(Image from Flickr and photographer azrainman)
Oboy. The climate skeptics are having a field day with two studies released last week that suggest scientists don’t know all the factors involved in global warming. The contrarian blogospere is especially excited about research, published in Nature Geoscience, that concluded carbon dioxide only accounted for half of the extreme warming that occurred 55 million years ago. The sceptics’ conclusion? Science models showing warming related to CO2 are all wet. Ergo, we can stop worrying about throwing up all that greenhouse gas from burning fossil fuels.
That’s not the way the researchers saw it.
About 55 million years ago, they found, the Earth’s temperature rose between 5 and 9 degrees Celsius (9 to 16 degrees Fahrenheit) over a period of about 10,000 years. (If you're a Creationist, I guess you can stop reading here.) Based on seabed borings, scientists from Rice University, the University of Hawaii and U Cal Santa Barbara said things were already pretty hot when it all started (there was no surface ice) and they speculate some event, like methane deposits bubbling up from warm seabeds, caused a 70% increase of CO2 in the atmosphere over 10,000 years. (Most hydrate methane turns into CO2.)
If only half the temperature increase can be explained by carbon dioxide release, what caused the rest of it? No one's sure but authors of the study said it could involve feedback loops. And they say the unexplained causes don't mean we can stop worrying about climate change. Rather, future global warming could be worse than we thought, because feedback loops caused by melting tundra, changing ocean currents, and water absorbing more sunlight than ice may have caused more warming then than today’s models would explain. (BTW, the UN’s IPPC report on future climate change left out feedback loops because we don’t understand them well enough, though they realized the melting of Greenland, for example, could have a profound effect.)
Forecasts likely underestimate warming
In commentary published along with the study, scientist David Beerling of Sheffield University, UK, said climate forecasts “could be severely underestimating the extent of the problem that lies in store for humanity as greenhouse gases accumulate in the atmosphere.”
An analysis by the Union of Concerned Scientists agrees the study suggests warming is potentially worse than previously believed.
So don’t let anyone tell you this study throws the global warming theory out the window. More likely we don’t know the half of it.
Looking at warming on a scale we can relate to, say the lifetime of our grandchildren, predictions of catastrophic warming in this century still hold – and may be a lot worse than forecast.
Since the Industrial Revolution, CO2 in the atmosphere has grown from 280 parts per million to 390 ppm or about 40%. C02 in the atmosphere could grow more than 70% in just a century (not 10,000 years) this time, one study author said.
Sunspots and flares
Another theory for changing temperatures on Earth has been the influence of activity on the sun. A second newly published study, in the Journal of Science, links the two together for the first time, but concludes the cyclical activity is similar to that of El Niño and La Niña, in warming the Pacific, but has only about half as much impact on the temperature as El Niño. The differences in the 11-year cycles are “very small,” relative to the sun’s total energy and are short-term cyclical rather than a long-term trend. The study was done by the National Center for Atmospheric Research (NCAR).
(Sources: Reuters PlanetArk, Reuters blog, Science Daily, Nature Geoscience, Union of Concerned Scientists, ClimateWire)
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