3 ms·

Thanks for tracking this down. It would be one thing if journalists on the science beat were generally accurate and reliable, but they get so much stuff wrong a

• mikeash 10y ago
  I believe that's what the linked paper is referring to by "base period" which it discusses a bit on page 2: https://pubs.giss.nasa.gov/docs/2010/2010_Hansen_ha00510u.pdf https://pubs.giss.nasa.gov/docs/2010/2010_Hansen_ha00510u.pd... If I understand it correctly, the 0 point is the average of the period from 1951 to 1980, which was chosen relatively arbitrarily based on when research on this stuff began in earnest, but is about as early as it can reasonably be.
• roter 10y ago
  Zero represents the 30-year mean of the years 1951-1980, i.e. some representation of a recent baseline climatology. Choosing 1880, or any other year, might skew perception positively or negatively. From the Earth Observatory [0]: > The period of 1951-1980 was chosen largely because the U.S. National Weather Service uses a three-decade period to define “normal” or average temperature. The GISS temperature analysis effort began around 1980, so the most recent 30 years was 1951-1980. It is also a period when many of today’s adults grew up, so it is a common reference that many people can remember. [0] http://earthobservatory.nasa.gov/Features/WorldOfChange/decadaltemp.php http://earthobservatory.nasa.gov/Features/WorldOfChange/deca...