Yes and the state seems to change due to forces that are so much more powerful than the measly BTU's added by anthropogenic warming.callmeslick wrote:it has varied a bit, I'd suspect, but it is the STATE that is important.Will Robinson wrote:....And just how much water, be it in any state, is there in, on, or surrounding, the earth, and how has that varied over the history of the planet?
The planet warmed up, dumped liquid across the low areas, pumped vapor into the air and biological growth took off like...well like weeds. And then it froze up again...and then it melted again...
So exactly how warm it gets before it gets cold again seems to be a minor concern. On the big time line anyway. What are a few degrees between ice ages? It might be buying us some time before we go inevitably extinct.
The last Ice Age, known as the Pleistocene Epoch, began almost 1.8 million years ago and lasted until approximately 11,700 years ago. During this time, massive glaciers covered most of the surface of the Earth. There have been four known Ice Ages on Earth in the 4.6 billion years that the planet has existed. It is very possible that there were many more that occurred that are undocumented from before the advent of mankind, about 2.3 million years ago.
As the last Ice Age ended, the Antarctic ice sheets began to melt. This caused waters to rise, drowning previously raised sections of the continents. The moving water gradually heated up and caused a rise in the temperatures of many different areas, creating the beginnings of the climate enjoyed by humans today. The Pleistocene Epoch is the first known Ice Age to involve humans, or homo sapiens. During this time period, humans continued to evolve. By the end of the Ice Age, human beings were spread all over the planet. The Pleistocene Epoch was the first epoch in the Quaternary Period and the sixth epoch of the Cenozoic Era. The Earth is now in a period known as the Holocene Epoch.