Handling clouds that trap IR radiation is brilliant. So is using Solar Geo-engineering to inject sulfate aerosol. On paper, that is. But what if we shake them both together? Would the ring marks be gone?
Gomme or Bitters? Dash or Splash?
Geo-engineering, as a device to rein in global warming’s impact, has often stood on the rims of skepticism, contradictory-effects and the trade-off between pragmatism and conscience.
Apart from the ‘can we manipulate nature’ philosophical jigger that this genre of Climate-Change control is subject to, there are technical and commercial spill-overs too when we look at Geo-engineering from the glasses of scale and real implementation.
For instance, take a Solar Geo-engineering method that supposedly arrests some level of warming by deflecting Sun’s incoming rays by dispersion of light-scattering particles in a given strata of atmosphere. Then there are cirrus clouds which work in the realm of heat escaping the planet to outer space.
But Solar Geo-engineering, which has been proposed in numerous climate modeling studies, continues to face questions on the amount of precipitation change per degree of temperature change. Can it simultaneously globally restore both average temperatures and average precipitation?
Interestingly, the same question clouds the second approach too – can we tackle thinning cirrus clouds, but be sure of the amount of precipitation change per degree of temperature change in the right way?
If both the methods face doubts on their anti-polar impact on the increase in rainfall, could the matter be resolved by mixing them together instead of using them in a neat way? If yes, how can that get done without too much of a muddle?
Carnegie’s Ken Caldeira, Long Cao and Lei Duan of Zhejiang University, and Govindasamy Bala of the Indian Institute of Science have recently tried something radical and with a twist. They have gone ahead and experimented with a cocktail of these two approaches to understand decrease precipitation and temperature in the same ratios as they are increased by CO2, for simultaneous recovery of preindustrial temperature and precipitation in a high CO2 world at global scale.
This is more than some flairing because this is a study that, perhaps, investigated for the first time the idea of a ‘cocktail’ of Geo-engineering tools in straining out the side-effects that usually give too much of a sour taste to the real potential one can harness. Like those trade-offs between changes in temperature and hydrological cycle in response to Solar Geo-engineering.
So, some lab-talk now:
These researchers went ahead and probed the possibility of stabilizing both global mean temperature and precipitation simultaneously, by combining two Geo-engineering approaches. One was stratospheric Sulfate Aerosol Increase (SAI) that deflects sunlight to space, and the other was Cirrus Cloud Thinning (CCT) that enables more longwave radiation to escape to space.
These folks used the slab ocean configuration of National Center for Atmospheric Research Community Earth System Model, and simulated SAI by uniformly adding sulfate aerosol in the upper stratosphere and CCT by uniformly increasing cirrus cloud ice particle falling speed.
They, thus, show that by combining appropriate amounts of SAI and CCT Geo-engineering, global mean (or land mean) temperature and precipitation can be restored simultaneously to preindustrial levels (of course, under an idealised warming scenario of abrupt quadrupling of atmospheric CO2).
This also hints that by optimizing distribution of SAI and CCT Geo-engineering, we might be able to design cocktail Geo-engineering schemes that better meet our climate mitigation target, such as changes in temperature, precipitation, water availability, and crop yields. Who knows. if we can also stir together other types of geoengineering approaches, such as marine cloud brightening and CCT.
It is an interesting and important research as this tells that the mixture of other types of Geo-engineering approaches, such as marine cloud brightening and CCT, and other off-sets like land mean temperature and runoff, might also be good ingredients for a cocktail strategy and studies.
Prof. Bala, Indian Institute of Science
Prof. Govindasamy Bala, Center for Atmospheric and Oceanic Sciences, Indian Institute of Science gives us a sip of the why and how here as well as helps in distilling other issues that surround Geo-engineering all over the world now.
There is a lot that leaves the glass half empty – possible side effects, scalability constraints, commercial what-ifs, ethical dilemmas, technological angles and a lot more. Questioning and doubting is good. So is being discreet and cautious.
But what really matters is having all options for solving the climate crisis on the table and letting them have the ground of reasonable research before judging them either way. Like, Prof. Bala is not in favour of implementing Geo-engineering and talks about the ‘Slippery Slope’ but, he, nonetheless, encourages the spirit of finding out.
So, let’s hear him straight up.
How did you start working on Geo-engineering?
It was around 2000 when I got involved in modeling of geoengineering to check if certain kinds of geo-engineering proposals will work. Sometime in 2006, the Nobel Laureate Paul Crutzen wrote an editorial piece in a journal advocating research in this space. The reason is that there have been so many COP meetings in the last few decades but there is still no adequate degree of consensus or meaningful action on carbon dioxide emission reductions yet. After his paper, several scientists around the world jumped into the field of geoengineering. I am of the opinion that all options for solving the climate crisis should be on the table and should, at least, be accorded a reasonable level of research before judging them either way.
