Category Archives: Climate

How did the Tonga eruption affect the atmosphere?

Hunga Tonga erupted on Jan. 15 and lasted 11 hours.

It devastated the region, covering the land in a layer of ash. The eruption blasted a plume of ash and water vapor 34 miles into the atmosphere — into the mesosphere.

The Hunga Tonga plume contained only a very small amount of sulfur dioxide (SO2). Sulfur dioxide from volcanic mega-eruptions that reach high in the atmosphere can have an impact on global temperature. The mega-eruption of Pinatubo in 1991 released enough sulfur dioxide to cool the Earth’s surface for three years. The Tonga eruption will not have that kind of impact. Continue reading

Category: Climate, Phenomena

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How does this winter measure up so far?

Two of the more popular (and telling) measures of the severity of a winter are extremes of cold and the presence of snow.

One reasonable way to consider extremes of cold might be to count the number of mornings on which the temperature drops below zero. So far this winter (defined as beginning on Dec. 1), we have had just five such mornings here in Madison. Continue reading

Category: Climate, Meteorology, Seasons

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Is permafrost permanent?

Permafrost is ground that has a temperature below freezing for at least two consecutive years.

Permafrost varies in thickness from less than a couple of feet to more than 4,000 feet thick. Permafrost is mostly located in polar regions, although it also occurs in some high mountains where it is called alpine permafrost. Much of the permafrost in Alaska is tens of thousands of years old. Continue reading

Category: Climate, History

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Is our recent cold snap a harbinger of things to come?

Our recent cold snap has brought the November average to just 0.5 degrees above normal through the first 17 days of November after a relatively warm October in Madison, where the average temperature was 5.9 degrees above normal. It is … Continue reading

Category: Climate, Meteorology, Seasons

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What is La Niña and the impact on Wisconsin’s coming winter weather?

La Niña refers to a departure from normal in the sea-surface temperature across much of the eastern tropical Pacific Ocean.

The water temperatures off the west coast of South America are typically 60 to 70 degrees. During a La Niña these waters get as much as 7 degrees colder than normal. La Niña conditions recur every few years and last nine to 12 months, though some events have lingered for as many as two years. This cooling results from a strengthening of the winds over the tropical Pacific and its interaction with the underlying ocean waters. Continue reading

Category: Climate, Meteorology, Seasons

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