In practice it's rocket science because:
- The climate is a function of a bazillion factors, many of which aren't well understood at all, and climatologists suck at programming them anyway. That's why the models are so unstable and frequently go crazy to Venus or ice-age like conditions even when simulating a theoretically stable climate with no CO2 emissions.
- There is evidence the CO2 greenhouse effect may saturate logarithmically, which if so would completely change the discussion around climate (in reality it wouldn't be allowed to change, but in theory)
- Nobody knows what the effect on temperature of doubling CO2 is! This is called ECS and over the decades, different teams of climatologists have estimated it yet their estimates have been drifting apart not closer together. The much vaunted consensus has actually been collapsing, with some researchers claiming ECS is a high number and others that it's a low number.
Where I live, in Europe, since I was a little child and until now, the climate has transitioned from winters during which there were three months or more of continuous snow cover to winters during which it snows at most once or twice and the snow melts immediately, usually in a few hours.
When I was a child, temperatures under minus twenty Celsius degrees were not unusual, while now there are more than ten years since the last time when I have used my winter jacket and my winter boots.
You can't extrapolate from a feeling about a single lifetime to hundreds of years into the future, that's just nowhere near enough data points. Speaking personally, I've seen no difference in number of snowy winters over my lifetime.
All the written texts that I have seen from the last few hundred years describe winters identical with those from when I was a child. The same is true for much more ancient texts, even ancient Latin and Greek texts, though those are more ambiguous.
There is no doubt that at least during the last two thousand years there has never been any period with temperatures as high as during the last 40 years, and during these 40 years the monotonic increase of the temperatures has been obvious, e.g. 15 years ago we still had a few weeks with snow per year, but then the weeks have become days, and then during the last few years the days have been reduced to hours.
I am living in an area with continental climate, far from the sea, which previously had large temperature differences between summer and winter. Now the average summer temperature has also increased, but that is much less obvious than the increase of the winter temperatures from below zero Celsius degrees to above zero. I assume that in areas closer to sea coasts the changes in the average temperature must be less noticeable, as they must be buffered by the water.
Besides the historical texts, the fact that during the last two thousand years there has never been such a warm climate in Europe has also been recently confirmed by the study of tree rings.
Personally I think it's insane to increase CO2 levels by that amount in just a few decades and expect there to be no bad consequences.
The archaeological record says the opposite. I don't know what Latin or Greek texts you're reading because they are full of references to things that can't be done today.
The Vikings were practicing agriculture in Greenland. [1] That's impossible now, it's too cold.
The Greenland climate was a bit warmer than it is today, and the southernmost tip of the great island was luscious and green and no doubt tempted Eric the Red and his followers. This encouraged them to cultivate some of the seed corn they brought with them from Iceland.
Bison skeletons have been found in mountain caves at altitudes that imply it was drastically warmer in the past [2].
From this it can be concluded that the beech limit but also the forest line during the »wisent time« (6,000 to 1,200 years before today) was much higher and the average summer temperature had to be at least 3 to 6 °C higher than today. Oaks (Quercus) at an altitude of 1,450 metres around 2,000 years ago also indicate a climate approximately 4 to 7 °C warmer than today.
This is well beyond the level that climatologists assure us means global destruction.
The fact that it was warmer in the past was not actually considered controversial up until Michael Mann started drawing his incorrect hockey-stick graphs. Go back just 20 years and you'll find the warmth of the Roman period being discussed quite openly, like this map [3] of suspected Roman England vineyard locations in which one is as far north as Lincolnshire, impossible in today's climate. This 2001 archaeological paper doesn't comment on the fact that it was warmer back then because everyone knew it and the fact was considered unremarkable.
Climatologists have done a great job of not only erasing this history but making it verboten to point out. Yet the problematic facts remain. Climatology doesn't have reliable methods for reconstructing past temperatures, has sparse data even for the modern era and routinely makes claims directly at odds with very well understood historical evidence.
[1] https://sciencenordic.com/agriculture-archaeology-denmark/vi...
[2] http://www.museumgolling.at/wp-content/uploads/2022/09/9_Sch...
[3] https://core.ac.uk/download/pdf/27661.pdf (figure 6)