2010 Hurricane Factoids

Adam Lea, of University College London, shares these interesting hurricane factoids related the the remarkable dearth of US hurricane landfalls in recent years.  His comments are reproduced here with his permission:

As the 2010 hurricane season (with 10 hurricanes) starts to wind down I thought I would share a few statistics on how unusual this season has been historically for its lack of US hurricane landfalls:

1. Since 1900 there is no precedent of an Atlantic hurricane season with 10 or more hurricanes where none has struck the US as a hurricane. The five previous seasons with 10 or more hurricanes each had at least two hurricane strikes on the US.

2. The last precedent for a La Nina year of the magnitude of 2010 which had no US-landfalling hurricane is 1973.

3. Since hurricane Ike (2008) there have been 16 consecutive non US-landfalling hurricanes. Such a  sequence last happened between Irene (1999) and Lili (2002) with 22 consecutive non US-landfalling hurricanes, and between Allen (1980) and Alicia (1983) with 17 consecutive non US-landfalling hurricanes.

4. The period 2006-2010 is one of only three 5-year consecutive periods without a US major hurricane landfall (the other two such periods were 1901-1905 and 1936-1940). There has never been a six year period without a US major hurricane landfall.

5. Historically one in four Atlantic hurricanes strike the US as a hurricane. Thus the recent dearth in strikes should be ‘corrected’ in the next few years.

The 2006 – 2010 RMS Hurricane Damage Forecast

Where is all the death and destruction? We were told global warming was here, and would ignite a fire under the storms, making them bigger and more frequent. Massive hurricanes like Katrina would become much more common. The world’s oceans were warming, and this would stoke the fires of these tropical monsters. But they are not here — the hurricanes are missing in action, and have been ever since 2005. The truth: there has been a dramatic decrease in the number of hurricanes in the last five years. The total energy of all hurricanes around the world has plunged since 1993 — the opposite of what was predicted. How could that be, if global warming is real and is impacting our climate today?

Let’s go back to the middle of last decade, and see what took place.

Pajamas Media: What Happened to All the Hurricanes, Al?

Worldwide hurricane activity hasn’t just slowed since Katrina, it’s dropped off a cliff.

Wang, B., Y. Yang, Q.‐H. Ding, H. Murakami, and F. Huang, 2010. Climate control of the global tropical storm days (1965–2008). Geophysical Research Letters, 37, L07704, doi:10.1029/2010GL042487.

Abstract:

The tropical storm days have a consistent global record over the past 44 years (1965–2008), which provides an alternative metric for integrated information about genesis, track, and lifespan. Seasonal-reliant singular value decomposition is performed on the fields of the global storm days and sea surface temperature by using the “best track” data. The leading mode, which dominates the variability of the global total number of storm days, displays an east-west contrast between enhanced activity in the North Pacific and reduced activity in the North Atlantic and a north-south contrast in the Southern Hemisphere oceans between active tropics and inactive subtropics, which are coupled with the El Niño and a positive phase of the Pacific Decadal Oscillation (PDO). The second mode reveals a compensating trend pattern coupled with global warming: upward trends over the North Atlantic and the Indo-Pacific warm pool (17.5°S–10°N, 70–140°E) and downward trends over the Pacific, especially the South Pacific. However, the global total number of storm days shows no trend and only an unexpected large amplitude fluctuation driven by El Niño-Southern Oscillation and PDO. The rising temperature of about 0.5°C in the tropics so far has not yet affected the global tropical storm days.

World Climate Report: No Trend in Global Hurricane Activity

Update: Current Year-to-Date analysis of Northern Hemisphere and Global Tropical Cyclone Accumulated Cyclone Energy (ACE) AND Power Dissipation Index (PDI) has fallen even further than during the previous 3-years. The global activity is at 33-year lows and at a historical record low where Typhoons form in the Western Pacific. Also see additional blog posting with recognition given to Rush Limbaugh’s tropical cyclone knowledge…

While the North Atlantic has seen 15 tropical storms / hurricanes of various intensity, the Pacific basin as a whole is at historical lows! In the Western North Pacific stretching from Guam to Japan and the Philippines and China, the current ACE value of 48 is the lowest seen since reliable records became available (1945) and is 78% below normal*. The next lowest was an ACE of 78 in 1998. See figure below for visual evidence of the past 40-years of tropical cyclone activity.

CRN comment: Didn’t Al Gore show hurricanes coming out of chimney stacks in his quackumentary AIT? Perhaps there is a 33-year low for chimney stacks.

A team of researchers under the auspices of the World Meteorological Organization has published a new review paper in Nature Geoscience (PDF) updating consensus perspectives published in 1998 and 2006. The author team includes prominent scientists from either side of the “hurricane wars” of 2005-2006: Thomas R. Knutson, John L. McBride, Johnny Chan, Kerry Emanuel, Greg Holland, Chris Landsea, Isaac Held, James P. Kossin, A. K. Srivastava and Masato Sugi.

