Over the course of the first three decades of the 21st the global climate began to experience a more rapid shift than it had in previous centuries. Stimulated by greenhouse gas emissions from human civilization over the course of the Petroleum Age that accelerated the natural warming cycles of the Earth, by the 2020s the Arctic circle was Ice Free year round, and the Greenland Ice Sheet had become extremely unstable. From the mid 2020s to the 2070s global weather patterns entered into a period of extreme instability where seasonal temperature extremes reached at times deadly levels.