Is the Pacific Decadal Oscillation having an effect on global climate?

Yes, PDO has been slightly negative overall during the past decade, so it's no doubt played a role in the slightly slower rate of global warming during that period. Probably not a huge role, but a small role at least.

http://jisao.washington.edu/pdo/

*edit* Don Easterbrook is an idiot. If he says something regarding the climate, you can be 90% sure it's wrong.

http://hot-topic.co.nz/easterbrooks-wrong-again/

http://www.skepticalscience.com/not-so-cool-predic...

Yes! Very much! I saw a graph of temperature over the 20th century with a straight line running through it. You could see oscillations with about a 30 years spread which corresponded nicely to the shifting PDO. There is an underlying warming trend, but the PDO can magnify the trend or reduce it to nearly zero. Look back over the last 100 years- cooling hit it's peak around 1970, there was a heating trend which peaked at the end of the 1930's, and another cold spelll around the turn of the century.

What makes this particular natural phenomenon so insidious (and the reason why alarmists want to deny it's existence) is that most satellite records only date back to the 70's when the PDO shifted back to the warm side. Warming over the last 30 years has been amplified greatly by the PDO. Now it has shifted again, and we can expect little or no warming for a while. But don't take my word for it, even leading warmist scientists are on board with this idea:

"According to research conducted by Professor Don Easterbrook from Western Washington University last November, the oceans and global temperatures are correlated.

The oceans, he says, have a cycle in which they warm and cool cyclically. The most important one is the Pacific decadal oscillation (PDO).

For much of the 1980s and 1990s, it was in a positive cycle, that means warmer than average. And observations have revealed that global temperatures were warm too.

But in the last few years it has been losing its warmth and has recently started to cool down.

These cycles in the past have lasted for nearly 30 years.

So could global temperatures follow? The global cooling from 1945 to 1977 coincided with one of these cold Pacific cycles.

Professor Easterbrook says: "The PDO cool mode has replaced the warm mode in the Pacific Ocean, virtually assuring us of about 30 years of global cooling."

Of course.

There are many competing processes that affect global climate, including not only the Pacific Decadal Oscillation, but in addition, for example, the Tropical Atlantic Decadal Oscillation and the Atlantic Multi-Decadal Oscillation. This is one of the straw men that is used by anthropogenic (or man-made) global climate change deniers. They point out these other large contributors to global climate and blame everything on them. It's a very complicated subject.