Which produces more CO2, volcanic or human activity?

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People who are fortunate enough to live in or visit Hawaii, or even those who have seen the right television documentaries know that the majestic presence of erupting volcanoes attests to their raw power.

Puu Oo crater from the Northeast.

(Public domain.)

Fossil fuel combustion.

(Public domain.)

Don't try this trick at home, but if we took Kīlauea (our own backyard volcano) and collected the lava that it erupted, just during the time it took you to read this sentence, there would be enough material to fill the gas tanks of about 1,000 Sport Utility Vehicles (SUVs.) And though Kīlauea is a medium-to-small-sized volcano, it has been discharging lava nearly continuously at this rate for the past 24 years.

Demonstrations like this one, or catastrophic eruptions like those of Mount St. Helens or Mount Pinatubo, understandably cause people to sometimes think that human-caused effects on the biosphere are small compared to volcanic ones. But, as the saying goes, "it ain't necessarily so."

At HVO, for instance, we are often asked about the influence of volcanic gas emissions on the atmosphere and whether these emissions dwarf those from human activity. Anyone who has stood downwind of Kīlauea's vents, and sometimes even people who live in Honolulu, 250 miles away, know first-hand how these emissions can affect air quality and life on the regional scale. It's a fact that Kīlauea has been releasing more than twice the amount of noxious sulfur dioxide gas (SO2) as the single dirtiest power plant on the U.S. mainland.

So it's also understandable that, with the emerging report of the Intergovernmental Panel on Climate Change (IGCC), some people want to understand how volcanoes might factor into the rise in greenhouse gas concentrations-specifically carbon dioxide (CO2)-that is being reported worldwide. The changes in global CO2 concentration during the past 600,000 years have mimicked the changes in global temperature. And, after all, volcanoes are awesome natural forces that release lots of carbon dioxide (CO2) right? Could volcanoes be a significant global-warming villain?

For numerous reasons, volcanologists have been interested in CO2 release from volcanoes for years and have been working to improve estimates on the amount of CO2 entering the atmosphere and oceans by volcanic processes.

Carbon dioxide is released when magma rises from the depths of the Earth on its way to the surface. Our studies here at Kīlauea show that the eruption discharges between 8,000 and 30,000 metric tonnes of CO2 into the atmosphere each day. Actively erupting volcanoes release much more CO2 than sleeping ones do.

Gas studies at volcanoes worldwide have helped volcanologists tally up a global volcanic CO2 budget in the same way that nations around the globe have cooperated to determine how much CO2 is released by human activity through the burning of fossil fuels. Our studies show that globally, volcanoes on land and under the sea release a total of about 200 million tonnes of CO2 annually.

This seems like a huge amount of CO2, but a visit to the U.S. Department of Energy's Carbon Dioxide Information Analysis Center (CDIAC) website helps anyone armed with a handheld calculator and a high school chemistry text put the volcanic CO2 tally into perspective. Because while 200 million tonnes of CO2 is large, the global fossil fuel CO2 emissions for 2003 tipped the scales at 26.8 billion tonnes. Thus, not only does volcanic CO2 not dwarf that of human activity, it actually comprises less than 1 percent of that value.

A short time ago (geologically speaking) the question "Which produces more CO2, volcanic or human activity?" would have been answered differently. Volcanoes would have tipped the scale. Now, human presence, activity, and the resultant production of CO2, through the burning of fossil fuels, have all climbed at an ever-increasing rate. On the other hand, looking back through the comparatively short duration of human history, volcanic activity has, with a few notable disturbances, remained relatively steady.

Volcanoes are still awesome, even though they don't produce CO2 at a rate that swamps the human signature, contributing to global warming. In fact, spectacular eruptions like that of Mount Pinatubo are demonstrated to contribute to global cooling through the injection of solar energy reflecting ash and other small particles.

There is now agreement at the top government level of the Earth's most prolific fossil fuel CO2 producer-the United States-that we need to reduce our dependence on oil in order to confront the challenge of global warming. As we work toward that goal, let's look forward to the day when volcanologists will give a different answer to the question "Which produces more CO2, volcanic or human activity?"

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Volcano Activity Update

This past week, activity levels at the summit of Kīlauea Volcano have remained at background levels. The number of earthquakes located in the summit area is low (usually less than 10 per day are large enough to locate).

Eruptive activity at Puu Oo continues. On clear nights, glow is visible from several vents within the crater. Lava is fed through the PKK lava tube from its source on the southwest flank of Puu Oo to the ocean. About 1 kilometer south of Puu Oo, the Campout flow branches off from the PKK tube. The PKK and Campout tubes feed two widely separated ocean entries, at East Laeapuki and East Kailiili, respectively. Both entries are located inside Hawaii Volcanoes National Park.

A third entry, fed by an offshoot of the Campout flow, has been active since December 26. It is located at Kamokuna, about midway between the two older entries. In the last week, intermittent breakouts from the Campout tube have continued on the slope of Pulama pali and on the coastal plain near Kamokuna. A new breakout from the main PKK tube has been advancing down the pali in the past three weeks, more than a kilometer west of the Campout tube. The terminus is now within the rope line above the East Laeapuki entry.

Access to the sea cliff near the ocean entries is closed, due to significant hazards. The surrounding area, however, is open. If you visit the eruption site, check with the rangers for current updates, and remember to carry lots of water when venturing out onto the flow field.

One earthquake beneath Hawai`i Island was reported felt within the past week. A magnitude-2.8 earthquake at 7:49 p.m. H.s.t. on Sunday, February 11 was located 5 km (3 miles) northwest of Kawaihae at a depth of 25.7 km (16 miles).

Mauna Loa is not erupting. During the past week, earthquake activity remained low beneath the volcano (one earthquake was located). Extension of distances between locations spanning the summit, indicating inflation, continues at slow rates.