Global El Niño
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There is a direct cause and effect between the Earth's rise in temperature and a whole slew of weather patterns. The connections between a warmer climate and abnormal weather are called teleconnections in the business. One of them, global warming and El Niño. Hi, I'm Dave Thurlow and this is the Weather Notebook.

So how does global warming affect El Niño? Well, research is now showing that global warming may be changing the frequency of air circulation patterns or regimes, as there're called. Regimes make up the entire global circulation, describing its regular behavior. In many parts of the world circulation patterns flip back and forth between two alternating regimes every couple of years or decades. The most familiar of these oscillations is El Niño and La Niña. The result; Pacific sea surface temperatures flip between warm and cold. Which brings about changes in the weather world wide.

For example, El Niño with its warm waters causes floods, mudslides and tornadoes in the southern part of the United States. La Niña on the other hand gives the central U.S. very cold weather along with tornadoes while the east is warm and tranquil, except for hurricanes.

Over the past two decades El Niño has stepped up its schedule and this may be thanks in part to global warming. The time interval between El Niños depends on how long it takes to recharge the tropical system by re-accumulating heat at the sea surface. Global warming just may enable to recharge the system faster; making El Niño appear more often.

So, it's the constant discovery of new-found teleconnections and the intricate atmospheric web that shows what is of most concern may yet to be even thought of.

The Weather Notebook is underwritten by Subaru, with major support provided by the National Science Foundation.