Question: What factors triggered the end of the last ice age?
Liz’s Answer: We believe that the fundamental trigger for the end of the last ice age was increasing insolation (more heating from the sun) over the northern hemisphere, where the main glacial ice cap sat. Increasing insolation happens as the earth’s orbit changes shape naturally – sometimes a component of this is referred to as the “wobble of the poles.” These changes have timescales of about 20,000 and 40,000 years and have a slow-paced influence on climate. These shifts in solar radiation can initiate carbon feedback loops, which causes more rapid changes within the climate system. Scientific evidence shows that as the increased solar radiation warmed the oceans, circulation patterns changed and CO₂ that had been sequestered in the deep ocean was released into the atmosphere. These increased CO₂ levels heated the atmosphere up further and were an important driver in the last deglaciation, the ice loss that ended the last ice age. We are seeing the same thing happening today. As we raise CO₂ levels through our greenhouse gas emissions, we are seeing increased deglaciation in our polar regions.