Will volcanoes cool the earth?

More than 60,000 would-be air travelers are grounded today in Chile, Argentina and New Zealand, because of ash from the eruption of the Puyehue-Cardon Caulle volcano chain in Chile.

Meanwhile, a volcano which has been dormant for 150 years erupted this week in the east African nation of Eritrea. The Dubbi volcano is spreading ash over that part of the world.

Last month, Iceland's Grimsvatn volcano erupted. And there was considerable activity earlier this spring at Hawaii's Kilauea volcano.

That raises the question, which is being asked in some meteorological circles, if the volcanic activity could put the brakes on the earth's recent warming trend. Joe Bastardi, formerly of Accu-Weather and now with the new private meteorological firm Weather Bell, is a big believer in this.

He says several factors, including reduced solar activity and increased volcanic activity, will drop global temperatures in the next several years.

As always seems to be the case, there's no consensus. But the impact of volcanic eruptions on global temperatures seems to be related to three factors:

-- The height that the ash is sent into the atmosphere. If it gets into the upper part of the stratosphere, there's a greater chance of it being sent around the globe.

-- The amount of ash spewed by a volcano. This is obvious.

-- Where the eruption takes place. The theory seems to be that eruptions near the equator, in tropical areas, are more prone to impact the rest of the world. That's because winds near the equator tend to spread northward and southward (the Coreolis effect).

Eritrea's volcano is not far from the equator, but the eruptions in Iceland and southern Chile are nowhere near the tropics.

There is a history of volcanoes affecting the world's climate, however.

The eruption of Mount Pinatubo in the Philippines in 1991 cooled global temperatures for two or three years, meteorologists say. Those were among the few years in recent decades when global temperatures didn't rise.

Perhaps the greatest example was in 1815, when Tambora erupted in Indonesia, sending thick clouds of ash around the world for several years. Temperatures in 1816 were far below average, and it was known in the United States as the "Year Without A Summer."

In fact, snow fell on June 6, 1816, in Albany, N.Y. Drought was widespread throughout the United States and Europe, and the winter of 1817 was among the coldest in U.S. history.

The current eruptions pale in comparison to Tambora, but keep in mind that some meteorologists believe 2011's volcanic activity could put a damper on global warming.