Solar geoengineering is the act of deliberately altering Earth's climate to mitigate global warming. Scientists estimate that it will cost just ~$36 billion over a period of 15 years to cool the planet.
But, is it safe?
With every year that passes by the carbon and climate problem grows even bigger. With every new scientific publication the consensus gets even stronger that climate change is not only real and man-made but its impacts are already upon us. The urgent need for unprecedented action means that very soon humanity would have to do anything and everything possible to address this issue and avoid the worst case scenarios. Solar geoengineering, which is the act of deliberately altering the Earth's climate system to counter man-made global warming, particularly solar radiation management is often cited as the last ditch effort to mitigate climate change.
Since the industrial revolution humans have emitted enough carbon dioxide and methane (both extremely potent greenhouse gases) into the atmosphere to increase the global average temperature by about 1°C. It is increasing further at the rate of 0.2°C per decade. This change is alarming because the enormous carbon emissions and subsequent warming are disrupting the natural cycles of the planet that humans and other species rely on, most importantly, the water cycle.
We are experiencing extreme precipitation, extreme droughts, super-charged storms and unpredictable weather conditions, among other effects. All the carbon that is in the atmosphere, most of it goes into the oceans which makes the ocean more acidic, combined with rising temperatures it is severely damaging marine life. The situation will only get worse if we continue on this path unabated.
Naturally, scientists and innovators across the globe are scratching their heads to come up with possible solutions to this precarious situation. While a vast majority of experts believe that reducing greenhouse gas emissions to zero should be our top priority, it is becoming increasingly apparent that this transition will be a long process with many hurdles along the way. Time is of the essence here.
We must come up with a 'Plan B' to deal with global warming.
One alternative approach that is proposed by many is solar radiation management (SRM). SRM methods work on the basic premise of reducing the total amount of solar radiation entering Earth's atmosphere by reflecting part of it back into space. Thereby, preventing warming by reducing the amount of radiation available for absorption by greenhouse gases in the first place.
Over the last decade, multiple potential techniques have been introduced by scientists to reflect incoming solar radiation. From placement of giant mirrors in space to injection of reflective aerosol particles into the stratosphere or brightening the marine clouds using small sea salt particles. Several studies have been published assessing the pros and cons of the different techniques in terms of technological, economic, societal and governance factors.
The leading approach among them is the injection of sulfate aerosols (tiny atmospheric particles) or their precursors at a height of ~20 km above the Earth's surface, into the lower stratosphere. These particles are known to reflect incoming solar radiation back into space and cool the planet. While there is no precedent of a large scale human experiment to actually prove this, there have been natural events which show that this is true.
For instance, in 1991, a giant volcano, Mount Pinatubo in the Phillipines, erupted, spewing out some 10 million tonnes of sulfur high into the air which was followed by a drop of ~0.6°C in global temperature for at least one year. Historically, it has been observed that major volcanic eruptions are followed by a dip in global temperatures, which has been attributed to the sulfur particles that are ejected into the atmosphere.
There are a couple of key aspects of SRM which make it a very attractive solution to mitigate climate change.
First and foremost, modeling studies show that the effect of SRM will be immediate, we will see the global temperatures drop as soon as we begin the program. Just like the climate response to the 1991 volcanic eruption was immediate.
Second, it is dirt-cheap (relatively speaking)! In almost all the studies so far, the estimated cost of solar geoengineering is only a small fraction of the costs associated with climate change impacts such as droughts, heatwaves, wildfires and super-storms.
Most recently, a study published in Environmental Research Letters  lays out a detailed 15 year plan for how we could use solar geoengineering in the future and how much it will cost. The total costs for this 15 year plan are estimated to be ~$36 billion. Where, ~$3.6 billion are the pre-deployment costs which include manufacturing costs of specially designed aircrafts that are capable of carrying millions of tonnes of sulfate aerosols and flying at ~20 km above the ground. Followed by ~$2 billion per year operational costs for running hundreds to thousands of flights which would loft increasing amounts of aerosols into the stratosphere each year, during the 15 year program.
These are peanuts compared to the costs of damages that would incur on the global economy if we take no action on climate change. 
While still in its early research stage, solar geoengineering appears to be a fast, cheap and technologically accessible solution to the greenhouse problem.
That begs the question, why is it not being used already?
Well, there is another side to the coin. Many experts fear that solar geoengineering, if implemented, will be another grand human experiment with mother nature (just like the burning of fossil fuels) and there could be unintended consequences. Some modeling studies show that SRM schemes deployed on a large scale could weaken the global water cycle.[5,6] This could lead to changes in regional rain- and snow-fall patterns around the world with consequences for freshwater availability and food production. Changing the stratospheric chemistry could also adversely impact the ozone layer which is essential for preventing harmful UV radiation from reaching the Earth's surface.[7,8]
Moreover, it is clear that solar geoengineering would at best be a 'quick fix' for climate change but not a real cure to the problem, which instead would be reducing greenhouse gas emissions to zero. Once initiated, it must scale up and continue indefinitely to counteract the growing greenhouse effect. If it is halted for some reason, the aerosol particles would eventually be washed out from the atmosphere in a couple of years and global temperatures will rise rapidly. Also, it does not help in any way in the problems that are directly related to excess carbon in the atmosphere. Air pollution and ocean acidification, for example, will continue to get worse with rising carbon emissions.
