Chile's volcano not likely to affect the climate
It's been a busy month for natural disasters, and I haven't found time to talk about Chile's Chaiten volcano, 760 miles (1,220 km) south of the capital Santiago. The volcano started erupting on May 2 for the first time in thousands of years, spewing ash, gas and molten rock into the air, forcing the evacuation of thousands of people. Did this mighty eruption have a cooling effect on the climate?
Figure 1. This May 5, 2008 image from NASA's Terra satellite caught Chaiten erupting. Image credit: NASA.
Many historic volcanic eruptions have had a major cooling impact on Earth's climate. However, Chaiten is very unlikely to be one of them. To see why this is, let's examine recent volcanic eruptions that have had a significant cooling effect on the climate. In the past 200 years, Mt. Pinatubo in the Phillipines (June 1991), El Chichon (Mexico, 1982), Mt. Agung (Indonesia, 1963), Santa Maria (Guatemala, 1902) Krakatoa (Indonesia, 1883), and Tambora (1815) all created noticeable cooling. As one can see from a plot of the solar radiation reaching Mauna Loa in Hawaii (Figure 2), the Mt. Pinatubo and El Chichon eruptions caused a greater than 10% drop in sunlight reaching the surface. The eruption of Tambora in 1815 had an even greater impact, triggering the famed Year Without a Summer in 1816. Killing frosts and snowstorms in May and June 1816 in Eastern Canada and New England caused widespread crop failures, and lake and river ice were observed as far south as Pennsylvania in July and August. Volcanic eruptions cause this kind of climate cooling by throwing large amounts of sulfur dioxide gas into the stratosphere. This gas reacts with water to form sulphuric acid droplets (aerosol particles), which are highly reflective, and reduce the amount of incoming sunlight.
You'll notice from the list of eruptions above that all of these climate-cooling events were from volcanoes in the tropics. Above the tropics, the stratosphere's circulation features rising air, which pulls the sulfur-containing volcanic aerosols high into the stratosphere, where the upper-level winds circulate them all around the globe. These aerosol particles take a year or two to settle back down to earth, since there is no rain in the stratosphere to help remove them. However, if a major volcanic eruption occurs in the mid-latitudes or polar regions, the circulation of the stratosphere in those regions generally features downward subsiding air, and the volcanic aerosol particles are not able to penetrate high in the stratosphere and get carried all around the globe. Chaiten is located near 40° south latitude, far from the tropics, and thus is unlikely to be able to inject significant amounts of sulfur aerosols into the stratosphere. Furthermore, the character of Chaiten's eruptions so far has been to eject a lot of silica and not much sulfur into the air. The total amount of sulfur ejected has been only about 1/10000 of what Mt. Pinatubo put into the air, according to NASA.
Figure 2. Reduced solar radiation due to volcanic aerosols as measured at Mauna Loa Observatory, Hawaii. Image credit: NOAA/ESRL.
Realclimate.org has a nice article that goes into the volcano-climate connection in greater detail. One interesting quote from the article: There can be some exceptions to the tropics-only rule, and at least one high latitude volcano appears to have had significant climate effects; Laki (Iceland, 1783-1784). The crucial factor was that the eruption was almost continuous for over 8 months which lead to significantly elevated sulphate concentrations for that whole time over much of the Atlantic and European regions, even though stratospheric concentrations were likely not particularly exceptional.
My next blog will talk about new research regarding the hurricanes/global warming connection.
Jeff Masters
Reader Comments
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I'm not liking waking up to snow and graupel on May 19th...
yeah, where iz Thel ?
I bet hes Lurking..and sniffing Magic Markers again. LOL
Sorry, Pat...today is my day to lurk and sniff Magic Markers
mine you that costs me 7 bucks a month 100 bucks a year to have access to that info
Looks like I picked the wrong week to quit drinkin.
You know here in New England we're going to skip spring and jumped right into summer.
What you talkin' bout KOFTG?
NEVER quit drinking!
Seemingly so.
Especially since the pattern thus far this year has been for extended periods of either below or above normal temperature patterns.
Back to the weather!
SJ, you, MLC and I seem to share a taste for fine music...LOL
Your avatar, your choice as to what to have on it!
315. NoNamePub 6:01 PM GMT on May 19, 2008
312. NoNamePub 5:59 PM GMT on May 19, 2008
Nash - There is your mistake...
NEVER quit drinking!
Bad advice.
Ok - Here is good advice...
PUT ON A SHIRT
Several people have avatars with shirtless photos...I never see anyone tell them to put one on!
Very well - Would anyone that has an avatar not suitable for the business place please change it.
Most people on here are grownups with real jobs.
My job the weather is important...so I log on at work to hear good opinions and use some of that advice to make decisions.
Thanks -
(steps down of the soap box he was forced onto)
w
And THAT was funny!
I had my money on Taz being the first one to say pinhole eye this season :~)
I seem to remember a girl (or whatever that whole episode last year was) that had to change a pic (or got booted) because it offended some peeps...
lol Flood, you beat me to it!
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