Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder

Study of Wildfire Plumes Provides Insights Into Methods That Might Cool the Planet

The dynamics that lift smoke from large wildfires into the upper atmosphere could potentially be employed one day to help temporarily cool the planet, based on the findings of a modeling study led by NOAA scientists. 

Inspired by a giant fire cloud generated over the Pacific Northwest in 2017, the researchers investigated whether heat from the sun could loft light-reflecting material mixed with heat-absorbing particles several miles into the stratosphere from lower altitudes. Once in the stratosphere, the reflective material would dim sunlight and cool the planet below. A description of the process, called solar-powered lofting, was published today in the journal Science Advances.

The NOAA-led team—which includes Christopher Maloney a CIRES scientist working at NOAA, Brian Toon from the Laboratory for Atmospheric and Space Physics at CU Boulder, and scientists from NCAR, the German Aerospace Center, and China’s Jinan University—used the NCAR Community Earth System Model to simulate solar-powered lofting in order to calculate the amount of light-absorbing black carbon particles required to effect substantial lofting. The suitability of the model was demonstrated by successfully reproducing the lofting in the 2017 Pacific Northwest fire plume.

“Greenhouse gases continue to increase, and there is concern that at some point the Earth system will reach a tipping point that it can't return from,” said Karen Rosenlof, a researcher with NOAA’s Chemical Sciences Laboratory and one of paper’s lead authors. “Reflecting sunlight with stratospheric aerosols, effectively mimicking what large volcanic eruptions do, may buy some time for decarbonization efforts to ramp up. We don't have the technology to do this today, but nature has shown us one way someone might propose to do it in the future.”  

The scientists concluded that solar-powered lofting is potentially feasible with existing aviation technology. It could also be easier, less expensive, and just as effective as introducing aerosols directly into the stratosphere, they said. Model simulations show that as little as 10 micrograms of heat-absorbing black carbon per cubic meter would be enough to loft air that also contained sulfur dioxide, which converts to light-reflecting particles, into the lower stratosphere in just a matter of days. 

There are currently no aircraft or other platforms that can directly deliver large amounts of aerosol material or aerosol precursors to altitudes 12 miles or higher and disperse the material evenly. Even less effort has been invested in understanding the practical aspects of aerosol injection in the stratosphere.

Rosenlof said the intent of this study is not to encourage implementation of planet-cooling methods, but to provide the scientific foundation for societal decision-making. The scientists associated with this study acknowledge, as have many other scientists, that increasing the stratospheric burden of aerosols would likely have unintended consequences, such as increased stratospheric temperatures, changes in surface precipitation patterns, and potentially depletion of the stratospheric ozone layer that absorbs harmful ultraviolet radiation.

This figure illustrates potential methods for climate intervention that would either intercept incoming or make it easier for outgoing solar radiation to escape the atmosphere. Credit: Chelsea Thompson, CIRES/NOAA

In 2020, NOAA initiated a research program to establish the scientific foundation needed to inform decision makers who may one day evaluate climate intervention proposals. NOAA scientists and partners are investigating the climate effects of aerosols potentially added to the stratosphere and troposphere, and evaluating modeling systems that realistically assess aerosol impacts on the Earth system and on society. Research into atmospheric aerosols will also improve weather and climate models.

NOAA has no plans to conduct experiments in the atmosphere that demonstrate this or any other climate intervention method. 

Read the full story at NOAA Research.

CIRES is a partnership of NOAA and CU Boulder.