Best-case historical
19th to mid-20th century
liquid-in-glass (LiG)
thermometers
had 1 degree C.
gradations.
That means the best-case
laboratory-conditions
temperature resolution
is ±0.25 C.
Sea surface "bucket"
LiG thermometers
through the 20th century
also had 1 degree C.
gradations.
The same ±0.25 C.
best case laboratory
resolution limit applies.
The best American
ship-board engine-intake
thermometers
included 2 degrees F.
(~1 degree C.)
gradations.
There were 2 degrees C.
gradations on British ships,
so the best possible resolution
for them is about ±0.50 C.
The detection limits
of the instruments
allows us to estimate
the uncertainty
in any surface
temperature record.
The government bureaucrats
compiling the global temperature
have ignored the detection limits
of their instruments.
Even worse, a majority of the planet
has no measurements at all --
so temperatures for those areas
are guessed by bureaucrats,
and their guesses (aka "Infilling")
can never be verified, or falsified.
It is very unlikely
that average global
surface temperature,
since 1850,
can be known
within ±1 degree C.
prior to 1980,
or within ±0.5 C
after 1990,
at the 95%
confidence level.
But NASA-GISS and NOAA
claim a fake +/- 0.1 degree C.
margin of error.
Then they ignore their
own fake margin of error
by claiming one year was
a few hundredths
of a degree C. warmer
than the prior year !
Including reasonable
margins or error,
of +/- 1 degree C.,
there is nothing
“unprecedented”
in the surface
temperature record
since 1880.
Surface temperature data
would be laughed at
by any other physical science,
outside of modern climate "science",
for LACKING standardization,
quality control, and a minimum of
annual instrument calibrations
and inspections of changes
to the environment surrounding
the measurement instrument.