EarthTalk

Dear EarthTalk: Could it really be true that a single large volcanic eruption launches more greenhouse gases into the atmosphere than the amount generated by all of humanity over history? -- Steve Schlemmer, London, England

This argument that human-caused carbon emissions are merely a drop in the bucket compared to greenhouse gases generated by volcanoes has been making its way around the rumor mill for years. And while it may sound plausible, the science just doesn’t back it up.

According to the U.S. Geological Survey (USGS), the world’s volcanoes, both on land and undersea, generate about 200 million tons of carbon dioxide (CO2) annually, while our automotive and industrial activities cause some 24 billion tons of CO2 emissions every year worldwide. Despite the arguments to the contrary, the facts speak for themselves: Greenhouse gas emissions from volcanoes comprise less than one percent of those generated by today’s human endeavors.

Another indication that human emissions dwarf those of volcanoes is the fact that atmospheric CO2 levels, as measured by sampling stations around the world set up by the federally funded Carbon Dioxide Information Analysis Center, have gone up consistently year after year regardless of whether or not there have been major volcanic eruptions in specific years. “If it were true that individual volcanic eruptions dominated human emissions and were causing the rise in carbon dioxide concentrations, then these carbon dioxide records would be full of spikes—one for each eruption,” says Coby Beck, a journalist writing for online environmental news portal Grist.org. “Instead, such records show a smooth and regular trend.”

Furthermore, some scientists believe that spectacular volcanic eruptions, like that of Mt. St. Helens in 1980 and Mt. Pinatubo in 1991, actually lead to short-term global cooling, not warming, as sulfur dioxide (SO2), ash and other particles in the air and stratosphere reflect some solar energy instead of letting it into Earth’s atmosphere. SO2, which converts to sulfuric acid aerosol when it hits the stratosphere, can linger there for as long as seven years and can exercise a cooling effect long after a volcanic eruption has taken place.

Scientists tracking the effects of the major 1991 eruption of the Philippines’ Mt. Pinatubo found that the overall effect of the blast was to cool the surface of the Earth globally by some 0.5 degrees Celsius a year later, even though rising human greenhouse gas emissions and an El Nino event (a warm water current which periodically flows along the coast of Ecuador and Peru in South America) caused some surface warming during the 1991-1993 study period.

In an interesting twist on the issue, British researchers last year published an article in the peer reviewed scientific journal Nature showing how volcanic activity may be contributing to the melting of ice caps in Antarctica—but not because of any emissions, natural or man-made, per se. Instead, scientists Hugh Corr and David Vaughan of the British Antarctic Survey believe that volcanoes underneath Antarctica may be melting the continent’s ice sheets from below, just as warming air temperatures from human-induced emissions erode them from above.

CONTACTS: U.S. Geological Survey, www.usgs.gov; Carbon Dioxide Information Analysis Center, cdiac.esd.ornl.gov; British Antarctic Survey, www.antarctica.ac.uk.

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From the Editors of E/The Environmental Magazine

Dear EarthTalk: It seems like more products are being packaged in #5 rather than #2 plastic today, and my local recycling agency won’t take #5. I’ve also heard that #5 plastics are more toxic, which concerns me more than the recyclability issue. Which plastic is the better choice?

-- Janice Shaffer, Chillicothe, MO

Polypropylene, which is marked with #5 inside the “chasing arrows” symbols on the bottom of plastic containers, is a lighter-weight plastic resin commonly used in dairy and deli packaging. Some companies have chosen this lighter plastic because it has a lower environmental impact to produce and transport.

High density polyethylene (HDPE), which is marked with #2, is a stiffer resin used to package cleaning products and also some dairy products. The most widely used resin type for consumer food products is polyethylene terephthalate, or PETE, which is marked with #1 and used for soda and water bottles.

According to Consumers Union’s “Greener Choices” website, all three of these plastics are considered safe for their original use, though any of them can leak toxins when reused repeatedly. And all three can be recycled, though a lagging market leads some recycling locations to limit what they’ll accept. There is also concern that widespread plastics recycling encourages more use of plastics, and that efforts would be better spent getting consumers to buy fewer plastic-encased products. Some even criticize the chasing-arrow labeling system for implying a higher level of recyclability than is presently available.

Why is a lighter-weight plastic better? According to dairy company Stonyfield Farm, their #5 one-quart yogurt container uses 30 percent less plastic than a #2 cup. Since it takes less material to make a thinner container, it reduces the amount of resin that needs to be manufactured. Stonyfield estimates that the use of #5 over #2 prevents the manufacture and disposal of more than 100 tons of plastic per year.

But savings comes from more than manufacturing. The heavier #2 plastics require more energy to transport. It’s not only getting the yogurt from Stonyfield’s plants to your store, but also getting the containers from the plastics manufacturer to their dairies. In fact, the company cites a packaging study by the Boston-based Tellus Institute which found that 95 percent of the environmental costs of packaging lie in production and less than five percent are associated with disposal.

According to the website Earth 911, a national directory of recycling outlets, the best thing consumers can do is to choose items with less packaging and buy in bulk when possible. So the next time you reach into the dairy case, grab the quart or gallon-size yogurt instead of the single-serving cups. Then, make sure you recycle only the allowable plastics so you don’t contaminate the lot. While recycling is important, it may be okay to landfill a product’s packaging if it was created with an environmentally responsible plan.

Besides seeking alternatives to plastic packaging, consumers can affect overall plastic use by supporting legislation that would require manufacturers to take back their plastic packaging, which would encourage “cradle-to-grave” practices. Further, you can support legislation that mandates more use of recycled plastic content, which would reduce the overall amount of virgin plastic produced in the first place.

CONTACTS: Stonyfield Farm’s Earth Actions, www.stonyfield.com/EarthActions, Consumer Reports’ Greener Choices, www.greenerchoices.org; Earth 911, www.earth911.com.