When scientists discuss increasing levels of carbon dioxide, they are generally referring to carbon that either stays in the atmosphere where it has a greenhouse effect, or dissolves into the ocean where it contributes to acidification. However, a new paper published in Nature describes the first evidence that confirms what climate models have predicted: the increase in CO2 is heating the crust of the Earth as well.
The study, funded in part by the U.S. Department of Energy’s Office of Science, utilized data from the NOAA CarbonTracker between 2000 and 2010. Measurements from the Atmospheric Radiation Measurement Climate Research Facility in Oklahoma were taken almost every day, with 8,300 readings altogether. A second research facility in Alaska provided 3,300 measurements during this time span. Despite the sites being very different in terms of climate and industrial development, they both confirmed that CO2 levels are increasing due to human activity, and that it's heating up the Earth’s crust.
"We see, for the first time in the field, the amplification of the greenhouse effect because there's more CO2 in the atmosphere to absorb what the Earth emits in response to incoming solar radiation," lead author Daniel Feldman of University of California, Berkeley said in a press release. "Numerous studies show rising atmospheric CO2 concentrations, but our study provides the critical link between those concentrations and the addition of energy to the system, or the greenhouse effect.”
The researchers measured the crust’s radiative force, which is the ratio of infrared energy released by the crust as thermal radiation compared to how much energy it receives from the sun. After correcting for potential confounders such as cloud cover and humidity, they discovered that the radiative force had indeed increased during that decade-long observation period by 0.2 Watts per square meter per decade. Though that number might sound small, it’s actually a 10% increase. The researchers were able to connect this to the 22 parts per million increase of atmospheric carbon that occurred during the same time span.
"We measured radiation in the form of infrared energy. Then we controlled for other factors that would impact our measurements, such as a weather system moving through the area," Feldman explained.
Though it’s not great news, having confirmation that this phenomenon is occurring and knowing the rate at which it’s increasing will allow scientists to refine climate models and better predict how increased CO2 will affect the Earth in the future.