The concept of marine cloud brightening is based on the idea that making clouds brighter or whiter can reflect more sunlight back into space. This reduces the amount of heat absorbed by Earth's atmosphere, offering relief from the impact of rising carbon emissions while we strive to reduce them.

Figure 1. How Cloud Brightening Could Aid in Fighting Climate Change.

It is believed that clouds over marine environments would benefit the most from these brightening efforts. But how exactly can a cloud be brightened, and does this approach work as effectively in practice as the theory suggests? Figure 1 shows How Cloud Brightening Could Aid in Fighting Climate Change.

The primary method scientists are suggesting to brighten clouds is by dispersing aerosols that contain fine particles of sea salt. These aerosols serve as 'condensation nuclei' in clouds, prompting water vapor to gather and form more droplets. This increases the concentration of droplets, resulting in thicker, brighter clouds. A similar effect occurs with pollution particles.

Determining the right-sized particles to deliver to the right types of clouds at the right times is a challenging task. These particles would also need to be dispersed on a large enough scale to achieve the desired effect of reflecting sunlight. Additionally, there’s the concern of potential unforeseen impacts on clouds or the climate.

Currently, most research is focused on small-scale experiments and computer simulations, though some real-world studies have sparked controversy. For example, in May, city officials in Alameda, California, halted a cloud brightening experiment after learning about it through media reports.

Meanwhile, experts have suggested that valuable insights could be gained from ‘natural’ experiments. Researchers examining clouds near Kilauea volcano in Hawaii found that the aerosols naturally produced during eruptions increased cloud cover by 50%.

Ultimately, the decision to implement marine cloud brightening on a large-scale rest with policymakers, who have yet to see sufficient evidence to support its benefits. However, as scientific understanding and the climate crisis evolve, this may change.

The Concept of Cloud Brightening

Marine cloud brightening is a geoengineering technique aimed at increasing the reflectivity of clouds over the ocean. The idea is that brighter clouds reflect more sunlight back into space, which helps to reduce the amount of heat absorbed by Earth’s atmosphere. This could provide a temporary relief from the warming caused by increased greenhouse gas emissions while we work to lower them.

How It Works

The process involves dispersing tiny particles of sea salt into the atmosphere to act as ‘condensation nuclei.’ These particles encourage water vapor in clouds to condense into smaller, more numerous droplets, making the clouds denser and more reflective. This increased cloud cover can help reflect more sunlight, which in turn reduces the amount of heat trapped by the Earth.

Marine Environments as the Focus

The marine environment, particularly over the oceans, is considered the most suitable area for cloud brightening. This is because oceanic clouds naturally have a higher albedo (reflectivity), meaning they are more likely to benefit from added particles. Since the oceans cover most of the Earth’s surface, cloud brightening could have a significant impact on global cooling.

Challenges and Risks

While the idea sounds promising, there are significant challenges. It’s tricky to determine the correct particle size and distribution needed for different types of clouds. Large-scale deployment is necessary for noticeable effects, and there are concerns about potential unforeseen consequences. For example, the introduction of aerosols might unintentionally alter weather patterns, cloud formations, or ocean currents, creating unintended side effects on global or regional climates.

Current Research and the Way Forward

Most research on marine cloud brightening is still in the experimental stage, with small-scale trials and computer simulations being conducted. Some natural ‘experiments,’ like eruptions from Kilauea volcano, have provided useful data about how aerosols affect cloud cover. While the technique is intriguing, policymakers are cautious, as they haven’t seen enough evidence to fully endorse it yet. Its future will depend on further research and the progression of the climate crisis, but it’s clear that marine cloud brightening should be considered a complementary approach rather than a standalone solution.

Source: Science Focus

Cite this article:

Priyadharshini S (2025),"How Brightening Clouds Could Help Combat Climate Change",Anatechmaz ,pp.128