Extreme Weather

2011-01-06 Scientific American
Extreme Weather Helps Drive Food Prices to New Highs
World food prices hit a record high in December thanks to crop failures from a series of extreme weather events around the world

PRICE HIKE:  Global prices for cereals, dairy, meat and other foods hit record highs in December thanks to a series of extreme weather events around the world.  Image: Rae Allen, courtesy Flickr

PRICE HIKE: Global prices for cereals, dairy, meat and other foods hit record highs in December thanks to a series of extreme weather events around the world. Image: Rae Allen, courtesy Flickr

The United Nations’ top food agency announced yesterday that world food prices hit a record high last month, igniting concerns among agricultural experts who are thinking back to the food riots that gripped developing countries just three years ago.


“It’s a worrisome situation with prices this high,” said Dan Gustafson, the director of the U.N. Food and Agriculture Organization’s Washington, D.C., office. “The year ahead is what I think is the real concern at this point. … It’s not by any means inevitable that prices will come down,” he said. …

“The record rise in food prices is a grave reminder that until we act on the underlying causes of hunger and climate change, we will find ourselves perpetually on the knife’s edge of disaster,” said Gawain Kripke, policy director for Oxfam America, in a statement.

More (click here)

Tornado Threat Increases as Gulf Hurricanes Get Larger

Tornadoes that occur from hurricanes moving inland from the Gulf Coast are increasing in frequency, according to researchers at the Georgia Institute of Technology. This increase seems to reflect the increase in size and frequency among large hurricanes that make landfall from the Gulf of Mexico. The findings can be found in Geophysical Research Letters online and in print in the September 3, 2009 issue.

“As the size of landfalling hurricanes from the Gulf of Mexico increases, we’re seeing more tornadoes than we did in the past that can occur up to two days and several hundred miles inland from the landfall location,” said James Belanger, doctoral student in the School of Earth and Atmospheric Sciences at Georgia Tech and lead author of the paper.

Currently, it’s well known that when hurricanes hit land, there’s a risk that tornadoes may form in the area. Until now, no one has quantified that risk because observations of tornadoes were too sporadic prior to the installation of the NEXRAD Doppler Radar Network in 1995. Belanger along with co-authors Judith Curry, professor and chair of the School of Earth and Atmospheric Sciences at Tech and research scientist Carlos Hoyos, decided to see if they could create a model using the more reliable tornado record that’s existed since 1995.

The model that they developed for hurricane-induced tornadoes uses four factors that serve as good predictors of tornado activity: size, intensity, track direction and whether there’s a strong gradient of moisture at midlevels in the storm’s environment.

“The size of a tropical cyclone basically sets the domain over which tornadoes can form. So a larger storm that has more exposure over land has a higher propensity for producing tornadoes than a smaller one, on average,” said Belanger.

The team looked at 127 tropical cyclones from 1948 up to the 2008 hurricane season and went further back to 1920 modifying their model to account for the type of data collected at that time. They found that since 1995 there has been a 35 percent percent increase in the size of tropical cyclones from the Gulf compared to the previous active period of storms from 1948-1964, which has lead to a doubling in the number of tornadoes produced per storm. The number of hurricane-induced tornadoes during the 2004 and 2005 hurricane seasons is unprecedented in the historical record since 1920, according to the model.

“The beauty of the model is that not only can we use it to reconstruct the observational record, but we can also use it as a forecasting tool,” said Belanger.

To test how well it predicted the number of tornadoes associated with a given hurricane, they input the intensity of the storm at landfall, it’s size, track and moisture at mid-levels, and were able to generate a forecast of how many tornadoes formed from the hurricane. They found that for Hurricane Ike in 2008, their model predicted exactly the number of tornadoes that occurred, 33. For Hurricane Katrina in 2005, the model predicted 56 tornadoes, and 58 were observed.

The team’s next steps are to take a look to see how hurricane size, not just intensity (as indicated by the Safir-Simpson scale), affects the damage experienced by residents.

Storm surge, rain and flooding are all connected to the size of the storm,” said Curry. “Yet, size is an underappreciated factor associated with damage from hurricanes. So its important to develop a better understanding of what controls hurricane size and how size influences hurricane damage. The great damage in Galveston from Hurricane Ike in 2008 was inconsistent with Category 2 wind speeds at landfall, but it was the large size that caused the big storm surge that did most of the damage.”

