Ice Age by John Gribbin and Mary Gribbin, 2001
Ice Age by John Gribbin and Mary Gribbin, 2001
From the citations in text, this seems a condensation of Imbrie and Imbrie, Ice Ages: Solving the Mystery. The Gribbins tack on the notion that the drying out of the East African plains forests pushed humans to walk upright on the increasingly treeless plain. They should skip that and update this book and expand upon the climate change debate.
The Gribbins seem like good science writers. Perhaps that's why they've refrained from the climate debate....
Before too long, unless human activities prevent it, the world will cool again, back into the Ice Age proper...
But in the long history of the Earth, polar ice caps are rare, and having two polar ice caps at the same time may be unique.
carrying thirty million cubic metres of water every second...
... consider that the rate at which heat is beign transported northward by the Gulf Stream today is more than a million billion watts, as if the current were a real conveyor belt covered with a million million one-bar electric fires, all pouring their heat out into the atmosphere. gotta be a better way to visualize that... 1e12 Watts / 3e7 m^3 H20
= 3e4 Watts / m^3
= 0.03 Watts / cm^3
= ???
The amount of heat received from the Sun over the course of an entire year stays the same; but Croll (James Croll) followed up the idea that it might be the way the heat is distributed between the seasons which matters, since this is undoubtedly affected by the eccentricity. When the orbital eccentricity is low, and the orbit is circular, the amount of heat received by the whole planet from the Sun each week is the same throughout the year; but when the orbit is more elliptical, with high eccentricity, the Earth receives more heat in a week at one end of its orbit, closest to the Sun, and correspondingly less heat in a week at the other end of its orbit, farthest from the Sun.
... sediment accumulates only very slowly in the wide Pacific Ocean, at a rate of about a millimetre every century...
Atlantic sediments turned out to be deposited about three times as fast, giving a more detailed insight into past climates, although only for the past half million years.
Some of the oxygen (isotopes) from the water is taken up by living creatures and, in the case of plankton, helps to build their shells; but the proportion of oxygen-18 taken up in this way depends on the temperature of the sea at the time. Creatures that live in colder water have a higher proportion of oxygen-18 in their shells. When the die and their shells fall to the bottom of the sea, the ratio of oxygen-18 to oxygen-16 in the shells is preserved as a kind of fossil temperature record.
... an enhancement in the oxygen-18 proportion found in the shells of these long-dead plankton was an indication that much of the Earth's water was locked up in ice sheets at the time they died -- and the exact isotope ratios even told you how much water was locked up in this way. What better indicator could there be of the advance and retreat of the ice?
It is concluded that changes in the Earth's orbital geometry are the fundamental cause of Quarternary ice ages. A model of future climate based on the observed orbital-climate relationships ... predicts that the long-term trend over the next several thousand years is towards extensive northern-hemisphere glaciation. John Imbrie and Nicholas Shackleton, 'Variations in the Earth's Orbit: Pacemaker of the Ice Ages', 1976
From 18,000 years ago until the present day, when the astronomical cycles conspired to increase the summer warmth of the crucial Northern Hemisphere region, the excess of insolation was 4.2 x 10^24 calories, which compares with the 3.2 x 10^24 calories required to melt the volume of ice known to have melted during this interval.