The Intersection


The 16 storm 2003 Atlantic hurricane season (click to enlarge) — a possible analogue for 2007?

As we get closer to hurricane season–and especially once the season starts–the forecasts become increasingly reliable. We’re still a month away, though, so what follows should be taken, as always, with a grain of salt.

Nevertheless, we now have two more forecasts predicting–as previous forecasts have consistently done–a quite active Atlantic hurricane season.

One just released forecast comes from Tropical Storm Risk (PDF), a group whose methodology relies upon assessing sea-surface temperatures (SSTs) and trade wind speed over the Caribbean and tropical Atlantic. Based upon this methodology, Tropical Storm Risk now forecasts 16.1 total storms (plus or minus 3.8), 8.9 hurricanes (plus or minus 2.6), and 4.0 intense hurricanes (plus or minus 1.5). This is a very slight downscaling from their forecast of last month (16.7 named storms, 9.4 hurricanes, and 4.2 intense hurricanes, all plus or minus yada yada).

Meanwhile, I’ve become aware of a paper that is in press at the Journal of Geophysical Research – Atmospheres that introduces a new Atlantic forecasting methodology and also includes a prediction for this year. The paper, entitled “The Influence of Climate State Variables on Atlantic Tropical Cyclone Occurrence Rates,” is by Thomas A. Sabbatelli and Michael E. Mann of Penn State University. Using a statistical technique based on SSTs and the state of the El Nino-Southern Oscillation, they reached the following conclusion:

Based on statistical models of annual Atlantic TC counts developed in this study and current forecasts of climate state variables, we predicted m=15±4 total named storms for the 2007 season.

Which, of course, is just slightly lower than the Tropical Storm Risk forecast.

Meanwhile, forecasts (PDF) of the state of ENSO continue to show that we’re in neutral conditions, with a possible transition into a La Nina state over the next 3 months. If that’s right, then El Nino will not be around to save the Atlantic from a busy hurricane season this year.

As usual, take it all with a grain of salt. But start thinking about it.

The next forecasts, from William Gray of Colorado State University and from NOAA, will be out towards the end of the month.

P.S.: You may have heard about the latest paper by Chris Landsea, challenging the notion that global warming is increasing annual Atlantic storm counts. I’ll have more on this soon.


  1. #1 andy
    May 4, 2007

    Is that the Michael E. Mann? Of “hockey stick” fame? I didn’t realize that a dendrochronologist had expertise in hurricane forecasting.

  2. #2 Chris Mooney
    May 4, 2007

    1) Yes.

    2) Don’t be nasty.

    3) Don’t you trust the peer review process? It’s a peer reviewed paper that I cited. Who cares who wrote it.

  3. #3 andy
    May 4, 2007

    Sorry, I wasn’t deliberately trying to be nasty, (only asking a question and showing surprise), but yes, in retrospect, I can understand how it could be so interpreted. The Internet (and brief responses to blog posts) are not good media for nuance and/or subtlety. I’ll be more careful in the future.

    Not having seen the article, could it be that Mann’s contribution was in the statistical analysis rather than in the forecast modelling?

    And having said that, have the various criticisms of Mann’s statistical approaches to paleoclimatology proxies been adequately addressed?

    These are meant as honest questions from someone far outside either field (nuclear theory).


    Andy G.

  4. #4 Michael Mann
    May 5, 2007

    Andy G.,

    Thanks for your interest in my research. You can find my CV here. I have been called many things before, but never a ‘dendrochronologist’. I am an applied mathematician and physicist by training, with an M.S. in Physics and a Ph.D. in Geology and Geophysics. Of the >100 peer-reviewed papers I’ve published, none of them could be characterized as focusing on ‘dendrochronlogy’ (the establishment of an age model based on the use of tree-ring data), a small number are related to ‘dendroclimatology’ (the reconstruction of past climates from one particular type of proxy–tree rings). Much of my earlier work was in the development of statistical signal detection techniques, including applications to statistical climate forecasting. So seasonal Hurricane forecasting using climate variables aint that much of a stretch. A few of my earlier papers are on theoretical condensed matter physics. And, no, I haven’t used any of the techniques from those studies in the recent work I’ve done on Hurricanes either.

    As for your question about “criticisms” of my paleoclimate work, why don’t you read what the latest report of the IPCC Scientific Assessment, the most authoritative report on the state of climate science, had to say about the these “criticisms”. From page 466 of chapter 6 (paleoclimate chapter) of IPCC 4th Assessment (available online here).

    The ‘hockey stick’ reconstruction of Mann et al. (1999) has been the subject of several critical studies. Soon and Baliunas (2003) challenged the conclusion that the 20th century was the warmest at a hemispheric average scale. They surveyed regionally diverse proxy climate data, noting evidence for relatively warm (or cold), or alternatively dry (or wet) conditions occurring at any time within pre-defined periods assumed to bracket the so-called ‘Medieval Warm Period’ (and ‘Little Ice Age’). Their qualitative approach precluded any quantitative summary of the evidence at precise times, limiting the value of their review as a basis for comparison of the relative magnitude of mean hemispheric 20th-century warmth (Mann and Jones 2003; Osborn and Briffa, 2006). Box 6.4 provides more
    information on the ‘Medieval Warm Period’.

    McIntyre and McKitrick (2003) reported that they were unable to replicate the results of Mann et al. (1998). Wahl and Ammann (2007) showed that this was a consequence of differences in the way McIntyre and McKitrick (2003) had implemented the method of Mann et al. (1998) and that the original reconstruction could be closely duplicated using the original proxy data. McIntyre and McKitrick (2005a,b) raised further concerns about the details of the Mann et al. (1998) method, principally relating to the independent verification of the reconstruction against 19th-century instrumental temperature data and to the extraction of the dominant modes of variability present in a network of western North American tree ring chronologies, using Principal Components Analysis. The latter may have some theoretical foundation, but Wahl and Amman (2006) also show that the impact on the amplitude of the final reconstruction is very small (~0.05°C; for further discussion of these issues see also Huybers, 2005; McIntyre and McKitrick, 2005c,d; von Storch and Zorita, 2005).

    See also this discussion, and other discussions at the website RealClimate which is run by a group of ten climate scientists including myself.

  5. #5 andy
    May 5, 2007

    Dr. Mann (and all),

    Thank you very much for your most kind and helpful post. Of course I will look at the links that you posted. Being from Toronto, perhaps I have been badly influenced by the writings of the “notorious” contrarian Terry Corcoran of the National Post. On the other hand, I also know Dr. McBean, of Environment Canada, a well-known advocate of (inter alia) the Kyoto Protocol.

    I guess I’m just very confused. But perhaps this confusion is exactly what the “contrarians” desire.

    Again, many thanks for your extensive reply and most useful links, and I do apologize if my questions appeared to be antagonistic. I assure you that that was not my intent.

    Cheers, and with kindest regards,