since the late 1750s.

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    Using [sup]14[/sup]C as a proxy for solar activity, we can project solar activity much further in the past than the 400 years of direct observation.

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    We know that solar activity interacts with the Earth's geodynamo and that this has a very significant impact on the magnetosphere.

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    We know that solar activity affects the height of the Earth's atmosphere. We can see this in how quickly the orbits of satellites in low Earth orbit decay. I'd show a pretty picture, but this site limits me to three images per post.

    What we don't know is whether the solar cycle impacts the Earth's climate. We strongly suspect that it does -- at least big changes such as the Maunder minimum. Whether smaller changes in the overall solar activity have much impact is much less agreed upon.


    That's the real rub.

    There's no doubt the Earth's temperature has gone up, on average, over the last 100 years. Whether its us or nature is a point of contention. It looks like it might well be our fault. Maybe.

    I make multi-million dollar decisions in my job (not bragging; any reasonably good engineer my age makes multi-million dollar decisions). And I dang well better have my numbers, my analyses, and my inferences down very solid in making those decisions.

    The potential negative economic from a full-on response to AGW is in the trillions of dollars. They make my multi-million dollar decisions look like child's play. They do not, in my opinion, have the facts down solid enough to justify making such a decision. They do not have the facts down solid enough to justify making million dollar decisions. If I used the shoddy data, shoddy analysis, and shoddy techniques used in climatology (e.g., one sigma variations reported because three sigma errors make graphs look like a big smudge) I would lose my job.
     
  20. iceaura Valued Senior Member

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    So is the potential negative economic impact from an inadequate response to AGW. And these economic estimates are based on data no more complete or reliable than the AGW stuff, and involve political speculations even less sound.

    And all these decisions will be made, one way or another. It's not a matter of postponing having a climate, or an energy policy, until adequate facts can be obtained.

    The question seems to be one of judgment in the absence of adequate facts. The engineering decision template seems to not apply.
     
  21. Trippy ALEA IACTA EST Staff Member

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    Henrik Svensmark proposed that variations in solar activity cause variations in the number of Galactic Cosmic Rays reaching the earth, he proposed that GCR's cause the formation of ultra fine aerosol particles, which become capable of forming cloud condensation nuclei, and so increased solar activity causes a decrease in the average cloud cover of the earth, resulting in overall warming of the earth.

    It's commonly accepted that increased sunspots are associated with an increased number of solar facula, and that the total irradiance of the sun is directly proportional to the number of sunspots - more sunspots, more overall irradiance. It has been pointed out that solar activity proxies appear to show indications of longer term cycles.

    There's the 87 year Gleissberg Cycle, which is (I think) a variation in the number of sunspots at the maxima (can also vary between 70 and 100 years).

    There's also been identified the 210 year de vries cycle, and the 2,300 year Hallstatt cycle.

    It has also been noted that it's more efficient to heat a room with a short duty cycle than a long duty cycle, and so consequently the variations in the length of time between solar maxima may play a role in climate forcing.
     
  22. BenTheMan Dr. of Physics, Prof. of Love Valued Senior Member

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    Would you say "It's not a matter of postponing an invasion of Iraq, until all of the facts are obtained"?

    I guess the only grounds to argue for your point of view is an economic one---sacrificing economic growth now at the expense of a comprehensive environmental policy is less costly than having to deal with the negative consequences later.

    What if this weren't the case?
     
  23. iceaura Valued Senior Member

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    The option of not invading Iraq is always available. The option of not having a climate isn't.

    We know that CO2 concentrations are rising, and we are almost sure - we have the facts to ascertain - that fossil fuel combustion is driving the rise. What are the most likely consequences, if good judgment is employed?
     

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