A group of UC Irvine researchers has concluded that global warming's impact on Earth will be more severe over the next century because the planet's soil absorbs less atmospheric carbon dioxide than previously thought.
In a study published Friday, a group of researchers, headed by lead author Yujie He, used radiocarbon dating — a method for determining the age of organic material — to determine that the current carbon trapped in the Earth's soil is about 3,100 years old. Original estimates pegged it at 450 years old.
The UCI study marked the first time radiocarbon dating was used to date the carbon in soil.
What these numbers indicate, He said, is that soil has been soaking up carbon at a slower rate than researchers had assumed during the last few decades. That means, He added, that more carbon dioxide is remaining in the atmosphere, contributing to the so-called "greenhouse effect."
"We have overestimated the capacity of soil's ability to absorb carbon," lead author James Randerson said.
Plants take in carbon dioxide through photosynthesis. The carbon is then stored in the plants' limbs, so when they die, the ground absorbs them and the carbon is stored in the soil.
Researchers originally believed that soil was a more substantial carbon sink, which means it more readily sops up atmospheric carbon. But radiocarbon dating is believed to be a more accurate measurement instrument, and it shows that soil has a weaker carbon capacity.
Radiocarbon dating is expensive, which is why the methodology has not been used until the UCI study. The researchers used a device called an accelerator mass spectrometer to measure 157 soil samples taken from around the world.
"We have to be even more proactive in finding ways to cut emissions of fossil fuels to limit the magnitude and impacts of climate warming," Randerson said. "Warming will be higher if it's just business as usual."
Randerson said the findings redefine current Earth system models, which are compilations of data on the planet's ice masses, oceans, plant life, atmosphere and landforms. The models are relied upon by the Intergovernmental Panel on Climate Change, a scientific organization of the United Nations, to make projections on climate change.
Randerson said he hopes the study will be used by the panel to make more accurate predictions so that policymakers can make better decisions about limiting carbon dioxide emissions in the future.