Nature: Atlantic hurricanes and climate over the past 1,500 years , doi:10.1038/nature08219

A statistical model for tornado frequency from Gulf of Mexico landfalling tropical cyclones (TCs) is developed using TC size, intensity, recurvature, and mid-level specific humidity data. New datasets are assembled for tornado frequency and for TC size at landfall as measured by the radius of outer closed isobar and distance of tornado from the TC center. Owing to systematic undercounting of tornadoes, the model is used to reconstruct the TC tornado climatology back to 1948, and further back to 1920 using a modified model that does not include mid-level specific humidity. Relative to the previous active period for Gulf TC landfalls of 1948–1964, the active period since 1995 has seen a statistically significant increase (95% level) in median TC tornadoes and in the frequency of large TC tornado outbreaks. These changes are linked to an increase in the median size and frequency of large Gulf landfalling TCs.

GRL: Variability in tornado frequency associated with U.S. landfalling tropical cyclones , Belanger, J. I., J. A. Curry, and C. D. Hoyos (2009), Variability in tornado frequency associated with U.S. landfalling tropical cyclones, Geophys. Res. Lett., 36, L17805, doi:10.1029/2009GL040013

Atlantic tropical cyclone activity, as measured by annual storm counts, reached anomalous levels over the past decade. The short nature of the historical record and potential issues with its reliability in earlier decades, however, has prompted an ongoing debate regarding the reality and significance of the recent rise. Here we place recent activity in a longer-term context by comparing two independent estimates of tropical cyclone activity over the past 1,500 years. The first estimate is based on a composite of regional sedimentary evidence of landfalling hurricanes, while the second estimate uses a previously published statistical model of Atlantic tropical cyclone activity driven by proxy reconstructions of past climate changes. Both approaches yield consistent evidence of a peak in Atlantic tropical cyclone activity during medieval times (around ad 1000) followed by a subsequent lull in activity. The statistical model indicates that the medieval peak, which rivals or even exceeds (within uncertainties) recent levels of activity, results from the reinforcing effects of La-Niña-like climate conditions and relative tropical Atlantic warmth.

Journal of Geophysical Research: Scientists expect wildfires to increase as climate warms in the coming decades

As the climate warms in the coming decades, atmospheric scientists at Harvard’s School of Engineering and Applied Sciences (SEAS) and their colleagues expect that the frequency of wildfires will increase in many regions. The spike in the number of fires could also adversely affect air quality due to the greater presence of smoke.

The study, led by SEAS Senior Research Fellow Jennifer Logan, was published in the June 18th issue of Journal of Geophysical Research. In their pioneering work, Logan and her collaborators investigated the consequences of climate change on future forest fires and on air quality in the western United States. Previous studies have probed the links between climate change and fire severity in the West and elsewhere. The Harvard study represents the first attempt to quantify the impact of future wildfires on the air we breathe.

“Warmer temperatures can dry out underbrush, leading to a more serious conflagration once a fire is started by lightening or human activity,” says Logan. “Because smoke and other particles from fires adversely affect air quality, an increase in wildfires could have large impacts on human health.”

… the scientists predict that the geographic area typically burned by wildfires in the western United States could increase by about 50% by the 2050s due mainly to rising temperatures. The greatest increases in area burned (75-175%) would occur in the forests of the Pacific Northwest and the Rocky Mountains.

See also GRL: Detecting the effect of climate change on Canadian forest fires Geophysical Research Letters, VOL. 31, L18211, doi:10.1029/ (pdf)

The area burned by forest fires in Canada has increased over the past four decades, at the same time as summer season temperatures have warmed. Here we use output from a coupled climate model to demonstrate that human emissions of greenhouse gases and sulfate aerosol have made a detectable contribution to this warming. We further show that human-induced climate change has had a detectable influence on the area burned by forest fire in Canada over recent decades. This increase in area burned is likely to have important implications for terrestrial emissions of carbon dioxide and for forest ecosystems.

PNAS: Temperature sensitivity of drought-induced tree mortality portends increased regional die-off under global change-type drought doi: 10.1073/pnas.0901438106
Biosphere 2 experiment shows how fast heat could kill drought-stressed trees

Widespread die-off of piñon pine across the southwestern United States during future droughts will occur at least five times faster if climate warms by 4 degrees Celsius, even if future droughts are no worse than droughts of the past century, scientists have discovered in experiments conducted at the University of Arizona’s Biosphere 2.

