Ancient global warming was jarring, not subtle, study finds

Los Angeles Times ^ | January 5, 2007 | Robert Lee Hotz

[presidio9]

Foreshadowing potential climate chaos to come, early global warming caused unexpectedly severe and erratic temperature swings as rising levels of greenhouse gases helped transform Earth, a team led by researchers at UC Davis said Thursday.

The global transition from ice age to greenhouse 300 million years ago was marked by repeated dips and rises in the amount of carbon dioxide in the atmosphere and wild swings in temperature, with drastic effects on forests and vegetation, the researchers reported in the journal Science.

"It was a real yo-yo," said UC Davis geochemist Isabel Montanez, who led researchers from five universities and the Smithsonian Museum of Natural History in a project funded by the National Science Foundation. "Should we expect similar but faster climate behavior in the future? One has to question whether that is where we are headed."

The provocative insight into planetary climate change counters the traditional view that global warming could be gradual and its regional effects easily anticipated.

Over several million years, carbon dioxide in the ancient atmosphere increased from about 280 parts per million to 2,000 ppm, the same increase that experts expect by the end of this century as remaining reserves of fossil fuels are burned.

No one knows the reason for so much variation in carbon dioxide levels 300 million years ago, but as modern industrial activity continues to pump greenhouse gases into the air at rapid rates, the unpredictable climate changes that took millions of years to unfold naturally could be compressed into a few centuries or less today, several experts said.

Carbon dioxide levels last year reached 380 ppm, rising at almost twice the rate of a decade ago, experts said. Average global temperatures have been rising about 0.36 of a degree Fahrenheit per decade for the last 30 years.

Still, the transformation

[cogitator]

I would ask the question how much of that 0.36 F figure takes into account the "heat island" effect from the massive metropolitan areas represented by the likes of major cities such as LA, Houston, Chicago, NY, Tokyo, the Dallas-Ft.Worth area, etc.?

Certainly a regional effect; not much of a global effect.

The Surface Temperature Record and the Urban Heat Island

Pithy excerpt:

"... there is little difference between the long-term (1880 to 1998) rural (0.70°C/century) and full set of station temperature trends (actually less at 0.65°C/century)."

If the effect of cities was substantial, the full set including city stations would be expected to be pulled upward by urban heat islands and be higher than the trend in the rural station set.

[cogitator]

The GW crowd has consistently harped on CO2 as the leading greenhouse gas and blah, blah, blah.

Unless there's a lot more methane (which could be an anthropogenic greenhouse gas if methane release from melting permafrost --> bogs increases), CO2 is going to have the largest effect on Earth's radiative balance.

[DustyMoment]

Certainly a regional effect; not much of a global effect.

I concur, I didn't mean to imply that the heat island effect of the large metropolitan areas were, in and of themselves, affecting global temps. However, at a macroscopic level, there should be some cumulative affect, especially when the heat island effect is measured against the regional temps of the LA basin, for example. I do have a hard time reconciling the fact that with all of the discussion about GW, the heat island effect has negligible impact. That doesn't mean that i believe it has a huge affect, but it has to have some.

[Reverend Bob]

That is, of course, correct. Recent studies have indicated, however, that rapid, rather than gradual, climate change is not a new phenomenon.

Here's a quote from page 295 of Prothero:

"But recent paleoclimatic studies have shown that the last glacial-interglacial transition was amazingly abrupt, taking place in a few decades or less, and was characterized by extreme swings in climate before the interglacial warming took hold."

It also appears, from several studies, that warming cycles happen much faster than cooling cycles.

My point is not that rapid climate change won't have some deleterious (as well as beneficial) effects, only that climate change is something that has happened again and again throughout Earth's history, and that, if forced to chose between the two, warming (at least at this point in Earth's history) is far better than cooling. Moreover, I think we often underestimate the ability of plants and animals to adapt to changing conditions. !8,000 years ago Chicago was under ice. The Tundra, now limited to the Arctic, stretched across Iowa and Southern Illinois. That's a lot of migration in such a short time. The Boreal Spruce Forest, shifted similarly, from the Central U.S. right up into Canada.

I'm no longer as much of a sceptic as I once was -- though I'm not sold on the idea that this is an ENTIRELY man-made phenomenon -- I just get tired of the "we're all going to die" hysteria that so permeates news coverage of these matters.

All best. :-)