There is no prospect of a magic bullet rescuing the world from the impact of global warming, scientists warned this weekend. As Earth completed the hottest month ever recorded on its surface, climate experts and engineers made it clear that only global reductions in fossil fuel burning could prevent the planet from entering an era of intense overheating.
There have been proposals that still-to-be-developed global technologies could avert impending climate catastrophe and prevent temperatures from soaring. Examples include projects that could capture carbon emissions and store them underground or schemes that could deflect sunlight away from Earth.
However, senior researchers say the only realistic hope for avoiding the worst impacts of climate change would be to halt the burning of coal, gas and oil. “The number one priority that we have is to replace fossil fuels with renewable energy sources,” said Dr Greg Mutch of Newcastle University.
“That is going to be critical. After you have done that, then you think about capturing any carbon emissions from industrial plants that cannot operate without producing CO2.”
Examples of industrial processes that produce carbon dioxide include cement and fertiliser manufacture. These generate carbon dioxide not just by burning fossil fuels for heat but as chemical byproducts from the processes involved in making these products. Industries like these generate about 5% of all carbon dioxide emissions, so it will be worthwhile tackling them, say scientists.
However, capturing carbon dioxide from the atmosphere and storing it underground – as a way to tackle the global problem of climate change – will be far trickier. Although massive amounts of carbon dioxide are emitted every year, it remains a very dilute component of the atmosphere. Around 400 parts per million of air around us is now made up of carbon dioxide. That is 0.04% of the atmosphere.
“That is very, very dilute and it will take an awful lot of energy to extract that carbon dioxide. From an engineering point of view, it’s much easier to separate a gas from a concentrated mixture than it is to extract a gas that is only 0.04% of the mixture,” said Mutch.
Nevertheless, some companies have begun development work on plants that would suck in air, extract its carbon dioxide and store it. The technology remains in its infancy and has not been helped by indecision over its use. The UK was one of the first countries to fund research into direct air capture and other greenhouse gas removal technologies by providing £100m in 2020 but since then has been overtaken by US funding of some $3.5bn on direct air capture alone.
“The problem is that climate change itself is already one huge experiment on our planet,” said Prof David Reiner of Cambridge University. “Now we are trying to combat that experiment with other experiments. That will have unknown consequences.
“On the other hand, I take solace from the fact that many more scientific minds are now turning to these problems, that more research is being started, and that a lot more public and private funding is going into ways of tackling global warming so there is room, in the long run, for some optimism.”
However, it is the second form of geoengineering – solar radiation modification (SRM) – that causes most unease. Among the proposed SRM projects are schemes that would scatter the upper atmosphere with tiny reflective particles, such as sulphate aerosols, which could then reflect sunlight back into space. Alternatively, this could be done by placing huge mirrors into orbit around Earth.
The problem is that such schemes would still allow carbon dioxide to build up in the planet’s atmosphere. The world might cool a little as sunlight was diminished, but how this would affect weather patterns is not clear. Carbon dioxide would still have to be removed some time in the future. More and more carbon dioxide would dissolve in the sea and ocean acidification would continue to intensify, triggering even more damage to coral reefs and other marine ecosystems.
Dismissing SRM technology, Prof Joeri Rogelj of Imperial College, London, called it “irresponsible, dangerous and a threat to the manageability” of our survival, saying: “It is not a solution but an extremely dangerous band-aid that covers up the global warming problem without healing it, creating a false and unwarranted sense of climate safety while the core of the problem continues to fester.”
