"Pre-industrial" was described as "1750" a long time ago, and more recently there was no definition, but the 1700s were assumed.
Whatever the definition, "pre-industrial" is, for unknown reasons, considered to be an ideal climate, because any changes from that point are treated as bad news.
That bad news claim has never made sense, for two reasons:
(1) The actual global average temperature and CO2 level in the 1700s is just a guess, based on climate proxies -- there were almost no real time temperature measurements, and no real time CO2 measurements, and
(2) People living in the 1700s thought their climate was too cool, and would have loved today's more moderate climate.
You would think 1850 to 1900 would have better measurements than the 1700s, but the global average temperature in that period is a guess too.
Pre-1900, there were few land weather stations outside the US, Europe, eastern China and Australia.
Far from global coverage.
And the sea surface temperature measurements were almost entirely in Northern Hemisphere sea lanes.
Far from global coverage.
Using buckets and a thermometers -- far from accurate measurements.
So based on rough estimates of the climate in pre-1900, we should be thrilled our planet is slightly warmer.
The warming measured by satellites since 1979 shows the most warming was in the northern, colder, half of the Northern Hemisphere, mainly during the six coldest months of the year, and mainly at night.
Warmer winter nights in Siberia and Alaska are good news, not a "climate emergency".
The claim that current compilations of the global average temperature (1880 to 2021) have a margin of error of only +/- 0.1 degrees C. is not true.
Claiming such accuracy for the 1800s is science fraud.
Claiming the past 45 years of global warming was bad news is a false description of reality.
Claiming the next 45 years of global warming will be a "climate emergency" is scaremongering, not logical, and not real science.
The average global circulation model (climate computer game) has predicted double the warming that actually happened, and predicted warming of Antarctica, which has not happened.
With such inaccurate climate predictions, it's obvious climate science is not settled.
People with sense should be enjoying the best climate our planet has had since the cold 1600's.
There are plenty of real problems to worry about.
How about air pollution over Asian cities?
How about one billion people in the world with no electricity?