3rd International Summit on Hurricanes and Climate Change

Over the past several years the topic of hurricanes and climate change has received considerable attention by scientists, the insurance industry, and the media. Building on the successful 1st and 2nd Summits, I am organizing the 3rd Summit to be held June 27-July 2, 2011 in Rhodes, Greece. The purpose is to bring together leading academics and researchers on various sides of the debate and from all around the world to discuss new research and express opinions about what is happening and what might happen in the future with regard to regional and global hurricane (tropical cyclone) activity. The goals are to address what research is needed to advance the science of hurricane climate and to provide a venue for encouraging a lively, spirited, and sustained exchange of ideas. Please consider joining us.

Spatial grids for hurricane climate research

We demonstrate a new framework for studying hurricane climatology. The framework consists of a spatial tessellation of the hurricane basin using equal-area hexagons. The hexagons are efficient in covering hurricane tracks and provide a scaffolding to combine attribute data from tropical cyclones with spatial climate data. The framework's utility is demonstrated using examples from recent hurricane seasons. Seasons that have similar tracks are quantitatively assessed and grouped. Regional cyclone frequency and intensity variations are mapped. A geographically-weighted regression of cyclone intensity on frequency and SST (results shown here) emphasizes the importance of a warm ocean in the intensification of cyclones over regions where the heat content is greatest. The largest differences between model predictions and observations occur near the coast. The framework would be ideally suited for comparing tropical cyclones generated from different numerical simulations (see U.S. CLIVAR hurricane working group). The hexagons have equal area and are plotted on a map using the Lambert conformal conic projection with standard parallels of 23 and 38 degrees.

Geographers poised to lead a new revolution in hurricane climate research

In my talk this week to the West Florida chapter of the American Meteorological Society I make a case that geographers are well positioned to lead a new revolution in hurricane climate research. Watch here.

Shorebirds benefit from hurricanes

Tiny threatened shorebirds on Florida’s west coast not only survive hurricanes, they seem to benefit from the storms’ aftereffects, according to new research findings that contradict conventional wisdom.

The findings could have implications for beach nourishment efforts throughout the world and how they affect wildlife.---Mickie Anderson, UF media relations. Read more. Photo credit: Western Snowy Plover, Mike Baird, Morro Bay, CA USA.

Book Review: Hurricanes of the Gulf of Mexico by B. Keim and R. Muller

Two professors from Louisiana State University, each having had personal experiences with hurricanes and extreme weather and each with a deep interest in weather and climate, join forces to highlight tropical storms and hurricanes that have affected the Gulf of Mexico over the past 100 to 150 years. They aim to provide a description of the climatology and history of the most notorious hurricanes of the Gulf coast for the weather and storm enthusiast as well as for the residents who “persevere in the face of hurricanes for the bounty the Gulf brings” (p. v), and they largely succeed. Read more.

Denver's R User Group

Applied spatial data analysis using R. Thomas Jagger will discuss packages used by Roger Bivand et al. in his book Applied Spatial Data Analysis with R. If you're in the area, consider joining the R-uckus.

http://www.meetup.com/DenverRUG/calendar/14863343/

Hourly Tornado Occurrence Relative to Local Sunset Time

Hurricanes and Solar Variability

How Can Solar Variability Affect Hurricanes?

An inverse relationship between hurricane activity over the Caribbean and the number of sunspots has recently been identified. Here we investigate this relationship using daily observations and find support for the hypothesis that changes in ultraviolet (UV) radiation are the cause. The relationship is statistically significant after accounting for annual variation in ocean heat and the El Nino cycle. A warming response in the upper troposphere to increased solar UV forcing, as measured by the Mg II core-to-wing ratio, decreases the atmosphere's convective available potential energy (CAPE) leading to a weaker cyclone. The response amplitude at a hurricane intensity of 44 m/s is 6.7 m/s +/- 2.56 m/s per 0.01 Mg II units (s.d.), which compares with 4.6 m/s estimated from the heat-engine theory using a temperature trend derived from observations. An increasing response sensitivity with increasing hurricane strength is found in the observations and in an application of the theory. Read more. Citation: Elsner, J. B., T. H. Jagger, and R. E. Hodges (2010), Daily tropical cyclone intensity response to solar ultraviolet radiation, Geophys. Res. Lett., 37, L09701, doi:10.1029/2010GL043091.

Oil Spills and Hurricanes

The oil slick over the northern Gulf of Mexico will reflect more incoming sunlight so will warm slower than the surrounding ocean. If this delayed warming continues into the hurricane season, then a tropical cyclone that visits the region might have slightly weaker winds. Reduced water evaporation from any remaining oil film at the time of the hurricane will contribute to the decrease in wind speeds assuming the high winds do not immediately disperse the oil.

