IPCC AR5: "CO2-induced warming is projected to remain approximately constant for many centuries following a complete cessation of emission. A large fraction of climate change is thus irreversible on a human timescale, except if net anthropogenic CO2 emissions were strongly negative over a sustained period."In other words, even if all the world ran on carbon-free energy and deforestation ceased, the only way of lowering temperatures would be to devise a scheme for sucking hundreds of billions of tonnes of carbon dioxide out of the atmosphere, 115%-180% of that which was ever produced by man, over the next 1000 years.
In essence, it is claimed that we're doomed no matter what.
Fortunately, any small effect of CO2 on the climate is overwhelmed by natural variability, thus nature will do what it wants regardless of man's attempts to control the weather with the harmless, essential, trace gas CO2. And even if you think CO2 has a significant climate effect, the lifetime of CO2 in the atmosphere is only about 14 years, not the hundreds claimed by the highly flawed IPCC Bern model.
Reversing climate warming by artificial atmospheric carbon-dioxide removal: can a Holocene-like climate be restored?
Andrew. H. MacDougall*
Abstract: Most climate modelling studies of future climate have focused on the affects of carbon emissions in the present century or the long-term fate of anthropogenically emitted carbon. However, after carbon emissions cease there may be a desire to return to a “safe" CO2 concentration within this millennium. Realistically this implies artificially removing CO 2 from the atmosphere. In this study experiments are conducted using the University of Victoria Earth system climate model forced with novel future scenarios to explore the reversibility of climate warming as a response to a gradual return to pre-industrial radiative forcing. Due to hysteresis in the permafrost carbon pool the quantity of carbon that must be removed from the atmosphere is larger than the quantity that was originally emitted (115–180% of original emissions). In all the reversibility simulations with a moderate climate sensitivity a climate resembling that of the Holocene can be restored by 3000 CE.