Response to Guardian article

July 18, 2012

David Keith and Jim Anderson

July 18, 2012

A response to "US geoengineers to spray sun-reflecting chemicals from balloon" (The Guardian, Tuesday 17 July 2012 08.21 EDT)

Recent media claims (see: that we have plans “... to spray thousands of tonnes of sun-reflecting chemical particles into the stratosphere…” in attempt to combat global climate change, are incorrect.

Instead, we are addressing the growing pressure to “geo-engineer” the climate by exploring techniques to demonstrate the effects of such proposals without adding the proposed sulfate species (which are naturally occurring in the Earth’s lower stratosphere) in any amount that could possibly alter the background stratosphere.

The Guardian article that first reported such claims (and subsequent articles mentioning the piece) was never fact-checked in even the most superficial sense with either one of us. A related New York Times article ( provides a more balanced approach and a piece in Business Insider also provides clarity (

In summary, we have been and are currently exploring possible new strategies for interrogating the stratospheric system without affecting the background stratosphere in any quantitative way. To date, we have not written any proposal to actually do so. We want to be absolutely clear that that we have no plans to implement a geoengineering field study to release “thousands of tonnes of sun-reflecting chemical particles into the atmosphere to artificially cool the planet, using a balloon flying 80,000 feet over Fort Sumner, New Mexico.”

It is premature to consider doing any such tests at a large scale to measure the climate response. Given the environmental threats to our planet and the growing pressure to seriously consider geo-engineering, we believe that we should actively begin to study (theoretically) what we might be able to learn if such proposals were advanced and ultimately undertaken.

We do not take the issue of geoengineering lightly. The care with which we have approached our research in this area over the decades speaks for itself.

David Keith, Gordon McKay Professor of Applied Physics at the Harvard School of Engineering and Applied Sciences and Professor of Public Policy at the Harvard Kennedy School, and James Anderson, Philip S. Weld Professor of Atmospheric Chemistry at the Harvard School of Engineering and Applied Sciences and Professor in the Department of Chemistry and Chemical Biology at Harvard University.