GISS Surface Temperature Analysis: The basic GISS temperature analysis scheme was defined in the late 1970s by James Hansen when a method of estimating global temperature change was needed for comparison with one-dimensional global climate models.
The scheme was based on the finding that the correlation of temperature change was reasonably strong for stations separated by up to 1200 km, especially at middle and high latitudes. This fact proved sufficient to obtain useful estimates for global mean temperature changes.
Combined land-surface air and sea-surface water temperature anomalies data is updated around the middle of every month and combines data files from NOAA GHCN v3 (meteorological stations), ERSST v4 (ocean areas), and SCAR (Antarctic stations).
The GLOBAL Land-Ocean Temperature Index is used.
CLIMATE CHANGE : THE MAGNITUDE OF THE PROBLEM
In its Fifth Assessment Report, the Intergovernmental Panel on Climate Change, a group of 1,300 independent scientific experts from countries all over the world under the auspices of the United Nations, concluded there's a more than 95 percent probability that human activities over the past 50 years have warmed our planet.
The ever-mounting evidence that Climate Change and its cascading impacts will become one of the greatest crises ever to face humanity.