Ellers ser vi en grum tid i møde. I hvert fald ifølge Kirk Myers i Examiner, som ser et muligt og uheldigt sammenfald af tre “kølende” effekter, nemlig en inaktiv sol, der historisk altid har betydet faldende globale temperaturer, et muligt kæmpemæssigt vulkanudbrud på Islands Katla (Eyjafjallajokull er sandsynligvis bare en præludium til den egentlige forestilling), der via en askesky kan blokere for noget af sollyset og så til sidst - langt mere sikkert - en vending i oceanstrømmende. De sidstnævnte bliver forklaret her

The Pacific Decadal Oscillation refers to cyclical variations in sea surface temperatures that occur in the North Pacific Ocean. (The PDO is often described as a long-lived El Niño-like pattern.) PDO events usually persist for 20 to 30 years, alternating between warm and cool phases. During these long periods there are sometimes short-interval phase switches that can last several years.

From 1977 to 1998, during the height of “global warming,” North America was in the midst of a warm PDO.  Since then, we have experienced several short-duration PDO fluctuations between cool and warm.

But the PDO has once again resumed its negative cool phase, and, as such, represents the first climate driver in the Triple Crown of Cooling. With the switch to a cool PDO, we’ve seen a change in the El Nino/Southern Oscillation (ENSO), which alternates between El Nino (warm phase) and La Nina (cool phase) every few years. The recent strong El Nino that began in July 2009 is now transitioning to a La Nina, a sign of cooler temperatures ahead.

“We’re definitely headed towards La Nina conditions before summer is over, and we’re looking at a moderate to strong La Nina by fall and winter, which, as these La Ninas tend to persist in the cold PDO for two years, should bring us cooler temperatures over the next few years,” predicts Joe D’Aleo, founder of the International Climate and Environmental Change Assessment Project (ICECAP) and the first director of meteorology at the Weather Channel.

He is not alone in his forecast. Bastardi also sees a La Nina just around the corner.

“I’ve been saying since February that we’ll transition to La Nina by the middle of the hurricane season. I think we’re already seeing the atmosphere going into a La Nina state in advance of water temperatures. This will have interesting implications down the road. La Nina will dramatically cool off everything later this year and into next year, and it is a signal for strong hurricane activity,” Bastardi predicts.

The difference in sea surface temperature between positive and negative PDO phases is not more than 1 to 2 degrees Celsius, but the affected area is huge. So the temperature changes can have a big impact on the climate in North America.

In fact, as Dr. Roy Spencer points out, the warm-phase PDO lasting from 1977 to 1998 might explain most of the warming we experienced in the late 20th century.

“This is because a change in weather circulation patterns can cause a small change in global-average cloudiness. And since clouds represent the single largest internal control on global temperatures (through their ability to reflect sunlight), a change in cloudiness associated with the PDO might explain most of the climate change we’ve seen in the last 100 years or more,” he writes.

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Says D’Aleo:  “Cold is far more threatening than the little extra warmth we experienced from 1977 to 1998 during the recent warm PDO. According to NASA, crop yield decreased 30 percent, and there was a 10 percent decrease in arable land during that period, which helped us feed many millions more of the earth’s population. A cooling down to Dalton Minimum temperatures or worse would lead to shortened growing seasons and large-scale crop failures. Food shortages would make worse the fact that more people die from cold than heat.”

Så lad bilen stå i tomgang natten over og red børnene i det Afrika, der alligevel ikke bliver som en ovn.