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48 A pair of aces up our sleeve in the fight against climate change?

Egon van der Loo

While “Wise men” continue to burn prehistoric solar energy, between the years 1980 and 2020, the yearly CO2 emissions have increased from ~20 billion tonnes to ~35 billion tonnes, an increase of 80%. In the scope of such increases, do we stand a chance to mitigate climate change? Could the Ocean and cloud albedo engineering help us in our endeavor?

Fertilizing the Ocean, a desperate cheat code to remove carbon from the atmosphere?

Some 350 million years ago, terrestrial plants, which are thought to have looked like green branches, underwent a severe selection process. Ever since their successful colonization of land, they were slowly but surely reducing atmospheric CO2. This induced a “famine” of carbon which resulted in plants having to innovate ways to capture the ever-decreasing levels of carbon dioxide. The outcome of this selection was the evolution of leaves, which greatly increased the exchange surface between plants and the air (Gosline, 2014), as well as the low levels of carbon dioxide (from a paleoclimatology perspective). Fast forward to the 21st century, as a result of our continuous CO2 emissions—now reaching ~35billion tonnes a year (Ritchie & Roser, 2020)—global photosynthesis levels increased by 12% between 1982 and 2020 (Lawrence Berkeley National Laboratory, 2021). Albeit this may seem beneficial as the biomass carbon sinks increase, a trade off with soil carbon stocks may be happening. Researchers found that “when plant biomass is strongly stimulated by [elevated CO2], [soil organic carbon] storage declines; conversely, when biomass is weakly stimulated, [soil organic carbon] storage increases” (Terrer et al. 2021), implying that as plant’s increase their biomass production with higher CO2 availability, they are inducing the release of carbon stocked in the soil. By contrast, the Ocean—a carbon sink just as important the others—does not present this issue.

The Ocean covers 70% of Earth’s surface and estimates say it has absorbed almost 40% of all anthropogenic emissions and stores some 143’000 Gt of CO2 (Stephen Rackley, 2010), which equates to about 4100 times our current yearly emissions. The main sources of carbon sequestration of our Ocean is photosynthetic plankton, dissolution of CO2 into carbonic acid (lowering the pH of oceans) and deadfall carbon (corpses that sink to the ocean floor). As an example, to illustrate deadfall carbon, scientists estimate that every individual whale “sequesters 33 tons of CO2, on average, when it dies and sinks to the ocean floor” (Chami et al. 2019). Scaling that up to the global level, if whale populations recover to pre-industrial whaling levels, some 160’000 tons of carbon could be sequestered every year through whale fall (Pershing et al. 2010). While that is negligible compared to yearly anthropogenic emissions, it only represents a minuscule fraction of the potential carbon sequestration the Ocean has to offer.

While terrestrial vegetation is, to some extent, limited by atmospheric carbon dioxide levels, ocean vegetation has always been greatly limited by nutrient availability. In that perspective, some researchers have suggested to locally supply, in a controlled manner, those essential nutrients in order to promote phytoplankton blooms which would in turn metabolize dissolved CO2, ultimately reducing its atmospheric levels. Lab essays seemed to indicate that for every ton of iron (an essential nutrient algae need) released into the Ocean, up to 110’000 tons of carbon could be removed from the atmosphere. Furthermore, computer models predicted that intentional iron fertilization could stimulate the Ocean to take up, in some regions, an extra 1 to 2 billion of carbon every year (Hugh Powell, 2007).

Although this may seem promising, there are some side effects to this method, such as altering ecosystem equilibriums. That being said, if emissions continue to rise and as desperate times call for desperate measures, perhaps this method can be a last resort to reduce atmospheric carbon and buy us humans more time.

 

Image n°1: Algae bloom in Lake Erie, USA. (NASA, Toxic Alagae Bloom in Lake Erie As Seen From Space, 2011)

Clouds to the rescue!?

For some regions of the world, the most pressing matter of climate change is water level rise. As of 2018, the average water level rose by up to 25cm, relative to 1901. A 2019 special report from the IPCC predicts that water levels will rise by up to 84cm by 2100, relative to 2005 (IPCC, 2019). The main contributors of sea level rise being volume increase due to thermal expansion and melting of land ice sheets (Glaciers, Greenland and Antarctica).

The rise of sea level poses a great threat to costal zones due to permanent loss of land, frequent floodings and salinization of soils and ground water, just to name a few. These threats will ultimately induce mass migrations, as people will seek new homes. To illustrate the scale of that issue, we can observe the sinking future of Jakarta, the capital of Indonesia. This coastal city, home to 10 million people, is not only threatened by sea level rise but is also literally sinking and it is foreseen that by 2050, 95% of the megacity will be flooded (Mei Lin & Hidayat, 2018). In view of that, one can ask: how do you re-locate a megacity in a world where humanity is trying to fight climate change? What will be the environmental cost of rebuilding this one megacity? Although rebuilding one megacity may seem plausible, an estimated 2 billion climate refugees will have to be re-homed by 2100, due to rising sea levels alone (Joe McCarthy, 2017). Furthermore, this number may increase further, post 2100, as sea level rise is not foreseen to stop any time soon.

In view of this global problem, Marine cloud brightening was proposed to try and mitigate climate change and potentially slow land ice sheets from melting and thus buying humanity some time to become sustainable. Essentially, this project aims to increasing the albedo and life time of stratocumulus clouds in order to partially reflect incoming solar radiations back into space (Geoengineering monitor, 2021). For instance, purpose-built ships could navigate around Greenland during the Antarctic winter and then sail down to the Antarctic Sea for the Antarctic summer all while shooting up sea water in order to maintain land ice sheets, somewhat, continuously hidden from the sun, resulting in slower melting of ice sheets. The presence of salt particles in the clouds increase the number of droplets, increasing the albedo of clouds, but does not encouraging precipitation.

Despite the climate models presenting promising predictions with regard to reducing incoming solar rays, no real time experiments have been conducted. Furthermore, a lot has still to be researched as, for example, weather patterns may alter which could result in ecological disasters in some areas.

Image n°2: An illustration of a Marine Cloud Brightening ships. (MacNeill J., n.d.)

Conclusion

Human lives do not depend on fossil fuel. However, our global economy does. Although it has done great things such as greatly reduce poverty and spread knowledge, it has also been eating away our only home. Albeit, these climate engineering ideas may seem like solutions for carbon sequestration and climate change mitigation, they do not address the root cause of the problem. Furthermore, with regard to climate engineering, could people get misled into the illusion that climate change is solved and they can therefore continue their fossil-fuel-dependent life styles?

Perhaps the next logical step, although very complex, would be to address the cause and move away from our global economy. While ambition can show the way, only our actions will get us there.

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