In the early 1900s, the global average distribution of measured surface temperature estimates ranged between 14 and 15°C. For the Northern Hemisphere. There were very few Southern Hemisphere measurements before 1920, and too few until after World War II.
Sea temperature measurement methodologies and instruments repeatedly changed, starting with wood buckets thrown over the sides of ships and mercury thermometers.
There were no experiments ever done comparing ALL the methodologies for measuring sea water surface temperature in one place. Such an experiment would help determine if methodology changes inadvertently caused a warming or cooling temperature trend for 70% of our planet's surface. Shouldn't scientists be interested in that? Not in modern climate (junk) "science".
For 1991-2018, HadCRUT, Berkeley, and NASA GISS also estimate today’s global temperature is about 14.5°C.
A new study (Kramm et al., 2020) suggests the generally agreed-upon global temperature from 1877 to 1913 from dozens of calculated results was about 14.4°C. Since HadCRUT, Berkley, and NASA GISS indicate the 1991-2018 had a global surface temperature of about 14.5°C, that would suggest there has been “no change in the globally averaged near-surface temperature over the past 100 years”.
https://www.scirp.org/pdf/ns_2020031013452917.pdf
The concept of “Average Near Surface Temperature” has no useful linkages to the thermal energy that drives Earth’s weather. To have any relevance, it would need to include a correction for the atmospheric water content. Measurement of ocean temperature to 2,000 meters is a better indicator of the energy that drives weather on Earth. The 65 year record indicates a rise of 0.1C. That tiny change is within the measurement error.
Any claim that there is Global Warming in the past 100 years, and not global cooling, cannot be validated with ANY scientific certainty using haphazard frequently "adjusted" surface measurements. Global Warming, aka Climate Change, aka The Coming Climate Crisis, is a fairy -- weak science that comes from the creators of frequently "adjusted" and wild guessed "data".
Perhaps 21st century degrees are bigger than 19th century degrees? Or maybe man-made CO2 makes degrees grow bigger? Or temperature readings in the rear view mirror are smaller than they appear?
I hope you can read the charts below -- I carefully edited what started out as one blurry jpg file, into two easier to read jpg files, using my MacBook Pro:
Additional information from 2012, not included here: