by M. Floyd, June 13, 2019 in PhysOrg
Since scientists first determined that atmospheric carbon dioxide (CO2) was significantly lower during ice age periods than warm phases, they have sought to discover why, theorizing that it may be a function of ocean circulation, sea ice, iron-laden dust or temperature.
Yet no computer model based on existing evidence has been able to explain why CO2 levels were as much as one-third lower when an ice age settled in.
A new study published this week in Science Advances provides compelling evidence for a solution—the combination of sea water temperature variation and iron from dust off Southern Hemisphere continents.
by Ralph Ellis, August 2018 in FriendsofScience
Why do ice ages occur? Surprisingly, even after many decades of paleoclimatic research we simply do not know for sure. Most scientists will agree that ice age cycles have something to do with precession: the slow wobble of the axis of the Earth. The ancient Egyptians and Greeks knew of precession and called it the Great Year, because it gives warm and cool seasons over its approximate 23,000-year cycle. But there is a problem with invoking the Great Year as the regulator of ice ages, because we should really get an interglacial warming every 23,000 years or so. And we don’t – they only happen every fourth or fifth Great Year.
But why should the global climate give a selective response to orbital warming and cooling? (Called ‘forcing’ in the climate trade.) This is one of the great unknowns of modern science.
La géologie, une science plus que passionnante … et diverse