They can contribute. Other contributing factors changes in the sun (biggest!), changes in the sun’s, earth’s, Jupiter’s & Saturn’s magnetic fields. One we are only now starting to get a glimmer of understanding changes in the cosmic ray showers as the solar system goes around the galactic rim. That position correlates strongly with major climate events. Correlation is not always causation, but so far the physics also makes sense.
Positions of continents and mountain ranges are another considerable long term factor. The present long term decline of average temperatures correlates well with the rise of the Himalayan Plateau (causing CO2 to be rained out of the atmosphere and bound up in rocks) and, more recently, perhaps also the formation of the Isthmus of Panama and the related changes in ocean currents. Further back, it is suspected that tremendous blooms of Azolla in the Artic Ocean, likely combined with other factors, sequestered equally tremendous amounts of CO2 into the sediments.*
...we are only now starting to get a glimmer of understanding changes in the cosmic ray showers as the solar system goes around the galactic rim. That position correlates strongly with major climate events. Correlation is not always causation, but so far the physics also makes sense.
That's most interesting. Do you have a link to an article, chart, etc.?
Those must be the really long term changes, as it takes the solar system something like 230-240 million years to make one orbit in The Milky Way, IIRC.
*This so-called "Azolla Event" is really fascinating. The sediments are there, and appear to correspond fairly well to the separately observed drop in CO2. However, the temperature drop is much more gradual than the CO2 drop, and the "Azolla Event" is in the middle of a much larger and gradual temperature slide.
https://en.wikipedia.org/wiki/Azolla_event
(Yes, many complaints about Wikipedia apply, but it is a place to start, at least.)
I also note that the Wikipedia page on the "Azolla Event" cites higher starting atmospheric CO2 levels (approximately 3500 ppm, dropping to 650 ppm atmospheric CO2) than do other Wikipedia pages, illustrating one of the many(!) uncertainties in all this. And, any parallels to the present or next few million years are almost worthless, as many other conditions are different now, than then.
That last also goes for the "PETM" spike in temps about 55.5 million years ago, often used by climate change alarmists to advance their arguments...