The graph also includes temperature measurements by satellite.
Since 1979, satellites have provided another check on surface temperature measurements.
More work is needed, Lukin said, to allow more temperature measurements to be taken more often.
As more ship travel occurred, and more measurements were made, the coverage of temperature measurements across the globe increased.
They use many thousands of temperature measurements taken across the globe, on land and at sea, each day.
The globally averaged combined land and ocean surface temperature measurements show a warming of 0.8C from 1850 to 2012.
A number of papers from climate 'skeptics' have sought to fit the surface temperature measurements with various cycles.
Each of these interferes with a station's temperature measurements, perhaps making it read too cold, or too hot.
In another email discussing graphs of past temperature measurements Jones says "we're choosing the periods to show warming".
Gradually, various problems with the satellite temperature measurements were identified, some by the Huntsville group, and several by other groups.
However, Lu used outdated and superseded surface temperature measurements with a cool bias that exaggerated that surface warming slowdown.
