Adding Juice to La Niña

Posted on July 15, 2012

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Climate Change Makes Climate Systems More Extreme

The flow of surface waters in the South Pacific ocean has a profound effect on the world’s weather.  The system known as El Niño-Southern Oscillation (ENSO) can both warm the planet with El Niño, or cool the planet with La Niña.  2011 was a double-La Niña year.

Of course, climate on a local scale is not necessarily in lock-step with everything happening everywhere on the planet.  While La Niña years are cooler on a global scale, they are also consistent with hotter, drier summers in the American southwest, for instance.  Of course, the heatwave that struck the USA last year led to the second-warmest summer for the country as a whole, and the hottest summers ever recorded in Texas, Oklahoma, New Mexico and Louisiana.

The La Niña system is consistent with heavy rainfall in places like Colombia.  But the rains in 2011 were catastrophically heavy, killing 425 across Colombia, causing billions of dollars in damages, with at least 3 million people affected by floods and mudslides.

La Niña also brought drought and famine to East Africa, adding to the affects of a long-term drying trend in the region.

In Zimbabwe, they experienced the heaviest January rainfall in three decades.  The second wettest summer in the Australian record brought record-breaking rain to New South Wales and Victoria and widespread flooding in Queensland.  The extent of the flooding in Queensland was almost the size of France and Germany combined.

What happened in 2011 was La Niña-plus.  Globally, it was the warmest La Niña-year on record.  Climate change has already raised the level of water vapour in the atmosphere by 4% which means that there is more rain to fall out of it when it does fall.  When La Niña drops rain on Colombia and Australia, it drops a lot of rain.  And, with the planet already warmed by climate change, with earlier springs and drier soils, that means when La Niña brings heat to Texas it is adding to what is already there.

The result is starvation in Africa, floods in Australia and Colombia, fires and agricultural failures in Texas.

Systems like El Niño or La Niña have always been around to influence the climate.  According to a recent study, however, La Niña-related heatwaves in Texas are now 20 times more likely to occur than 50 years ago.

La Niña doesn’t really mean quite what it used to mean and the difference is not in our favour.  Chaos seldom is.  Unfortunately, because of the ongoing influence of changes in atmospheric composition, the addition of carbon dioxide from deforestation and the burning of fossil fuels, the chaos is likely to ramp up for the foreseeable future.

Climate change is already a fact of life.  That’s obvious.

It’s also obvious that we need to act before the chaos that climate change brings is beyond the capacity of our civilization to cope with.

Looking around, looking at merely the last three or four years, that critical point–beyond which effective action is impossible–doesn’t seem very far off.  Not far off at all. 

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See Global Warming Punched Up Some 2011 Weather Extremes

NOAA State of the Climate in 2011 – highlights

Heat Wave USA 2011