@roger,
theres much research on consequential events. Richard Alley stated that we can expect an indefinite period of intense effects from the overheating followed by a critical weakening of the North Atlantic Overturning Circulation system ((they call it NAMoC) as well as the entire global "return" oceanic currents. I know that this research pace and gizmo dvelopment has kicked into a high gear in the last 10 years or so.(Some wag recently developed a micro reflection seismic tool that is able to distinguish the density differences between warm v cold thermohaline water lines), and these tools show that the NAMoC has declined about 20% since the mid last century.
This means that , as the poles melt, that resulting cold meltwater, more fresh than the warmer currents will dive beneath and mix with the currents like the gulf stream and lessen their abilities to modify and warm mid latitude climates. I can remember walking around Dublin in Januaries and seeing daffodils bloom and see palm trees in the public parks while across the Atlantic, in the same latitude at the same time of year sits Labrador where the ground is deeply covered with snow and its a Northern boreal forest(no wild palms in Labrador ). So, WIthout the Gulf stream Much of France and the British Isles would be like Northern Canada in winter.
Yeh, Global warming can trigger the next ice age. What we cannot answer is "How long will the intense warmup last? 200 years? 1000 years? ". In all cases the scenario that probably will play out is an intense global warmup with really significant insolation increases that can raise the planets temp to dangerous levels. Then , if the carbon bank is significant it could stimulate the ice age theory because the global circulation shuts down (OR), if the available carbon is really high and a warmup is more intense, the planet could shoot past a new ice age altogether, like what occured in several geologic ages during which the polar regions were tropical seas.
A few supervolcanoes precisely timed by the intelligent overlord could, of course , mollify the heat binge and bring about a "nuclear winter' where we could possibly lose Canada to 2 mile thick snowdrifts.(, on second thought, naaah,At least Canayja is prepared to handle it way better than the UK and (heeh Heeh) FRANCE). An ice age in France would be like a heavy frost in Miami. People would die in the millions trying to shovel the damn stuff. But, thats another topic entirely, "can the French even shovel snow?"