the "normal" it's comparing against is 1981-2020 averages, probably at monthly resolution. i think the process of logging monthly climate "normals" started in the 1950-ish and are based on 30 year averages that jump forward every 10 years. i should know all this in much better detail because i've given presentations and put together articles about it, but i'm running late for a meeting and my brain is farting.
they do this to show how long range forecasting compares to these "recent" normals. so when you see like all red maps of temperature, it's saying "yeah, it's gotten hotter around here for a while, but it's getting even hotter than that, baby!"
the "normal" it's comparing against is 1981-2020 averages, probably at monthly resolution. i think the process of logging monthly climate "normals" started in the 1950-ish and are based on 30 year averages that jump forward every 10 years. i should know all this in much better detail because i've given presentations and put together articles about it, but i'm running late for a meeting and my brain is farting.
they do this to show how long range forecasting compares to these "recent" normals. so when you see like all red maps of temperature, it's saying "yeah, it's gotten hotter around here for a while, but it's getting even hotter than that, baby!"