The Marine Cloud Brightening Program is an academic collaboration of atmospheric scientists and other experts to study how clouds respond to particles — also called aerosols — in the atmosphere. This research aims to further our understanding of how interactions between aerosols and clouds impact our climate system, and to investigate the feasibility and potential impacts of marine cloud brightening.

Overarching goals of the research effort are to:

• provide open, objective scientific information to improve society’s ability to understand the climate system and address near-term climate risk
• help expand the global community of scientists and stakeholders with access to this scientific information
• provide scientific data and information to inform regulation, governance and decision-making on atmospheric aerosols and climate

The Program includes multiple parallel research efforts in different areas to help achieve these goals, including global, regional and high-resolution modeling; analysis of observations; studies of sea-salt particle (aerosol) generation; and scientific studies using small-scale releases of particles into the atmosphere to help inform model simulations of their effects at larger scales.

Read more about the Marine Cloud Brightening Program here.

Program Governance

The Marine Cloud Brightening Program’s overarching approach to governance is to deliver open, objective scientific information in service of the public good in compliance with, and helping to inform, public regulatory and scientific review mechanisms and institutions. This approach emphasizes oversight by experts qualified to review and comment on the nature of the Program’s scientific research studies and their findings, including studies that include outdoor releases of aerosols. The program also promotes and supports extensive direct engagement with its studies from a wide array of stakeholders and the public.

Transparency and open science

The Program favors a high degree of transparency and activities that foster a broad research ecosystem and robust scientific assessment. Thus, wherever practical, the program will publish its findings and methodologies for peer review; support access to its data, models and tools; and provide input on scientific assessments. To date, various contributors to the MCB Program have been among the earliest to publish information about outdoor aerosol process studies and cloud aerosol experiments (Wood et al., 2013). The team is also collaborating with commercial cloud service providers on cloud-based deployment of models and data to provide greater accessibility for researchers globally.

Outdoor field studies and regulatory compliance

Scientific studies that involve releasing aerosol particles into the atmosphere are a common part of environmental research, for example, to inform projections of the impacts of pollution emissions. The Program is housed at the University of Washington, a public university in Washington state. The principal investigators for the Marine Cloud Brightening Program have extensive experience in observational campaigns to study aerosol emissions from anthropogenic sources. In this context, the program has adopted processes and controls to ensure compliance with Federal, state and local regulations as well as processes common to similar publicly funded field research campaigns in the U.S.

Scientific review board

The Program includes scientific review by an international set of scientific experts of the design of currently planned field programs. These are assessed, in writing, for:

• the value of the stated scientific objectives, within the larger goals of the MCB Program
• whether the planned observations, modeling and analyses are suitable to meet these objectives
• whether any intentional emissions included as part of the study could pose a measurable physical risk to the environment
• the feasibility of conducting the planned observations, modeling and analyses as described in the field study plan
• any additional areas of concern raised by scientific review board members

An expert panel was assembled for scientific review of planned coastal studies. Their report is available here.

Education and engagement

The Marine Cloud Brightening Program acknowledges a high level of public and societal interest in its areas of research, and as such, will support ongoing availability of information for the public, including online information and in-person engagement. It provides support for enquiries and makes experts available to media, educational organizations, policymakers and interest groups as feasible. Importantly, the Program seeks to engage a diverse set of stakeholders locally and globally on the research, and has established a facility to support direct engagement with outdoor atmospheric research.

Coastal Atmospheric Aerosol Research and Engagement (CAARE)

To support small-scale outdoor research on the basic science of aerosols in the marine atmosphere, as well as its objectives of fostering scientific collaboration and public engagement, the Marine Cloud Brightening Program is launching the Coastal Atmospheric Aerosol Research and Engagement (CAARE) facility.

Leveraging the new capability provided by the Cloud-Aerosol Research Instrument (CARI), CAARE is designed to:

• support scientific studies of the evolution and transport of aerosol in the marine atmospheric boundary layer in service of improving model representation of aerosol-cloud interactions, by our team and by other research teams globally
• provide information and tools for environmental and regulatory evaluation of aerosol releases
• inform models to support projections of the impacts of marine cloud brightening and to “off-ramps” for marine cloud brightening research, as recommended by scientists convened by NOAA
• provide a means of direct engagement with the public and other stakeholders, including Global South communities, Indigenous Peoples, youth, and historically underserved communities who are often the most vulnerable to climate change
• support K-12 STEM education on atmosphere and climate science
• support broad societal engagement and to benefit from input from a diverse community of informed stakeholders

This new facility is located in the USS Hornet Sea, Air and Space Museum, an Affiliate of the Smithsonian in Alameda, California. Working with the Hornet staff, our team is conducting science studies on the Hornet’s flight deck and engaging with visitors to the museum through educational displays and demonstrations.

In addition to its location in the marine environment and its ability to physically support atmospheric scientific studies and their operations, the site is rare in its ability to offer public engagement in the context of a museum. In this way, there are very few facilities in the world like it.

Atmospheric studies at CAARE

The CAARE facility is designed to support small-scale studies of the transport and evolution of aerosol particles in the marine atmosphere by releasing sea-salt particles and measuring their evolution over a small area outdoors in a marine environment. The studies involve intermittent brief releases of sea-salt particles, generally undertaken for 5-10 minutes (max 30 minutes) a few times a day, a few days a week, during different seasons of the year.

The goals of the study are to:

• Improve modeling of how aerosols interact with each other in the natural turbulence of the lower atmosphere
• Improve modeling of how a point source of aerosols at the surface is dispersed and spreads out in the lower atmosphere.
  • This will be of utility for modeling aerosol from point sources like smoke stacks and ship emissions, as well as a sea salt plume generated for marine cloud brightening studies
• Determine what the generated sea salt aerosol sizes are after mixing with ambient air, at up to 200 meters downwind of the CARI instrument
  • The aerosol size distribution at this distance is expected to be representative of what the aerosol size would be when it reaches clouds in our future studies over the open ocean

The studies and site are within the permitting boundary of the USS Hornet, in Alameda, California on the San Francisco Bay. As part of its compliance efforts, the program commissioned a review of permitting and other approvals, available here. The particle releases planned for the site are below the thresholds identified for approval processes or permitting requirements and do not include any regulated substances at the small scale they are being released. The studies at CAARE are not expected to have any impact on local weather or climate. However, the studies’ relevance to climate intervention research requires registration with NOAA’s Weather Modification reporting process, which was completed in March 2024.