Historic CO2 levels, climate change

[MikeeMiracle]

TL;DR Summary

Historic CO2 levels, climate change

Not trolling here, just have genuine confusion over CO2 levels comparied to what we believe CO2 levels have been historically and their effect on climate change.

I recently saw some Facebook group infographic posts which claimed that CO2 concentration in the atmosphere is the lowest it has ever been. I didn't believe this initially but even Wikipedia states that current levels are around 400ppm but have potentially been as high as 4000ppm in the past around 500 million years ago. If we take just this single fact at face value then it would seem the current fear of a runaway greenhouse effect from higher CO2 levels doesn't quite add up, however...I have been a member of this forum long enough to know that the above statement is a huge over simplification and not to take a single piece of "evidence" by itself as a sole reason for any cause and effect.

So to my question, what am I missing? I suspect quite a bit...I am vaguely aware of the Carbon cycle where CO2 relased into the atmosphere needs to balance with CO2 absorbed through various process's by the planet to cancel each other out so I suspect that the amount of CO2 being absorbed by the planet must be a hell of a lot lower now than it has been in the past when CO2 levels were higher? Otherwise we should have had runaway climate change in the past when level of CO2 were higher? What's changed so that the absortion ability is so much less now than it was in the past? Am I even on the right track with this train of thought?

Thanks

 

[PeroK]

Summary:: Wikipedia states that current levels are around 400ppm but have potentially been as high as 4000ppm in the past around 500 million years ago. If we take just this single fact at face value then it would seem the current fear of a runaway greenhouse effect from higher CO2 levels doesn't quite add up,

Do you think that the Earth 500 million years ago could have sustained a population of 7.7 billion human beings?

https://www.climate.gov/news-features/climate-qa/whats-hottest-Earth's-ever-been

 

[berkeman]

Thread closed temporarily for Moderation...

 

[bhobba]

While climate science is a legitimate topic to discuss on this forum, experience has shown that, unfortunately, it often degenerates into politics which is off-topic. Also, precisely what to do about it, if anything, most definitely is political. Still, the OP deserves an answer. So I looked about for the most authoritative sources I could find on the issue and found the following from The Royal Society, which of course, is an acknowledged authority on scientific matters:
https://royalsociety.org/topics-policy/projects/climate-change-evidence-causes/question-7/

For further scientifically factual information on Climate Science, the American Chemical Societies write up can also be considered authoritative:
https://www.acs.org/content/acs/en/climatescience.html

With that, the thread will remain shut.

Thanks
Bill

 

[fresh_42]

For the sake of information:
A paper about the albedo effect of earth, one of the parameters that contribute to all models.

Abstract​

The reflectance of the Earth is a fundamental climate parameter that we measured from Big Bear Solar Observatory between 1998 and 2017 by observing the Earth'shine using modern photometric techniques to precisely determine daily, monthly, seasonal, yearly and decadal changes in terrestrial albedo from Earth'shine. We find the inter-annual fluctuations in albedo to be global, while the large variations in albedo within individual nights and seasonal wanderings tend to average out over each year. We measure a gradual, but climatologically significant

0.5

decline in the global albedo over the two decades of data. We found no correlation between the changes in the terrestrial albedo and measures of solar activity. The inter-annual pattern of Earth'shine fluctuations are in good agreement with those measured by CERES (data began in 2001) even though the satellite observations are sensitive to retroflected light while Earth'shine is sensitive to wide-angle reflectivity. The CERES decline is about twice that of Earth'shine.

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021GL094888