Fergus is interested in the effects of El Nino on sea ice. So I looked at http://climexp.knmi.nl/. At first I thought it didn’t have sea ice, and it doesn’t in the indices, but it does have in the monthly data, which you can average. And then end up with:
The shows Arctic sea ice correlated to SST over the sea. I used the Reynolds SST, so its 1982-2008. Oddly enough, more sea ice makes it colder in the Arctic. More interestingly, this applies to the Atlantic, but much less to the Pacific, though there is some effect (but outside Nino 3.4?). This is all months, as I failed to persuade it to do just September.
Though if you’re interested in the monthly anomaly plots, it will do them: click here. Very nice.
I’ve just realised that sea ice against Nino 3.4 is probably more interesting, in principle. Here it is:
Hmm, needs more work. Fergus asks, what about a 6 month lag? Not done: an exercise for the reader. The site supports it.
Disclaimer: I’m only playing.