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21 oktober 2010

Droogte gaat grote delen van de wereld teisteren

Matthew McDermott, Treehugger / Alternet, 19 oktober 2010

Plenty of studies have shown that climate change is going to affect precipitation and water supplies, but a new one from the National Center for Atmospheric Research starkly lays out how droughts, some so extreme that they are nearly without precedent, may spread throughout many of the world’s most densely populated places by the end of the 21st century.

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New study puts the ‘hell’ in Hell and High Water - Must-read NCAR analysis warns we risk multiple, devastating global droughts even on moderate emissions path
Joe Romm, Climate Progress, 20 oktober 2010

The NCAR study (...) shows that in a half century, much of the United States (and large parts of the rest of the world) could experience devastating levels of drought — far worse than the 1930s Dust Bowl, especially since the conditions would only get worse and worse and worse and worse, while potentially affecting 10 to 100 times as many people. And this study merely models the IPCC’s “moderate” A1B scenario — atmospheric concentrations of CO2 around 520 ppm in 2050 and 700 in 2100. We’re currently on the A1F1 pathway, which would takes us to 1000 ppm by century’s end, but I’m sure with an aggressive program of energy R&D we could keep that to, say 900 ppm.

Indeed, the study itself notes that it has ignored well understood climate impacts that could worsen the situation:
As alarming as Figure 11 shows, there may still be other processes that could cause additional drying over land under global warming that are not included in the PDSI calculation. For example, both thermodynamic arguments124 and climate model simulations125 suggest that precipitation may become more intense but less frequent (i.e., longer dry spells) under GHG-induced global warming. This may increase flash floods and runoff, but diminish soil moisture and increase the risk of agricultural drought.
That is, even when it does rain in dry areas, it may come down so intensely as to be counterproductive.
(...) a very large population will be severely affected in the coming decades over the whole United States, southern Europe, Southeast Asia, Brazil, Chile, Australia, and most of Africa.

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