The analysis that I'm waiting to see is "of the global CO2 production each year, how much of it is due to humans?"
If we contribute 90% of CO2 production, then reducing it may change things.
If we contribute 10% of CO2 production, then even reducing our portion to zero, the overall change is near-negligible.
The ecosystem produces vast amounts of CO2 ... and consumes a similarly vast amount. It is the imbalance that you need to worry about. And that imbalance is largely caused by humans either damaging CO2 sinks or releasing CO2 that ha been sequestered over the last few billion years
If the faucet is on and your kid is dropping pennies in, both are contributing to the overflow but stopping your kid is going to be irrelevant.
Do we know which humans are?
Of course, turning down the faucet would still help. But in this analogy, the faucet is jammed on, but the kid might stop if you ask him the right way.
For humans, it's pretty simple: we're burning the oil on the timescale of centuries that the nature has been storing on the timescale of billions of years. For nature, the longest CO2 cycle is at most a multiple of the longest life-span (~500 years), and there's no indication that the cycle has changed (i.e. that suddenly more trees are burning in natural fires than have for the past few millenia).
"While CO2 emissions come from a variety of natural sources, human-related emissions are responsible for the increase that has occurred in the atmosphere since the industrial revolution."
Ref: https://www.epa.gov/ghgemissions/overview-greenhouse-gases (on the carbon dioxide tab)
And the Energy Information Association goes on to include magnitudes here:
If those numbers are accurate, humans contribute 0.2% of CO2 and 60% of methane. So my follow up is: Which gas is a worse contributor? Because we can greatly influence one of those.
It's a lot like saying "prove it to me with numbers, because all the numbers you're giving me are bunk."
"Nature generates X million tons of CO2 each year. Humans generate Y million tons of CO2 each year which primarily comes from A, B, and C."
From my own search, there are lots of numbers around X and Y and they're wildly different. Do they converge around a range?
Thus, net CO2 from natural causes must average very close to 0 on long time scales.
PS: If you look into it natural carbon sequestration increases slightly as atmospheric CO2 increase which is why things end up in balance. Natural carbon sequestration is also why there are huge sources of coal and oil to begin with.
Which is to say, the natural net contribution to CO2 in the atmosphere is negative. If we somehow put a stop to natural processes involving CO2 and just carried on with human activity, the rate of CO2 accumulation would go way up.
This is the relevant bit for how much emitted CO2 has accumulated in the atmosphere:
"From 1870 to 2014, cumulative carbon emissions totaled about 545 GtC. Emissions were partitioned among the atmosphere (approx. 230 GtC or 42%), ocean (approx. 155 GtC or 28%) and the land (approx. 160 GtC or 29%)."
If you want to double-check against increasing CO2 concentration, the mass of the entire atmosphere is about 5.15e18 kilograms, so one part per million is about 5e12kg or 5 gigatonnes.
The preindustrial CO2 concentration was roughly 280ppm. We're now at about 400ppm, so that's 120ppm or about 640 gigatonnes more CO2 in the atmosphere today. Things are a bit confusing here because for some reason emissions are measured in gigatonnes of carbon alone, not CO2, so you need to multiply emissions by 3.67 (the mass ratio of CO2 to just C) to get CO2. Taking the cited 230 GtC added to the atmosphere and multiplying by 3.67 gets us 873.46 gigatonnes, which is roughly in the same ballpark, considering this is an off the cuff internet comment using random googled sources.