Do give a peek into what you have attempted here?
Cirrus clouds occur at high levels in the atmosphere and these ice-crystal clouds trap IR radiation much like the greenhouse gases. To reduce such clouds could mean reducing greenhouse effects. But cirrus reduction scheme alone cannot mitigate a substantial amount of global warming. The Solar Geo-engineering approach of injecting sulfate aerosol particles into the stratosphere, while offsetting global warming, would cause a reduction in rainfall. In contrast, a reduction in cirrus cloud can lead to a rise in rainfall so combining it with stratospheric sulfate approach creates a good trade-off. A Cocktail format can simultaneously restore pre-industrial levels of precipitation and temperature simultaneously.
How would you rate Geo-engineering solutions against the traditional approach of CO2 sequestration?
Geo-engineering solutions do not necessarily address the root cause of Climate Change. They can mask C02 effects.But some of the Solar Geo-engineering proposals are cheaper in comparison to conventional mitigation technology. Its effects are also more immediate while conventional carbon mitigation takes a minimum of a few decades to cause meaningful reduction in global temperatures. .
Can Carbon Removal be a good way of addressing the problem in a strong way – taking the bull by its horns?
It is again more like an engineering solution for solving the climate change problem. Any Geo-engineering solution, be it Solar Geo-engineering or CDR, would have a scale that would be as large as our current energy system. It would be massive and could be costly too. Many climate scientists, including me, are not in favour of implementing Geo-engineering but it is important to continue scientific research into it as all options should be on the table for solving the climate crisis. However, our first and foremost focus should be on carbon dioxide emission reductions.
Is a combination Solar Geo-engineering and CDR (Carbon Di-Oxide Removal) a good way to fill in the gaps that Climate Change Solutions have been facing? Can more than a ‘1+1’ mathematics work in such a combination? What other methods can fit together in a combination if someone wants to pick this approach further?
A suite of approaches can find some resonance in the real world where one may deploy a portfolio approach of solutions that combine Solar-oriented and Carbon-oriented approaches. However first and foremost, one should focus on emission reduction which can be achieved via conservation, improved energy efficiency and renewable energy resources.
As for CDR, yes, while it is less risky and good in many ways but it may not work so rapidly. If you need a faster and cheaper way to solve the climate change problem, solar approaches are the answers. But Solar Geo-engineering approaches could be risky. We could use Solar Geo-engineering to reduce global warming and simultaneously use CDR methods to remove carbon dioxide from the atmosphere. Once the CO2 levels are reduced to desired levels in the atmosphere, we can turn off Solar Geo-engineering.
How reliable are today’s climate models?
The climate models that we have today are definitely far more sophisticated than what they were 30 years back. These models are the only tools at our disposal to understand the sensitivity of our planet to any disturbance.
What role do local-global differences play?
Temperature metrics could mean different numbers for different regions – like a polar region vs. a tropical region. We have targeted the global mean levels in our study.
The study also put engineering aspects as one of the caveats. Could you explain?
It is about challenges like taking aerosols or aerosol precursors to the stratosphere, creating aerosol particles of the right size as well some design and technology resource-requirements pertaining to the context.
Surely, there must be some ifs-and-buts flanking such concepts?
Geo-engineering is a controversial idea and many are opposed to it because geoengineering involves not only science but also ethical and moral values. There is a fear that research into geoengineering could lead to the so-called ‘Moral Hazard’ problem: countries might stop working towards emission reductions as there could be an engineering solution to the climate problem. There is also the fear of ‘Slippery Slope’ – once a research program on Geo-engineering is initiated, we might ultimately end up implementing geoengineering. Developing a consensus on Geo-engineering is as challenging as arriving at a consensus on emission reductions in climate negotiation meetings.
What next can this move towards?
We know the science of Geo-engineering but the technology and engineering aspects have not been thoroughly researched yet. Most natural science research on Geo-engineering has focused only on climate modeling so far. Models are not perfect and hence there could be a lot of uncertainty. If we make progress on some small-scale experiments, that could help to improve climate models.
Interestingly, today we can thoroughly monitor events that are analogous to Geo-engineering – like major volcanic eruptions that happen once in 20- 30 years. If a major volcanic eruption like the 1991 Pinatubo eruption takes place in the future, we should be ready to study that carefully. So, a mix of modeling and observational studies will pave the road ahead.
Pratima H
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