The issues with Ozone

Ozone depletion, the process of O₃ being ‘destroyed’ follows the free radical substitution mechanism by which a radical (typically molecules containing halogens) initiate a reaction with Ozone which propagates. This propagation involves the destruction of Ozone and the conservation of the radical producing a chain reaction. A common misconception is that Sulphur Dioxide directly causes Ozone depletion. It doesn’t. The presence of Sulphur species in the Stratosphere act as a surface for these reactions to occur, hence they are named heterogeneous reactions.

Using the Whole-Atmosphere Community Climate Model, Rasch et al., produced the figure below to spatially represent the differing concentrations in ozone for a baseline and geo-engineering scenario in Antarctica; images a) and b), respectively. Image b) shows a greater region of ozone loss with the geoengineering simulation showing a reduction up to 60° away from the pole. Ozone concentrations are given in Dobson Units (DU), the geo-engineering results show an increased rate of ozone depletion with a difference of 25-35 DU compared to image a).

The authors realise, to better quantify the risk geo-engineering poses to ozone research must be conducted to better represent aerosol dynamics and chemistry in the computational fluid dynamics models utilised. Although a better quantification is needed, it is still clear the risk geo-engineering poses to the climate system. Much of the concern, regarding a reduction in Ozone, are the health hazards associated with increased exposure at the surface to UV-B and UV-C. Again, it is here where perspective must be taken on the advantages and disadvantages of Stratospheric Sulphate Injection as a method of Geo-engineering. Polar regions are one of the greater beneficiaries for geo-engineering with respect to temperature, with respect to feedback systems and the sensitive eco-systems. Dr. Friederike Otto of the EnvironmentalChange Institute at Oxford University has recently reported arctic temperatures to be almost 20°c warmer than average, an event with a return period of 1/1000 years, and it was only in December 2015 the temperatures were very similar.

Could geo-engineering influence lightning?

The main draw to geo-engineering for me, specifically stratospheric sulphate injection was mechanisms in cloud condensation nuclei as well as aerosol optical properties and dynamics. Recently, I produced a literature review on the evolution of lightning with respect to climate change across the Contiguous United States (CUS). As I sit here now questioning life choices, I'm also questioning how would SSI influence lightning frequency? Would it even influence lightning frequency?!

I am well aware this question far surpasses anything I could achieve here, (possible PhD proposal? Comments welcome) but during my review I came across research by Tan et al., whom studied the Nanjing region of China and the influence pollutant aerosols had on the regions lightning frequency. Considering the variables of convertible available potential energy (CAPE), flash density and surface temperature against an aerosols optical depth they concluded a negative correlation suggesting aerosols dampen the electrification of a cloud as a result of their radiative properties. A previous study characterised flash density increased up to aerosol concentrations of 1000cm^-3 but decrease when levels exceed 1500cm^-3 though much more research is required to better validate such results.

Another consideration, the aim is to inject into the Stratosphere, these processes occur solely in the Troposphere which would then make the problem dependent on both the method of injection as well as sedimentation species and rates. 

P.s. I like this idea, a lot so be nice.

Discovery channel woes.

Whilst geo-engineering may be my one love in climate and atmospheric science, I have been trying to find a documentary, a worth while conference discussion, something I can share with you all in which hopefully you'll enjoy. 

Project Earth, airing back in 2008 on the discovery channel is a series where in each episode a new method of geo-engineering is discussed by leading scientists in respective fields. Episode 8 actually illustrates methods of carbon capture, as discussed previously in en earlier post, with David Keith. Even if you don't have time for all 8, I am well aware that is valuable time to be spent watching annual holiday favourites, 'Brightening Earth' and 'Fixing Carbon' were two personal favourites.

Whilst I look into the legality of recommending you towards illegal streaming sites, I have included a link to watch clips from the series via the Discovery Channel. Enjoy! 

An unlikely friend for a common foe.

Whilst geo-engineering, and specifically stratospheric sulphate injection, has very transparent advantages and disadvantages, yesterday I came across a paper and geeked out, massively. Xia et al., conducted research studying possible SSI scenarios and their influence on terrestrial rates of photosynthesis. The graph below extracted from the paper shows an RCP6.0 simulation as well as the G4SSA scenario which simulates injection of 8 Tg SO₂ yr^-1 throughout tropical regions between 2020 and 2070. The blue line is indicative of the latter simulation. Via increased photosynthesis rates the vegetation sink would proposedly increase in capacity by 3.8 Gt Cyr^-1, and in 2014 global industrial carbon emissions were estimated at 35.7 Gt Cyr^-1. The storage capacity of Earths vegetation could increase by over 10% of emission output. Obviously, the study carries multiple error estimates and to assume such research is fool proof would be naïve and this is noted, however, such research acts as a great argument against the mask geo-engineering perpetrates. Personally, I am very excited to follow the direction of such research by Xia et al., as this novel study has provided a strong foundation in which increased photosynthesis rates via SSI could be implemented further. Photosynthesis truly is an unlikely friend for Stratospheric Sulphate Injection.

A graph illustrating the photosynthesis rate for i) the RCP6.0 scenario run (red line) and ii) the G4SSA SSI injection scenario (blue line), extracted from Xia et al., 2016.