After several months of relative quiet there seems to be a flurry of activity in the UK climate conversation around 'geo-engineering'. Most recently there was a piece in the Sunday Times that labels geo-engineering "a bad idea whose time has come".
For folks who haven't been following this conversation, geo-engineering is an umbrella term for a wide range of approaches to reversing some of the impacts of climate change, usually involving some kind of pro-active scientific intervention or manipulation of the environment.
These approaches fall into two main camps. Those concerned with keeping temperatures down by reflecting sunlight are called 'solar radiation management' or SRM. They include, amongst others, mirrors in space, sulphate aerosols in the upper atmosphere (mimicking the cooling effect of a volcanic eruption), and cloud seeding or brightening in the lower atmosphere to reflect sunlight.
SRM approaches are likely to be cheaper and shorter-term in their impact (and therefore easier to 'switch on and off'). But while they might keep temperatures down, they won't completely reverse the impacts of climate change.
Changes in rain and snowfall patterns, for example, could stay the same or even get worse. And these approaches would do nothing to address the threat of ocean acidification, caused by the increased carbon in our atmosphere being absorbed by our seas.
The other set of geo-engineering approaches are concerned with drawing carbon dioxide out of the atmosphere, and so are called 'carbon dioxide removal' or CDR approaches.
These options include: dumping iron filings in the oceans to encourage phytoplankton and algae to grow and photosynthesize, absorbing and trapping atmospheric carbon; burning biofuels instead of oil and coal, and capturing the CO2 given off before it returns to the atmosphere; large-scale accelerated weathering of rocks that absorb CO2 as part of the weathering process; and even mechanical 'carbon scrubbing' - removing extra CO2 from the air by using 'artificial trees', as they're sometimes called.
CDR approaches are likely to be longer-term and more expensive than SRM approaches. But they do address the fundamental cause of climate change and ocean acidification, which is that there's more carbon in the atmosphere than humans have ever encountered before.
An important point to note, of course, is that very few of these approaches, either SRM or CDR, have been tested at any sort of scale. Most don't exist outside of a lab, and several haven't moved from the drawing board or the back of an envelope. Many may pose serious environmental risks, and major challenges in being deployed at any meaningful scale. This contrasts with low-carbon sustainable energy solutions, many of which are becoming increasingly mature industries.
All of this presents challenges for a conservation organisation like WWF. Clearly in a perfect world we wouldn't support the idea of deliberately tampering with the Earth's atmosphere. But to paraphrase the old joke, if you were to ask us how to get to a sustainable future, well, we wouldn't start from here.
Sadly, in this less than perfect world, we have been interfering with the atmosphere since the industrial revolution. We've been digging up every bit of fossilised carbon fuel we can find and burning it, releasing its carbon back into the atmosphere.
Our best data suggests that CO2 levels in the atmosphere didn't exceed 280 parts per million (ppm) at any time between 600,000 years ago and about 160 years ago. Since 1850, though, they've been climbing, and they're now at about 394ppm, and already hitting 400ppm in places.
So we need to know what our options are. Certainly by far the best option is to reduce our greenhouse gas emissions with huge urgency. There's only so much carbon we can put into the atmosphere without causing massive climate change - the so-called global carbon budget - and at current levels of growth in carbon emissions we'll have spent the lot in about 16 years.
So priority one is reduce, reduce, reduce. WWF and other organisations have shown that the world can shift almost entirely to sustainable renewable energy by 2050 based on existing, proven technologies - we must get on urgently with doing so. Like the process of grieving, the first stage of most people's reaction to climate change is denial, and false hopes of a simple geo-engineering solution to a changing climate must not be allowed to feed and sustain that denial, distracting from the very real emissions reduction work that needs to be done.
But so far it's clear that either the exhortations to reduce our emissions are not being heard quickly enough, or the world cannot respond quickly enough, because greenhouse gas emissions are still going up.
So any approach that would allow us to remove CO2 from the atmosphere without massive environmental side-effects would be extremely useful to know about, allowing us to add some 'credits' to the global carbon budget. This wouldn't be enough to make a huge difference, and certainly it doesn't offer an alternative to the global mitigation effort, but it might buy us a bit more time and compensate a little for some of our tardiness over the past few years.
So alongside our main efforts to reduce greenhouse gas emissions through smarter use of sustainable energy and through reducing and reversing deforestation, WWF is cautiously supporting research into geo-engineering approaches in order to find out what is possible.
Such research needs to be transparent and consultative, and any results need to be shared globally and freely. And clearly, because the atmosphere doesn't recognise human borders, any sizeable field experimentation quickly becomes international and potentially global in its impacts, and so will require global oversight and global representation. This is not something that can be done lightly if it's to be done properly.
Unfortunately most of the public talk around geo-engineering, including the piece in the Sunday Times, is tempted to focus on solar radiation management rather than carbon dioxide removal. Perhaps these approaches are easier to visualise by a generation brought up on Hollywood movies - or perhaps we're more inclined to look for a short-term techno-fix rather than a less dramatic and longer-term effort to clear up our own mess.
But whether or not SRM has any value as a short-term damage limitation exercise, the fundamental truth is that if we want our planet's climate to remain even vaguely stable - if we want to protect the Arctic and tropical coral reefs, and the people who depend on them - then we need to keep levels of atmospheric carbon as low as possible.
That may involve developing techniques to pull some of the excess carbon dioxide out of the atmosphere, so we ought to find out what's possible. But by far the best approach is not to put so much carbon up there in the first place.
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