AN ASSAULT ON SCIENCE

That's because his background is complex computer modeling. That should have answered your q. LOL

https://en.wikipedia.org/wiki/Carbon_dioxide_in_Earth%27s_atmos

Earth's atmosphere currently constituting about 0.04% (400 parts per million) of the atmosphere.[1][2] Despite its relatively small concentration, CO2 is a potent greenhouse gas and plays a vital role in regulating Earth's surface temperature through radiative forcing and the greenhouse effect.[3] Reconstructions show that concentrations of180 parts per million during the Quaternary glaciation of the last two mi CO2 in the atmosphere have varied, ranging from as high as 7,000 parts per million during the Cambrian period about 500 million years ago to as low as llion years.Earth's atmosphere currently constituting about 0.04% (400 parts per million) of the atmosphere.[1][2] Despite its relatively small concentration, CO2 is a potent greenhouse gas and plays a vital role in regulating Earth's surface temperature through radiative forcing and the greenhouse effect.[3] Reconstructions show that concentrations of CO2 in the atmosphere have varied, ranging from as high as 7,000 parts per million during the Cambrian period about 500 million years ago to as low as 180 parts per million during the Quaternary glaciation of the last two million years.

Six hundred and fifty thousand years is indeed a long time but I forgotten how old is the earth somewhere in four and a half billions years range?

Is there some reason that the cut off date was 650,000 years ago instead of going back a few hundreds of millions of years?

Because it's irrelevant.

Quote:

Because it's irrelevant.

Or because it been at least 17 times higher in the earth history then it is now.

slightly intoxicating, breathing and pulse rate increase, nausea: 30,000 ppm
above plus headaches and sight impairment: 50,000 ppm
unconscious, further exposure death: 100,000 ppm

The Cambrian world differed greatly from that of the present, but it was also quite different from the preceding Proterozoic Eon (2.5 billion to 541 million years ago) in terms of climate, geography, and life. Average global temperatures during much of the Neoproterozoic Era (1 billion to 541 million years ago) were cooler (around 12 °C [54 °F]) than the average global temperatures (around 14 °C [57 °F]) of the present day, whereas the global temperature of Cambrian times averaged 22 °C (72 °F). Low temperatures during the Neoproterozoic helped to sustain a series of worldwide events known as the Sturtian (748 to 713 million years ago), Marinoan (650 to 600 million years ago), and Gaskiers (595 to 565 million years ago) glaciations. Climate studies suggest that Cambrian temperatures were the norm for most of the Phanerozoic Eon (the last 541 million years), and these were exceeded only by a brief increase during the Permian Period (298.9 million to 252.2 million years ago) near the end of the Paleozoic Era. Cooler temperatures, similar to the average global temperature of the present day, occurred during the end of the Ordovician, during the later part of the Carboniferous (358.9 million to 298.9 million years ago), in the early part of the Permian, toward the end of the Jurassic (201.3 million to 145 million years ago), and in the early part of the Cretaceous (145 million to 66 million years ago) periods, as well as near the end of the Oligocene Epoch (33.9 million to 23 million years ago).

Game player.........and a nasty game player at that.

...To argue that the display does not have a complete enough range on the x-axis is simply red herring.
...

The evolution of man-made technologies post the industrial revolution being a primary variable responsible for the observed changes in CO2 seems a very reasonable explanation.