Can't we just make the clouds brighter?

The next solar radiation proposal under scrutiny will be marine cloud brightening. This idea has been up in the air (get it?) since 1999 when it was first proposed by James Latham, a climatologist at the National Centre of Atmospheric Research. He proposed seeding marine stratocumulus clouds with seawater aerosols generated at the ocean surface (Latham et al. 2012) to result in additional cloud condensation nuclei within the cloud. These generated particles are held 1000 metres into the air, to help increase cloud reflectivity. Marine stratocumulus clouds cover over a quarter of the ocean surface and are hundreds of metres cubed in volume with albedos ranging between 0.3 and 0.7 (Hanson, 1991). Therefore by increasing the reflectivity of these clouds, it reduces a large proportion of incoming solar radiation to Earth and prevents excess warming induced by anthropogenic greenhouse gases.

In fact - did you know that clouds are already reflecting more than the amount of solar radiation which has been captured by anthropogenic carbon dioxide (Mims, 2009)? Ergo, Latham's idea utilises and optimises the current functionality of clouds to our advantage to reduce the induced impacts of climate change, and encourage a greater reflectivity of sunlight through the artificial generation of a seawater mist to the clouds in our atmosphere.

Source: Giphy

So how can we generate this additional seawater mist?

Many have debated different ideas; from collisions between air-saturated jets of water, a hydraulic equivalent of a photomultiplier, vibrating piezoelectric vapourisers, or to simply forcing water through 0.8 micron diameter holes in a wafer-thin sheet of Silicon. Over 1.5 billion holes would be required for a silicon slice only 20cm in width (Mims, 2009). This is an obstacle in itself- what is the most appropriate method? Silicon was suggested as the material of choice but its ability to withstand high pressure in experiments has been discouraging. There is also a need for uniformity in size of the water droplets, as to not run the risk of larger heavier droplets falling as rain prior to elevation of the mist (Mims, 2009).

Let's say hypothetically that the ability to generate a seawater mist is achieved- how are we to elevate it to 1000 metres high into the air?

Well, Stephen Salter from Edinburgh University has been engineering a concept of wind-powered, remote-controlled, unmanned Flettner vessels (Salter et al. 2008), otherwise known as 'albedo yachts' (see image below). The Flettner motors can transform wind energy into thrust to generate lift of the seawater particles upwards (Mims, 2009). Over 1500 of these vessels would need to be deployed worldwide and transforming 30 litres of saltwater per second in order to correspond to the rate of increasing carbon dioxide concentrations, but not without a hefty construction cost of between $3.2-4.8 billion (Mims, 2009)!

Source: UCAR

However, this idea has caused concerns, particularly with regards to changes in precipitation patterns. Plenty of General Circulation Models (GCMs) have been produced - including that by Latham himself, which all suggest that deployment of marine cloud brightening will cause a dramatic decrease of precipitation in the Amazonian Basin, and both the Hadley Centre and the UK MET Office in particular, suggested that desertification could result in the Amazon rainforest, as cooler temperatures, as a consequence of less incoming solar radiation, in the South Atlantic will result in less evaporation and therefore a reduction in excess of 1mm per day (Latham et al. 2012) of precipitation in the Amazon (Mims, 2009). If this were to occur, this would have huge implications on biodiversity- the rainforest is home to 40,000 plant species alone (WWF, 2014) and that's not even including birds, mammals, reptiles, fish, or amphibians! As well as social and economic consequences of livelihood and loss of homes.

Models have similarly suggested that under conditions of double the current carbon dioxide levels in the atmosphere, full seeding of marine cloud brightening would reduce precipitation in the Amazon, North America and South East Asia, but would however increase precipitation in Africa and Australia (Latham et al. 2012)! Is this a fair compromise to make? The influence of marine cloud brightening will definitely result in a global environmental change and affect the entirety of the global population.

Source: Eating jellyfish

So should maritime cloud brightening be given the go ahead? A complexity (as always) resolves in its application on the large scale- can we ensure success? Can we ever be certain that it will work? What if there are unintended consequences? Another trouble with this proposal is that it meddles with the dynamics of clouds, of which the microphysical processes are not yet even fully understandable within science. With so much uncertainty, how can we trust that the generated seawater mist will add to cloud condensation nuclei concentrations without a glitch? The problem of rainfall patterns similarly suggests corrections and certainty before deployment.

