MSimon wrote:During the last ice age Chicago was covered by 2 miles of ice. How does that fit?
Actually the Earth is in an Ice Age now, which is why we have ice at the poles at all, but in one of the warmer periods within the age, when the glaciers are mostly retreated, called an interglacial period. It was during the last glacial period within this present Ice Age that Chicago was covered by ice.
There are about a dozen theories for what causes the Earth to warm and cool so much that there is or is not ice, and when there is ice that it is cold enough for there to be glaciers down to Chicago (and further.) No one really knows the answer to these things since we can't observe them, but a few of them leave records, such as the magnetic field flipping of the planet as locked into magnetic cores in metal laden ores like magnetite (though I'm not sure about the argument that this is connected with the planet's temperature.) What we have observed is the number one indicator for small variations in temperature is the variation in temperature of the Sun. And that makes sense. The sun is our heat source. Though we may one day gain a sizable measure of control over the planet's temperature within an Ice Age, it is hard to imagine altering it enough to defy the Sun's activities. Ultimately we're at the Sun's mercy until we can control that--don't hold your breath. What we can do however, is choose to pursue plans for what to do when the planet significantly heats or cools so we can cope with what we can't control. How do we put a parka on North America? That's likely a better short term option than thinking with the shabby state of the art in climate modeling, that we're going to control it, or even the much simpler issue of the weather.
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis
MSimon wrote:During the last ice age Chicago was covered by 2 miles of ice. How does that fit?
Actually the Earth is in an Ice Age now, which is why we have ice at the poles at all, but in one of the warmer periods within the age, when the glaciers are mostly retreated, called an interglacial period. It was during the last glacial period within this present Ice Age that Chicago was covered by ice.
There are about a dozen theories for what causes the Earth to warm and cool so much that there is or is not ice, and when there is ice that it is cold enough for there to be glaciers down to Chicago (and further.) No one really knows the answer to these things since we can't observe them, but a few of them leave records, such as the magnetic field flipping of the planet as locked into magnetic cores in metal laden ores like magnetite (though I'm not sure about the argument that this is connected with the planet's temperature.) What we have observed is the number one indicator for small variations in temperature is the variation in temperature of the Sun. And that makes sense. The sun is our heat source. Though we may one day gain a sizable measure of control over the planet's temperature within an Ice Age, it is hard to imagine altering it enough to defy the Sun's activities. Ultimately we're at the Sun's mercy until we can control that--don't hold your breath. What we can do however, is choose to pursue plans for what to do when the planet significantly heats or cools so we can cope with what we can't control. How do we put a parka on North America? That's likely a better short term option than thinking with the shabby state of the art in climate modeling, that we're going to control it, or even the much simpler issue of the weather.
I like all of GIThruster's points in the above. Practical solutions. For example, fusion would allow for unlimited water as desalinated from the sea to alleviate droughts. Energy to heat and cool homes and buildings. Even indoor farming and advanced hydroponics is doable with enough energy, during a long icy period. It is an engineering perspective that politics is usually not receptive to.
One plausible theory of climate change involves various factors (solar activity, Geomagnetic changes, nearby supernovas, etc.) changing cosmic ray levels hitting Earth. Cosmic rays seed upper level cloud formation, which influences solar input.
Also, once polar ice cover approaches temperate latitudes the albedo feedback starts to break down.
The daylight is uncomfortably bright for eyes so long in the dark.