Frequency and Intensity Changes

Today 20% of the strongest cyclones exceed 49 m/s on average globally. With a 1C rise in SST, 20% of the strongest cyclones could exceed 51 m/s according to Elsner et al. (2008). Thus the 80th percentile increases from 49 to 51 m/s. Today, on average, 17 cyclones/yr exceed 49 m/s and 13 exceed 51 m/s. If 51 m/s is the new 80th percentile (after a 1C warming) then, without a change in the overall number of cyclones, 13 becomes 17.

3rd International Summit on Hurricanes and Climate Change

The 3rd International Summit on Hurricanes and Climate Change will be held next summer in Rhodes, Greece. The dates are set for June 27-July 2, 2011 at the Sheraton. Please join us.

Environmental Signals in Property Damage Losses

The strongest Atlantic hurricanes are getting stronger as ocean temperatures warm (Elsner et al. 2008) and the strengthening is expected to continue (Knutson et al. 2010). However, along the U.S. coast the intensity of hurricanes has not gone up and there is considerable debate about potential future damage losses from these catastrophic events. Here we model the historical damage losses and show the magnitude of losses at a return period of 50 years is largest under a scenario featuring a warm Atlantic Ocean, a weak North Atlantic surface pressure gradient, El Nino, and few sunspots. Results are consistent with our current understanding of hurricane climate variability and they suggest a future of greater long-term loss potential if seas continue to warm.

Old Hurricanes

The record of past tropical cyclones provides an important means to evaluate the hurricane hazard. Historical chronologies are a source of information about tropical cyclones prior to the modern era. Chenoweth (2006) describes an archive of 383 tropical cyclones occurring during the eighteenth and nineteenth centuries, largely before the official hurricane record.

We demonstrate a novel way this archive can be used to articulate historical tropical cyclone activity across space. First, an event in the archive is assigned a series of latitude/longitude coordinates approximating the descriptive locations of the cyclone’s affect. Second, tropical cyclones from the modern record that approach these locations (modern analogs) are mapped. Third, a probable pathway and a realistic track of the archived event is created by averaging the modern analog tracks. As an example, the procedure is used to generate a map showing the tracks of the Atlantic tropical cyclones of 1766. Sensitivity of the methodology to changes in event location and event timing are considered.

Results show historical hurricane chronologies when combined with a history of cyclone tracks can provide new information about the older events not directly related to where the original information was gathered. When this new information is available for all cyclones it should help climatologists better understand long-term variations in tropical cyclone activity.

For more information see here.

A Climate Hurricane

A month after hackers broke into the CRU email server and released to the web email (it could have been a leak) correspondences between top climate researchers, what it all means is still being sorted. It apparently had little influence on the Copenhagen Summit as world leaders had momentum going in as well as other issues to sift through.

It is tempting to see the affair (dubbed climategate) as a small tempest on the otherwise tranquil sea of climate research--damaging perhaps to the scientists involved but lacking broader impacts. That would be a mistake. Limited in scope, though certainly broadcast widely, it reveals a suspicion scientists harbor about the research process that rarely gets articulated to a wider audience.

In my opinion the most important repercussion concerns scientific integrity. Climategate demonstrates that scientists can be quick to dismiss research ideas when they threaten their own. This can be relatively benign as rejecting/accepting a paper without careful review (editor's decide using multiple reviews) or worse when failing to cite the relevant literature undermining an essential scientific commitment to evaluating ideas on intellectual merit. It assumes a certainty of methods and ideas of one's own that's counter to the essential self-skepticism of the scientific enterprise. And it can be insidious when the behavior is passed on to a generation of students.

In basic fields, like particle physics, consequences of this type of behavior might decay rather quickly. In climate science where multiple plausible explanations are the norm as evidence is based on observations (not controlled experiments) and theory is incomplete or lacking, consequences have a much slower decay rate. And in a field with policy relevance, this can have a negative impact on the enterprise of science and thus on society as a whole.

The enduring lesson should be greater scientific integrity. Read and cite the relevant literature, analyze the data with proper tools, acknowledge the underlying assumptions, create information-rich graphs, write clearly, and most importantly, explain why you might be wrong.

Reproducible Codes for Climate Science

Foundational pillars of science include transparency and reproducibility. Unfortunately too few climatologists take advantage of the powerful R language for statistical computing. It's a shame because it makes developing, maintaining and documenting code easy, thus facilitating replication. As an example see our blog entry for July 5th 2008 on how to use quantile regression to quantify the increasing trends in hurricane intensities over the period 1981-2006. This is obviously the future for climate research and the faster we move in this direction, the better off climate science will be.

Alternative Risk Transfer

Imagine an insurer of coastal properties concerned about the next hurricane season. A severe storm happens once every few decades; if the severe storm hits this year, she’ll have to pay out most of her money in claims. To help remain solvent, she could buy reinsurance. Alternatively, she could issue a catastrophe (cat) bond, which would pass the risk on to an investor. An investor could buy the bond valued at, say, $100,000; over time, the insurer would repay the bond with, say, 15% interest. If no hurricane hits during the year, the investor makes 15% on his investment. The insurer also turns a profit because she continues to collect premiums. But if this low-probability severe hurricane does hit, then the investor loses his $100,000, which is used by the insurer to pay claims.

