La Niña: Bad science?

La Niña, the climate event caused by unusually cool waters in the eastern Pacific, has strengthened and, according to some scientists, has been responsible for many recent extreme weather events.  With the latest data on the phenomenon due out on Wednesday, this latest episode may not have reached its peak.  However, there is little consensus as to what can and cannot be attributed to La Niña, and scientists are divided as to whether or not La Niña may produce more extreme weather conditions in the future.

Bad girl

La Niña is the meteorological baby sister of the better-known El Niño event: 

• During an episode of La Niña, waters in central and eastern areas of the Pacific Ocean cool, while those in the west remain warmer.  This is associated with the frequency of heavy rainfall on the western side of the Pacific Rim.  El Niño, on the other hand, is associated with warmer waters in central and eastern areas of the Pacific. 

• La Niña leads places such as north-eastern Australia, south-east China, southern Africa and southern Asia to experience wetter than usual weather.  By contrast, El Niño causes some dry areas to become even dryer. 

These phenomena, which are known in the scientific community as the Southern Oscillation, occur cyclically every four to five years.  A strong El Niño is usually followed by a La Niña that persists for around 12 months.  

Bad science?

The current La Niña is the strongest in eight years -- that much at least is uncontroversial.  However, due to the complexity of the Southern Oscillation and the difficulties of long-term meteorological forecasting in general, there is little consensus as to which events can be attributed to La Niña.   For example, some scientists have claimed that recent flooding in Ecuador and Bolivia were the result of unusually heavy rainfall caused by La Niña.  However, others blame deforestation and soil erosion, which accelerate the transfer of water down river.  

Similarly, La Niña’s role in recent snowstorms in China is disputed.  A recent report by the World Meteorological Association claimed the events were a ‘text-book style expectation’ from La Niña.  However, while many climatologists agree that a link is possible, they argue that the blizzards -- the worst for five decades -- were the product of many overlapping factors.

Unsurprisingly, the linkages between La Niña and global warming are no less controversial.  This month an international team of scientists released a study, which concluded that ‘the most realistic’ climate change models demonstrate that global warming will increase the intensity of the Southern Oscillation.  Yet other studies have failed to find a link with either the intensity or the frequency of El Niño/La Niña episodes. 

One thing is certain: with Bolivian President Evo Morales calling upon developed countries to pay off their ‘ecological debt’ to Bolivia -- on account of the fact that they bear the blame for causing global warming -- the controversy surrounding La Niña will swirl as fiercely as the Southern Oscillation.