insolation_CO2_ice_ages_triplets_1400.gif

Yellow lines show changes in incoming sunlight in the Northern Hemisphere due to Milankovitch cycles over the next 500,000 years. (left panel) At pre-industrial levels carbon dioxide levels of around 280 parts per million (ppm), insolation must drop below about 455 watts/m² (red line) to trigger an ice age, a threshold that will be reached around 50,000 years from now (blue snowflake). The higher the atmospheric carbon dioxide level, the lower the insolation has to fall to trigger an ice age, delaying the possibility for the next ice age by tens of thousands of years (center panel) or more (right panel). NOAA Climate.gov graphic, based on data from Archer and Ganopolski, 2005.