We are quite used to hearing warnings of 'catastrophic climate change' if we don't reduce emissions of greenhouse gases, but how many of us have a clear idea of what this might mean? An article published in New Scientist a few weeks ago looked at this issue, and it made me feel quite nostalgic for the things we used to worry about -- at least with a nuclear war you have a chance of missing the worst by getting killed quickly at the beginning, and running out of fossil fuels would be a welcome solution to the problem of climate change.
The article considered the effects of a 4ºC rise in global average temperature by 2099, which is not unrealistic -- see below. Its conclusions are illustrated by a map on which most of the tropics and a broad band on either side are shown either in light brown ('uninhabitable desert') or dark brown ('uninhabitable due to floods, droughts or extreme weather') -- the Sahara Desert is shown as extending north to central Europe. The areas at risk from rising sea levels look quite small by comparison, but would not be insignificant. (Unfortunately the map in the online version of the article is not so graphic -- it's a plain map that you have to click on to get verbal descriptions). The countries that would suffer the most are, on the whole, those that have contributed least to the problem and received fewest of the benefits of industrialisation (although some are catching up fast in both respects); but even if we in the rich temperate countries didn't care about them, we would face significant problems too.
On the bright side, the article estimates that, as land in northern and southern latitudes would become suitable for agriculture as the climate warmed (but how good would the soil be, I wonder), it would be possible to feed the predicted world population of around 9 billion people. However, this would require population movements on an enormous scale, and I rather doubt if the necessary international political agreement could be reached -- famine and war seem more likely than an orderly transfer of Africans and Indians to Siberia and Canada. A letter in last week's New Scientist points out that it might be easier to try and adapt by means of water storage and irrigation; but we cannot be sure that this would work on the scale required, and in such a situation the world economy would probably be in no shape to pay for large-scale engineering, or for food shipments to the affected countries.
Significant loss of biodiversity would be inevitable as natural habitats disappeared -- starving people may not worry about this in the short term, but it would be a great pity from our current perspective, would reduce the resilience of ecosystems to cope with further environmental stresses, and would make it harder to develop and breed new crops..
Even if we did cope with a 4ºC rise, there is no guarantee that it would stop there.
Of course in the absence of major increases in life expectancy (unlikely if the world is not stable and prosperous), neither I nor the great majority of readers of this blog will be around in 2099, but it's unlikely that everything will carry on as normal until a sudden disaster in that year -- in my lifetime we could easily be halfway to the scenario described above (I wonder if we should take up unhealthy diets or dangerous hobbies to reduce our chances of being here when things get serious!). And anyone who has young children or grandchildren, or might in future, needs to be worried for them.
The question that probably occurs to you is 'how likely is this to happen?' A 4ºC temperature rise is certainly possible -- it is in the middle of the range predicted by the Intergovernmental Panel on Climate Change in its 2007 report if fossil-fuel-intensive economic growth continues (and possible even if it does not). As my colleague Halina heard at the recent climate congress in Copenhagen (see her blog entry on the conclusions of the conference), we are currently on course for this worst-case scenario, as greenhouse gas emissions continue to rise (not to mention the problem of methane from melting permafrost, poorly understood and so not emphasised in the IPCC report, but with the potential to make things much worse). My impression as a non-expert is that the consequences of such a temperature rise are harder to predict (the summary of the IPCC report is not as specific as the article), but that the scenario described in the article is sufficiently based on the work of climate scientists to be a serious possibility. Even if you assume that it errs on the side of pessimism, any rise greater than 2ºC, a figure likely to be reached under all the scenarios considered by the IPCC, would still cause serious problems according to Halina's blog entry from the conference.
Another article in the same issue of New Scientist discusses the idea of geoengineering -- if we don't reduce greenhouse emissions quickly enough, we might be able to prevent climate disaster at comparatively small expense by, for example, placing giant mirrors into orbit to reflect the sun's rays, spraying sulphate particles (normally considered a pollutant) into the stratosphere to achieve the same end, or fertilising the oceans to stimulate CO2-absorbing plankton. However, most of these technologies are unproven, and most would probably have unpredictable adverse effects, leading to political problems between countries that implemented them and those that suffered from them.
Some might argue that climate models make things look worse than they will actually be, that technological development will enable us to engineer our way out of trouble, that economic growth will enable us to spend our way out, that it's too late and we're all doomed whatever we do, or that some other disaster (how about bird flu?) will get us first. However, I think most people would agree that given the potentially devastating consequences of inaction, and the authoritative predictions that the later we act the worse the problem will be, hoping for the best is a high-risk strategy and over-pessimism will be self-fulfilling -- it is important to act soon. Almost any amount of investment now would be worth making to avoid the consequences discussed above, and Lord Stern of Stern Report fame estimates that investment of as little as 2% of global GDP would be sufficient. He points out that in the unlikely event of the world's climate scientists being wrong, this would be a comparatively small amount of money to waste and would have other beneficial effects anyway. Let's hope that the politicians at next December's UN Climate Change Conference can agree on measures that ensure our future, and that they and we can successfully implement them.
The conference website, with webcasts of the plenary sessions, and abstracts of all presentations, is here. All findings are to be compiled in a book on climate change due to be published in 2010 (an extensive summary will be available in June this year).
The latest IPCC report is here.
New Scientist has a list of articles on climate change here.
CABI has produced an internet resource (Environmental Impact) which concentrates on climate change and human impact on the global environment.
The website of the recent Sustainable Development UK conference, at which Professor Sir John Beddington, the UK government's Chief Scientific Adviser, warned of a 'perfect storm' of shortages of food, water and energy by 2030, is here.
In a changing world with a growing population to be fed, the work of organizations like CABI is likely to be in demand; CABI is organising a conference next autumn on food security in relation to issues such as climate change.