Warming may bring Oregon monsoons.

Byline: Greg Bolt The Register-Guard

If you think a little bit of global warming might be just the thing to dry out the perpetually soggy Pacific Northwest, don't put your galoshes on eBay just yet.

New research by a University of Oregon professor suggests a warmer world could mean wetter winters for many of us. Wet, as in monsoons.

That's what happened during another global warming event, this one 55 million years ago and triggered by a sudden and catastrophic release of methane stored in permafrost and ice beneath the sea bed. Average temperatures shot up six degrees and seasonal rainfall rose by some 50 percent in areas from North America well into South America.

UO geology professor Greg Retallack analyzed soils laid down during the ancient greenhouse event to see how the climate changed and to get a better idea of how the current warming could alter weather.

The episode is well documented for its effect on temperature, but Retallack wanted more details of any other climatic changes.

"What the soil seems to tell us is it got wetter, quite a bit wetter, and there was also a much greater seasonal contrast between the wettest and driest months," said Retallack, an authority on ancient soils whose research recently was published in the journal Geology.

That's a classic monsoon pattern, which is marked by a season of drenching rain followed by one of baking heat and dryness. It's one that's still the norm in many subtropical regions, but during the greenhouse spike in the late Paleocene epoch, monsoon climates extended well into what are now temperate latitudes.

For example, Retallack's analysis of soils in Utah's Axhandle Canyon found that rainfall jumped from 16 inches per year to 26 inches a year along with an average temperature increase of almost 10 degrees.

In Northwest areas such as Lane County, he said that translates into a rise from the current 50 inches a year to 80 inches.

Retallack tracked seasonal rainfall using nodules of calcium carbonate found in the soil.

The nodules typically are found deeper in the soil in rainier climates and also are more spread out in monsoonal climates where the variations between wet and dry seasons are more extreme.

What happened 55 million years ago probably was triggered either by a sudden intrusion of magma into the buried ice and permafrost or possibly a meteor impact.

Once the ice melted and released its stored methane - which is created by microbes eating away at organic material in the sediments - it oxidized into carbon dioxide and created a greenhouse environment.

Greenhouse gases allow heat from the sun to penetrate the atmosphere but block it from being radiated back out into space. The result is an increase in global temperatures, which sets off a chain of climate changes.

Retallack said the Paleocene event was much more extreme than the kind of global warming seen today, which so far is on the order of 1.5 to 2 degrees Celsius. But he said it still provides a model for what to expect from the current changes.

"It does seem to confirm the general prediction that a more carbon dioxide-rich atmosphere is going to be more stormy and have a greater seasonal contrast," he said. "There will be more precipitation. A warmer atmosphere can store more moisture, but it's also more unstable."

Retallack's analysis tracks closely with the views of a panel of scientists advising the governors of Oregon, Washington and California on responses to regional climate change. Their report predicts warmer but wet winters, resulting in smaller snowpacks and drier summers with higher fire danger.

But it's not out of the question that the Earth could experience another atmospheric disaster such as the ancient event Retallack studied. It might not even take a meteor or magma release to set it off.

"What if the atmosphere gets warmer for other reasons, for example because of our activities, and that destabilizes these methane ice reservoirs in the continental shelves and permafrost?" he said.

"There could be a kind of runaway effect if that happens. That's quite a danger, I think, because that stuff is still there, poised on a pretty delicate balance."

However much danger there is, don't expect it to happen in your lifetime. The Paleocene release and others that have occurred over the past several hundred million years happen over a period of about 10,000 years, although that's a relative blink in geological time.

And while a monsoon climate may not be much of an improvement over the current one, it's a long way from the fictional disaster scenario portrayed in the movie "The Day After," in which North America is swept up in an instant Ice Age.

To the contrary, Retallack said the current trend suggests we've broken the geologically recent pattern of advancing and retreating ice sheets.

"If this last glacial termination had been like all the other ones before it, we should be halfway to an ice age now," he said. "But we're not."