also, the biomass of marine flora is believed to have increased four-fold over the past 150 years. so if we cut CO2 emissions too quickly then the plants would begin rapidly suffocating, and the combined effect on the oceanic carbon cycle would result in a large enough shock to atmospheric carbon to create a runaway global cooling that would make The Day After Tomorrow look like Winnie the Pooh's Blustery Day, by comparison... we'd be back to "snowball earth" within a decade, and this time it would likely last forever