Haiyan: Is This a Trend?

November 13, 2013

cyclonepower

Figure 1 | Analysis and model results of satellite-derived tropical cyclone
lifetime-maximum wind speeds. a, Box plots by year. Trend lines are shown
for the median, 0.75 quantile, and 1.5 times the interquartile range. b, Trends
in global satellite-derived tropical cyclone maximum wind speeds by
quantile, from 0.1 to 0.9 in increments of 0.1. Trends are estimated
coefficients from quantile regression in units of metres per second per year.
The point-wise 90% confidence band is shown in grey, under the assumption
that the errors are independent and identically distributed. The solid red line
is the trend from a least-squares regression of wind speed as a function of
year and the dashed red lines delineate the 90% point-wise confidence band
about this trend.

A leading oceanographer referred me to this study, from 2008, which he says remains accurate - graph above. I include the caption for those who speak stats.
Takeaway for the rest of us – its a graph of wind speeds in tropical cyclones -
and it’s going up.

Abstract from Elsner et al 2008:

Atlantic tropical cyclones are getting stronger on average, with a
30-year trend that has been related to an increase in ocean temperatures
over the Atlantic Ocean and elsewhere1–4. Over the rest
of the tropics, however, possible trends in tropical cyclone intensity
are less obvious, owing to the unreliability and incompleteness
of the observational record and to a restricted focus, in previous
trend analyses, on changes in average intensity. Here we overcome
these two limitations by examining trends in the upper quantiles
of per-cyclone maximum wind speeds (that is, the maximum
intensities that cyclones achieve during their lifetimes), estimated
from homogeneous data derived from an archive of satellite
records. We find significant upward trends for wind speed quantiles
above the 70th percentile, with trends as high as 0.36
0.09ms21 yr21 (s.e.) for the strongest cyclones. We note separate
upward trends in the estimated lifetime-maximum wind speeds of
the very strongest tropical cyclones (99th percentile) over each
ocean basin, with the largest increase at this quantile occurring
over the North Atlantic, although not all basins show statistically
significant increases. Our results are qualitatively consistent with
the hypothesis that as the seas warm, the ocean has more energy to
convert to tropical cyclone wind.

Update: Here’s a clearer graphic from Jeff Master’s WeatherUnderground.

Greg Laden’s Blog:

Tropical cyclones run on heat, and much of that heat comes from the sea surface. If the surface of the ocean is below a certain temperature, about 82 degrees F, about 28 degrees C, a hurricane or typhoon is very unlikely to form. Above that temperature, if other conditions are right, it may form. Warmer seas can make bigger or stronger storms, and as the storm passes over the ocean, the temperature of the sea surface has a strong influence on whether the storm increases or decreases in strength . As the storm moves over the sea, the interface between the windy storm and the roiling ocean becomes something of a mess, as though the surface of the ocean was in a blender, and there is a lot of exchange of heat across that interface. Also, deeper, cooler water is mixed with warmer surface water. A powerful storm moving across the ocean will leave in its wake a strip of cooler water. This sometimes causes subsequent storms moving along the same path to be weaker or to downgrade in strength more quickly.

This should indicate, one would think, that as sea surface temperatures (SST) have gone up with global warming, there should be more “hurricane” out there on the oceans. It has been hard to make the link between global warming and frequency of hurricanes, however. This may be because of the nature of hurricane formation. Once a hurricane forms in a given spot and gets big, it may reduce the chance of the next hurricane forming. Also, hurricanes are usually born as waves in a very large scale pattern of air masses. The total number of waves that form may not change with global warming, and the hurricane season is only a part of the year, and other factors have to come into play that are also ponderous in their timing to turn a wave into a major storm. An analogy might be this: Imagine that everyone in the working population of a downtown neighborhood becomes hungrier, perhaps because all the companies they work for insist on a two hour high intensity exercise program for everyone to lower their health insurance costs. Will this increase in hunger mean more lunches, snacks, and dinners consumed in the local restaurants? Or will the lunches, snacks, and dinners become larger, with people ordering more food with each sitting? Since there are only so many opportunities to go grab a bite to eat, there will probably be very few additional visits to the local eateries, but more food may well be consumed per event. Increased SST may be like increased hunger. There may not be very many more hurricanes, but among those that occur, some may be much stronger.

