The increase from 1930 to today is more accurate than any of those but is much larger than any increase measured by the old methods. Stomata records have shown up to 60 ppm per century (IIRC) and we will soon have a rate of increase of 60 ppm per 20 years. Also the rise from 1930 must be explained. Can't simply say because prior knowledge is imperfect the current rise could be natural. It requires a explanation. There's a well-supported manmade explanation, and no natural explanation that I have read about.
“There are other proxies they don’t mention showing thousands of years of lower CO2.”
And how have those proxies been VALIDATED?
To know if the proxies accurately measure past conditions, you would have to climb in to a time machine, go back in time, measure the actual air in the past, then come back in your time machine to the present, and then re-measure the proxy.
On what basis would anyone speculate that a proxy is an accurate measure of CO2 content in the atmosphere.
“Those are inexact just like the ice cores.”
That would lead to the conclusion that they are worthless.
“Another flaw in their argument is that chrmical analysis has been used since 1812”
That is incorrect. Attempts to measure CO2 content in the air were notoriously unreliable, difficult, and unsuccessful.
CO2 was not even known until around 1750.
All measurements prior to 1930 are worthless.
“Also the rise from 1930 must be explained.?
WHY?
The proponent of a hypothesis must prove it.
The hypothesis that human industrial activity producing CO2 affects the temperature of the planet must be proven.
You deny science when you say that others must disprove the hypothesis.
That’s not science.
Science requires that you prove the hypothesis.
“Can’t simply say because prior knowledge is imperfect the current rise could be natural.”
Yes, we can say that.
But what you are missing is that there is no relationship between CO2 in the atmosphere and the temperature of the Earth.
It does not matter if the observed change in atmospheric CO2 — which is probably measurement error due to local conditions like on the Hawaiian volcano — is natural or not.
Who cares if CO2 content in the air is natural or man-made?
CO2 does not change the planet’s temperature.
“It requires a explanation.”
Your hypothesis requires an explanation as well as proof. You are turning science on its head. The hypothesis must be proven true.
“There’s a well-supported manmade explanation, and no natural explanation that I have read about.”
There is no explanation. It has never been tested by science.
Plants eat CO2. The extremely tiny amount of CO2 transformed by humans from where nature stored it into the free air would stimulate plant growth, and CO2 would immediately return to equilibrium.
Human industrial activity cannot explain CO2 in the atmosphere because plants are eagerly and busily consuming that same CO2 as fast as they can.