El Nino and La Nina have a significant impact on the local precipitation and temperature patterns. If La Nina gets stronger, the tropical storms move from the Pacific Ocean to the Atlantic Ocean. Although the local variations are both positive as well as negative at various places, the overall temperature is a bit warmer during El Nino events. You may imagine that La Nina cools down the Pacific and because the Pacific is the largest ocean, it also means a decrease of the global temperatures. For example, January 2007 - a month during the El Nino event - was one of the warmest months ever altough it was much (0.25 C) cooler than the warmest month on record, namely April 1998.
February 2007 was already different. In America, it was much cooler. On record, February 2007 was, for example,
- coldest February ever in Waterloo, Canada
- coldest, snowiest in decades in Indiana
- third coldest in Fort Wayne, Indiana
- sixth coldest in Ohio
- snowiest and fourth coldest elsewhere in Ohio
- fourth snowiest and ninth coldest in Illinois, in 137 years
- sixth coldest in Chicago
- snowiest in 29 years in New York state
- coldest February since Jimmy Carter in Pennsylvania
Other places such as Japan, Korea, Malta etc. continue to see one of the warmest winters ever. In the record cold regions, you don't see any comments about the climate. On the other hand, almost all articles informing about the warm regions mention "global warming". That's what I personally call shoddy journalism, dirty propaganda, and fraud.
La Nina - history and comments
The effect of El Nino / La Nina events is usually felt on globally averaged temperatures around 4 months later. So it is still plausible that even with La Nina, we will have warm months up to May. But I would personally bet that 2007 won't be the warmest year. ;-)
David Smith gave me slightly different and more realistic data: he says that El Nino peaked in October or November 2006 and its temperature effect peaked in January 2007.
The previous La Nina episode came right after the 1998 El Nino - in 1998-2001. Look what it did with the global temperatures. Moreover, we may be in a cool phase of the Pacific Decadal Oscillation (PDO). Note that this phenomenon is much more correlated with the observed global temperatures than anything you have heard about: in 1905, a warm phase started. It was replaced by a cool phase that started in 1946, and a warm phase that started in 1977 - you may view this ocean pattern to explain the recent "global warming". Around 1998, attempts to switch to a cool phase started to occur again.