First we lead a breeding pair of every plant and every animal onto Noah's Ark.
Temperatures rise enough to slide Greenland into the ocean, triggering a sea level rise of about 3 to 6 meters. Methane clathrate hydrates degas, accelerating warming.
Hurricanes march across the tropics: the first one starts in April and they run without letup until November.
50% of humanity perishes by flood. Gasoline consumption goes down 50%. Coal burning goes down 50%. Methane production goes down 50%.
People finally stop buying real estate in Florida.
The change in albedo helps the temperature vs CO2 graph to catch up: the world becomes 10°C warmer.
Paris blooms in winter. Food production drops. Another 20% of humanity perishes by famine. Malthus proven right.
Summertime temperatures in the USA reach 130F. Another 20% of humanity perishes by fire.
The world's forests go up in smoke. First the smoke precipitates a nuclear winter. The world goes dark for five years. Then the smoke precipitates into the ocean, resulting in enormous blooms of Azolla filiculoides. Carbon falls back below 300ppm.
Things cool just in time for the Holocene interglacial to end. The Arctic refreezes. The ice shelves re-form. Glaciers come back.
(The Azolla blooms fall to the bottom of the sea and, ironically, start the slow conversion back into petroleum, for some later civilization to burn.)
Noah plants a vineyard.