Their study is the first to isolate the impact of just temperature on tree mortality during drought. The temperature effect is usually confounded by varying weather and bark beetle and other pest attacks. Quantitative information on how sensitive drought-stressed trees are to hotter temperatures is critical for predicting drastic, sudden and widespread die-offs, the scientists said. …

International climate scientists who were convened at the request of the United Nations reported in February 2007 that if greenhouse gases accumulate at rates which moderate scenarios project, global climate will be between 3 and 5 degrees Celsius hotter by the year 2100 than it was at the beginning of the Industrial Revolution in the mid-18th century. Global average temperature has risen 0.8 of a degree Celsius since 1750, the panel concluded.

NASA: Drought, Urbanization Were Ingredients for Atlanta’s Perfect Storm

On March 14, 2008, a tornado swept through downtown Atlanta, its 130 mile-per-hour winds ripping holes in the roof of the Georgia Dome, blowing out office windows and trashing parts of Centennial Olympic Park. It was an event so rare in an urban landscape that researchers immediately began to examine NASA satellite data and historical archives to see what weather and climatological ingredients may have combined to brew such a storm.

Though hundreds of tornadoes form each year across the United States, records of “downtown tornadic events” are quite rare. The 2008 Atlanta tornado — the first in the city’s recorded history — was also unique because it developed during extreme drought conditions.

NASA Study Links Severe Storm Increases, Global Warming

December 19, 2008, PASADENA, Calif. —
The frequency of extremely high clouds in Earth’s tropics — the type associated with severe storms and rainfall — is increasing as a result of global warming, according to a study by scientists at NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

In a presentation today to the fall meeting of the American Geophysical Union in San Francisco, JPL Senior Research Scientist Hartmut Aumann outlined the results of a study based on five years of data from the Atmospheric Infrared Sounder (AIRS) instrument on NASA’s Aqua spacecraft. The AIRS data were used to observe certain types of tropical clouds linked with severe storms, torrential rain and hail. The instrument typically detects about 6,000 of these clouds each day. Aumann and his team found a strong correlation between the frequency of these clouds and seasonal variations in the average sea surface temperature of the tropical oceans.

Extreme Weather in ManitobaClimate change will affect the frequency, severity and duration of extreme weather events (1). A roof-ruining, car-smashing hailstorm every twenty years is both memorable and tolerable. The same type of storm every five years would tax our patience and our pocketbooks.

We can expect an increase in extreme weather events as greenhouse gases change the climate. From searing heat and drought to powerful storms, Manitobans will be spending more time and money picking up after wild weather.

This page, updated August 8, 2008 from the “Climate Change Connection and the Manitoba Eco Network”, describes the impact of windstorms (including tornados), thunderstorms, haol storms, flooding and extreme heat.

The European Heat wave of 2003 as seen from MODIS on board of NASA’s TERRA satellite

Europe was experiencing a historic heat wave during the summer 2003. Compared to the long term climatological mean, temperatures in July 2003 were sizzling. Figure 1 below shows the differences in day time land surface temperatures of 2003 to the ones collected in 2000, 2001, 2002 and 2004 by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite.
Fig. 1: The visualization displays TERRA MODIS (MODerate resolution Imaging Spectroradiometer) derived land surface temperature data of 1km spatial resolution (Click on the image to get the high resolution TIFF file). The difference in land surface temperature is calculated by subtracting the average of all cloud free data during 2000, 2001, 2002 and 2004 from the ones in measured in 2003, covering the date range of July 20 - August 20. (Cite this image as: Image by Reto Stöckli, Robert Simmon and David Herring, NASA Earth Observatory, based on data from the MODIS land team. Correspondance: rstockli -at- climate.gsfc.nasa.gov).

Wikipedia – 2003 European heat wave
The 2003 European heat wave was one of the hottest summers on record in Europe, especially in France. The heat wave led to health crises in several countries and combined with drought to create a crop shortfall in Southern Europe. More than 52,000 Europeans died as a result of the heat wave.

