Good evening everyone,
I know its late and I should be sleeping, but I just had to write something. Its been too long and I miss it, plus I couldn’t wait to get to another post on cloud seeding.
***This is probably a good time to mention that reading my introductory post on Cloud Seeding will catch you up on everything you need to know for this post.
There’s so much I want to discuss when it comes to cloud seeding, from the ridiculous claims regarding chemtrails to China’s extensive program. But I don’t want to blow through it all too quickly; I enjoy the subject too much and want to have more posts to look forward to. Tonight I’ve decided to discuss cloud seeding as a possible tool against climate change.
There are no shortage of ideas out there on ways to reverse climate change; some sensible, others not, but an idea involving cloud seeding caught me eye last year. Cloud seeding is usually used to create rain, but the process can be used to produce a variety of different results. To combat climate change, scientists could use seeding to brighten clouds. The brightened clouds would reflect more solar radiation back in to space and cool the planet. And why do brighter clouds do this? Albedo!, which it seems will be involved in over half my posts. Maybe the Wiki page for albedo should have a link in every post.
Marine Stratus Clouds
Now if you’re going to conduct a program of such scale you’ll want to maximize your chances. You’ll need large, semi-permanent cloud decks where seeded clouds will remain stationary for maximum effect. As it so happens, there are several areas that fit this criteria over the world’s oceans. Marine stratus decks, like the one that brings San Francisco its morning fog, form where air is sinking from above and upwelling keeps the ocean water cool. The subsidence, or sinking, creates an inversion (warm air over cool air) that prevents air from rising further and holds the clouds in place. Marine stratus decks cover thousands of square miles and sit in the mid-latitudes off the west coast of major continents. They are large, they are accessible, and they are consistently there.
For the stratus decks, this subsidence is caused by the Hadley cells, a global-scale air circulation caused by solar heating. I may get to this subject in the future, but for now here is the Wiki page.
Brightening the clouds
Think of an ominous storm cloud, what color is it? You’re probably thinking dark, anywhere from a dull gray to seemingly black. This is because of the large raindrops present in the cloud. Larger raindrops are darker because they absorb more light. The larger the droplets the darker the cloud, and therefore the more solar energy it will absorb.
To brighten a cloud you want to decrease the droplet side, and cloud seeding is a great way to do this. The seeding adds cloud condensation nuclei into the cloud deck, and the available moisture is spread across more droplets, decreasing the average size and reflecting more sunlight.
The marine stratus decks already reflect a lot of heat. Check out the next image, it shows the radiation balance of difference areas across the globe. Red areas absorb more radiation then they emit, and blue areas emit more then they absorb. The white regions marked by arrows are regions where marine stratus decks exist, and these areas do not have the positive balance that most regions at the same latitude. The clouds are reflecting a significant amount of incoming radiation from ever reaching the surface.
A Proposed Program
The idea for cloud brightening was hatched back in 1990 by John Latham, a British cloud physicist. His calculations has shown that increasing the reflectivity of maritime clouds from 50 to 60 percent would offset the warming caused by a doubling of natural carbon dioxide levels. The current lead researcher on the subject, Stephen Salter, has proposed a fleet of 1,500 ships equipped to suck ocean water and spray a fine, salt water mist into the clouds. For the project Salter has developed nozzles with small-enough perforations to produce the correct size particle.
The idea is ambitious, with a conservative cost estimate of $2.5 billion. It will be hard to find a backer without more research, but with the USA’s budget in the trillions you could imagine such a program in place in the future. Climate change should be solved by switching from fossil fuels to nuclear, wind, or solar power, but they may comes a point where political realities create a need for other options.
I guess that’s enough for tonight, e-mail me any questions you have on cloud seeding or any other weather topic. And don’t forget to hit the Twitter follow button up top. Thanks for readings again!
Til next time,
~Wildcard
wildcard weather 