The latest emissions data from the International Energy Agency suggest that our current methods for dealing with climate change have not worked.
This means we will have to adapt to climate change, for example by selecting crops more suited to a warmer climate and abandoning low-lying coastal areas.
But adaptation cannot be our only response; there are limits to adaption, particularly if the rate at which temperature rises is such that the natural ecosystems we depend upon cannot adjust in time.
That leaves mitigation as our main response. We could:
- reduce fossil fuel use by using alternative energy sources
- employ carbon capture and storage to prevent fossil fuel carbon dioxide from entering the atmosphere
- use energy efficiency and conservation to cut overall energy use
- geoengineer the Earth’s climate.
The continued steady rise in atmospheric greenhouse gas concentrations, especially from fossil fuel combustion, has shown the first three methods to have been ineffective so far.
Because of this failure, geoengineering is being increasingly considered, and has even been cautiously endorsed by the Royal Society in the UK.
Geoengineering can be defined as the purposeful manipulation of the climate on a very large scale.
The general idea is to increase the Earth’s albedo. This means reflecting more incoming solar radiation back into space, before it is absorbed by clouds, land and oceans.
The most commonly canvassed method is to introduce millions of tonnes of fine particles (sulphate aerosols) into the stratosphere. Other methods (such as placing several thousand square km of reflective mirrors in space) have also been proposed.
We could place aerosols, for instance, by loading the particles into naval cannon shells and lofting them upwards from ships in tropical waters.
Because the aerosols would be rained out of the atmosphere every couple of years, we would need to continually replenish the supply.
We do have some idea of the probable effects because of our experience with massive volcanic eruptions.
The 1991 Mt Pinatubo eruption in the Philippines ejected some ten million tonnes of sulphur into the lower tropical stratosphere.
This led to a significant global cooling of 0.5ºC in the following year. Similar effects have been observed following other major volcanic eruptions.
This natural geoengineering tells us several things:
Aerosol placement would act rapidly to cool the climate.
The tropics are the best location for aerosol placement.
If serious side effects are found, it is easy to end the intervention by not renewing stratospheric aerosols.
Another important advantage of geoengineering is that it promises to be far cheaper than the other mitigation methods already mentioned.
But the potential risks from geoengineering are already becoming apparent, even before it has been attempted.
We face two CO₂ problems, not just one.
And unlike the global warming problem, there is no argument about progressive ocean acidification.
This occurs because of rising levels of dissolved CO₂ in the oceans, the fate of about half of all emitted CO₂ to the atmosphere.
Acidification will eventually inhibit or slow calcification in some marine organisms such as corals and some zooplankton, with potentially devastating consequences for ocean ecosystems.
And unfortunately, geoengineering cannot help with this problem.
Because geoengineering does not reduce CO₂ emissions, it cannot reduce the effect these increasing CO₂ emissions have on the acidification of the ocean.
Unless CO₂ emissions are reduced, oceans will continue to acidify irrespective of any geoengineering.
(Alternative proposals are to dump chemicals in the ocean which neutralise the effect of CO2, but this is not geoengineering.)
Climate models and the experience of large volcanic eruptions point to another problem.
Geoengineering will lower global rainfall, which will not be welcome in an increasingly water-short world.
And what would happen if the side effects of geoengineering were so serious that we had to stop?
The world’s temperature would rapidly rise to the level it would have reached without aerosol placement, because of the higher CO₂ atmospheric concentrations from continued releases.
It is this abrupt temperature rise that poses a serious threat to the viability of many natural ecosystems. We would be riding the tiger’s back – dangerous to stay on, dangerous to get off.
Whatever the balance of the benefits and costs of geoengineering, it’s clear that neither will be shared uniformly across the globe.
There will be winners and losers. Unlike carbon mitigation, aerosol placement could be implemented by a group of nations (think OECD) or even by one nation.
It is unlikely that the country or countries initiating the action will want to be among the net losers. Given the history of weather modification for military purposes, geoengineering is unlikely to be politically feasible in our divided world.
Mitigation – stabilising CO₂ levels or even returning to earlier, lower levels — is the only safe approach.
We will have to cut emission levels fast, but have little time to act. It will require an end to our economic growth obsession.
An extension of this argument can be found in Damon and Patrick’s book: Rise and fall of the carbon civilisation