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Flooding in Bristol

The effects of a changing climate affect us all. Pictures taken by hydrologist Jim Freer on 21 November 2012 at Whiteladies Road in Bristol.

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Converting probabilities between time-intervals

This is the first in an irregular sequence of snippets about some of the slightly more technical aspects of uncertainty and risk assessment.  If you have a slightly more technical question, then please email me and I will try to answer it with a snippet. Suppose that an event has a probability of 0.015 (or 1.5%) of happening at least once in the next five years. Then the probability of the event happening at least once in the next year is 0.015 / 5 = 0.003 (or 0.3%), and the probability of it happening at least once in the next 20 years is 0.015 * 4 = 0.06 (or 6%). Here is the rule for scaling probabilities to different time intervals: if both probabilities (the original one and the new one) are no larger than 0.1 (or 10%), then simply multiply the original probability by the ratio of the new time-interval to the original time-interval, to find the new probability. This rule is an approximation which breaks down if either of the probabilities is greater than 0.1. For exa...

1-in-200 year events

You often read or hear references to the ‘1-in-200 year event’, or ‘200-year event’, or ‘event with a return period of 200 years’. Other popular horizons are 1-in-30 years and 1-in-10,000 years. This term applies to hazards which can occur over a range of magnitudes, like volcanic eruptions, earthquakes, tsunamis, space weather, and various hydro-meteorological hazards like floods, storms, hot or cold spells, and droughts. ‘1-in-200 years’ refers to a particular magnitude. In floods this might be represented as a contour on a map, showing an area that is inundated. If this contour is labelled as ‘1-in-200 years’ this means that the current rate of floods at least as large as this is 1/200 /yr, or 0.005 /yr. So if your house is inside the contour, there is currently a 0.005 (0.5%) chance of being flooded in the next year, and a 0.025 (2.5%) chance of being flooded in the next five years. The general definition is this: ‘1-in-200 year magnitude is x’ = ‘the current rate for eve...

Your Waste of Time: Art-Based Geographical Practices and the Environment

This blog post thinks through the themes of aesthetic interventions, sensing time and engendering response-ability using artistic responses to climate change. Here, these themes are drawn from one piece of art, Your Waste of Time, by Danish-Icelandic artist Olafur Eliasson. This performative showcasing of glacial ice establishes interactions and relations between human bodies and icy materialities- but what is at stake here and what potentialities could be created through artistic practices? These are questions that have arisen through my current dissertation, where I hope to explore artistic responses to environmental degradation through the materialities of ice and plastic. For the piece Your Waste of Time, Danish-Icelandic artist Olafur Eliasson transported several large blocks of ice from Vatnajökull, the largest and oldest glacier in Iceland, to the Berlin gallery Neugerriemschneider (Eliasson, 2006). This glacier is almost incomprehensibly ancient, with some parts dating fro...