The Earth is Warming, But We Already Knew That

Are trends in the Earth's surface temperature derived from instrumented records reliable?  At least three groups, the Climate Research Unit at East Anglia University (HadCRUT), NASA's Goddard Institute for Space Studies (GISS), and the NOAA/National Climatic Data Center (NCDC) produce analyses of the Earth's surface temperature during the instrumented period.  This is a difficult job.  Observing sites move, the land-surface changes around them (e.g., urbanization), instruments change, etc., and these changes need to be considered.  Hansen et al. (2010) provide a detailed overview of the process used by NASA/GISS and it is extensive and exhaustive.  Although the three groups have differing approaches, their results are generally quite similar and show a consistent picture of a warming planet.

Source: Hansen et al. (2010)

Another group, The Berkeley Earth team, has recently developed its own analysis and, as reported today in the Guardian, has just submitted four papers to Geophysical Research Letters that describe their work to date.  These papers are available here, and they report trends consistent with the analyses above.  Yes, minor adjustments will continue to be made as analysis approaches are refined, but the big picture is quite clear.  The Earth is warming, but we already knew that.