NASA researchers have identified feasible emission scenarios -which have accounted for about 80 percent of the rise of atmospheric carbon dioxide since the pre-industrial era- that could keep carbon dioxide below levels that some scientists have called dangerous for our climate.
To better understand how emissions might change in the future,
Pushker Kharecha and James Hansen of NASA"s Goddard Institute for Space
Studies in New York considered a wide range of fossil fuel consumption
scenarios, which shows that the rise in carbon dioxide from burning
fossil fuels can be kept below harmful levels as long as emissions from
coal are phased out globally within the next few decades.
Global warming has plunged the planet into a crisis and the fossil fuel
industries are trying to hide the extent of the problem from the
public, Hansen, NASA"s top climate scientist says.
"We"ve already reached the dangerous level of carbon dioxide in the
atmosphere," according to James Hansen. "But there are ways to solve
the problem" of heat-trapping greenhouse gases like carbon dioxide,
which Hansen said has reached the "tipping point" of 385 parts per
million.
Hansen calls for phasing out all coal-fired plants by 2030, taxing
their emissions until then, and banning the building of new plants
unless they are designed to trap and segregate the carbon dioxide they
emit.
The major obstacle to saving the planet from its inhabitants is not
technology, insisted Hansen, named one of the world"s 100 most
influential people in 2006 by Time magazine.
"The problem is that 90 percent of energy is fossil fuels. And that
is such a huge business, it has permeated our government," he
maintained. "What"s become clear to me in the past several years is
that both the executive branch and the legislative branch are strongly
influenced by special fossil fuel interests," he said, referring to the
providers of coal, oil and natural gas and the energy industry that
burns them.
"You need a new Kyoto protocol with all the major emitters committed to it. Then you are cooking with gas."
Previously published research shows that a dangerous level of global
warming will occur if carbon dioxide in the atmosphere exceeds a
concentration of about 450 parts per million, only 17 percent more than
the current level of 385 parts per million. The carbon dioxide cap is
related to a global temperature rise of about 1.8 degrees Fahrenheit
above the 2000 global temperature, at or beyond which point the
disintegration of the West Antarctic ice sheet and Arctic sea ice could
set in motion feedbacks and lead to accelerated melting.
To better understand the possible trajectory of future carbon
dioxide, Kharecha and Hansen devised five carbon dioxide emissions
scenarios that span the years 1850-2100. Each scenario reflects a
different estimate for the global production peak of fossil fuels, the
timing of which depends on reserve size, recoverability and technology.
"Even if we assume high-end estimates and unconstrained emissions
from conventional oil and gas, we find that these fuels alone are not
abundant enough to take carbon dioxide above 450 parts per million,"
Kharecha said.
The first scenario estimates carbon dioxide levels if emissions from
fossil fuels are unconstrained and follow along "business as usual,"
growing by two percent annually until half of each reservoir has been
recovered, after which emissions begin to decline by two percent
annually.
The second scenario considers a situation in which emissions from
coal are reduced first by developed countries starting in 2013 and then
by developing countries a decade later, leading to a global phase out
by 2050 of the emissions from burning coal that reach the atmosphere.
The reduction of emissions to the atmosphere in this case can come from
reducing coal consumption or from capturing and sequestering the carbon
dioxide before it reaches the atmosphere.
The remaining three scenarios include the above-mentioned phase out
of coal, but consider different scenarios for oil use and supply. One
case considers a delay in the oil peak by about 21 years to 2037.
Another considers the implications of fewer-than-expected additions to
proven reserves due to overestimated reserves, or the addition of a
price on emissions that makes the fuel too expensive to extract. The
final scenario looks at emissions from oil fields that peak at
different times, extending the peak into a plateau that lasts from
2020-2040.
The researchers suggest that the results illustrated
by each scenario have clear implications for reducing carbon dioxide
emissions from coal, as well as "unconventional" fuels such as methane
hydrates and tar sands, all of which contain much more fossil carbon
than conventional oil and gas.
"Because coal is much more plentiful than oil and gas, reducing coal
emissions is absolutely essential to avoid "dangerous" climate change
brought about by atmospheric carbon dioxide concentration exceeding 450
parts per million," Kharecha said. "The most important mitigation
strategy we recommend – a phase-out of carbon dioxide emissions from
coal within the next few decades – is feasible using current or
near-term technologies."
Posted by Casey Kazan with Rebecca Sato.