Monthly departures from 1961-1990 in the Met Office Hadley Centre records: global land + sea (HadCRUT5), global sea surface and tropical (30S-30N) sea surface (HadSST4).
Limits. Monthly, about 4-8 weeks behind.
How to read it
degC above 1961-1990; HadCRUT5 rows carry a 95 % range in meta.ci95.
Why it matters for Koh Samui
Independent confirmation of NASA/NOAA; the tropical sea series tracks El Nino warmth.