File:Global Warming Map.jpg From Global Warming Art This figure
shows the difference in instrumentally determined surface
temperatures between the period January 1999 through December
2008 and "normal" temperatures at the same locations, defined to
be the average over the interval January 1940 to December 1980.
The average increase on this graph is 0.48 °C, and the
widespread temperature increases are considered to be an aspect
of global warming. This plot is based on the NASA GISS Surface
Temperature Analysis (GISTEMP), which combines the 2001 GISS
land station analysis data set (Hansen et al. 2001) with the
Rayner/Reynolds oceanic sea surface temperature data set (Rayner
2000, Reynolds et al. 2002). The data itself was prepared
through the GISTEMP online mapping tool, and the specific data
set used is available here. This data was replotted in a
Mollweide projection with a continuous and symmetric color
scale. The smoothing radius is 1200 km, meaning that the
reported temperature may depend on measurement s