The old saying that "what goes up must come down"
doesn't apply to carbon dioxide pollution in the air, which just hit
an unnerving milestone.
The chief greenhouse gas was measured Thursday at 400 parts per
million in Hawaii, a monitoring site that sets the world's
benchmark. It's a symbolic mark that scientists and
environmentalists have been anticipating for years.
While last week's number has garnered all sorts of attention, it
is just a daily reading in the month when the chief greenhouse gas
peaks in the Northern Hemisphere. It will be lower the rest of the
year. This year will probably average around 396 ppm. But not for
long - the trend is going up and at faster and faster rates.
Within a decade, the world will never see days - even in the
cleanest of places on days in the fall when greenhouse gases are at
their lowest - when the carbon measurement falls below 400 ppm,
said James Butler, director of global monitoring at the National
Oceanic and Atmospheric Administration's Earth Science Research Lab
in Boulder, Colo.
"The 400 is a reminder that our emissions are not only
continuing, but they're accelerating; that's a scary thing," Butler
said Saturday. "We're stuck. We're going to keep going up."
Carbon dioxide stays in the air for a century, some of it into
the thousands of years. And the world carbon dioxide pollution
levels are accelerating yearly. Every second, the world's
smokestacks and cars pump 2.4 million pounds of the heat-trapping
gas into the air.
Carbon pollution levels that used to be normal for the 20th
century are fast becoming history in the 21st century.
"It means we are essentially passing one in a whole series of
points of no return," said Michael Mann, a climate scientist at
Pennsylvania State University.
Princeton University climate scientist Michael Oppenheimer said
the momentum in carbon dioxide emissions has the world heading
toward and passing 450 ppm. That is the level that would essentially
mean the world warms another 2 degrees, what scientists think of as
dangerous, he said. That 2-degree mark is what much of the world's
nations have set as a goal to prevent.
"The direction we've seen is for blowing through the best
benchmark for what's dangerous change," Oppenheimer said.
And to see what the future is, scientists look to the past.
The last time the worldwide carbon level probably hit 400 ppm was
about 2 million years ago, said Pieter Tans of the National Oceanic
and Atmospheric Administration.
That was during the early Pleistocene Era. "It was much warmer
than it is today," Tans said. "There were forests in Greenland. Sea
level was higher, between 10 and 20 meters (33 to 66 feet)."
Other scientists say it may have been 10 million years ago that
Earth last encountered this much carbon dioxide in the atmosphere.
The first modern humans only appeared in Africa about 200,000 years
ago.
Environmental activists, such as former Vice President Al Gore,
seized on the milestone.
"This number is a reminder that for the last 150 years - and
especially over the last several decades - we have been recklessly
polluting the protective sheath of atmosphere that surrounds the
Earth and protects the conditions that have fostered the flourishing
of our civilization," Gore said in a statement. "We are altering the
composition of our atmosphere at an unprecedented rate."
Carbon dioxide traps heat just like in a greenhouse. It accounts
for three-quarters of the planet's heat-trapping gases. There are
others, such as methane, which has a shorter life span but traps
heat more effectively. Both trigger temperatures to rise over time,
scientists say, which is causing sea levels to rise and some weather
patterns to change.
When measurements of carbon dioxide were first taken in 1958, it
measured 315 ppm. Some scientists and environmental groups promote
350 ppm as a safe level for CO2, but scientists acknowledge they
don't really know what levels would stop the effects of global
warming.
The level of carbon dioxide in the air is rising faster than in
the past decades, despite international efforts by developed nations
to curb it. On average, the amount is growing by about 2 ppm per
year. That's 100 times faster than at the end of the Ice Age.
Back then, it took 7,000 years for carbon dioxide to reach 80
ppm, Tans said. Because of the burning of fossil fuels, such as oil
and coal, carbon dioxide levels have gone up by that amount in just
55 years.
Before the Industrial Revolution, carbon dioxide levels were
around 280 ppm, and they were closer to 200 during the Ice Age,
which is when sea levels shrank and polar places went from green to
icy. There are natural ups and downs of this greenhouse gas, which
comes from volcanoes and decomposing plants and animals. But that's
not what has driven current levels so high, Tans said. He said the
amount should be even higher, but the world's oceans are absorbing
quite a bit, keeping it out of the air.
"What we see today is 100 percent due to human activity," said
Tans, a NOAA senior scientist. The burning of fossil fuels, such as
coal for electricity and oil for gasoline, has caused the
overwhelming bulk of the man-made increase in carbon in the air,
scientists say.
The world sent 38.2 billion tons of carbon dioxide into the air
in 2011, according international calculations published in a
scientific journal in December. China spews 10 billion tons of
carbon dioxide into the air per year, leading all countries, and its
emissions are growing about 10 percent annually. The U.S. at No. 2
is slowly cutting emissions and is down to 5.9 billion tons per
year.
The speed of the change is the big worry, said Penn State's Mann.
If carbon dioxide levels go up 100 ppm over thousands or millions of
years, plants and animals can adapt. But that can't be done at the
speed it is now happening.
Originally published by SETH BORENSTEIN Associated Press.
(c) 2013 Tulsa World. Provided by ProQuest LLC. All rights Reserved.
