4 ms·
To be precise, these are global averages, so from this alone it is clear the numbers aren't measurements but rather the output of some analysis. The linked fil
by SiempreViernes 9y ago
To be precise, these are global averages, so from this alone it is clear the numbers aren't measurements but rather the output of some analysis.
The linked file is simply the analysis output, the source is the Goddard Institute for Space Studies, presumably their GISTEMP dataset (since that's the one about global average surface temperature).
The original GISTEMP analysis is documented here: https://pubs.giss.nasa.gov/abs/ha00700d.html https://pubs.giss.nasa.gov/abs/ha00700d.html
with later refinements found elsewhere on the GISS site.
In brief they simply use weather station data, and build their global average from that. They also talk about change in the average rather than the absolute value, which makes sense since you are then much less sensitive to the absolute calibration error of each station.
Then they do a lot of statistics on it to compensate for lack of coverage etc etc, read it yourself if 30 year old statistics papers are interesting to you.
- IncRnd 9y agoThank you for that, but if you look once more, you will see that you didn't answer my question.
- Certhas 9y agoThey did. As they said, they use (weather) station data + statistics to compensate for missing data. We have temperature records from weather stations going back to the 18th century. Just quickly googling I found this paper that works to make historical records usable for today: https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/gdj3.11 https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/gdj3.... "Daily observations of weather and climate for the province of Québec, Canada, start in the 18th century and continue to the present day. Daily temperature observations from 12 observers ranging from 1742 to 1873 are described here." That's why the 1880 forward data is different from other reconstructions going further back. These are measurement instruments by scientists recording temperature.