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Originally Posted by The Avon Lady
[Can you, too, explain what the errors are in the test's answers? :hmm:
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I'll have a go!
*edit*
ARRRGH! My spell checker messed up and I lost most of my post. I will post again wlater today with the rest of the questions/answers. Too pissed off right now, it took bloody ages.
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Originally Posted by Question 10
Orbiting satellites provide the most accurate global temperature readings-- accurate to 0.1 degree C. Interestingly, in the 18 years that satellites have been recording temperature they have actually showed a slight decrease in average global temperatures.
Ground-based thermometers that were originally in rural areas have been reading increasingly hotter temperatures with time due to urban encroachment. The asphalt and concrete structures replacing green leafy plants makes for hotter local ground temperatures. This phenomena is known as the "urban heat-island effect" and has been well-documented by climatologist Dr. Patrick Michaels, Professor of Environmental Sciences, University of Virginia.
In a November 1997 press release Vice President Gore proclaimed that 1997 was the hottest year on record. Ground-based temperature readings were the basis for this announcement. Had the data from orbiting satellites been cited the report would have been much different: no net increase in global temperatures in 1997.
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Where to start!
Well, firstly the effects of
Urban Heat Islands on
http://en.wikipedia.org/wiki/Satellite_temperature_measurements]satalite temperature readings[/url] have been well studied and have been found to have little impact of satellite heat readings. The little effect they do have is taken into account when the results are processed.
This, however, is academic when compared to the more major problems of satellite temperature readings. Satellites measure the Earth's temperature in a totally different way to ground based thermometers. The satellites take a reading of thermal emissions that are averaged out from the ground to the outer stratosphere. We know that much of the stratosphere has been rapidly cooling and is expected to continue to do so due to o-zone depletion, this gives a bias to satellite readings which is extremely difficult to account for. This is bad news for anyone wishing to look at tropospheric temperature trends (which are close to surface temperature trends anyway!).
Satellites also pick up inaccuracies in their data collection such as orbital drift and cross-calibration of different satellites. Many different answers have been put forward for solving these difficulties, but each produces different results and it is not clear which is right.
In short; the notion that the satellite data is the "most accurate" is at best misleading, at worst completely wrong.
Finally, it says that the satellite data shows a slight cooling, which is completely wrong and, I suspect, based on data which is hopelessly out of date. The latest data for the full period of the satellite record 1979-2005 shows a warming trend somewhat similar to the surface thermometer record, although the exact value differs between the various analyses as I mentioned above.