One of the most important foundations of scientists' understanding of global climate change is the land surface air temperature record, the long-term observations of air temperature measured 2 meters (6.5 feet) above the ground.
These observations have been made around the world, with varying degrees of accuracy and consistency, for more than a century in some places. Those air temperature records have shown a long-term warming trend and the researchers in a new paper say that is solidly due to anthropogenic climate change. Variability seen in the air temperature record is used to guide models of the future climate.
Throughout the long observational record, the techniques used to measure air temperature have evolved. Observation stations have been moved, the land around the stations has changed, and the distribution of research stations has been heavier in urban and agricultural regions than in remote plots of land.
Gridded temperature data sets have been designed to account for these biases and sources of uncertainty. However, for these and other reasons, some scientists and political figures have questioned the accuracy and validity of the historical air temperature record, arguing against its usefulness for understanding historical temperature trends and variability.
In response to these global warming skeptics, climate change scientists calculated an independent record of historical land surface air temperatures that used a range of historical observations but did not use any measurements of air temperature itself. As such, any problems in the existing air temperature record that stem from changing techniques or tools or other factors would not appear in the authors' new record.
The authors find that their independent temperature record largely aligned with existing air temperature records from 1901 to 2010, corroborating the validity of the widely used land surface air temperature record.
Paper: Gilbert P. Compo, Prashant D. Sardeshmukh and Chesley McColl: Cooperative Institute for Research in Environmental Sciences, University of Colorado, Jeffrey S. Whitaker: Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Philip Brohan: Met Office Hadley Centre, Philip D. Jones: Climatic Research Unit, University of East Anglia, 'Independent confirmation of global land warming without the use of station temperatures', Geophysical Research Letters, 2013 hDOI: 10.1002/grl.50425