Report to the Greening Earth Society, "The Surface Record: ‘Global Mean Temperature’ and how it is determined at surface level"More/complete report: http://www.greeningearthsociety.org/Articles/2000/surface1.htmBy John L. Daly
Greening Earth Society Science Advisor
May 2000Measuring Surface Temperature
The ‘surface record’ comprises the combined average of thousands of thermometers in every country, worldwide, recording temperatures in standard, white, louvered boxes called Stevenson Screens. The boxes usually are mounted one meter above the ground. They mostly are placed where there are suitable people to read and maintain them, e.g. post offices in town and city centers, airports, pilot stations, lighthouses, radio/TV stations, farms, and cattle stations. By far the majority is located in towns and cities.
Marine temperatures are determined from ship data. Temperature measurements of the marine atmosphere usually are performed from Stevenson Screens mounted near the ship's bridge, while sea surface temperature measurement utilizes intake pipes in the ship's hull.
Two leading institutions statistically collate the resulting data. They are the U.S. National Aeronautic and Space Administration’s Goddard Institute for Space Studies (GISS) and the Climatic Research Unit (CRU) at the University of East Anglia in Britain [11]. The process they follow is:
1) Select the stations to be used in the global database
2) Apply corrections for urbanization to data originating from urban areas.
3) Divide the globe into 5°x5° latitude/longitude boxes
4) Determine the temperature "anomalies" for each box based on available data.
5) Combine the trends from all the boxes to arrive at an overall "global mean temperature." Boxes that have no data are left blank. They are not estimated from neighboring boxes.
...
Is the Surface Record Wrong?
Because the second option that the satellites are wrong has been ruled out, and because the third option, that both the records are "good" is merely a compromise to appease conflicted interests, one is left with Option #1: the surface record must be wrong. In posing this solution, we must first be clear about where errors might creep into the surface record.
There are five potential sources of error:
1) Errors caused by environmental change in the general location of the measuring instrument.
2) Errors arising at the point of measurement, such as equipment or procedural faults.
3) Errors arising from statistical processing by GISS and CRU, such as poor station information
4) Errors arising from station closures altering the homogeneity and balance of the network
5) Errors caused by uneven geographical spread
Regards, Davey