Whitening the atmosphere....

Hey all, so after a week in Greece with leading scientist in the past global and regional climatic change, Mark Maslin, the topic of climate change came up! This coupled with one specific day devoted to understanding micro-climates has inspired the blog post of today!

A couple of years ago, I went to San Francisco. Now seeing how the city is located relatively close to regions such as Los Angeles and Las Vegas, and I was going in summer, I packed very few warm clothes. My family and I realised only after a couple of hours that this was a big mistake. Therefore, we now each have a very warm fleece with a San Francisco label on it that we say we bought as a souvenir on our very first day!. So why am I going down memory lane? And what does this have to do with climate change and micro-climate...well when looking into the concept of micro-climates during the fieldtrip, we learnt the importance of cloud cover and how the concentration of cloud cover influences the amount of solar radiation that reaches the ground. When using this understanding along with typical photos of San Francisco’s Golden Gate Bridge (see Figure 1), the cold temperatures experienced on my summer holiday are now very much understood!

Figure 1:

This brings me on to one geoengineering approach that I have particularly found interesting: the idea of enhancing cloud albedo. The idea that by increasing the white and shiny parts of our earth to increase solar reflectance and reduce temperatures; without severely altering ecosystems or polluting the atmosphere or even crossing the border into space, seems like a wish come true. And people like John Latham put across a very convincing argument!

In the same way that San Francisco has its fog and cloud cover to protect it from the sun, academics such as John Latham and Steven Salter, argue that this idea could be replicated and could influence temperatures on a global scale. Using a fleet of futuristic cloud seeding yachts (see Figure 2) that work by atomising sea water to feed clouds, making them denser and more reflective, the temperature of the earth could be influenced. 

Figure 2:

As the sea water is sprayed into the atmosphere, the freshwater evaporates leaving salt particles which rise into the clouds, attracts water vapour, condenses and increases the density of the clouds. Latham predicts that the warming produced by carbon dioxide emissions could be balanced by 15-20% increases in cloud cover (Latham, 1990). This would roughly equate to 500 litres of water being sprayed into the atmosphere per second, which would require 50 ships to be built per year to keep temperatures stable. This seems doable, especially compared to more radical ideas of solar shades in space.  

So now that we know the science, lets break down this option to see if it is viable solution to climate change?

Advantages: (Latham, 2002)

1. The amount of cooling can be controlled by measuring cloud albedo and using satellites
2. If any unforeseen or adverse impacts occurred, the entire system could be switched off, and cloud properties will return back to normal after a few days
3. This action is benign ecologically and also would not contribute further GHGs

Disadvantages: (Latham, et al.,2008)

1. A lot of further work and understanding is needed
2. Increased water vapour between the oceans and clouds is likely to have a high impact in localized regions
3. If implemented on a global scale, it would result in significant changes to the distribution of temperatures
4. Since the cloud albedo is enhanced only over the oceans, this may result in changes to the land-sea temperature gradient which drives precipitation
5. Unknown climatic impacts e.g on storms

Overall, like with the other Geoengineering options discussed, further work is desperately required (Feingold, et al., 1999). John Latham appears to be spearheading the research in this field, without little opposition or debate regarding the science (He has his name in nearly every paper read on enhancing cloud albedo..the few that exist anyways!). I would feel a lot more comfortable if we threw some more academics into the mix to join in the debate and extend the understanding of what could be a viable option to ameliorate the impacts of climate change!