
Well, it’s a kind of stretched thought experiment, to imagine they had precise satellite-like temperature measurements in those days. But if you really want to ask, when did humans first have a discernible influence on the climate, it surely goes back much earlier than that - due to deforestation and associated changes in albedo (as well as CO2), also desertification in some regions (north africa?). I don’t see albedo or land-use change in this paper, only fossil emissions.
There are renewables available cheaper than coal( if you take into account subsidies ), especially in China (the country that dominates those graphics (if you look carefully at the vertical scales). However, there are many political leaders - mainly of older generation - who cannot imagine abandoning coal, they prefer to keep on subsidising, to save traditions and communities, to defend their concept of what made ‘great’ decades ago. In China and India there is also a widespread concept that since the west did this in the past, so now they have to use up an equivalent per-capita share of the atmospheric space - a kind of collective global suicide.