D is quite far from certain....
"D" is the the claim that the increase in CO2 is anthropogenic. That is indeed known beyond even vaguely reasonable doubt - first, from simple accounting (we know fairly well how much CO2 we release) and secondly by isotope fingerprinting (the C we burn is from fossil fuels, which is depleted in 13C, and we can detect the resulting change in the atmosphere).
... For instance, take the end of the end of the Younger Dryas period. Rather than our current warming of 1C in 100 years, the end of the Younger Dryas period was marked by a warming of ~7C in 5 - 50 years.
The Younger Dryas was primarily an event in the Northern Atlantic region, and much less well-defined on a global scale. And we have good candidates for what caused it - primarily a slow-down of the thermohaline circulation as the result of the abrupt emptying of the large glacial lakes in North America.