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Q. With this flood epidemic, which parts of the British Isles do you think will be the best places to live to avoid future floods? Also, do you think the climate change will involve a sudden drop in temperature similar to an Ice Age? If so, which parts – if any – of the British Isles do you think will be the best places to live to avoid that? (Valerie Roberts, Amlwch)
A. Clearly, living on a flood plain will generally carry with it the risk of flooding unless suitable flood management measures are in place. It is not really possible to say whether any specific parts of the UK will be at greater or lesser risk of flooding than others as a consequence of climate change – intense rainfall can strike any part of the country. A warmer climate is generally expected to lead to more of our rainfall coming in extreme events (eg: a warmer ground can cause the air to rise more rapidly, leading to more intense thunderstorms).
Around the coasts, flood risk is also expected to increase as a result of sea level rise. Average sea level around the world rose by between 12 and 22cm over the 20th Century, and is expected to rise by another 18 to 59cm or possibly more by the end of the 21st Century – although the risk of increased frequency of short-lived coastal flooding arising from storm surges arguably poses a more imminent threat than long-term average sea level rise (by the way, the maps you may have seen in the popular press of the shape of the UK changing dramatically and permanently as a result of sea level rise are based on projections of sea level rise several centuries or even millennia away).
A sudden drop in temperature in the UK due to a shutdown of the Gulf Stream is a theoretical possibility, but is considered unlikely to occur this century. The Gulf Stream is an ocean current which brings warm water northwards from near the equator, keeping our part of the world warmer than other regions (such as central Russia or Canada) which are a similar distance from the equator. The Gulf Stream depends on the sinking of salty water in the north Atlantic, and in theory, the melting of the Greenland ice sheet might release enough freshwater into the north Atlantic to slow this sinking motion drastically and hence cause the Gulf Stream to shutdown and stop its warming influence on the climate of the north Atlantic (including the UK). However, this has been examined in detail by oceanographers using computer models of the ocean circulation under scenarios of global warming, and the overall assessment (as reported in the IPCC report http://ipcc-wg1.ucar.edu/wg1/wg1-report.html ) is that although this part of the ocean circulation is very likely to slow down to some extent, it is very unlikely to shut down completely, at least during this century. Therefore the most likely scenario is still for a warming climate in the UK over the next hundred years.
It is not possible to make reliable assessments of the chance of this phenomenon occurring further into the future – however, if the world has warmed anyway by then, this could well offset any cooling of the north Atlantic region that may occur.
Q. Is it not true that the Earth's climate is controlled by the sun, sun-spot activity, solar radiation and so forth? Is it not true that the majority of carbon dioxide in the atmosphere is produced by the oceans, by a factor of hundreds to one compared to man-made CO2? Is it not also true that, in terms of "greenhouse gases", carbon dioxide isn't even in the top ten of most volumetric (and therefore relevant) in the atmosphere (water being billions of times more relevant)? Is it not true that the whole man-made climate-change movement is purely driven by politics and money and is in fact the biggest hoax in history? (Paul Barker, by e-mail)
A: No, the evidence is that the sun was not the main influence on 20th century temperature rise. The increase in solar irradiance since 1750 was about 0.12 Wm-2, whereas the perturbation to the Earth’s radiation balance caused by increased CO2 concentrations was 1.66Wm-2. The heating effect of the CO2 rise was therefore more than ten times greater than that of solar changes.
The CO2 rise is caused by man-made emissions, and the oceans actually absorb more carbon dioxide from the atmosphere than they release, as do land ecosystems, which means that the CO2 rise has actually been slower than it would have been without these natural sinks.
It is true that water vapour is the most important greenhouse gas, but CO2 is also important. The point is that water vapour is not being directly increased by human activities (except for a tiny amount due to irrigation), so its contribution to the greenhouse effect is hardly changing. In contrast, we are increasing CO2 rapidly, so its contribution to the greenhouse effect is increasing significantly.
Man-made climate change is not a hoax. The evidence base is extremely strong and has been rigorously examined and debated. The latest IPCC report on the Physical Science Basis of climate change, http://ipcc-wg1.ucar.edu/wg1/wg1-report.html, was based on hundreds of scientific papers, and its various drafts were subject to open examination and critique by hundreds of reviewers. You can see the review comments and author responses at http://ipcc-wg1.ucar.edu/wg1/Comments/wg1-commentFrameset.html.