A cat bond triggers payments based on the occurrence of a specified catastrophic event. Most cat bonds to date have been linked to hurricanes and earthquakes, but some have been issued to respond to mortality events. Capital raised by issuing a cat bond is invested in a safe security like a treasury bill, which is held by a special-purpose vehicle (SPV). A SPV is often a company created to execute specific financial transactions. The bond issuer holds a call option on the bond principal (option to buy all or part of the principal) in the SPV with triggers that are specified in the bond contract.

The triggers can be defined in terms of the insurance company's total losses from the catastrophe or some hazard event characteristic. If the defined catastrophic event occurs, the bond issuer can withdraw bond funds from the SPV to pay claims, and part or all of the interest and principal payments are forgiven. If the catastrophe does not occur the investor receives the principal plus interest equal to the risk-free rate (e.g., London Inter-Bank Offered Rate--LIBOR), plus a spread above LIBOR. Cat bond maturity is typically on the order of 1 to 5 years.

Ahmet Birol Kara

Back in the middle 1990's I had the great fortune to work with and help mentor A. Birol Kara. Birol was a graduate student in meteorology when he approached me and asked if I needed help with a book project I was starting. I quickly put him to work drafting figures. It was clear from the start that Birol was a remarkable student. He approached his work with the utmost care and from a deep analytical perspective. This gave me the opportunity to try new ideas and approaches to the study of hurricanes and climate. I decided he would be co-author and the book would be a joint effort. Although his research passion remained in understanding the physics of the atmospheric boundary layer and in air-sea interaction his habits of the mind help me became a better scientist. In the years following the book project I got to know Birol personally and counted him as a friend. In fact I believe Birol's deep sense of loyalty to himself, family and friends helps explains his approach to research; an approach rooted in the "brutally honest", which I too often find lacking in climate research. After obtaining his Ph.D., Birol worked at the Naval Research Laboratory and lived in New Orleans. Tragically he died of cancer a few weeks ago. His legacy will live on through his publications and through those who were lucky to know him.

Catastrophe Finance: An Emerging Academic Discipline

The recent and on-going events in the world's financial markets demonstrate that finance theory remains far from perfected. Meanwhile, the threat of natural disasters continues to increase due to population growth, economic development, climate changes, geologic activity, and political unrest. To better understand and predict natural disasters and their consequences research and training are needed at the interface of geoscience and economics. New academic programs for graduate students in the area of catastrophe finance would help fill this need and could provide better tools and models for risk management and assessment. In turn, greater awareness of the geosciences by market professionals could help assist the spread of scientific knowledge. Importantly, such programs would train the next generation of professionals in finance and environmental organizations to use markets to the advantage of environmental programs and to anticipate the adverse consequences of financial innovation necessary for creating a sustainable future.

Eos, v90, 281-282. [membership required].

Listen to a BBC Radio 4 Podcast interview with Quentin Cooper.

A New Way to Define Anomalous Years

Recently we used networks to examine year-to-year relationships in hurricane activity. This requires mapping the time series of hurricane counts onto a network. In this way the network is physically related to the variation of hurricanes from one year to the next. This idea is relatively new and was introduced by Lacasa et al. [2008]. By doing this we address the following two questions: How can the occurrence of hurricane landfalls over time be examined from the perspective of network analysis? And, what advantages are gained from this perspective? The intellectual merit of the work is an advance in our understanding of historical coastal hurricane activity and the broader impact is a new method for identifying anomalies from time series data. The paper will appear in a forthcoming issue of Geophysical Research Letters. It is coauthored with Thomas Jagger and Emily Fogarty.

The picture shows the visibility network based on the time series of U.S. hurricane counts over the period 1851--2008. The colors indicate the node degree (number of links); 2 or less (red), 3--5 (orange), 6--10 (yellow), 11--20 (green), 21--30 (blue), and more than 30 (dark blue). The network suggests a novel way to think about anomalies in a time series. Years are anomalous not in a statistical sense of violating a Poisson assumption, but in the sense that the temporal ordering of the counts identifies a year that is unique in that it has a large count but is surrounded in time by years with low counts. Thus we contend that node degree is a useful indicator of an anomalous year. That is, a year that stands above most of the other years, but particularly above its "neighboring" years represents more of an anomaly in physical terms than does a year that is simply well-above the average. Node degree captures information about the frequency of hurricanes for a given year and information about the relationship of that frequency to the frequencies over the given year's recent history and near future. With this definition 1985 stands out as the most anomalous of the hurricane years with 1933, 1886, and 1964 also unusual.

Lacasa, L., B. Luque, F. Ballesteros, J. Luque, and J.C. Nuno (2008), From time series to complex networks: The visibility graph. Proc. Nat. Acad. Sci., USA, 105, 4972--4875.