Thursday, July 01, 2010

Hot or not?

The appearance of another month of HadCRU temperatures is the spur I need to finally write something about the prospects for a temperature record this year. Recall I have a bet with David Whitehouse on whether the 1998 temperature record is broken by 2011. While this doesn't have to happen this year, it might be the best chance I've got of a win.

The first point to make is that the current ENSO is just about over. It was a significant event, but nothing compared to 1998. In fact based on the forecasts I happened to download over the past few months, it has slightly undershot expectations. Here is a comparison of 1997-8 with 2009-10:

These data are actually 3-month smoothed so the last point labelled as April actually represents March-April-May and presumably the next datum is not far away. So at its maximum the recent ENSO was nothing like as strong as the one back then, but neither is it collapsing as quickly. Current forecasts are for a moderate La Nina later in the year.

Here's a comparison of the Hadcru temperatures:

The dotted lines are a 12-month backwards-looking smooth. As you can see, in 1998 December pretty much caught the peak in the temperature although the anomaly had collapsed a few months earlier. It looks to me like the red line will struggle to keep above the blue one over the next few months, and it is not at all certain that it will be on top come December. There's got to be a chance but I don't think I'd put it higher than 50% now (based on nothing more than eyeballing the graph plus the expected death of the ENSO - I haven't tried to find any more detailed forecasts of temperature).

Hansen (and to some extent the Hadley Centre) is still talking up the chance of a record temperature. For example, the former said it was "likely" in a recent widely-circulated draft paper. But that is using GISTEMP which already has 2005 hotter than 1998. In fact based on that analysis, the past 12 months are the hottest on record (in terms of anomaly) which is not the case for HadCRU.


pointer said...

One thing that's struck me is that HadCRU has in the eyes of the media become the standard for global temperature despite not even attempting to cover the polar regions. They barely mention GISTEMP.

So help me, it pains me to think this way, but the long-term prospects for action on mitigation could actually be helped if 2010 beat 1998 in the HadCRU.

crandles said...

HadCRUT correlates well with MEI.

2 Weeks ago ONI got down to -0.5 and it seemed likely to go further but since then has steadied at -0.5.

Assuming MEI for May/June is -0.2 and for the rest of the year -0.5 seems quite optimistic assumptions for you. A quick and dirty multiple linear regression then came out predicting HadCrut at .5 compared to 1998's .548.

For GISStemp however it comes out at 63 versus 62 for 2005.

Intrade which works on GISS has a range of 78 to 84 which may be a touch high but not worth the effort of betting on.

crandles said...
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Steve Bloom said...

pointer, HadCRUT gets publicized much more than GISTEMP (which mostly just gets an annual summary) and NCDC emphasizes U.S. temperatures in the publicity they do, so it's no surprise that the HadCRUT global results get the most attention. To Be fair, HadCRUT has dibs on the global since they with it first.

O-N-D look to be a nail-biter for James. The northern high lats may yet save him from minor embarrassment. Melt, sea ice, melt, and pass the popcorn.

crandles said...

>"O-N-D look to be a nail-biter for James."

Or not. Only 5 out of 40 years showed the error of 0.045 necessary for James to win. The variability in an out of sample year may be a litle higher but I doubt I would put James's odds at better than 20%. Unless of course you have a more compelling case for a higher probability.

Steve Bloom said...

Flying blind by the seat of some entirely non-scientific pants and observing that the past may not be a perfect guide to future when it comes to the Arctic and adjacent areas, there's been some unusual warmth there so far this year. If it holds, James has a chance. Regardless, I expect that he will be way behind as of September and then catch up a bit through O-N-D, thus the nail-biting aspect.

crandles said...

Signals seem a bit mixed at the moment:

ONI has crept towards (weak?) La Nina from 3 weeks at -0.5 to -0.6 this week.

MEI at -.412 for MayJun from +0.539 for AprMay "dropped faster than any other case on record for this time of year"

SOI after a strong El Nino 2.1 in Feb had changed to a La Nina'ish
+1.2 and +0.8 for April May is now back to a neutral 0.1 for June.

SOI could be a lead indicator or it could just be a blip.

MEI could be more reliable taking more factors into account but could also be showing change without yet making clear where it will go to.

ONI seems to be creaping towards weak La Nina and this may have the benefit of being the middle suggestion between heading for strong La Nina and back to neutral. However, the range of suggestions seems large with neither of other two agreeing with ONI on weak La Nina.

You pays your money .....