why did scientists monitor average global surface temperature instead of temperature at a specific location?

Answer 1

Local temperatures would not reflect a global condition therefore they monitor a large number of localities to average the temperatures for a global mean.

BTW, it's quit rising you know.
See the latest Senate report. Even the E.U. has decided that anthropogenic global warming is not valid.

Answer 2

You might be onto something here Mike, but you really need to do better than a table comparing average temps between planets which is not an accurate indication of average temperature (none of the values contain error margins or indication of rounding). You'd need to show what the 1990 data really looked like. I'd be surprised if it wasn't included in graphical form similar to the fourth report somewhere later in the FAR document. Is there a reason why you have chosen this particular chart? Did you scan the FAR and couldn't see a depiction of average global temps? Or was this the only reference used on a denialist blog? I would be really interested to see a meaningful comparison of the data, but at this stage it is not compelling.

Answer 3

Because the temperature at a specific location can be influenced by location specific characteristics like mountains, valleys and oceans. Only by looking at global temperature, can global trends be established.

p.s. Joe U below should check his facts before he goes spouting off http://www.cnn.com/2007/TECH/science/12/13/warm.weather.ap/index.html

Answer 4

Scientists got the averages from individual location measurements. Looking at the average "smooths" out the variation within a particular spot and variation from one spot to another spot. The average is one way to look for effects over a larger picture.