03 August 2010

Droughts and Floods


Navy Memorial Fountain, Pennsylvania Avenue NW, Washington, DC 2010
©EOP

Todays feed from Huffington Post includes a rather apocalyptic piece by Toby Barlow "Let's Call it Climate Chaos." I have enough experience with both climatology and statistics to realize that the current nexus of climate related issues worldwide is in itself neither proof nor disproof of climate change—only trends over a longer period can serve that purpose—but current conditions give powerful reasons to fret about the future of a warmer world. Those of us unfortunate enough to live in the Mid-Atlantic states have experienced a prolonged spell of very hot and uncomfortable weather, though neither New York nor Washington, DC actually set new records for the month of July, merely matching older ones. Just the discomfort of hotter summers is adequate to make one hope global warming is limited to only a few degrees at most. It is clear that warming has many effects, most of them much scarier than simple discomfort.




Much of European Russia has had one of its hottest and driest summers ever. It seems that Moscow is posting new heat records almost daily even as its residents are forced to breathe smoke filled air from countless brush, field, and forest fires in the surrounding region. In addition to the dessicating heat, rainfall in the breadbasket areas south of Moscow are far below long term norms with some areas receiving only a tiny fraction of the precipitation expected. Grain yields are in turn now expected to be well below long-term averages, and it will soon be too late, if it is not already, for additional rainfall to benefit the current year's crop. The expected deficit in grain production is likely to raise world grain prices, for it has already raised grain futures.

The drought in Russia points to the changes in the global distribution of precipitation during a hotter Northern Hemisphere summer. The summer of 2010 is entrain to be the hottest ever recorded (just as the 2009-10 winter was the warmest recorded). Common to post el Niño seasons, the southwestern United States, including Southern California and the lower Colorado River Basin has enjoyed above average rainfall, somewhat breaking the years long drought. That has started to refill the various reservoirs, though it is unlikely to leave Lake Mead, Lake Powell or the others anything close to bank-full. For the moment at least, a drought has been broken in an area where water supplies are historically very limited.

In Asia excess rainfall is the issue with deadly flooding in both Pakistan and China. Pakistanis wish for rain in the wet part of the monsoon in mid to late summer, but this year has brought rainfall far in excess of long term averages, and 1,000 or more people have been killed by flood-related causes even as bridges, roads, and rail lines have been severed, towns destroyed, and agricultural areas devastated as rushing waters was away topsoil and growing crops. Instead of providing needed water for crops, the monsoonal rainfall of 2010 has caused massive damage. The situation in southern China is similar to that in Pakistan, though it is a function of typhoon circulation rather than the Asian Monsoon. 

The combined effects of these weather conditions, especially droughts and flooding, could have substantial impact on food prices throughout the world. European Russia and southern China export food to other parts of those countries and to world markets. Pakistan is a net food importer, and destruction of good agricultural land is likely to lead to greater demands for imported food. The combination of reduced production and demand from those areas made unproductive by drought and flood is almost certain to led to increased prices for at least some commodities. Those price increases are already apparent in world agricultural markets.

Once again it is important to note that the current summer is not in itself evidence for climate change, but it offers us a shocking preview of what warmer global temperatures portend. From the point of view of water supplies, a massive global redistribution of precipitation will be making some areas much drier than they have been in the past while other areas suffer from excessive precipitation. Severe storms are likely to become much more common, and 100-year floods may become 10-year floods. Instead of being expected not more than once in a century, those water levels will be expected once a decade. Some presently habitable areas will be erased from the map by flooding (granted other areas currently uninhabitable may be added to the ecumene but a net loss of usable land is the most likely outcome), while others will become too dry to use for crops. The world's food supplies are likely to be reduced and food prices increased by the combined effects of drought, flooding, and loss of land accompanying an increase in average world temperatures. It is all quite scary to contemplate!

1880-2009 global mean surface temperature diff...Image via Wikipedia

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