A study revealed new clues about how it controls the weather, which would allow us to predict if there are possibilities of inducing its actions.
Rocks, rain, and carbon dioxide helped control Earth’s climate for thousands of years, just like a thermostat works, through a process called weathering.
A new study that has just been published in the journal Science, led by scientists at Penn State University, allows a better understanding of how this thermostat responds as temperatures change.
“Life has been on this planet for billions of years, so we know that the Earth’s temperature has remained constant enough for there to be water to sustain life,” said Susan Brantley, a professor at the University of Evan Pugh and a geoscientist from the Barnes Laboratory at Penn State.
The idea is that the weathering of silicate rocks is this thermostat, but no one has really agreed on its sensitivity to temperature.”
Because so many factors go into weathering, it has been challenging to use only the results of laboratory experiments to create global estimates of how weathering responds to changes in temperature, the scientists explained in their new paper.
The team combined laboratory measurements and soil analyzes from 45 sites around the world and many watersheds to better understand the weathering of major rock types on Earth and used those findings to create a global estimate of how weathering responds to temperature.
Weathering represents part of a balancing act of carbon dioxide in Earth’s atmosphere. Volcanoes have emitted vast amounts of carbon dioxide throughout the planet’s history, but instead of turning it into a greenhouse, the gases are slowly removed through the weather.
The rain takes carbon dioxide from the atmosphere and creates a weak acid that falls to Earth and wears away silicate rocks on the surface. The byproducts are transported by streams and rivers to the ocean, where the carbon is ultimately stored in sedimentary rocks.
But much remains to be known about how sensitive weathering is to changes in temperature, in part because of the long spatial and temporal scales involved.
“In a soil profile, what you see is an image where the camera shutter was open, sometimes, for a million years: there are built-in processes that occur during that time, and so we tried to try to compare that with a two-year experiment,” Brantley explained.
She said the field of hotspot science, which examines landscapes from the highest vegetation to the deepest groundwater, has helped scientists better understand the complex interactions that influence weathering.
For example, they now know that rocks must fracture for water to enter the cracks and begin to break down the materials.
For that to happen, the rock must have large exposed surfaces, and that is less likely to happen in regions where the ground is deeper. “It’s only when you start to cross spatial and temporal scales that you start to see what’s really important,” Brantley said.
“The acreage is really valuable. You can measure all the rate constants for analysis in the lab, but until you can tell me how surface area forms in the natural system, you’ll never be able to predict the real system,” he added.
The scientists reported that the temperature sensitivity measurements in the laboratory were lower than the estimates from the soils and rivers in their study.
Using observations from the laboratory and field sites, they extended their findings to estimate the global temperature dependence of weathering.
Their model can be useful in understanding how weathering will respond to future climate change, and in evaluating man’s attempts to increase weathering to pull more carbon dioxide out of the atmosphere, such as with carbon footprinting.