Why do global temperature records differ?
Why do global temperature records differ? | Earth | EarthSky
The National Oceanic and Atmospheric Administration (NOAA) announced earlier this month that March 2015 was the warmest March in the modern temperature record. NOAA also said January-March, 2015 was the warmest start of any year on record. When NOAA says “on record,” it means a record extending back 135 years to 1880. Data from the Japanese Meteorological Agency also showed March, 2015 as the warmest March, with record extending back until 1891. Meanwhile, NASA data showed agreement that 2015 has had the warmest start on record. But NASA data showed March, 2015 as the third-warmest March on record.
Why do these institutions sometimes disagree? For example, why do NASA and NOAA disagree on the status of March, 2015 in the global temperature record?
The four major keepers of records on global temperature – the fourth is the UK Met Office, which posts its data here – commonly publish slightly different conclusions from their separate analyses. Contrarian arguments, by those who don’t believe Earth is warming, often point out that one group’s ranking is slightly different than another’s.
And the differences are surely there, although they are small.
However, when you look at the graphics below – March 2015 temperatures data from NASA, NOAA and Japan – do you see differences, or similarities?
I see similarities. And, in fact, the slight differences show how science works, and why it works so well.
In science, different groups will nearly always use slightly different ways of collecting and analyzing data; science is a human process, after all, and we humans don’t think identically.
In science, if two groups of results come extremely close to confirming each each other – as the temperature data sets of NASA, NOAA and the Japanese Meteorological Agency surely do – scientists themselves understand the reason for the small differences in the data. They assume those small differences will always be there.
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