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.
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