Arctic Melting Is Good. You do not want those summer low ice extents getting higher (showing more retained ice each summer, year over year)
You Want Arctic Ice Cap Melting
Why you want it is a bit harder to explain. The simplest form is that as long as the Arctic melts, we do not have the Next Ice Age Glacial. The mechanism took a very long time to work out.
The story of that “working out” is in a fascinating little book that is very easy to read. The title is “Ice Age” with the subtitle “The Theory That Came In From The Cold”. Written by John and Mary Gribbin. A slim book of 105 pages, it is a very easy and very pleasant read. The bulk of the story is given over to the character and history of the folks who worked out the existence and mechanism of the Ice Ages. Along the way you learn, rather painlessly, how the Ice Age Glacial cycle works.
Before getting too far into it, a word or two on terminology. “Ice Age” is ambiguous. It can mean either of two very different things. One is an “Ice Epoch”. Long periods of ice that happen every few millions of years. These look to be driven by our position relative to the galactic arms. We are presently in just such an Ice Epoch. Within these Ice Epochs, we have periods of heavy icing of the Earth. These are properly called “glacials”. They are periodically interrupted by “interglacials” when the ice melts. We are presently living in just one such interglacial. One Glacial / Interglacial cycle runs about 120,000 years with the interglacial typically being about 12,000 years, give or take a few thousand.
We are presently nearing the end of our warm interglacial. It started about 18,000 years ago, had a brief setback, then warmed to a maximum about 6000 years ago. We’ve been getting colder ever since. Because of that potential for confusion, I will typically use “Ice Age Glacial” for the times of ice and “interglacial” for times without the ice. Rarely do we really mean the last “Ice Epoch” when we say “the last Ice Age”. What we really mean is “the last glaciation of this Ice Epoch”. So I try to avoid using the term “Ice Age” unadorned by something that tells you if it means “Ice Epoch” or “glaciation”.
What causes an Interglacial?
The key to it all is melting of the Arctic Ice Cap in the summer. When that happens, we get an “Interglacial”. A time like now when the world is a relatively warm and pleasant place to live. When that does not happen, we have a “Glacial” episode and ice covers Canada, Sweden, Scotland, Russia and many other places to great depth. The rest of us are not covered in ice, we’re simply frozen and starving.
The Earth has three motions that matter most in this. The Earth tilts on its axis, it leans over about 23 degrees. But this is not a constant. It slowly changes and bobs up and down. Sometimes the top of the Earth points more directly at the Sun. Sometimes it points more directly straight “up”.
The orbit of the Earth can get more round, or more elliptical. This can put the pole closer to the sun, or further away. Not much, just a little. The degree of ’roundness’ changes over time.
The direction our “tilt” points drifts relative to our position in the orbit. Sometimes the “tilt” causes the North Pole to point at the sun when the Earth is closest to the Sun. Sometimes it makes this happen when the Earth is furthest away from the Sun.
For the Ice Age Glacial to end, the northern polar ice sheet has to be warmed just enough more to melt. This only happens when all three of those cycles “sync up” with the happy circumstance that the North Pole points most fully at the Sun, and is well ‘tipped over’ to get a good warming, right as the Earth is closest to the Sun in summer. In June, we want the North Pole tilted fully over and basking in the Sun at closest approach in our orbit.
If we don’t get that, we get an Ice Age Glacial.
What is the first sign of the return of the Ice Age Glacial? The North Pole Ice Cap does not melt in summer, but carries over, from year to year, so that ice can build up. Starting the process of building up an Ice Age Glacial ice sheet. That, we don’t want. So we want that ice to melt each summer.
Ice Age – The Book
Here are some selected passages from the book, with some of my comments about the biggest ‘take away’ for me. I’ve added the bolding.
As we mentioned earlier, given the present day geography of our planet – the distribution of the continents and oceans – the natural state of the Earth is in a full Ice Age. Koppen was correct in highlighting the importance of summer warmth in influencing the advance and retreat of the ice in the Northern Hemisphere. But in a sense, he too, got the argument backwards. It isn’t so much that Ice Ages occur when the environmental influences conspire to produce particularly cool summers; rather what matters is that Interglacials only occur when the astronomical influences conspire to produce unusually warm summers, encouraging the ice to retreat.
There is then a very interesting discussion of the history of the development of ocean bottom core samples and analysis, including an overview of how microscopic sea shells are used along with other things. Then the discussion turns to oxygen isotopes, and some of the early results showing one degree of change, with later results being clarified by a different technique. Of particular interest to me was how little cooling is needed to the downside to put us into an Ice Age Glacial event.
