Climate and Brains

At the heart of unravelling the complexities of long-term climate change lies a simple concept: climate is cyclical. The concept draws its inspiration from the marked seasons of wet and dry in the tropical monsoon belts and the contrasts between winter and summer in more northerly latitudes. It establishes an agricultural calendar with times of scarcity and plenty and a timetable for planting, harvesting and moving flocks to fresh pastures. What happens from year to year and decade to decade is a matter of weather. These variable conditions never alter the cyclical pattern but do affect the outputs. Weather marks the difference between famine and feast.

This agricultural concept has been applied to the long-term climates of Terrae 1 and 2 where cycles had a frequency of up to 400ka years. A full cycle moves from predominantly cold conditions through to warmer climates; the classic pattern of glacial to interglacial. This stemmed from the demonstration by geologist Louis Agassiz in the middle of the nineteenth century that extensive glaciations once existed in the agricultural heartlands of Europe and North America. Now the date of 1.8Ma sees the first significant glaciations in the Northern hemisphere. It also marks the boundary between Terrae 1 and 2.