| 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
| |
Despite
rumors and arguments to the contrary, greenhouse gas
emissions from volcanoes comprise less than one percent
of those generated by today's human endeavors.
© Lyn Topinka, courtesy U.S. Geological
Survey |
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; Carbon
Dioxide Information Analysis Center; British
Antarctic Survey.
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
| |
Some companies have switched from #2 to #5 plastic
food containers because it is lighter and has a lower
environmental impact to produce and transport. Consumers
Union says that, as with #1 or #2 plastic, #5 is safe
for original use, though any of these materials can
leak toxins when reused repeatedly.
© bitzcelt, courtesy Flickr
|
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; Consumer
Reports’ Greener Choices; Earth
911. |