Considering all the open scientific, political, and societal, questions and concerns regarding SRM, research must continue in this area to better understand and evaluate this option. If at all SRM is to be considered seriously, it should be seen as a complimentary solution to reducing greenhouse gas emissions and not a stand-alone holy grail. It can certainly be useful in that it can buy us time to make the transition from fossil fuels to clean renewable energy. With the future climate change predictions getting more dire each year, it is an all-hands-on-deck situation. In the end, we might have to explore any and all possible solutions to tackle the most pressing issue of our time.
Last month the United Nations Intergovernmental Panel on Climate Change (IPCC) published its findings in a landmark report on the impacts of climate change in a 1.5°C warmer world as opposed to 2°C warmer relative to pre-industrial times (before 1850). The report is an exercise to assess the goals agreed upon at the COP21 conference in Paris to keep the global average temperature rise this century well below 2°C. A key focus was to outline the efforts that would be required to accomplish this incredible feat and the associated economic costs. The report bluntly states that nothing less than a complete transition from fossil-fuels to clean renewable energy worldwide is needed to reduce global greenhouse gas emissions to zero .
Having analysed more than 6,000 scientific studies, 91 scientists from across the globe concluded that climate change is already having significant and widespread impacts on all forms of life on Earth. The planet has already warmed about 1°C since pre-industrial levels and is gaining about 0.2°C every decade . There is enough scientific evidence now to show that rising temperatures are causing an increase in the frequency and intensity of heatwaves, droughts, wildfires, floods and extreme weather events around the world.
Such climate-related disasters incur huge costs on international economies every year.
In 2017 alone, US witnessed three major hurricanes - Harvey, Maria and Irma which cost the tax payers a whopping US$280 billion [2,3]. Same year Super Typhoon Hato that struck China and Hong Kong coasts raked up an estimated US $6.4 Billion in economic losses [4,5,6]. The recent unprecedented flooding in Kerala caused extensive damage to crops and infrastructure to the tune of US$4 billion. While these numbers seem unfathomable, the IPCC report projects that by 2100 the total cost will be nearly $54 trillion dollars in global damages in the 1.5°C scenario and $69 trillion in the 2°C scenario .
The IPCC report is especially significant as for the first time ever a UN report put a price tag on climate change. These calculations are not limited to the cost of damages done to the environment and the various ecosystems but also include costs of the widespread adoption of new and disruptive technologies needed at a rate the world has never seen before. Entire sectors of the global economy like transportation, distribution and heating will have to transition off of fossil fuels and onto renewable or other zero-emission sources of energy. There is a need for transformational change in all sectors of our economies to embrace policy changes in our effort to solve the carbon and climate problem.
This is easier said than done. In order to prevent 2°C of warming, greenhouse pollution must be reduced by 45 percent from 2010 levels by 2030, and 100 percent by 2050 . IPCC also estimates that by 2050 the use of coal as an electricity source would have to drop from nearly 40 percent today to between 1 and 7 percent. This implies that renewable energy such as wind and solar, which make up about 20 percent of the global electricity mix today, would have to increase to as much as 67 percent.
Laszlo Varro, the chief economist with the International Energy Agency rightly summarized the report ina LinkedIn post  by saying “The IPCC was very clear that the impacts of high warming is the equivalent of a national emergency but at a planetary scale.” Varro appraised the challenge in front of us; global investments in wind and solar, which currently total approximately $250 billion per year, would need to be increased several folds to meet the 1.5°C target. "The energy that you get from this $250 billion investment buys you the equivalent of 1 percent of global electric demand," Varro said. "But global electricity demand is growing at 2 percent per year, so you don't even catch the growth of global electricity consumption let alone rapid decarbonizing."
He goes on to stress in an interview to Inside Climate News  that only through sustained investment on a global scale can we begin to roll back some of the anthropogenic damage done to our planet. To keep global warming in check, the world will have to invest an average of around $3 trillion a year over the next three decades. The IPCC summarizes that the transformation will require a global investment in clean energy and infrastructure to the tune of $1.6 trillion to $3.8 trillion a year (in 2010 U.S. dollars), with an average of about $3 trillion to $3.5 trillion a year from 2016 to 2050 . Even though this might seem like a lot to ask, the authors of the report are still optimistic because this $3 trillion yearly investment compares to an estimated $2.4 trillion a year that would otherwise be invested in energy systems as it is.