The paper reaches a number of interesting (but for those paying attention, ultimately unsurprising) conclusions. On North Atlantic hurricanes the paper states (emphasis added):

Hurricane counts (with no adjustments for possible missing cases) show a significant increase from the late 1800s to present, but do not have a significant trend from the 1850s or 1860s to present3. Other studies23 infer a substantial low-bias in early Atlantic tropical cyclone intensities (1851–1920), which, if corrected, would further reduce or possibly eliminate long-term increasing trends in basin-wide hurricane counts. Landfalling tropical storm and hurricane activity in the US shows no long-term increase (Fig. 2, orange series)20. Basin-wide major hurricane counts show a significant rising trend, but we judge these basin-wide data as unreliable for climate-trend estimation before aircraft reconnaissance in 1944.

The paper’s conclusions about global trends might raise a few eyebrows.

In terms of global tropical cyclone frequency, it was concluded25 that there was no significant change in global tropical storm or hurricane numbers from 1970 to 2004, nor any significant change in hurricane numbers for any individual basin over that period, except for the Atlantic (discussed above). Landfall in various regions of East Asia26 during the past 60 years, and those in the Philippines27 during the past century, also do not show significant trends.

The paper acknowledges that the detection of a change in tropical cyclone frequency has yet to be achieved:

Thus, considering available observational studies, and after accounting for potential errors arising from past changes in observing capabilities, it remains uncertain whether past changes in tropical cyclone frequency have exceeded the variability expected through natural causes.

The paper states that projections of future activity favor a reduction in storm frequency coupled with and increase in average storm intensity, with large uncertainties:

These include our assessment that tropical cyclone frequency is likely to either decrease or remain essentially the same. Despite this lack of an increase in total storm count, we project that a future increase in the globally averaged frequency of the strongest tropical cyclones is more likely than not — a higher confidence level than possible at our previous assessment6.

Does the science allow detection of such expected changes in tropical cyclone intensity based on historical trends? The authors say no:

The short time period of the data does not allow any definitive statements regarding separation of anthropogenic changes from natural decadal variability or the existence of longer-term trends and possible links to greenhouse warming. Furthermore, intensity changes may result from a systematic change in storm duration, which is another route by which the storm environment can affect intensity that has not been studied extensively.

The intensity changes projected by various modelling studies of the effects of greenhouse-gas-induced warming (Supplementary Table S2) are small in the sense that detection of an intensity change of a magnitude consistent with model projections should be very unlikely at this time37,38, given data limitations and the large interannual variability relative to the projected changes. Uncertain relationships between tropical cyclones and internal climate variability, including factors related to the SST distribution, such as vertical wind shear, also reduce our ability to confidently attribute observed intensity changes to greenhouse warming. The most significant cyclone intensity increases are found for the Atlantic Ocean basin43, but the relative contributions to this increase from multidecadal variability44 (whether internal or aerosol forced) versus greenhouse-forced warming cannot yet be confidently determined.

What about more intense rainfall?

. . . a detectable change in tropical-cyclone-related rainfall has not been established by existing studies.

What about changes in location of storm formation, storm motion, lifetime and surge?

There is no conclusive evidence that any observed changes in tropical cyclone genesis, tracks, duration and surge flooding exceed the variability expected from natural causes.

Bottom line (emphasis added)?

. . . we cannot at this time conclusively identify anthropogenic signals in past tropical cyclone data.

The latest WMO statement should indicate definitively (and once again) that it is scientifically untenable to associate trends (i.e., in the past) in hurricane activity or damage to anthropogenic causes.

CRN comment: You wouldn’t glean the above from the paper’s abstract, which paints alarming future predictions based on…yes, you’ve guessed it….computer modelling!

Read the entire article at The Register: Now IPCC hurricane data is questioned

Bootnote

The IPCC’s AR4 chapter lead was Kevin Trenberth, who features prominently in the Climategate emails. In 2005, the National Hurricane Center’s chief scientist Chris Landsea resigned his post in protest at the treatment of the subject by Trenberth.

“I personally cannot in good faith continue to contribute to a process that I view as both being motivated by pre-conceived agendas and being scientifically unsound. As the IPCC leadership has seen no wrong in Dr. Trenberth’s actions and have retained him as a Lead Author for the AR4, I have decided to no longer participate in the IPCC AR4.”

Critics point out that an increase in low-intensity storms being recorded is due to better instrumentation. Most are at sea, and thanks to radar and satellites, more are now observed.

