Sunlight Reflection Management Primer
Recent News
In January of 2024, the Kleinman Center for Energy Policy published “An Assessment of the 2023 White House Research Plan and Recommendations for Future Research Governance.”
On November 2, 2023, renowned former NASA scientist James Hansen and his colleagues held a webinar in which Hansen spoke of SRM: “When Pinatubo went off, it put aerosols in the stratosphere, which changed the planet’s energy budget by three watts per meter squared reduction. If you had that now, that actually cools off the planet. That’s more than enough to put you from warming into cooling.” See 1:07:00 in the full webinar, here. Watch the four minute highlight YouTube video of the November 2, 2023 webinar of James Hansen and his co-authors, here.
The White House Office of Science and Technology Policy (OSTP) released a report in response to a Congressional mandate in the Consolidated Appropriations Act 2022 related to Sunlight Reflection Management. See this June 30, 2023 update.
A Brief Introduction to The Primer
In 1991, Mount Pinatubo (Luzon, Philippines) erupted in what was (by one metric) the largest volcanic eruption of the 20th Century, sending 17 million tons of sulfur dioxide into the stratosphere. At that elevation, it oxidized into aerosols, which in turn reflected sunlight. For the next two years, global temperatures were reduced by approximately half a degree Celsius.
The implications of that episode of planetary cooling may be significant, and scientists are studying whether sulfur dioxide ought to be intentionally released into the atmosphere at certain elevations and latitudes, and at certain times of year, in order to generate that same cooling effect again.1
SRMprimer.org aggregates foundational science involving Sunlight Reflection Management (SRM) and is designed to be a companion site to CDRprimer.org, which aggregates foundational science involving Carbon Dioxide Removal (CDR).2
It sounds like science fiction - a fleet of planes operating high above the Arctic, distributing sulfur dioxide to reflect sunlight.3 The fact that serious scientists are now researching it is unfortunately a testament to how dire our climate crisis has become.
There is no reason to think that SRM has the potential to reverse all of the damage caused by the climate crisis. Methane, once released, does not get recaptured into refrozen ice. Ocean acidification will continue until CO2 levels drop. And ice sheets, once melted, would require another ice age to reform.4
This four-page 2021 paper on SRM in the Arctic is an excellent place to begin: Sustaining the Arctic in Order to Sustain the Global Climate System.5
Created with the generous involvement of the Cornell University Climate Geoengineering group, the SRM Primer itself may be found [here][1]. We welcome your input to help us improve future versions.6
1. Scientists are also researching whether it would be better to use something other than sulfur dioxide.
2. The team that built SRMprimer.org is unrelated to the team that built CDRprimer.org, which is highly recommended. The work of its leaders Jennifer Wilcox and Jeremy Freeman are also highly recommended. If CDR scales to capture tens of gigatons of CO2 per year, there will be far less need for anyone to ever consider SRM.
3. Approaches aside from Stratospheric Aerosol Injection (SAI) are also being researched. One of the more viable of those is Marine Cloud Brightening (MCB), by which seawater would be pumped into the air, forming temporary reflective clouds, similar to the exhaust trails left behind by ships at sea.
4. See the work of the International Cryosphere Climate Initiative, most notably their November 2021 report.
5. The referenced paper focuses on the Arctic. However, research on regionality of SAI is nascent. The citation of this paper is: Bodansky, D.; Pomerance, R. Sustaining the Arctic in Order to Sustain the Global Climate System. Sustainability 2021 , 13, 10622. https://doi.org/10.3390/su131910622.
6. Two additional suggested resources are: For a scientific analysis of SAI, see the 2022 paper “A subpolar-focused stratospheric aerosol injection deployment scenario” in IOP Science. And, for an overview of Sunlight Reflection Management , see the 2022 book Pandora’s Toolbox by Wake Smith.
The Solar Geoengineering Primer
The Cornell University Climate Engineering Group co-created
this introduction to Solar Radiation Management (SRM) generally,
and to Stratospheric Aerosol Injection (SAI) in particular.
Continuing input is welcome from others, regardless of academic affiliation.