The Guardian reports: Cooling waters in the tropical Pacific Ocean appear to be a major factor in dampening global warming in recent years, scientists said on Wednesday.

Their work is a big step forward in helping to solve the greatest puzzle of current climate change research – why global average surface temperatures, while still on an upward trend, have risen more slowly in the past 10 to fifteen years than previously.

Waters in the eastern tropical regions of the Pacific have been notably cooler in recent years, owing to the effects of one of the world’s biggest ocean circulatory systems, the Pacific decadal oscillation.

Many people are aware of the El Niño and La Niña weather systems, which affect the Pacific and bring hotter and stormier or cooler weather in cycles of just a few years, and can have a strong effect on global weather. But few are aware that both of these systems are just part of the much bigger Pacific decadal oscillation, which brings warmer and cooler weather over decades.

The system is now in a cooling phase, scientists have noted, which could last for years. The last such phase was from the 1940s to the 1970s. [Continue reading…]