Here is an excerpt as related to that last point:

Focusing on the past six decades, we observe no sustained upward trends in wind speed distributions (Figs. 1 and 3), the mean wind speed at landfall or the annual frequency of occurrence of landfalling segments (Fig. 8). (Note that this annual frequency is specific to landfalling segments and different from the annual frequency of landfalling events since some events have multiple landfalling segments, e.g. in 2005 Hurricane Katrina made landfall in both South Florida and Louisiana.) This being the case, the dramatic increases in total economic and insured losses from TCs, which have been manifest over the past six decades, indicates that the increasing losses must be attributed to the factors other than wind speed alone. This is in accord with recent studies (Pielke, 2005; Pielke et al., 2008; Crompton and McAneney, 2008), which demonstrate the importance of demographic changes in driving the increasing economic cost of hurricane losses.

The paper concludes as follows:

The quality of observational data is central to the ongoing debate between a warming climate and consequences for TC frequency and intensities. Our analyses show clear, anomalous differences in the wind speed distributions between the early historical period and the very recent six decades. While these differences cannot unequivocally exclude a possible Global Climate Change cause, we suggest that data quality issues are more plausible.

An enormous challenge lies ahead for recovering reliable wind estimates in the early historical record, especially for highly dynamic and short-lived extreme TCs. The counting of events by Saffir-Simpson Hurricane categories is determined by threshold wind speeds, and if the wind estimates are themselves unreliable, how can derivative statistics be trusted sufficiently for long-term trend analysis? It is timely to recognise that using the early historical record will inevitably involve some irreducible uncertainties and “fixing” these may not be possible and that more physically-based models are needed to help resolve the data impasse. Conclusions drawn from scientific and insurance applications using the inherently lower-quality components of the record should be treated with caution.

Roger Pielke Jr.’s blog: The “Shameful Article”: A Review and Update

Abstract:

This paper asks whether one- to five-year predictions of United States hurricane landfalls and damages improve upon a baseline expectation derived from the climatological record. The paper argues that the large diversity of available predictions means that some predictions will improve upon climatology, but for decades if not longer it will be impossible to know whether these improvements were due to chance or actual skill. A review of efforts to predict hurricane landfalls and damage on timescales of one to five years does not lend much optimism to such efforts in any case. For decision makers, the recommendation is to use climatology as a baseline expectation and to clearly identify hedges away from this baseline, in order to clearly distinguish empirical from non-empirical justifications for judgments of risk.

The new study, reported in the online edition of the American Meteorological Society’s peer-reviewed Journal of Climate, shows that short-lived tropical storms and hurricanes, defined as lasting two days or less, have increased from less than one per year to about five per year from 1878 to 2008.

“The recent jump in the number of short-lived systems is likely a consequence of improvements in observational tools and analysis techniques,” said Chris Landsea, science and operations officer at NOAA’s National Hurricane Center in Miami, and lead author on the study. “The team is not aware of any natural variability or greenhouse warming-induced climate change that would affect the short-lived tropical storms exclusively.”

Several storms in the last two seasons, including 2007’s Andrea, Chantal, Jerry and Melissa and 2008’s Arthur and Nana, would likely not have been considered tropical storms had it not been for technology such as satellite observations from NASA’s Quick Scatterometer (QuikSCAT), the European ASCAT (Advanced SCATterometer) and NOAA’s Advanced Microwave Sounding Unit (AMSU), as well as analysis techniques such as the Florida State University’s Cyclone Phase Space.

“We do not dispute that these recent systems were tropical storms,” said Landsea. “In fact, the National Hurricane Center’s ability to monitor these weaker, short-lived storms provides better warnings to mariners of gale force winds and high seas.”

According to Dr. Brian Soden, a professor at the University of Miami’s Rosentiel School for Marine and Atmospheric Sciences, “The study provides strong evidence that there has been no systematic change in the number of north Atlantic tropical cyclones during the 20th century.”

Co-authors Gabriel Vecchi and Thomas Knutson, both of the NOAA Geophysical Fluid Dynamics Laboratory, developed a sampling methodology to measure whether meteorologists missed medium- to long-lived tropical storms and hurricanes from the late 1800s through the 1950s. They found that about two of the medium- to long-lived storms per year were unaccounted for in the late 1800s. By the 1950s, forecasters missed less than one per year.

When the researchers discounted the number of short-lived tropical storms and hurricanes and added the estimated number of missed medium- to long-lived storms to the historical hurricane data, they found no significant long-term trend in the total number of storms.

The team also noted that the finding of no increasing trend in hurricane and tropical storm counts in the Atlantic is consistent with several recent global warming simulations from high-resolution global climate model and regional downscaling models.

“This new study is one piece of the puzzle of how climate may influence hurricanes. Although Atlantic storm counts overall have not changed, this study does not address how the strength and number of the strongest hurricanes have changed or may change due to global warming,” noted Knutson.

Lennart Bengtsson of the University of Reading, United Kingdom, was also a research team member and co-author on the journal paper.

NOAA understands and predicts changes in the Earth’s environment, from the depths of the ocean to the surface of the sun, and conserves and manages our coastal and marine resources.

NOAA  11th August 2009

Study: Better Observations, Analyses Detecting Short-Lived Tropical Systems