Joe Romm at Climate Progress comments on recent research that suggests a significant increase in global temperatures may be imminent.

‘Significant’ here means two- or three-tenths-of-a-degree Celsius, which compares to the 0.16°C/decade average seen in this graph from NASA:

Clearly in this graph there was a jump in the temperature around 1998, then a period of consolidation of near record temperatures or small increases in the temperature. All the years from 2001 on were hotter than 1997.

Kevin Trenberth explains that most of the additional warmth (over 90%) goes into the ocean and global increases tend to happen towards the end of an El Niño event, while La Niñas tend to be cooler. This pattern of El Niños and La Niñas (ENSO) which last 6 to 18 months is superimposed on the pattern of PDOs (Pacific Decadal Oscillations) which can last a decade or more. The importance of the PDO was outlined in the post Explaining the pause that wasn’t last December.

The pattern of PDOs is shown in this graph:

The 1998 jump came with the super El Niño in 1998 at the end of an extended period of positive PDO, from 1992 and 1998. Now we are entering an El Niño at a time when the PDO has turned strongly positive.

Romm interviewed Kevin Trenberth:

I interviewed Trenberth this week, and he told me that he thinks “a jump is imminent.” When I asked whether he considers that “likely,” he answered, “I am going to say yes. Somewhat cautiously because this is sticking my neck out.”

What is not said here is that the current El Niño is a weak one and may not have much effect on the weather. Trenberth thinks the PDO has the greater effect, which is then modulated by ENSO. Given the shape of the PDO over the last 15 years, the current El Niño might be like pulling the cork on a bottle of fizz.