There is evidence for this. Kerry Emanuel did a study several years ago that linked sea surface temperatures in the Pacific with an index called PDI, which measures the overall energy involved in typhoon/hurricane activity. (Emanuel, K. (2005). Increasing destructiveness of tropical cyclones over the past 30 years, 436(August), 686–688. doi:10.1038/nature03906.) He came up with this graph:

The graph shows that hurricanosity, as it were, goes up and down with sea surface temperature more or less. And, SST goes up and down with decadal oscillations like ENSO (El Nino) but with an overall upward trend caused by global warming.

Here’s the new part. If you look at a map of Sea Surface Temperature you are seeing a measurement of, well, the surface of the sea … the top of the water. As a hurricane chugs along on the surface of the sea, turning the top meter or so of ocean into spray and creating a very wavy situation, that heat is certainly directly affecting the storm, but the temperature of the water several meters down also matters. It turns out that sometimes this shallow-deep water (as opposed to deep deep water, way down farther) can be quite warm. When that happens, the dissipation of SST does not occur to the same degree. The leading edge of the hurricane gets a good dose of heat from the surface, but instead of the SST dropping as the top warm water is mixed with somewhat deeper cooler water, the heat supply is not attenuated, or at least not by much, as the massive storm moves along. More of the storm gets more heat, and the storm as a whole gets more heat. And there’s more heat left over for the next storm.

We think this happened with Haiyan. Have a look at the following map. It is sea surface temperature anomaly (how much more or less than expected the SST is) for the top 50 meters for the western Pacific at the time of the typhoon. The Philippines is down near the bottom of the map straddling the 10 and 15 degree N lines. (Maps are from here) Notice that the surface is not unusually warm.

This does not mean that the sea surface was not warm. It was plenty warm as it is this time of year i that part of the ocean, just not warmer than expected. Here is the raw temperature (not anomaly) map so you can see that the tropical ocean is, well, tropically warm:

The purple area along the south is sufficiently warm to form typhoons. The ocean to the east of the Philippines is warm enough to form typhoons, but is there any source of extra heat to form a super typhoon? Have a look at this map. This is the water temperature at depth, here at 100 meters. This is an anomaly map, so its shows if the temperature is more (or less) than expected. Notice that east-west band of red indicating several degrees warmer than it usually is, at depth.

[Updated:] Here’s the same map with Haiyan/Yolanda’s track and history, graphic generated by Jeff Masters.

So, it would appear that Haiyan/Yolanda passed over the usual very warm waters that allow the formation of typhoons, but also, over water that was warm at depth so as the top of the sea is churned up by the growing storm, there would be extra heat to feed that storm.

One final map. This is the actual temperature (not anomaly) at the 100 meter level. Notice the purple area.

At 100 meters depth, the sea was warm enough to form a typhoon. That, dear reader, is extreme.

The same thing happened with Katrina. According to a report from NOAA:

A number of factors contributed to making Katrina a strong Category 5 hurricane…Sea surface temperatures (SST) in the Gulf of Mexico were one to two degrees Celsius above normal …, and the warm temperatures extended to a considerable depth through the upper ocean layer. Also, Katrina
crossed the “loop current” (belt of even warmer water), during which time explosive
intensification occurred. The temperature of the ocean surface is a critical element in the
formation and strength of hurricanes.

We know that the ocean is absorbing a lot of the extra heat caused by global warming. Well, this is some of that heat, causing megastorms.

I’ve noticed that climate science denialists are very adamant about two things: Denying the importance of major storms like Haiyan, and denying the fact that heat is going into the oceans. Perhaps they see the link, and are frightened that people will believe that anthropogenic changes to our climate can kill thousands of people at a time, in a few hours, through the mechanism of anomalously high temperature at modest depth below the surface of the already tepid tropical sea.