Many researchers agree that the cheapest ways to reduce carbon emissions and raise money in the interim are through the implementation of a carbon tax and the ‘cap and trade’ approach. It is believed that until cleaner energy alternatives become cheaper, some form of a carbon tax should become the de-facto way of governments to reduce carbon emissions. The report states “A price on carbon is central to prompt mitigation”. It estimates that to be effective, such a price would have to range from $135 to $5,500 per ton of carbon dioxide pollution in 2030, and from $690 to $27,000 per ton by 2100 .
The process of translating the Paris Agreement into national agendas has already started as the 195 member states agree that with a modest increase in our electricity budgets we can ensure that the world is powered by sustainable energy considering the cost of no action grossly expedites global catastrophe. For instance, countries like Canada have already started levying a revenue-neutral tax by passing the “Greenhouse Gas Pollution Pricing Act” . The federal carbon pollution price will start low at $20 per ton in 2019, rising at $10 per ton per year until reaching $50 per ton in 2022. If such a trend continues, Canada will be well on its way to be in the $135 to $5,500 bracket by 2030.
Such a move seems almost impossible in the world’s largest economy and second-largest greenhouse gas emitter behind China, the United States, considering the current political climate. Lawmakers around the world, including in China, the European Union and California, have started enacting carbon pricing programs. These efforts are the building blocks of the international effort and together they can bring into effect the stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent the worst impacts of climate change.
While governments may be leading the charge in our fight for a cleaner and cooler Earth, big corporations seem to have joined the fray when faced with the rising costs of fossil fuel emissions and climate change. A research and sustainability advocacy group Ceres has been working with companies and large investors for years to help them understand both the risks to their portfolios from high-carbon sources and the opportunities of investing in cleaner infrastructure as renewable energy prices fall. Ceres has been partnering with corporate giants like Google and Apple who have instituted organizational change by purchasing enough renewable energy to cover 100 percent of their power needs recognizing the huge impacts on their future supply lines.
It is often a gripe with people who refuse to ‘believe’ the science behind climate change because the predictions seldom present a redeemable future and are deemed extremely pessimistic. In truth, the scientific community continues to remain optimistic and is offering us the tools for the planet’s survival, the only thing that stands in our way, however, is political will. Dr Drew Shindell, a climate scientist at Duke University, put the political view in perspective when he stated “For governments, the idea of overshooting the target but then coming back to it is attractive because then they don’t have to make such rapid changes. But, it has a lot of disadvantages. It's not necessarily asking for some new pot of money to be magically created, but its a redirection from investment in fossil fuels to efficiency and renewables".
Ceres has been advocating for some time now that achieving what they call the first clean trillion entails an additional $1 trillion in clean energy investment per year through 2050 to avoid the worst impacts of climate change is imminently feasible. Sue Reid, Ceres’ vice president summed it up nicely when he stated that "We are in an all-hands-on-deck situation that requires transformational change in the public and private sectors, the likes of which the world has never seen. Fortunately, we already have at hand a range of tools that are needed—from clean energy technologies to effective policy models—to get us there.” The only question is whether our elected representatives will acknowledge what climate scientists have been saying for decades now - the clock ticks ever closer to midnight.
1. IPCC, 2018: Global warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty [V. Masson-Delmotte, P. Zhai, H. O. Pörtner, D. Roberts, J. Skea, P.R. Shukla, A. Pirani, W. Moufouma-Okia, C. Péan, R. Pidcock, S. Connors, J. B. R. Matthews, Y. Chen, X. Zhou, M. I. Gomis, E. Lonnoy, T. Maycock, M. Tignor, T. Waterfield (eds.)]. In Press.
2. Costliest U.S. tropical cyclones tables update (PDF) (Report). United States National Hurricane Center. January 12, 2018. Archived (PDF) from the original on January 26, 2018. Retrieved January 12, 2018.
3. Blake, Eric S; Zelinsky, David A (January 23, 2018). Tropical Cyclone Report: Hurricane Harvey: August 17 – September 1, 2017 (PDF) (Report). National Hurricane Center. Retrieved January 27, 2018.
4. "Member Report: China" (PDF). CMA. China Meterelogical Agency. Retrieved 26 October 2017.
5. Nikki Sun (23 August 2017). "Typhoon Hato could cause HK$8 billion in losses after No 10 signal storm brought Hong Kong to standstill". South China Morning Post.
6. "Typhoon Hato losses around MOP12.55 billion". Macau News Agency. February 22, 2018. Retrieved September 7, 2018.
8. Inside Climate News Article "https://insideclimatenews.org/news/11102018/ipcc-clean-energy-transformation-cost-trillion-climate-change-global-warming-renewable-coal-fossil-fuels". Published October 11, 2018.
9. Greenhouse Gas Pollution Pricing Act (S.C. 2018, c. 12, s. 186) https://laws-lois.justice.gc.ca/eng/acts/G-11.55/
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