Just a days after the Nobel prize was awarded for global warming work, an alarming new study finds that warming signals are stronger, and happening sooner than expected, due to increased human emissions of carbon dioxide and an Earth less able to absorb them.
Carbon dioxide emissions were 35 percent higher in 2006 than in 1990, a much faster growth rate than anticipated, researchers reported in Tuesday’s edition of the peer-reviewed Proceedings of the National Academy of Sciences.
The researchers cited three factors: global economic growth; the global economy becoming more carbon intense — since 2000 more carbon is being emitted to produce each dollar of global wealth, they noted — and a decline in the land and oceans’ ability to absorb carbon from the atmosphere.
"The carbon cycle is generating stronger-than-expected and sooner-than-expected climate 'forcing' — that is, mechanisms that 'force' the climate to change," said co-author Mike Raupach, a co-chair of what's known as the Global Carbon Project. "In turn, climate change itself is feeding back to affect the carbon cycle, decreasing land and ocean sinks."
“The new twist here is the demonstration that weakening land and ocean sinks are contributing to the accelerating growth of atmospheric CO2,” added co-author Chris Field, director of the Carnegie Institution’s Department of Global Ecology at Stanford University.
The researchers said that human-induced warming had caused changes in wind patterns over the Southern Ocean that brought carbon-rich water toward the surface, reducing the ocean’s ability to absorb excess CO2 from the atmosphere.
On land, where plant growth is the major means for soaking up CO2, droughts have curbed that ability, they stated.
Ocean sink 'really shocking'
Two climate researchers not involved with the study called it significant.
The “paper raises some very important issues that the public should be aware of," said Kevin Trenberth of the National Center for Atmospheric Research in Boulder, Colo. "Namely that concentrations of CO2 are increasing at much higher rates than previously expected and this is in spite of the Kyoto Protocol that is designed to hold them down in western countries.”
Alan Robock, associate director of the Center for Environmental Prediction at Rutgers University, added that “what is really shocking is the reduction of the oceanic CO2 sink” —meaning the ability of the ocean to absorb carbon dioxide, removing it from the atmosphere.
The researchers blamed that reduction on changes in wind circulation, but Robock said he also thinks rising ocean temperatures reduce the ability to take in carbon dioxide.
“Think that a warm Coke has less fizz than a cold Coke,” he said.
Carbon dioxide is the leading “greenhouse gas,” so named because their accumulation in the atmosphere can help trap heat from the sun, causing potentially dangerous warming of the planet.
While most atmospheric scientists accept the idea, finding ways to reduce greenhouse gas emissions has been a political problem because of potential effects on the economy. Earlier this month, the Nobel Peace Prize was awarded to the United Nations Intergovernmental Panel on Climate Change and former Vice President Al Gore for their work in calling attention to global warming.
“It turns out that global warming critics were right when they said that global climate models did not do a good job at predicting climate change,” Robock said. “But what has been wrong recently is that the climate is changing even faster than the models said. In fact, Arctic sea ice is melting much faster than any models predicted, and sea level is rising much faster than IPCC previously predicted.”
Will future repeat recent past?
According to the new study, carbon released from burning fossil fuel and making cement rose from 7.0 billion metric tons per year in 2000 to 8.4 billion metric tons in 2006. A metric ton is 2,205 pounds.
The growth rate increased from 1.3 percent per year in 1990-1999 to 3.3 percent per year in 2000-2006, the researchers added.
Trenberth noted that carbon dioxide is not the whole story — methane emissions have declined, so total greenhouse gases are not increasing as much as carbon dioxide alone. Also, he added, other pollution plays a role by cooling.
There are changes from year to year in the fraction of the atmosphere made up of carbon dioxide and the question is whether this increase is transient or will be sustained, he said.
“The theory suggests increases in (the atmospheric fraction), as is claimed here, but the evidence is not strong,” Trenberth said.
The paper looks at a rather short time to measure a trend, Robock added, “but the results they get certainly look reasonable, and much of the paper is looking at much longer trends.”
The research was supported by Australian, European and other international agencies that are part of the Global Carbon Project.
The Associated Press contributed to this report.