[Geezer (OP)]

Is it possible to measure Earth's mean temperature from space? Presumably, if I get far enough away from a planet, I can measure the integrated thermal output from the entire planet. If so, could we use such a measurement to help quantify global warming? Do astronomers use techniques like this to measure the temperatures of other planets in our solar system?

We should be able to quantify the total energy received by the Earth from the Sun, and if we can quantify the amount of energy being radiated by the earth, the difference might help us quantify global heating/cooling.

It would be nice if something like this could work, but I suspect it's probably too simple!
 

[Soul Surfer]

This has been measured many time both from the earth and from space and so have the other planets.  The information is useful but not critical for the understanding of global warming

[Geezer (OP)]

Is that because it is insufficiently accurate to quantify the actual rate of warming, or does it fail to indicate any actual warming trend?

Question: How do you measure the integrated thermal output of Earth from Earth?

[Soul Surfer]

The integrated measurement is not constant because it depends on many factors at many frequencies.  for example the percentage of cloud cover and the season and angle with respect to the sun.  This makes it just as difficult to measure the small temeperature chages from spase as it does from the earth.

The traditional (old fashioned) way of making this measurement is by using a bolometer a very sensitive thermocouple  upon which the image of the object is projected using a telescope. These have been in use for more than one hundred years.  nowadays there are many sorts of radiation anf image detectors.

[Geezer (OP)]

Thanks for the information. I guess my idea was too simple!  []