Would volcanic ash and dust or the same volume of sulfer-based aerosols have a longer effect on climate?
Which would have a longer effect on climate changes- volcanic ash and dust or the same volume of sulfur-based aerosols? Why?
Which would have a longer effect on climate changes- volcanic ash and dust or the same volume of sulfur-based aerosols? Why?
Sulphur based aerosols would have a longer term effect.
Volcanic ash and dust is sold matter but in very tiny particles. Much of it falls to Earth of it’s own accord (gravity) and the remainder is washed back down to Earth in rain, snow, sleet etc.
In respect of volcanic activity, the primary sulphur based aerosol is sulphur dioxide which is a gas. Because it’s a gas it stays in the atmosphere for a long time.
Ash and dust has a short ‘atmospheric residency period’, it can be anything from a few hours to a few days. Whereas sulphur dioxide can remain in the atmosphere for up to 3 years.
Here’s more details…
The Sulphur dioxide in the atmosphere reacts with water vapour in the air to form sulphuric acid: SO2 + H2O = H2SO3.
This can fall to earth as tiny particles of acid (dry deposition) or in the form of acid rain (wet deposition).
If the sulphur dioxide does not fall back to Earth it can react with oxygen in the air to form sulphur trioxide: 2SO2 + O2 = 2SO3. Sulphur trioxide reacts with water vapour in the air to form sulphuric acid: SO3 + H2O = H2SO4 and this can fall back to earth as dry or wet deposition.
The biggest effect is sulfur dioxide. Sulfur dioxide isn’t an aerosol when it is a gas. When it is blasted into the the stratosphere, it is converted to sulfuric acid. The sulfuric acid condenses into fine particles which reflect sunlight and absorb heat. They heat up the upper atmosphere but less light gets to the surface so it is cooler.
It is the sulfuric acid particles, aerosols. that are responsible for much of the warming on Venus. In spite of the fact that it has about 250,000 (off the top of my head) times as much CO2, a much denser atmosphere, and it is also much closer to the sun than the earth, the CO2 only theoretically accounts for about 400 degrees of the warming. The H2SO4 and a heavier CO2 molecule account for much of the rest.
On Venus H2SO4 makes it warmer. On earth, it has a cooling affect because when it is lower in the atmosphere it is quickly removed by water. In the stratosphere it takes very long to be removed because there is very little water up there and it takes it a long time to fall as tiny particles.
Just FYI since I mentioned it.
Larger CO2 molecule may be responsible for greater greenhouse effect on Venus as well, heavier oxygen isotopes and wider IR absorbance spectrum. That increases the wavelength absorbed and I think the pressure does as well. The biggest problem for CO2 on earth as a greenhouse gas is that it only absorbs 8 percent of the thermal bandwidth.
Source
http://futurismic.com/2007/10/12/new-carbon-dioxide-molecule-found-to-heat-venus-more/
Good answers above. A couple of corrections:
1) Longevity of SO2 verses dust in the atmosphere:
– Stratosphere: If fine dust gets up there, it can stay up for years: http://en.wikipedia.org/wiki/Nuclear_winter#Climatic_effects
This is due to the high speed horizontal winds above 10 Km. http://en.wikipedia.org/wiki/Jet_stream
– Troposphere: The SO2 has a short life in the lower atmosphere due to its high solubility in water and rain.
It seems that the answers above assumed tropospheric dust and stratospheric SO2. Taking away those assumptions, there really is not much difference in the longevity of either pollutant remaining.
2) Magnitude of effects: It seems that the answers above forgot that you asked about the "same volume", not the "same mass". When dealing with dust this is difficult. Did you mean if the air was removed and only the volume of the remaining SO2 and dust were considered? In that case, the dust would have the greater effect, since there would be very little SO2 mass wise in the equivalent of a gram of solid dust.
Calculating the exact forcing for both is difficult, and it is hard to answer this in a quantitative manner.
Consider that 31 thousand short tons of SO2 were released in the USA alone in 1970 before the push to install scrubbers on smoke stacks.
http://en.wikipedia.org/wiki/Sulfur_dioxide#Emissions
Compare that to Mount Pinatubo in 1991: 20 to 30 million tons SO2.
The molecular weight of SO2 is 64
Thus assuming the lowest estimate of 20 million tons = 88 trillion grams
88 trillion grams = 1.4 trillion moles
At standard temperature and pressure: 1.4 trillion moles SO2 = 31 trillion liters
31 trillion liters = 31 billion cubic meters = 31 cubic kilometers SO2 for Pinatubo.
Krakatoa ejected 21 cubic kilometers of ash and rock.
http://en.wikipedia.org/wiki/Krakatoa
Pinatubo ejected 5 cubic kilometers of ash and rock.
http://library.thinkquest.org/17457/volcanoes/effects.pinatubo.php
Here is what happened after Pinatubo:
http://www.drroyspencer.com/latest-global-temperatures/
Average global temperatures dropped 0.4 kelvins world wide for less than 4 years. It is unknown how much of the 0.4 kelvin drop was attributable to Pinatubo.
Here is what happened after Krakatoa (1883):
"Average global temperatures fell by as much as 1.2 degrees Celsius in the year following the eruption. Weather patterns continued to be chaotic for years and temperatures did not return to normal until 1888."
– Wikipedia on Krakatoa link above -
It is unknown how much of that Krakatoa did.
Climate models: According to the Wikipedia link above, "a small-scale, regional nuclear war could disrupt the global climate for a decade or more. In a regional nuclear conflict scenario where two opposing nations in the subtropics would each use 50 Hiroshima-sized nuclear weapons (about 15 kiloton each) on major populated centers, the researchers estimated as much as five million tons of soot would be released, which would produce a cooling of several degrees over large areas of North America and Eurasia …"
"5 million tons of soot" is less than 0.005 cubic kilometers of fine ash from Pinatubo. The take home lesson from this is that climate models have not proven themselves yet, and we really do not know the relative forcing of the dust.
SO2: Forcing on Venus is about 370 Kelvins of warming as compared to earth. http://answers.yahoo.com/question/index;_ylt=Ajq_XxmNEe3LH54K0rfdvfzsy6IX;_ylv=3?qid=20100424030603AA59uB0&show=7#profile-info-TQyCQKPUaa
It is unknown how much of that is due to SO2.