First Direct Observation of Carbon Dioxide's Increasing Greenhouse Effect at Earth's Surface

Scientists have directly confirmed what they have long assumed to be true:  increasing amounts of greenhouse gases in the atmosphere, such as carbon dioxide, are trapping heat from escaping back into space and are thereby causing global warming.

The observations of what is known as radiative forcing were made over the course of 11 years between 2000 and 2010 from two locations in North America, in Oklahoma and the North Slope of Alaska.  Highly specialized instruments in both locations were used to measure thermal infrared energy fluctuations and analyze the source of such changes.

The study, published Wednesday in the advance online edition of the journal Nature, explores the Earth's energy account balance.  It found that over time, the planet is running a surplus of energy at the surface, causing global air and ocean temperatures to increase with a wide variety of mostly negative impacts.

Before this study, scientists already knew that the energy balance was tilted in the direction of a growing surplus, but they lacked precise measurements at the surface.  The researchers were also able to trace this energy surplus mainly to man made emissions of carbon dioxide and other greenhouse gases through the burning of fossil fuels such as coal and oil, as well as forest fires.

The research provides observational evidence that the increased heating of the atmosphere during the period was due in large part to the increase in carbon dioxide concentrations at the time.  The study found that the 22 parts per million increase in carbon dioxide during this period caused the amount of energy absorbed at the Earth's surface to increase by about two-tenths of a Watt per square meter per decade.

"We see, for the first time in the field, the amplification of the greenhouse effect because there's more carbon dioxide in the atmosphere to absorb what the Earth emits in response to incoming solar radiation," Daniel Feldman, a scientist in Berkeley Lab's Earth Sciences Division and lead author of the study, said in a press release.

"Numerous studies show rising atmospheric carbon dioxide concentrations, but our study provides the critical link between those concentrations and the addition of energy to the system, or the greenhouse effect," Feldman added.

Earth's energy surplus is growing
The study's findings confirm longtime predictions as well as observations of a man made enhancement of the greenhouse effect, and also help to reinforce the results of many climate models that are predicated in part on accurately simulating the effects of carbon dioxide in the atmosphere.

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