We Could Cool the Planet Almost Immediately—But We Need to Understand the Broader Consequences

You spent a few weeks in Prague. What impression did the Czech Republic and Prague make on you?

My time in Prague was wonderful! My colleagues in the Department of Atmospheric Physics, Charles University were very welcoming, and there is so much to explore in the city. Some of my favorite places were Vyšehrad, the Průhonice castle and park, and Nový Svět (I didn’t know that Tycho Brahe lived here!). I was also impressed by the public transit system which made it so straightforward to get around the city. After two weeks, I still feel like I barely scratched the surface!

How do you collaborate with Czech scientists? And how did this collaboration even begin?

I met Eva Holtanová, an associate professor in the Charles University, while she was visiting the Colorado State University, Department of Atmospheric Science on a Fulbright fellowship in 2025. At the time, I was a Ph.D. student in the department and we found that there seemed to be the potential for synergies between her work, the work of her colleagues, and my research area in climate science, ecosystem change, and data science. I was honored that her department invited me to visit this year to talk about my research and provide workshops about data science methods such as neural networks that many scientists here were interested in applying in their work. One of the best things about science is its collaborative nature. I’m excited to continue working with the people here after my visit!

One of your joint research topics is the so-called climate interventions. What exactly is it about?

Climate intervention refers to the study of potential methods to intervene in the Earth system to reduce risks from climate change. These include a broad range of approaches, from those that would remove greenhouse gases from the atmosphere to those that would hypothetically directly cool the planet. Climate interventions are not a substitute for efforts to reduce greenhouse gas emissions. However, they may be a potential way to complement those efforts by reducing risks from climate change while decarbonization continues.

Deliberate climate intervention is no longer just the domain of science fiction films or books. When did geoengineering become a serious research problem and what sparked interest in this area?

Research on deliberate climate intervention dates back to the middle of the 20th century–stratospheric aerosol injection was first discussed by scientists in 1977. In recent years, recognizing the slow pace of emission reductions and increasing impacts from climate change, leading scientific organizations such as the United States National Academies of Sciences, Engineering, and Medicine, the United Nations Environmental Programme, and the World Climate Research Program have called for further research on this topic. These organizations emphasize the need for research into fundamental questions about the physical processes involved and broader implications for society to make sure that any future public discussion considering these interventions can be informed by evidence.

Among the most discussed is the SAI method inspired by volcanic eruptions. How should it work?

Stratospheric aerosol injection (SAI) is a hypothetical method of climate intervention to emit reflective particles into the upper atmosphere (higher than where most airplanes fly), where the particles would reduce temperature at the surface by reflecting away a very small portion of incoming sunlight. These processes occur naturally after volcanic eruptions: for example, after the eruption of Mount Pinatubo in 1991 global temperatures were reduced for approximately 2 years. SAI would involve deliberately mimicking these natural processes for an extended period of time while society continues to reduce greenhouse gas emissions.

How are methods like SAI tested? How realistic is it that they could one day be put into practice?

SAI is currently tested primarily through computer simulations using the same models that are used to make projections about future climate change. We additionally use observations of naturally occurring processes, such as volcanoes, to test whether these models effectively represent the real world. SAI is not presently tested by directly carrying out experiments in the real world. It is technologically possible to deploy SAI with near-future aerospace technology. Key questions include what the subsequent effects on the climate would be, where the benefits would be felt, and who would bear any risks that arise.

Video introducing climate interventions. More videos by D. Hueholt and collaborators on the topic are available here.
(Art by Heartwood Visuals)

Can climate interventions function as an effective defense against sudden climate change?

SAI intervention is sometimes visualized as an “emergency response option” to climate change since aerosols exert a cooling influence almost immediately after they enter the atmosphere. However, the impacts of SAI depend on characteristics of the intervention scenario, including where the aerosols are emitted and the amount of aerosols released. For example, prior research shows that a large intervention scenario that rapidly reduces global temperature could cause additional risks to ecosystems that are not adapted to fast temperature changes. A more moderate intervention that maintains global temperature and is carefully planned to maintain global atmospheric circulation patterns may have fewer side effects. Risks also include social questions beyond the physical climate such as how to maintain the intervention over a long-time horizon, or how natural variability in the climate system may affect whether SAI is perceived as a success or failure.

Given this dependence on scenario and the potential risks, an important broader question about these scenarios is how decisions about these interventions can be made in a just and inclusive fashion. Who would decide the “effectiveness” of an intervention, for example? These questions cannot be fully addressed through physical science alone and show the need for further scholarship that is conducted transparently and includes a diverse range of disciplines and voices from around the globe.

What brought you to climatology? What attracted you to this field?

Weather was one of my earliest interests when I was a child (my parents tell me that I learned to walk during a hurricane!) and one of the primary reasons I love it is because of its interdisciplinary nature. To study atmospheric science, one needs to draw on knowledge from many different fields ranging from math, computer science, physics, and chemistry. Climate science, and especially the study of climate intervention, then brings in even broader disciplines such as social science. I find this inherently interdisciplinary nature to be deeply compelling, particularly in how it encourages broad collaboration.

What specifically will you be collaborating on with your Czech colleagues?

One specific project that we are working on involves studying the speed at which different climate zones determined by temperature and precipitation conditions are moving in response to climate change. This will help us to test whether our traditional classifications for major climate zones of the world are still useful in a changing climate, or whether new approaches are needed to help inform management decisions and planning practice.