“There is so much discussion of uncertainty in the public debate about climate change that the term now seems ambiguous and politically loaded.”
— Mark Bradford
While scientists might never eliminate all uncertainty when it comes to evaluating the mechanisms driving changes in soil carbon stocks, new research advances are making it possible to predict the full range of potential outcomes, said Mark Bradford, an Associate Professor of Terrestrial Ecosystem Ecology at the Yale School of Forestry & Environmental Studies (F&ES) and lead author of the study.
And that, he says, will increase confidence.
“There is so much discussion of uncertainty in the public debate about climate change that the term now seems ambiguous and politically loaded,” Bradford said. “The discussion should not be about how much uncertainty there is, but rather about how much confidence we have that the real planetary response lies somewhere in the range of projected uncertainty.”
“You gain scientific confidence by representing the best — and sometimes polar opposite — ideas about the how the world works in your models. If someone tells you they have high confidence that something will happen, you can then take actions based on the best knowledge available.”
Warming temperatures can trigger two very different changes in soil carbon soil levels. On the one hand, they can stimulate the growth of plants, increasing the amount of carbon storage potential. Conversely, those higher temperatures can also accelerate the activity of organisms that live in the soil and consume decaying plant matter. In that case, there is a net increase in the amount of carbon released from the biosphere into the atmosphere.
In other words, one function puts carbon into the soil, keeping it out of the atmosphere, while the other emits it into the atmosphere. The twist, however, is that the processes that emit carbon from the soil also convert a small fraction of the decaying plant matter into stores of carbon that can be locked away over millennial timescales, which would be optimal to minimizing climate impacts.
While scientists have made great advances in understanding how plants will respond, their ability to evaluate how much carbon goes into the soil, and where it ends up, is made difficult because it’s not possible to measure directly.
“In the soil, we don’t know how things are working because, if you like, it’s as clear as mud,” Bradford said. “Often we can’t measure what we’re trying to measure because we can’t see the organisms. You have millions of individual microbes — from thousands of cryptic species — in just a handful of soil.”