Just recently you may have overheard conversations like “the Earth has heated up by around 0.7 or 0.75 or 0.8 degrees Celsius since the start of the Industrial Revolution”. “No it hasn’t, it’s only warmed by 0.2 or 0.4 degrees Celsius !”
So who’s right ? And how can you tell ? It all depends on where you choose your baseline, the year you count from. And it also depends on the reach or spread of the data in the data set you are looking at.
If you believe that the 1800s were colder than normal, then you will think that the Earth has not warmed up so much, because you will discount everything before about 1940 because it was, to you colder than “average”.
Some of the data available on global temperatures “interpolates” for areas where measurements may be missing in certain geographical regions of the world. This can give the appearance that the data sets are different, when actually, they’re not.






