05 March 2007

On Average

Let's say you had a time machine that would take you to some random point during the last 40 million years? How should you dress? On average, this photo represents a warm and balmy day on during the current ice age, which, over the last 40 million years, has seen long periods of glaciation sporadically broken by short warming periods. Now, are people better off with the temperatures we know of from recorded history, or would it be better if world climate was simply stuck at its average point? The question answers itself: there is a reason that recorded history coincides with warm weather. But if we are the beneficiaries of past warming, why do we assume that the next warming period will be catastrophically bad?

[Note: This post has been changed slightly to conform to the facts.]


Susan's Husband said...

Are you sure about that? Ice Ages are a relatively recent phenomenon, about 40 MYA. Even then, it looks like the average global temperature was around 10°C, which is a bit warm for that kind of snow fall.

I also thought that the average global temperature for all of Earth history was significantly warmer than today because of the very long periods of much warmer temperatures from the Cambrian through the Cretaceous.

P.S. Check this out for real global warming.

David said...

I think that the answer is that nobody really knows, but that there have been several ice ages over the last three billion years. I think what you're thinking of is that the current ice age is 40 million years old, with human civilization arising during the current temperate inter-glacial period.

See, e.g., this Wikipedia article. I think, though, that I will change the post to play it safe.

Susan's Husband said...

Yes, the whole Cryogenian Age was unknown last I spent time on this stuff.

On the other hand, should you average in the time spent cooling from the original coalescence? Or just post-biotic temperatures?

Oroborous said...

Just post-biotic temps.

Conditions before then are interesting intellectually, but are irrelevant to us physically.

Harry Eagar said...

Well, yeah, sure. Almost all that carbon locked up in the coal must have been in the atmosphere once upon a time.

Surprisingly, however, it is now thought that the coal swamps were not the steaming, vaporous bogs we were told in the '50s. It seems they were cool.

I wonder how many climate commenters on the Internet -- either side -- know that?