Warming may bring monsoons

EUGENE, Ore. – New research by a University of Oregon professor says global warming could lead to monsoons in the Pacific Northwest.

That’s what happened during another global warming event 55 million years ago. That was triggered by a sudden release of methane stored in permafrost and ice beneath the sea bed. Average temperatures shot up six degrees and seasonal rainfall rose by an estimated 50 percent in North and South America.

University of Oregon geology professor Greg Retallack analyzed soils laid down during the ancient greenhouse event to see how the climate changed and 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 other climatic changes, such as precipitation.

“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 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 Oregon’s Lane County, he said that translates into a rise from the current 50 inches a year to 80 inches.

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.