Scientists Investigate Drying out the Stratosphere to Reduce Warming
In recent years, scientists have been exploring strategies to offset global warming by manipulating the climate system. Now, a new study published in Science Advances examines the feasibility of a new approach to reduce warming: removing water vapor — a greenhouse gas — from the stratosphere.
Drawing on observations from an airborne campaign led by NASA, researchers provide an early-stage assessment of intentional stratospheric dehydration by investigating the practical details and potential effectiveness of injecting ice-nucleating particles (INP) into the stratosphere.
Although the approach would likely have some cooling effect, they say, it wouldn’t be nearly enough to counteract more significant warming from carbon dioxide (CO2) emissions. INP injection would have to considered among a portfolio of other climate interventions to determine whether there are any alternatives to reducing CO2 emissions that would meaningfully reduce climate impacts.
It also outlines several technical barriers to consider before such a strategy could be employed, including where, what, and how particles could be injected into the top layer of the tropopause. The tropopause is the boundary between the troposphere (Earth’s lowest atmospheric layer) and the stratosphere. Researchers are focused on the tropopause at tropical latitudes because this is where the sun’s heating causes air to rise into the stratosphere.
“We need more measurements of how water is distributed in the [tropical tropopause layer] to better understand its sources and sinks in the region,” said Joshua “Shuka” Schwarz, a research physicist at the National Oceanic and Atmospheric Administration (NOAA) Chemical Sciences Laboratory and first author.
PROBING THE STRATOSPHERE
Water vapor is an important greenhouse gas in Earth’s climate system. It helps keep the planet warm, but unlike other greenhouse gases, it doesn’t accumulate in the atmosphere because it can transform into snow, ice and rain. In this way, water vapor can’t drive climate change like human-emitted CO 2 does.
Nonetheless, the United Nations Intergovernmental Panel on Climate Change (IPCC) 6th report suggests that water vapor levels will rise in the atmosphere as the climate warms, because warmer air can hold more of it — a positive climate feedback that is expected to exacerbate warming. This has led researchers like Schwarz to question whether finding ways to reduce atmospheric water vapor