Rasch et al. (2009) have similarly suggested that an increase in planetary albedo cannot and will not compensate for increasing greenhouse gases especially in relation to consequences such as ocean acidification which could destroy many marine ecosystems. It merely provides extra time for us to ponder over future uncertainties and hopefully come up with an appropriate mitigation response.

However, the problem of time is that it always runs out.

Till next time!

S xx

Time to put your sun shades on...

So our first solar radiation method is: Sun shades- and no I'm not referring to these:

Source: Wry smiles

However, the concept does have the same effect!

Just like sunglasses, the purpose of the sunshade is to reduce incoming solar radiation, but instead from the top of the atmosphere to counterbalance warming induced by increasing greenhouse gases! Thin refractive mirrors reflect incoming solar radiation away from Earth, reducing the amount of radiation reaching Earth and warming the climate.

The 'Sun Shade World' was an idea proposed by Early in 1989. He proposed the implementation of a sunshade, composed of tens of thousands of metre-sized small spacecrafts, comprised of a thin refractive screen,  at the Lagrange Point (L1) between Earth and the Sun, which would be designed to reduce incoming solar radiation to Earth (Lunt et al. 2008). Lagrange points are "positions where the gravitational pull of two large masses precisely equals the centripetal force required for a small object to move with them" (NASA, 2012). L1 in particular is the point directly between the Sun and the Earth, and is approximately 1.5km away from Earth (Washington University) with the same annual orbit of Earth- 365 days.

Source: NASA

However, ultimately, does a solar reduced world solve any of our climate problems? Firstly, yes! By reducing incoming solar radiation, the sunshade would successfully reduce annual global mean temperatures to mirror that of the pre-industrialised world prior to 1750. This has been one of the main goals of mitigation strategies thus far, and scientific research has always encouraged attempts to return to pre-industrial levels, to re-stabilise our climate. A sunshade world can do this!

Interestingly, the world has been in a reduced solar radiation and high carbon dioxide level environment before in our geological past of the Cambrian era! This means the Earth has been in a similar climatic situation before, and it was actually an era of an evolution boom, with a warming climate and rising sea level (National Geographic, 2014).

However, reducing solar radiation does not dampen the effects of increased carbon concentrations in the atmosphere, and the forcings of radiation from increased carbon dioxide differs from solar forcings (Govindasamy & Caldeira, 2000). Firstly, carbon dioxide, and other greenhouse gases trap heat all day, all night, and all year round. Solar radiation, in contrast, is more attributed to daylight hours and is expected seasonally, and most abundantly towards the equator (Govindasamy & Caldeira, 2000), so it cannot completely characterise our pre-industrial world.

A Community Climate Model was produced by National Centre of Atmospheric Research (NCAR) which simulated three different global scenarios: pre-industrial, doubled carbon dioxide emissions, and finally, doubled carbon dioxide emissions with reduced solar radiation- i.e. geoengineering. From the three scenarios, the sunshade geoengineered response, cooled the climate the greatest by 1.88 Kelvin and particularly in the equatorial regions, but could intensify carbon dioxide's impact on stratospheric temperatures through enhancing stratospheric cooling (Murphy & Mitchell, 1995) which could lead to damage of the ozone layer (Houghton et al. 1990)!

Other issues of the Sunshade world, is it causes a reduction of intensity in the hydrological cycle such as a decrease in precipitation- particularly in the tropics, which has a web of social and economic issues attached, and in the Arctic sea ice melt would increase (Lunt et al. 2008). However most importantly, a dominant issue, and this has been highlighted above, is that carbon concentrations in the atmosphere will continue to increase. Therefore any atmospheric carbon effects will not be mitigated through the adoption of a Sunshade world. For example, ocean acidification will not be stopped, and the impacts this has for marine ecosystems is humongous, and has a domino effect on the ocean's future capabilities as a carbon store.

Also, lastly and foremost, is should this 'World' be adopted, what if a) it fails or b) we decide it needs replacing or no longer want to use it; this will cause a rapid increase in global warming, and as carbon concentrations were still increasing during the geoengineered time, this could have hugely adverse effects on the world, in terms of re-adapting to an anthropogenically intensified climate.

The 'Sunshade World' remains a proposal for the time being, and the list of uncertainties suggest if or when it is deployed, is a long way off, as does the economic expense of a few trillion dollars to spare. The only way this scheme could work effectively, is if carbon mitigation strategies are employed harmoniously, which could help reduce the rapid climate change potential, should the Sunshade be removed.

What do you think?

S xx

Solar Power!

