Cooling Earth to fight warming
Sulphur dioxide injection may be last tonodl in toolbox
Considerable progress has been made to move to renewable sources of energy, such as wind and solar power, and electrification of motor vehicles in an effort to reduce greenhouse gas emissions.
There have also been a few “carbon capture” pilot projects undertaken to remove carbon compounds from the atmosphere.
Despite these efforts, it will take at least a few decades to solve climate change.
It seems there is nothing more we can do to reverse global warming fast enough except one thing — cooling the Earth artificially until we get carbon dioxide (CO2) levels in hand.
In the mid-1970s, the term climate change meant global cooling since some scientists believed that we were in the beginnings of an ice age. I recall that a renowned climatologist in one of my graduate school classes predicted that the Earth would cool as a result of reflection of sunlight back into space by increasing amounts of sooty industrial emissions made up of particulates and gaseous compounds, notably sulphur dioxide (SO2).
In contrast to CO2 and methane (CH4), which are the two gases largely associated with global warming, SO2 actually lowers atmospheric temperatures.
Air temperature measurements after volcanic eruptions attest to this phenomenon. Mount Pinatubo’s volcanic eruption in 1991 cooled the Earth by 0.5 C.
It has been said that we just need more Pinatubos to counter global warming.
WORTH THE RISK?
However, there are also risks associated with SO2.
When SO2 reacts with water, oxygen and other chemicals, it forms an acidic aerosol, commonly known as “acid rain.” To offset the detrimental effects of acid rain on nature and human health, governments mandated reductions in smokestack emissions from power plants and factories (particularly coal-burning ones) and shipping, which were the primary sources of particulate and SO2 emissions into the atmosphere.
While this approach was largely successful at dealing with the acid rain problem, CO2 and CH4 emissions continued to grow as a result of burning other fossil fuels for energy generation.
While cooling of the Earth with SO2 is predicted to lead to a loss of ozone, it would be less than existing contributions from large volcanic eruptions such as Mount Pinatubo. SO2 injection might have other unintended consequences, such as changes in precipitation patterns and shifts in weather systems, as well as ethical and governance concerns.
Fortunately (or unfortunately), the cooling effect of SO2 injection would diminish relatively quickly (compared to greenhouse gases) if the injections were stopped.
It raises the question: Can artificial injection of SO2 reverse global warming? The idea would be to fully offset the contributions of CO2 with SO2. At first glance, this approach seems feasible since it only takes one gram of SO2 to offset one ton of CO2. The most promising and perhaps the only way to do that is sending SO2 to the stratosphere — safer than current releases of SO2 into the lower atmosphere.
IS SO2 INJECTION FEASIBLE?
Scientists have modelled where to inject SO2 and have concluded that the optimal release location for widespread distribution would be at a high altitude (into the stratosphere at about 20 kilometres above sea level) close to the equator.
The operation is technically feasible using hot air balloons. The moment the particles are up, they start reflecting the sunlight. Within six months, we would notice a temperature reversal.
SO2 injection holds promise as a potential climate intervention strategy to reverse global warming by reflecting sunlight away from the Earth’s surface. The nature of it entails the risks and uncertainties of “meddling” with nature. Overreliance on SO2 injections could also detract from efforts to address the underlying drivers of climate change.
However, the time to accept the small risks associated with SO2 injection versus the potential benefits of fewer floods, droughts, dust storms and wildfires and having to deal with the broader effects of global warming — millions of deaths, famines, wars, mass migrations — may be closer than we think.
Ultimately, we may have to put our concerns aside and dip into the climate change toolbox to choose an “out of the box” technique like this one if global warming continues to accelerate at its current pace.