I have watched lectures from Patrick Moore, former co-founder of Green Peace, who left when he realized they became a communist organization. He has done detailed study of the Earth's temperatures and CO2 levels going back in time to waaaay back. Has a lot of graphs and stats. Videos online.

My take, based on his work and other things I've read:

• Life as we know it (animals that breathe oxygen and plants that breath CO2) began about 500,000,000 years ago with the Cambrian Explosion.
• In those 500,000,000 years, there is NO CORRELATION between temperatures and CO2 levels.
• 98% of the Earth's CO2 is stored in the oceans, and it seems that the oceans absorb and release it as needed, through some not yet understood mechanism.
• The highest temperatures on Earth since the Cambrian Explosion occured about 50,000,000 years ago. There were no polar ice caps then.
• When temperatures heat or cool, the tropics stay about the same, and the farther away from the tropics, the more extreme the change. When the Earth is warm all over, it is about as warm at the poles as at the equator, but the temps at the equator don't change much during the cycles.
• About 2,000,000 years ago, the Earth entered the current ice age. We are still in that ice age.
• During an ice age, there are glacial periods (when the glaciers come down from the Artic and temps drop) and interglacial periods (when the ice recedes back and temps rise).
• We are living in an interglacial period within the ice age, and that has been going on for about 10,000 years -- about the same time man invented agriculture (because the large animals were dying off).
• Within that 10,000 years, there have been 300-year cycles and 30-year cycles (maybe others, too). The 30-year cycles are why the climate change hoaxers are always wrong in their predictions (the main reason, anyway). They don't factor natural forces into it because they want everyone to believe it is man-made, and therefore political controls can be implemented.
• The average glacial period in this ice age has lasted about 200,000 years, but the average interglacial period only about 10,000 years.
• We are due for the end of the interglacial at anytime, but there is no telling when that will happen. These are averages.
• When an interglacial period ends and the glacial period begins, it sometimes happens very quicky -- within 10-20 years.

My take is that all of these fluctuations are due to the Earth's orbit vs the Sun and the slightly changing position of the Earth relative to the Sun, not only in its orbit but also on its axis. Could also have to do with activities on the Sun that affect the Earth.

Mankind has had some effect on the rise of CO2 levels in the atmosphere, but it has been a positive effect, not a negative one. We are taking carbon resources from beneath the crust and under the oceans, putting them into the air, and they are recycled by the Earth's system. Plants thrive in such an environment, and that helps animals, too.

Pollution is a different topic, but CO2 increases are excellent for the health of the planet and all living things.

500,000,000 years ago, at the beginning of the Cambrian Explosion, CO2 levels were 2,000 times higher than they are now, and plants and animals thrived.

We have nothing to fear from CO2 or global warming, in general. We should consider the devastating effects of a fast-approching glacial period if it were to occur. Other than that, the polticians and their puppetmasters above them are the real threat to humanity.