It is time for action.

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15 Responses to “Haiyan: Is This a Trend?”

  1. omnologos Says:

    Reluctance by major mainstream climate scientists to make a fuss over Haiyan (eg Peter Stott of the Met Office live on the BBC, or even Emanuel to Borenstein) suggests that either ‘denialism’ is more pervasive than once thought, or that there is something wrong in obsessing about denialism on a topic where the debate is extremely robust.

    As for warm waters down below, I hope somebody tries to do something useful out of it and establish a way to forewarn Haiyan-style events, rather than yet again find an explanation after the fact.

    Priority in any case seems to be improve monitoring of typhoons to the level hurricanes are followed at already. It is beyond belief that it’s currently done all from afar, and even today we do not know how strong were Haiyan’s winds really at landfall.


    • Or, if you’re a member of the reality based community, you’ll note there’s no reluctance at all, but rather a recognition that, hey, we knew this all along. Thanks for catching up.

  2. redskylite Says:

    Once the survivors are safe and the shock/grief clears, the priority for the remaining will be restarting and rebuilding their lives. As climatic events will get worse for the Philippines they need to look especially to architecture, town planning/architects and the very way they use/occupy land to be able to resist and adapt to such ever increasing powerful forces. I am very hopeful that eventually governments will take climate change seriously (just as they did for the dreaded tobacco industry and the billions of addicts – including me), and finally we can stop increasing the GHG concentrations and allow nature to rebalance.

    • omnologos Says:

      Careful redskylite you’re talking sense now. Accusations of trollism and denialism can’t be far

      • stephengn1 Says:

        “As climatic events will get worse for the Philippines….”

        …doesn’t sound like a denial

        “…ever increasing powerful forces”

        … doesn’t sound like denial

        “finally we can stop increasing the GHG concentrations and allow nature to rebalance.”

        …doesn’t sound like a denial

        You, however, though you attempt to cleverly parse your words, pretty much always sound like a denialist

        • omnologos Says:

          That’s right Stephen. But to suggest resilience to be dealt with first and before trying to reduce emissions, has been more than enough in the past to receive the standard stupid answer ‘denier!’.


    • finally we can stop increasing the GHG concentrations and allow nature to rebalance.

      We got Haiyan at a mere 400 ppm CO2, and systems are nowhere near in balance; the ocean temperatures lag well behind the equilibrium values, while CO2 continues to surge upward.  Further, Haiyan itself is part of the equilibration.  Super-hurricanes stir the deep hot water and dump some of its heat back to the atmosphere and to space.

      What we need is to pull CO2 back down to 350 ppm, maybe less.  I know exactly one way to even stop the upward trend, let alone bring it down again.  You know what that is.

      • stephengn1 Says:

        You are under the illusion your way would work, but when you do the numbers it’s almost a wash. THIS way, however …

        http://phys.org/news199005915.html

        … might just work

        I imagine enormous solar catalytic mats laid out upon our oceans lifeless “desert” regions.

        Please learn more about quickly advancing solar catalysis – it CAN get us to where we need to be


        • Take the one thing that’s been providing energy on demand in mass quantities, without carbon emissions, FOR DECADES, and demand that it be replaced with a hypothetical system which may turn out to be snake oil (just like Range Fuels and so many others).

          Yeah, that’ll work.  Bet the biosphere on it, why doncha.  Oh, wait, you really would.

          • stephengn1 Says:

            No sir – YOU are the one that took the one thing that’s been providing energy on demand in mass quantities, without carbon emissions, TO ALL LIFE, FOR BILLIONS OF YEARS, is based on fusion, not fission, is nuclear waste free and is responsible for the existence all life on this planet, and demanded that it be replaced with a system that has proven exceedingly problematic, expensive, is resource dependent, requires triple, quadruple and quintuple redundancies, is based on enormous mechanical technology from the last century, and is not politically feasible in the time frame allotted to us.

