On decade timescales volcanic activity is insignificant compared to human activity - U.S. Politics Online: A Political Discussion Forum

onon · #1 (**permalink**) 01-14-2007

Think a thread like this is kind of relevant.

One widespread myth is that volcanos emit more co2 than humans. This might seem likely because volcanoes emit masses of material. But reality is that co2 is only a very minor component of erruption material. Most of the materials are other gases and dust.

Quote:

VOLCANO VS MAN - Myth vs Reality

Present-day carbon dioxide (CO2) emissions from subaerial and submarine volcanoes are uncertain at the present time. Gerlach (1991) estimated a total global release of 3-4 x 10E12 mol/yr from volcanoes. This is a conservative estimate. Man-made (anthropogenic) CO2 emissions overwhelm this estimate by at least 150 times.
Gases: Man versus the Volcanoes

The insiginificant amount of co2 volcanoes emit relative to man can also be seen in the measured co2 record. co2 rises at a rate of about 2ppm per year due to human emissions, but no increase was seen in this rate shortly after either the 1991 Pinatubo erruption or the 1982 El Chichon eruptions, indicating that they did not emit significant amounts of co2 compared to man:

There is a myth that if anything is warming the planet, it must be volcanos more than man. But reality is the opposite of that. Volcanic erruptions actually cause a cooling effect due to all that dust and gas they release blocking sunlight in the atmosphere.

Quote:

IN GENERAL, VOLCANOS CAUSE GLOBAL COOLING
Explosive eruptions can inject large quantities of dust and gaseous
material (such as sulphur dioxide) into the upper atmosphere (the
stratosphere - see Figure 1.1, section 1.2.2), where sulphur dioxide is
rapidly converted into sulphuric acid aerosols. Whereas volcanic pollution
of the lower atmosphere is removed within days by the effects of rainfall
and gravity, stratospheric pollution may remain there for several years,
gradually spreading to cover much of the globe.
Gases: Man versus the Volcanoes

In fact the 1991 eruption of Mt Pinatubo caused 0.5C cooling that lasted for two years afterwards.

Quote:

The cloud over the earth reduced global temperatures. In 1992 and 1993, the average temperature in the Northern Hemisphere was reduced 0.5 to 0.6°C and the entire planet was cooled 0.4 to 0.5°C. The maximum reduction in global temperature occurred in August 1992 with a reduction of 0.73°C.
Mount Pinatubo Eruption

The dust and gas released soon falls out of the atmosphere within a few years, and so the cooling effect of a volcanic erruptions is only temporary. So over decade timescales their impact is very minor.

Human activity, not volcanic activity, has the potential to strongly effect climate over multiple decades.

kinetic · #2 (**permalink**) 01-18-2007

Quote:

Originally Posted by onon

This might seem likely because volcanoes emit masses of material. But reality is that co2 is only a very minor component of erruption material.

The reality is, CO2 is the second most abundent vapor behind steam.

Quote:

Types of volcanic gases

The most abundant gas typically released into the atmosphere from volcanic systems is water vapor (H20), followed by carbon dioxide (C02) and sulfur dioxide (S02). Volcanoes also release smaller amounts of others gases, including hydrogen sulfide (H2S), hydrogen (H2), carbon monoxide (CO), hydrogen chloride (HCL), hydrogen fluoride (HF), and helium (He).

In fact, there is so much CO2 released that it can literally wipe out a forest.

Quote:

These dead and dying trees on the south side of Mammoth Mountain volcano (peak in distance) in eastern California were first noticed in 1990. Since then, about 170 acres of trees have died. When the area was examined in 1990, exceptionally high concentrations of carbon dioxide gas were found in the soil beneath the trees. What caused such high concentrations of carbon dioxide gas? The most likely sources of the carbon dioxide are (1) magma that intruded beneath Mammoth Mountain during an earthquake swarm in 1989; and (2) limestone-rich rocks surrounding the intrusion (CO2 is released from limestone (CaCO3) when heated).

onon · #3 (**permalink**) 01-18-2007

Steam from volcanic erruptions falls as rain within weeks. Volcanoes cannot cause a rising water vapor trend over many years.

co2 from volcanoes is concentrated, yet atmospherically insignificant.

kinetic · #4 (**permalink**) 01-18-2007

Quote:

Originally Posted by onon

co2 from volcanoes is concentrated, yet atmospherically insignificant.

It's not insignificant. The CO2 that comes from even minor eruptions are strong enough to kill entire forests.

The larger the eruption, the more damage it causes. Mt. St. Helen devastated the region with a co2 ash cloud that sufficated everything in it's path with thick, dark, smoke, heat and choking fumes that took years to recover from.

onon · #5 (**permalink**) 01-19-2007

Quote:

Originally Posted by kinetic

It's not insignificant. The CO2 that comes from even minor eruptions are strong enough to kill entire forests.

co2 are insignificant at explaining a rise in co2 levels in the atmosphere. That is what I meant.

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