This is one of the most complicated topics of our age I think. I've seen this "documentary" about 4 years ago I believe. The reason for me to watch it was that I had difficulty understanding how climate change could be caused by only one factor: CO2, a gas that these days makes up only 0.04% of our atmosphere, and about 0.035% back then (https://en.m.wikipedia.org/wiki/Carbon_dioxide
). I think that just presenting only this relatively tiny factor as 'absolute proof' for a theory that explains a huge phenomenon as our climate and how it changes is weird and incomplete.
So I went searching for explanations that included other factors. The activity of the sun comes to mind, because it obviously has a big influence on our weather and climate. So the sun has cycles, generally explained by the number of sunspots as an indication of the intensity and activity of our star. Looking there still not explained everything to me.
But I did figure out a couple of things:
- the sun explains most, if not all, of the energy involved in our climate.
- CO2 could be either an indicator of or the cause of climate change, but I was still impressed by clouds (water vapor, up to 20% of atmospheric conditions) which fluctuate with warming and cooling also and moderate both overheating and excessive cooling.
- I learned oceans are a big moderator of climate, so how did that fit in?
- weather forecast are notoriously wrong from time to time, so if weather is so complicated to predict, how can we build models of our climate with any accuracy?
I still could not get a clear picture. I did sense that our climate had become more erratic, temperatures were much higher where I live for years than what was normal before. Droughts would last longer. Storms were heavier. Climate clearly is changing.
Then I stumbled on another study. This one was looking at other undeniable factors that also influence climate, and these factors were all influenced by mankind. These all came down to how we modified our landscapes to huge extends. I published a review on it on permies: https://permies.com/t/56655/Water-Recovery-Climate-Water-Paradigm
If you'd rather have a summary, I wrote one for pur blog: https://permaculturesj.wordpress.com/articles/trees-water-and-climate/
Climate is a complex issue. I'm not sure if the main focus on CO2 came from a desire to simplify the issue so people could understand what is happening, or if it is another example of our flawed sciences where everything gets broken down into smaller and smaller bits so we can finally isolate one issue that we can properly measure instead of looking at the whole of things. CO2 could be a symptom or a part of the explanation, but climate is too complex to explain it with only one tiny factor. Most climate change deniers get their 'fuel' from this simple awareness. But as always, you can deny reality, but not the consequences of reality, and climate change or climate emergency is clearly happening.
On our blog I have tried to go deeper into some factors.
Energy in nature (compared to how civilization uses energy): https://permaculturesj.wordpress.com/articles/energy-in-nature/
Technology cannot save civilization (but nature can heal the earth): https://permaculturesj.wordpress.com/articles/technology-cannot-save-civilization/
What the heck is wrong with us? (Some thoughts on why we seem powerless, but we can actually be in control): https://permaculturesj.wordpress.com/articles/what-the-heck-is-wrong-with-us/
I hope this gives you some arguments to broaden the insight of your friend. Most things I wrote about are common Permaculture knowledge, nothing extreme or farfetched there.