            You are proving your ignorance. Solar Catalytics and artificial photosynthesis are proven concepts – not hypotheticals, not snake oil. Even before Vogtle shows itself to be total boondoggle it is (and make Solyndra look like child’s play) rapid advances in solar catalytics (a technology that is SOLID STATE – no moving parts) will utterly surprise you.

            The future is rapidly approaching and you are looking backwards.


          • YOU are the one that took the one thing that’s been providing energy on demand in mass quantities, without carbon emissions, TO ALL LIFE, FOR BILLIONS OF YEARS, is based on fusion, not fission, is nuclear waste free and is responsible for the existence all life on this planet, and demanded that it be replaced

            Bull puckey.  I didn’t demand squat, and it’s a foul lie to even suggest that I did.  Humanity lived on your “fusion-based” energy from its emergence as a species, and found it woefully inadequate.  All the countries allegedly following your “green energy” ideology are failing to replace fossil fuels, and some are even increasing their carbon emissions.

            Coal, oil and gas substituted for fitful wind, irregular sun and scarce wood starting in the 17th century.  The only place your “fusion-based” energy keeps electric grids running is where it provides an abundance of water that humans now pen up behind dams.  There are only a few places on earth where this is sufficient.  The remaining needs WILL be served somehow.  The only question is if they’ll be supplied by splitting atoms of heavy metal, or digging up dirty black liquids and solids and dumping their combustion products in the atmosphere.

            demanded that it be replaced with a system that has proven exceedingly problematic, expensive, is resource dependent, requires triple, quadruple and quintuple redundancies, is based on enormous mechanical technology from the last century, and is not politically feasible in the time frame allotted to us.

            How ironic.  It’s the “green” vision of energy which requires double, triple and quadruple redundancies in supply systems just to keep a grid operating… and can’t even get rid of fossil fuels except in the rare cases of copious hydropower.  It’s the “green” vision of wind farms and solar-thermal fields everywhere which is based on enormous mechanical technology spanning tens and hundreds of miles.  And it’s the “green” ideology of “fusion-based energy” which has politcally forced true alternatives from consideration, while being technically and maybe even physically impossible to achieve itself.

            Solar Catalytics and artificial photosynthesis are proven concepts

            And not supplying one watt of grid power nor one gallon of fuel to consumers anywhere.  Meanwhile, the province of Ontario and the entire nation of France get essentially all their electric power from carbon-free sources, the majority of which is nuclear.

            Even before Vogtle shows itself to be total boondoggle it is (and make Solyndra look like child’s play) rapid advances in solar catalytics (a technology that is SOLID STATE – no moving parts) will utterly surprise you.

            Do feel free to surprise me.  I’m not willing to bet the planet on your claims, even if you are.

          • stephengn1 Says:

            I don’t need to surprise you. The renewables market will do that


          • I’ll believe it when I see it.  Until then, I’m going with the technology that nearly eliminated oil-fired electric generation in the USA and has pretty much killed coal in Ontario.


  3. Therese quite a few affects that a warming climate will have on storms. It cant not affect them can it. The profile is changes. Anecdotally it seems to me that powerful storms are spinning up much quicker.

    They are also happening earlier and later. Their tracts are also changing. They are also starting and traversing over wider regions due to a greater spread of warmer surface temperatures. Are they lasting longer? Seems that way. This means they are combining with other weather phenomena more often like what happened with Sandy.

    Higher sea levels are having an impact on bigger storm surges. Their intensity certainly seems to be getting more or peaking higher at certain times.

    Precipitation for less intense storms is going through the roof. Thus making those quite devastating on a region. Not only for humans but for wild life etc.

    The frequency of more powerful storms seems to me to be increasing. See also this…

    So there are all these things and a few more (as you tackle above) which are happening due to global warming.

    We need to have a central reference repository that meteorologist and climate scientist can use as a base line when talking about storms and global warming. There is still too much confusion when this topic is presented to the public unfortunately.


  4. missing link for above…. some times simple is the way to go…

    intensity-or-frequency
    http://residualanalysis.blogspot.ca/2010/04/intensity-or-frequency.html


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