An anticyclone stationed above western Europe prevented precipitation and led to record high temperatures over sustained periods. Temperatures rose to 20-30 percent above average in Europe during the heat wave, with nightly temperatures hotter than the average summer mid-day highs. The heat effected France in particular where temperatures sustained highs of 37°C for more then a week in August in some areas.

In the aftermath concerns were raised that anthropogenic climate change (/global warming) was partly the cause of such a severe heat wave. However due to the nature of climate change, it cannot be defined whether or not it is the specific cause of any particularly extreme weather. Changes in climate increase/reduce the risks and likelihoods, and research has since shown that the heat wave could have happened with or without human emissions, while confirming that greenhouse gas emissions do increase the risk of such extreme weather.

2008-11-26 – Scientific American: Hurricane season ends, bringing record storms

A record number of consecutive hurricanes made landfall on the U.S. East Coast this year, making it one of the most active storm seasons ever, government meteorologists report today. …

The blustery year is due to lingering, light wind shears from La Niña (which began in fall 2007 and ended in June) and a phenomenon called the Atlantic Multidecadal Oscillation that produces alternatingly warm and cold sea surface temperatures. Temperatures vary across the tropical Atlantic, but overall, they were about one degree warmer than usual during the season’s peak, hurricane forecaster Gerry Bell tells us.

The Atlantic Multidecadal Oscillation is “a major factor influencing hurricane activity,” Bell says. We’re just 13 years into a warm period that could last 25 to 40 years, he says. Right now, the oscillation is producing stronger monsoons in West Africa and weaker rainfall in the Amazon basin. Those effects are associated with a lower wind shear, which favors hurricanes that require little change in wind patterns to form.

Tne NOAA report titled Atlantic Hurricane Season Sets Records dated 26 Nov. 2008 included this graphic of the 2008 hurricane tracks (click for a high resolution image):

Tropical Storms and Hurricanes of 2008

Tropical Storms and Hurricanes of 2008

2009-07-03 – Science: Impact of Shifting Patterns of Pacific Ocean Warming on North Atlantic Tropical Cyclones
DOI: 10.1126/science.1174062

Two distinctly different forms of tropical Pacific Ocean warming are shown to have substantially different impacts on the frequency and tracks of North Atlantic tropical cyclones. The eastern Pacific warming (EPW) is identical to that of the conventional El Niño, whereas the central Pacific warming (CPW) has maximum temperature anomalies located near the dateline. In contrast to EPW events, CPW episodes are associated with a greater-than-average frequency and increasing landfall potential along the Gulf of Mexico coast and Central America. Differences are shown to be associated with the modulation of vertical wind shear in the main development region forced by differential teleconnection patterns emanating from the Pacific. The CPW is more predictable than the EPW, potentially increasing the predictability of cyclones on seasonal time scales.

NOAA Atlantic Oceanographic and Meteorological Laboratory – Hurricane Research Division – Frequently Asked Questions


4 Responses to Extreme Weather

  1. Neil Rowland says:

    I wonder if the increased tornado activity in the United States may contribute to a heat wave in the UK, or if the tornado season will mean stormy weather, in a kind of “wash back” effect?

    • Alan Burke says:

      Much of the unusual weather recently has been a result of the “Greenland block”. I suggest that you search for that term online (e.g., via Google) and look at some of the descriptions. The resulting shift in the atmospheric jet streams has brought extreme and unusual weather to many parts of North America and Europe.

  2. Alan Burke says:

    For extensive background concerning extreme weather, have a look at Hurricanes, floods and wildfires – but Washington won’t talk global warming.

  3. Alan Burke says:

    From a Munich RE Reinsurance press release, 27 September 2010 (thanks to Darryl Williams in commentary at the Globe & Mail for the link):

    Two months to Cancún climate summit Large number of weather extremes as strong indication of climate change

    Floods in central Europe, wildfires in Russia, widespread flooding in Pakistan. The number and scale of weather-related natural catastrophe losses in the first nine months of 2010 was exceptionally high. Two months ahead of the World Climate Summit scheduled for 29 November to 10 December in Cancún, Mexico, Munich Re emphasises the probability of a link between the increasing number of weather extremes and climate change. In the run-up to the summit, Munich Re will focus attention on this issue with a series of communications on natural catastrophes, climate change and potential solutions. Research facts and findings will be available for download in an electronic press folder at http://www.munichre.com.

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