The ups and downs of global warming over time

Written by Thomas Fuller, SF Environmental Policy Examiner | 17 October 2009

While we're fussing and feuding over temperature rises and falls over the past decade, some people think it's better to look at things over a longer period of time. Bill Illis has written a guest post over at Watt's Up With That, a skeptical website, that charts temperatures, CO2 and sea level rises over a very long period of time. 600 million years. I'm posting it here, but I strongly recommend you pop over to Anthony Watt's weblog and read the accompanying article. I'll wait until you get back. Here's the chart (right).

You have to read this chart from right (older time periods) to left (now). In case it's too small for you to read, the thin yellow line is CO2, which you can see has quite often been much higher than today--in fact, we're pretty close to historic lows. The blue line is variation from recent averages--how much higher or lower temperatures were compared to now.  Again, for most of the past 600 million years, you can see we're at one of the low cycles, not matched since the Ordovician/Silurian ice ages. The brown fuzzy line is sea levels, which have been 265 meters higher and 120 meters lower than today.

The data is there for you to download and examine, and comes from identified and respected sources--although to be sure, they're not the only sources out there.

So let's discuss. Obviously, there is more than one way to look at this. If you accept the figures (and I would ask those who don't to please provide evidence, hopefully in the form of a chart as clear as this), then a couple of important corrollaries emerge: First, climate can change radically, as it has in the past. Second, we're pretty much at the bottom of the CO2 and temperature cycles, and about in the middle of the range for sea levels. What would we expect next if we were not contributing CO2?

The interesting fact of the day I learned from this piece is that the massive extinction that killed 96% of marine life and 70% of land animals 250 million years ago coincided with a massive series of volcanic eruptions that covered a land area the size of Australia with magma hundreds of meters deep and lasted for a million years. I think I'll block that period off from the time travel machine.

What would you expect to happen to today's climate if we were not contributing CO2 to the atmosphere? That's my question for today.

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