The multi-factor technique showed that changes in salinity of the surface waters of the Caribbean had, indeed, played an important part in influencing the foram populations; but it also showed that the temperature fluctuations in the region associated with Ice Ages corresponded to a drop of only 2 degrees C, whereas Emiliani’s analysis had indicated a drop of 6 degrees C. Something else was amplifying the isotope changes when the Earth cooled.
The obvious candidate for that something else was the way water gets locked up in great ice sheets during an Ice Age. When water evaporates it is easier for the lighter molecules to escape into the air, so the water left behind tends to have a higher proportion of oxygen-18; much of the evaporated water, relatively rich in oxygen-16 compared to the water left behind ( exactly how rich also depends on the temperature), falls as snow during an Ice Age, and gets locked up as ice instead of being recycled back into the sea.
Just 2 C and we’re hard core into an Ice Age. To the extent there is a tipping point, it is to the downside. Into an Ice Age Glaciation.
This insight also lets you use the oxygen ratios to tell just how big the ice sheets were, as the ratio changes in sync with the mass of snow and ice trapped on land.
They then note that ‘raised beaches’ were noticed by Charles Darwin on his expedition aboard HMS Beagle. “Darwin, who was a geologist before he made a name as a naturalist, was one of several such pioneers who noticed raised beaches, several metres above the present day sea level, in different parts of the world”
Very early on folks were noticing that water has been deeper in the past, and that implies that the Earth has been warmer in the past, all without our help.
By the middle of the 1960s, Wallace Broecker and his team at Columbia had used the thorium technique to show that raised beaches in islands of both the Pacific and the Atlantic oceans corresponded to a period 120,000 years ago when the sea level was six metres higher than it is today; slightly less compelling evidence indicated another, but less extreme, increase in sea level about 80,000 years ago.
This work encouraged other researchers to investigate the raised features carved by ancient waves at sites around the world, and by 1968 it was clearly established that sea level had been high around the world 125,000 years ago, 105,000 years ago, and 82,000 years ago, as well as today. These dates correspond to warm periods predicted by the Milankovitch Model, provided that all three of the astronomical effects, and the way they interact with one another, are allowed for.
Clearly the Earth goes through very natural cycles of warming and cooling all the time, and by amounts far greater than anything seen in the last couple of thousand years.
Let me quote from pages 88-89:
The escape from Ice Age conditions, beginning 18,000 years ago, required the combined influences of all three astronomical cycles to drag the Earth into a peak of warmth about 6,000 years ago. Orbital eccentricity changes combined with a shift in the wobble of the Earth which made June the month of closest approach to the Sun, boosting the heat of Northern Hemisphere summers, just at a time when the tilt of our planet reached a maximum, putting that summer Sun particularly high in the sky. Since 6,000 years ago, all these factors have turned around, and conditions for Northern Hemisphere summer warmth are becoming less favourable. The prospect is for a return of Northern Hemisphere glaciation, on a timescale of thousands of years.
There are other lines of evidence that support the notion that the world was warmer 6000 years ago than it is today. Even just a couple of thousand years ago, sea level was higher than now. We are already 6,000 years into the start of The Next Ice Age Glacial. It is simply arriving so slowly that we don’t notice much.
And just a bit further down on page 89:
It seems likely that the reason for this is that the overall climate is driven by what happens in the Northern Hemisphere ( which is particularly sensitive to the astronomical influences, for reasons we already explained), with the addition of feedbacks, such as changes in the ocean currents of the kind discussed originally by Croll. Another way of looking at this is to start from the fact that the conditions which are required to melt snow and ice on land in the Northern Hemisphere ( warm summers, causing an interglacial ) go hand in hand with relatively warm winters in the Southern Hemisphere, and this discourages the formation of extensive sea ice. The land of Antarctica is always covered by ice, even during an Interglacial, and particularly cold winters are what you need to freeze the top layer of the oceans.
So here we also find that those ice shelves in the Southern Ocean calving from Antarctica are not something to fear, but something to cheer. It is only when the sea ice in Antarctica is failing in slightly warm winters and the Arctic Ice Cap is melting in warm summers that we have our present warm planet.
The things that are most desired by the Warmistas, growing winter ice shelves in Antarctica and stable multiyear ice in the Arctic Ice Cap are “exactly wrong”. They are the harbingers of doom in an icy grave, the signs of the Next Ice Age Glaciation underway.