One difficult to explain relationship when looking back at geologic history, has been that following ice ages, data seemed to show global temperature increasing before atmospheric CO2 levels increased. It turns out that this data was all for the Antarctic region, and now when scientists look at true global temperatures (based on proxy measurements derived from fossil records at 80 locations around the globe), CO2 does rise before global temperatures rise. This of course is far more in line with the the expected cause and effect of CO2, a greenhouse gas, and global temperature.
After having read several articles about this recent work, the one by Jonathan Amos of the BBC was selected as the title link because it gives a more detailed explanation of all the factors involved. An oversimplified summary would be that: as the the Earth's wobble changed so that the northern hemisphere received more sunlight, the vast ice sheets began to melt. Fresh water from them slowed down the Atlantic overturning circulation (ocean conveyor). This trapped more heat near the equator and southern hemisphere, which in turn contributed to an increase in CO2 release from the deep waters of the southern oceans. And finally, the increase in CO2 levels, from about 180 ppm to 260 ppm, increased the rate of global warming. Here we are today at about 390 ppm CO2 and rising.
After having read several articles about this recent work, the one by Jonathan Amos of the BBC was selected as the title link because it gives a more detailed explanation of all the factors involved. An oversimplified summary would be that: as the the Earth's wobble changed so that the northern hemisphere received more sunlight, the vast ice sheets began to melt. Fresh water from them slowed down the Atlantic overturning circulation (ocean conveyor). This trapped more heat near the equator and southern hemisphere, which in turn contributed to an increase in CO2 release from the deep waters of the southern oceans. And finally, the increase in CO2 levels, from about 180 ppm to 260 ppm, increased the rate of global warming. Here we are today at about 390 ppm CO2 and rising.
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