marked a new high for the third year in a row, according to the UN, the World Meteorological Organisation, NASA and other global observatories. Estimates indicate that global temperatures in 2016 ran 1.2 degrees Celsius above pre-industrial levels taking us dangerously close to the 1.5 degrees Celsius target included as an aim of the Paris climate agreement concluded in December 2015. It also means that 16 out of the 17 hottest years on record will have been this century [1,2].
As unwelcome as it may sound, it is unfortunately unsurprising that extreme weather and climate related events have damaged farming and food security, affecting more than 60 million people. With CO2 levels in the atmosphere also breaking a record in 2016, human-induced global warming is estimated to have contributed to at least half the extreme weather events studied in recent years, with the risk of extreme heat increasing by 10 times in many cases .
With climate change quickly reaching a tipping point, scientists are trying to develop ways in which the effects of climate change can be mitigated by intervening in the Earth’s natural processes and not simply reducing emissions. This approach is called geoengineering, climate engineering or climate intervention.
Such innovative methods for tackling climate change have gained popularity not only because of the quick results they may yield but also because in some ways they can be perceived as removing the urgency for amending our existing production and consumption models and transitioning to a low carbon economy.
What is geoengineering?
Geoengineering or climate engineering are umbrella terms used to describe two types of measures: carbon dioxide removal and solar radiation management .
The first, carbon dioxide removal, is a technology that seeks to address the cause of climate change, in other words the ever-increasing amounts of greenhouse gases, by removing substantial quantities of one of the key culprits, carbon dioxide, from the atmosphere.
The second, solar radiation management, follows a similar logic but rather than removing greenhouse gases it attempts to offset their effects by causing the Earth to absorb less solar radiation .
Developing and putting those technologies in practice sounds a bit like a science fiction novel. But there are scientists and experts that adamantly support research into such solutions. A number of organisations have already investigated whether climate engineering can make a real dent to climate change, including the US Congress, the National Academy of Sciences, the Royal Society and the UK Parliament.
There is of course some well-warranted hesitation given the fact that climate engineering requires a large-scale intervention to our climate which may have other unforeseen consequences. But proponents of geoengineering argue that the potential risks of such technologies need to be counter-balances with the overarching risk of climate change.
The controversy about safety of geoengineering methods
Most experts and major reports advise against relying on climate engineering techniques as a simple solution to climate change, in part due to the large uncertainties over effectiveness and side effects. However, most experts also argue that the risks of such interventions must be seen in the context of risks of dangerous climate change.
It is indicative that the UN Convention on Biological Diversity has cautioned against the impacts of climate-related geoengineering. More recently, in December 2016 when countries met in Cancun they adopted a decision to reaffirm the global moratorium on geoengineering that was adopted in 2010 . This development was partly in response to the 2014 report of the Inter-Governmental Panel on Climate Change which had referenced geoengineering; crucially however the report did not look at the environmental or biodiversity impacts of these technologies even though the report mapped out scenarios where those technologies were used to limit the increase in global surface temperature to 2 degrees Celsius by 2100 .
But despite these concerns, in March 2017, experts gathered in Washington DC to discuss the potential of climate-related geoengineering. As greenhouse gas emissions are not falling fast enough and climate change is affecting an ever-increasing number of people, these experts are arguing that further tools need to be considered as part of our arsenal to combat climate change. During this meeting, they acknowledged that there are barriers towards deploying climate engineering technologies, not only in terms of the impacts of the technologies but also because of an appropriate governance structure.
Ultimately, the all agreed that more research needs to be conducted and that the research agenda must include an open, international debate about how to deploy these technologies and how it would affect society and the natural system. Their message was to remove geoengineering from the science-fiction world and start looking at it as a potential solution to be deployed in a few decades [6,7].
Closer look at discussed geoengineering technologies
Given the ongoing debate about these methods, it is worth considering their technologies and what they involve in practice [8,9].
As mentioned earlier, solar radiation management or solar geoengineering aims to reflect a small proportion of the Sun’s energy back into space, to counteract the temperature rise caused by increased levels of greenhouse gases in the atmosphere which absorb energy and raise temperatures. This could be done in several ways:
- Albedo enhancement or modification: this involves increasing the reflectiveness of clouds or the land surface so that more of the Sun’s heat is reflected into space by placing numerous and flexible reflectors on the ground.
- Space reflectors: a similar concept where space reflectors would be placed in orbit around the Earth blocking a small proportion of sunlight before it reaches the Earth.
- Stratospheric aerosols: this would involve releasing into the atmosphere various types of reflective particles to reflect some sunlight before it reaches the surface of the Earth.
Carbon dioxide removal or carbon geoengineering, directly counters increased greenhouse effects and ocean acidification by removing carbon dioxide in the following ways:
- Afforestation: global-scale tree planting effort.
- Bio-energy with carbon capture and sequestration: growing biomass, burning it to create energy and capturing and sequestering the carbon dioxide created in the process.
- Ambient Air Capture: developing large machines that can remove carbon dioxide from the air and store it elsewhere.
- Ocean Fertilisation: adding nutrients to the ocean in selected locations to increase primary production which draws down carbon dioxide from the atmosphere.
- Enhanced Weathering: exposing large quantities of minerals that will react with carbon dioxide in the atmosphere and storing the resulting compound.
- Ocean Alkalinity Enhancement: adding limestone, silicates, or calcium hydroxide to the ocean to increase its ability to store carbon and ameliorate ocean acidification.
As interesting as these technologies appear to be, it is worth noting that some types of carbon dioxide removal are already taking place in terms of halting deforestation or restoring peatlands. However, the scale at which these efforts would have to be taken to have a substantive effect on climate change is unprecedented.
Moreover, the effects of technologies such as solar radiation management are almost entirely unknown. And while the challenge of climate change creates a moral imperative to leave no stone unturned, it is widely understood that these technologies are not a silver bullet, but rather a powerful supplement to eradicating carbon emissions. So while research into technologies such as geoengineering can be pursued to determine their safety and cost it should not be at the expense of implementing changes to deliver zero emissions.