> We are in fact much worse off if humans aren't the primary cause, because it would mean simply reducing human emissions would not be enough.
Enough for what? I'm not convinced the climate changing is a bad thing. Nor have I seen evidence it in fact is changing at any alarming rate (and I worked in this space for a while).
Increasing the temperatures and increases in carbon mean more food and more habitable land. "Global warming" is the best thing that has ever happened to humanity. The world has been warming for around 20,000 years and even if we take the argument "global warming" is bad at face value... Supposedly, there is no evidence we caused global warming until the industrial revolution -- right?
Recall history class, when the North American continent was covered in a sheet of ice. Recall history class, when you learned the largest dessert in the world was a green oasis until the last few thousand years.
> We know humans are responsible because we can look at the gases involved and check the isotope ratios of the carbon in those gases. Carbon from living or recently living sources has a different isotope ratio than does carbon that has never been involved with life or has not been involved with life for a very long time. This is because cosmic rays hitting the upper atmosphere convert nitrogen into C14 which gets distributed throughout the atmosphere, and gets included in living things, and gets put back into the atmosphere when living things that breath exhale or when they die and decay unless the die someplace where they won't be eaten or used as fertilizer by some other living thing.
Oh boy... C14 comes from nuclear reactions and atmospheric production. If we get hit with a solar storm you're going to see an increase in C14. You'll also see a spike after nuclear testing. I see what you're saying regarding the idea that we can see how much carbon came from ancient sources, but IMO that is pseudo-science. The baselines simply aren't there.
Which brings me to my next point, you say a very authoritative statement "Second, humans are in fact the primary cause." --
Again to my parent comment, politicians are using this "science" to hammer home their political agenda. They aren't funding contrarian research and if you share an alternative, research backed view, you wont get published. It'll be blocked by the editors of the journal (who happen to also be publishing research on how climate change is dire & are often political ideologues).
Having read a LOT of these "research papers" and having worked on climate models. I can tell you, at least I am highly unconvinced. Often these papers will cherry pick their results that they want. In simulations they'll modify their variables and make assumptions. If you read the papers you can see these curves that look too perfect for their theories. Then in a decade or two they don't pan out. The reality is "science" is hard. Anything said with certainty is almost certainly an opinion or belief.
You want to know how I know the authoritative statement "Second, humans are in fact the primary cause." is unknowable? Because we only have ~100 years of measured data. We have statistical reasons to believe certain things (like temperatures in particular regions), but we don't have proof. It is conjecture. It could be right, it could be wrong. Frankly, I don't know. I also know no one else actually can prove their correct -- so all theories should be on the table.