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Saturday, July 21, 2012

Strong words

My first-pass answer is that we have a global economy that is adapted to historically normal climate — not just in terms of what is grown where, but in terms of where we locate our cities. In the long run, after a couple of centuries’ worth of urban development and infrastructure has been drowned by rising sea levels and/or made useless because previously habitable regions need to be abandoned, we might be able to reconstruct an equally productive economy; but in the long run … But Hansen et al make a stronger point: life as we know it evolved to fit the historical range of planetary temperatures. In the long run it might be able to adapt to a changed world — but now we’re talking millions of years. In the long run, we are all extinct.
Dicing With The Climate
Although extreme heat waves and record floods receive most public attention, we wonder if there is not also a more pervasive effect of warming that affects almost everyone. Natural ecosystems are adapted to the stable climate of the Holocene. Climate fluctuations are normal, but the rapid monotonic global trend of the past three decades, from an already warm level, is highly unusual. The fact that warmer winters have led to an epidemic of pine bark beetles and widespread destruction of forests in Canada and western United States is well known. However, as an anecdotal data piece suggesting the possibility of more widespread effects, consider that several tree species (birch, pin oak, ash, some maple varieties) on the eastern Pennsylvania property of one of us (JH) exhibit signs of stress. Arborists identify proximate causes (borers and other pests, fungus, etc.) in each case, but climate change, including longer summers with more extreme temperature and moisture anomalies, could be one underlying factor. The tree species in this region have existed for millennia; it is implausible that Native Americans had to water the birch trees to keep them alive, as is the case at present during summers with anomalously hot summers. Climate change of recent decades is also having effects on animals, birds and insects that are already noticeable (17, 27, 28). Although species migrate to stay within climate zones in which they can survive, continued climate shift at the rate of the past three decades is expected to take an enormous toll on planetary life. If global warming approaches 3°C by the end of the century, it is estimated that 21-52% of the species on Earth will be committed to extinction (3). Fortunately, scenarios are also possible in which such large warming is avoided by placing a rising price on carbon emissions that moves the world to a clean energy future fast enough to limit further global warming to several tenths of a degree Celsius (29). Such a scenario is needed if we are to preserve life as we know it.
Perceptions of Climate Change: The New Climate Dice

Strong words. Imminent danger.

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