"Have a look around today, and most scientists seem to agree that we're rather heading into the next ice age."

What scientists are you talking about? Also, didn't you JUST claim "we have no clue"?

By the way, global warming is not the case of some weird uptick in data correlating with some other data being interpreted as causally linked. In the case of global warming, it's really common sense (if you're trained in physics): We understand the infrared spectrum of CO2, and that by absorbing and retransmitting far infrared, it acts to slow the radiative transport of heat. This can be shown in the laboratory. Now, normally you think of the atmosphere being in a steady state, as plants grow they absorb CO2 (converting it into their cellular structure), and as plants die and are digesting or decay, CO2 is ultimately generated. A small amount is buried, but the amount buried is small compared to the overall cycle in a typical year, such that the atmosphere is roughly in equilibrium over the near term, although over the very long term (hundreds of millions of years), CO2 levels have dropped. (By the way, stars generally increase in brightness as they age, so when the CO2 levels were much higher, the Sun was dimmer). This buried carbon becomes fossil fuel, such as coal. Humans dig it up and burn it, but we've really only got good at this process on a large scale within the last 100-150 years (and even in the last 75 years, we've improved productivity by roughly an order of magnitude such that it takes a tenth as much manpower nowadays).

People about a century ago realized that the rate at which we were digging up this long-buried carbon was faster than the rate it was absorbed and buried naturally (makes sense, as the coal was produced over hundreds of millions of years), thus causing the CO2 level of the Earth to start to increase and thus the greenhouse effect to increase. It was just a side note at the time, a whimsical thought about the far future.

But today, the CO2 level has already dramatically changed since the 1800s, and we've also noticed that hey, we can see that predicted temperature rise as well, faster than would be explained just by coming out of the last ice age. This is a totally unsurprising finding if you know the infrared spectrum of CO2 and the rate at which fossil fuel is produced and burned (8-10 cubic kilometers of coal, 3.5 cubic kilometers of oil, about 4000 cubic kilometers of natural gas every year). You can reproduce the change in CO2 level over that time if you assume that roughly half of the carbon we burn every year is absorbed (by ocean, rocks, etc) and the other half stays permanently in the atmosphere.

That CO2 produces an insulating effect on the atmosphere is an indisputable fact. Earth would be much colder without this fact, and you can test it in the laboratory (and this effect is why Venus is hotter than Mercury, even though Mercury is much closer to the Sun).

That humans produce a very large amount of CO2 (i.e. significant fraction of atmosphere's total CO2 over decades) by burning long-buried fuels is an indisputable fact.

That the CO2 level has increased dramatically over the last 100 years is an indisputable fact.

The conclusion is that there MUST be some level of warming from human activity even before you look at the temperature data (which ALSO indisputably shows significant, off-trend warming over the last century), although the exact amount you'd expect depends strongly on the details of our climate system, such as feedback effects (both positive, i.e. increasing the effect, and negative, i.e. stabilizing or counter-acting the effect) from clouds, ice cover, vegetation changes, etc. We DIDN'T have to merely /guess/ at the causality direction after the fact once we saw that all the CO2 was not being fully reabsorbed, as it's a direct physical consequence of the infrared spectrum of CO2, something we can measure in the lab and even replicate from first principles quantum mechanics if we really felt like it. The fact that we observe warming is, to me, just the final validation of what we already knew would happen if we pumped a bunch of CO2 in the air.

By the way, I laugh at the idea that scientists (who can study anything and get grants one way or the other... and are pretty darned poor compared to similarly trained colleagues in the oil and gas business) have a "huge monetary incentive" to push this "agenda" but that somehow, corporations with tens of trillions of dollars worth of fossil fuel assets on the line don't have a similar agenda... I mean, the difference in financial incentive is absolutely absurd!