Food security: I think we'd be very foolish to expect that we can just import everything from somewhere else and imagine that that's going to last for ever and ever and ever.
WHAT YOU NEED TO KNOW ABOUT CLIMATE CHANGE
The most peculiar thing about Climate Change, as Sherlock Holmes might have observed, is how little most people in the West do about it. A typical laconic Buxton observation, only half in jest, might be: 'Any change in our climate would be an improvement!' In fact, humanity faces the greatest challenge since the last Ice Age. Ask people in, say, Bangladesh, Sub-Saharan Africa, Moscow, New Orleans, Greenland or the Maldives.
You need to decide whether you think current Global Warming is mainly the result of natural cycles (in which case all we can do is to adapt and hope that the World's climate will settle down again) or mainly the result of human activity in burning fossil fuels, clearing forests, keeping cattle etc. In which case we all need to take urgent action. Climate Change Deniers are simply burying their heads in the sand (of which there will be plenty with expanding deserts).
Simple laboratory experiments show that carbon dioxide and other 'greenhouse gases' transmit visible light but block infra-red. Were this not so, the Earth would be very much colder and we would not be here to argue about climate! Therefore increasing the concentration of greenhouse gasses in the atmosphere must raise the mean temperature of the Earth. Increased temperatures mean that more water will evaporate from seas, lakes and vegetation. Which may well mean more clouds and more rain and snow in Buxton.
This is where it becomes interesting. Water vapour is itself a greenhouse gas, so this will multiply the heating effect of the carbon dioxide. But water vapour tends to form clouds and low-level clouds have a shading effect. On the other hand, high-level clouds have a warming effect and a hotter Earth's surface may cause low-level clouds to thin, letting through more of the Sun's radiation. So, with this and other uncertainties, the Intergovernmental Panel on Climate Change can only give a wide range for the expected temperature rise by 2100 of somewhere between 1 and 6oC above pre-industrial. The biggest uncertainty, of course, is how quickly we are willing or able to reduce greenhouse gas emissions.
In order to keep the mean temperature rise to 2oC, atmospheric concentrations of CO2 must be limited to 450 ppm. That is equivalent to the EU cutting by 30% (and the UK by 40%) of 1990 levels by 2020 and by at least 80% by 2050. In layman's language, we have all got to do a lot. In fact, if the Country as a whole is to cut by 80%, you and I would have to cut by close to 100%.
There is a catch! 2oC is the middle of the calculated range of temperature rise. If we were lucky it could be 1oC. If we were unlucky it could be 3oC. At the worst, that might cause runaway global heating. We are taking a gamble on our children's future. For Western governments, a 2oC limit is reasonable because food production is only expected to fall if temperature rises above 2oC. And achieving much less than 450 ppm is predicted to cost a lot of money.
Look at what is already happening for a mean temperature rise of only 0.8oC. The IPCC considers that these effects are likely to be a result of anthropogenic global warming: an accelerated rate of species extinction, melting glaciers and ice sheets, erratic water supplies, unusual heat waves, rising sea levels, unpredictable weather patterns with storms, droughts and floods and inevitably disrupted agriculture. The worst effects are felt by vulnerable groups but even if we did not care about other species, or about threatened communities, we could not isolate ourselves.
Transition Towns believe in taking serious action now. We need to be 100% renewable energy based. We need to grow more of our own food. We need to stop wasting increasingly scarce resources. On our own, it is a daunting task. Together we can build a resilient, sustainable community that does not make life harder or even impossible for other communities across the globe.