Having assessed the opportunities that carbon reduction methods uphold in response to the ever increasing global warming... I think it is safe to assume that proposals so far are still very much hypotheses, and none are yet ready to be deployed across the globe (at least on the large scale in the case of biochar)- not to mention the fact that some responses cannot resist against rapid changes in climate, and lets face it, we need emergency answers and pronto.

Luckily, carbon reduction methods aren't the only answer; solar reduction methods are a second category of geoengineering proposals, aimed to respond to recent anthropogenic climate changes.

Solar radiation methods differ from carbon reduction methods as they are not designed to remove any atmospheric carbon concentrations but instead reduce the amount of solar radiation reaching the Earth, which is enhancing global warming.

Source: The Economist

The following posts will explore the different proposed methods of solar radiation management to ultimately allow us to draw a comparison against carbon reduction methods!

Here's a teaser trailer of what is yet to come! (As you can see there still remains controversy regarding the issues of climate change and global warming!)

Sourced from YouTube.

Ready?


S xx

Biochar

The final carbon reduction method that this blog will explore is upon us and how should we end this spell? With Biochar.

Biochar is created via a process known as pyrolysis, which is the combustion of organic material with little or no oxygen present. The outcome is a high density (black) carbon which can be used for carbon sequestration via underground terrestrial burial (Massachusetts Institute of Technology, 2009) (Seen below). Biochar has been championed due to its carbon storage capabilities, and its ability to enrich soils for crop production, hopefully enhancing a global food security (Levitan, 2010).

Source: DIY Natural

The idea to explore biochar as a carbon sequestration opportunity derived from the Amazon Rainforest. The terra preta soils were discovered to store 2.7 times as much carbon compared to regular soil (Glaser et al. 2001) but the idea had been speculated since 1996 by Kuhlbusch et al.

Biochar is actually produced by many farmers around the world as a fertiliser, and the pyrolysis is carried out in traditional kilns, which are easy to build and largely cheap to purchase (Massachusetts Institute of Technology, 2009). In order to translate biochar production onto a global scale, and as a geoengineering prospect, commercial pyrolysis machines are required. This is because the traditional method allows the escape of byproduct- synthetic gas (or syngas as it is known) which has a high carbon concentration and contributes to atmospheric carbon emissions. Commercial pyrolysis machines also reduce hydrocarbon levels, which also result from the pyrolysis process. It can be harvested as fuel if in liquid state, but residual (solid) hydrocarbons can actually limit crop productivity in plots with buried biochar. Ergo, commercial pyrolysis machines are therefore needed to prevent the result of residual hydrocarbon and have already solved the problem of potential carbon leakage to the atmosphere.

It has been suggested by Matovic (2011) that the combustion and burial of 10% of global biomass waste could sequester ~5 gigatons of Carbon per year. Putting this in perspective, humans emit 28 gigatons of carbon per year, of which a large proportion is taken up by the biosphere and oceans (Levitan, 2010) which means that global biochar production could have the potential to significantly reduce atmospheric carbon concentrations. Carbonscape have already been in talks of converting 930 hectares of land for biochar production (Monbiot, 2009) with hopes of being the first commercial company involved on a geoengineering scale!

Source: Re-Char

However, biochar has been a controversial proposal as to whether it really does classify as a geoengineering scheme. Surely it is just a method of carbon sequestration-  is its intent to be a large scale manipulation of the climate? This is why this post has become my ultimate carbon reduction post. Controversy revolves around its geoengineering status, but as long as it is still being considered as a potential geoengineering solution, it shall remain an interest within this blog feed!

Other concerns of biochar include that the global biochar initiative is subject to the same risks as any other carbon reduction method: The unknown. We cannot guarantee the outcome of global biochar- will it be successful? Can it respond to rapid climate changes? Will indirect consequences of land-use change or social or chemical problems arise? Similarly optimum biochar production would require a colossal number of commercial pyrolysis machines which is hugely expensive and largely impractical (Massachusetts Institute of Technology, 2009)! Can it possibly suit large scale implementation?

These questions are a constant to any geoengineering attempt, however, the difference between biochar and the carbon reduction attempts assessed so far, is that biochar is already happening at a local scale, and it is working. Even if this continued on a local scale alone, progress will be made to reduce atmospheric carbon concentrations, but as a geoengineering scheme- is it worth taking such a giant risk?

Apparently not yet anyway!

Source:Arctic Cartoons

Who knows, perhaps solar radiation methods will be more effective geoengineering techniques?

Until next time!


S xx