19/4/14: Westerly bursts and and throwing a six

By Mike Johnson

Predictions based on sound science have a way of coming true.

Radio talk-back hosts and other willful ignoramuses will often repeat the ‘joke’ that if climate scientists can’t predict the weather for next week, how can they predict it forty or fifty years in advance? The joke is designed to make climate scientists look stupid, as if because you don’t know where the next wave may fall you can’t tell if the tide is coming in or not.

Climate science predictions are based on probabilities, and the imagery scientists use reflect that. Bill McKibben came up with the metaphor of weather on steroids. Just as a player is more likely to hit a six on steroids, but you can’t tell which ball it will be, the weather, pumped by Greenhouse gasses, is more likely to deliver extreme weather events. Jim Hansen of NASA uses the dice analogy. If you load the dice in favour of the six, you will get more sixes, but you will not be able tell in advance if any particular throw will be a six. All you can know is that the more you load the dice in its favour, the more likely the six will come up. The more we change the earth’s energy balance, the more we court extreme weather events: it’s not rocket science.

Now a new probability has entered the mix. A super El Nino.

 To understand the importance this, we need to look yet again at the Annual temperature anomaly, which I explain here. It’s worth looking at yet again.

As I pointed out in that previous post, the natural question would be, when will the next red line appear, and how high might it go? In other words, how hot might the next El Nino be? I almost wish I hadn’t written the words I wrote in that post, for as soon as I started to wonder when the next El Nino might be due, I came upon the Washing Post article. I tried to ignore that until I found this follow up article. The article comments:

This is an extraordinarily intense temperature extreme that well exceeds those observed during the ramp-up to the record 1997-98 El Nino event.

That event is clearly shown on the chart as the first of the very tall red lines. If the temperature were to take another such quantum leap, the subsequent effects will be severe. Most the literature deals with the effects of this developing El Nino on the Norther Hemisphere. However, the Sydney Morning Herald has picked up the story and predicts worsening drought for Australia. Bad news for Aussie farmers who are desperately hoping that things will return to normal.

Whether this will apply to NZ is yet to be seen. This final quote, however, is from NZ’s NIWA, and broadly sketches in the effects we might expect under normal, non-steroid conditions.

During El Niño, New Zealand tends to experience stronger or more frequent winds from the west in summer, typically leading to drought in east coast areas and more rain in the west. In winter, the winds tend to be more from the south, bringing colder conditions to both the land and the surrounding ocean. In spring and autumn south–westerly winds are more common.