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Waste Awareness and Reduction Network

NC WARN

Global Warming Impacts on the Weather and Climate of North Carolina

By Matt Huxley April 2005

1.1 Executive Summary Climate records across North Carolina, the United States, and around the world indicate beyond any doubt that temperatures are rising at an unprecedented rate and are now higher than they have been in 1,000 years. Records also indicate that global precipitation has increased in line with rising temperatures. The overwhelming scientific consensus is that this warming is being driven by human caused greenhouse gas emissions, and that temperatures will continue to rise in line with increasing emissions. Scientists and the best climate models also predict that heat-driven extreme weather events such as droughts, floods, and destructive storms will become more common in North Carolina, the United States, and around the world as the global temperature continues to rise. The evidence strongly suggests that the North Atlantic hurricane season of 2004 may well be a harbinger of the future. Specific temperature trends and predictions include the following:

• The average temperature in North Carolina has risen approximately 1oF since 1950. This is concurrent with the rise in global average temperature for this period.

• The average temperature in the state is very likely to rise at least 3oF by 2100, even if greenhouse gas emissions could be halted immediately.

• Higher estimates suggest that average temperatures in the state could rise as much as 13oF by 2100 if the rate of greenhouse gas emissions continue at their current pace.

Specific trends and predictions for precipitation and extreme weather include the following:

• Annual precipitation within the state has increased since 1950. This is consistent with an increase in global precipitation for this period.

• Precipitation patterns have shifted so that the state now experiences lower summer precipitation but higher winter precipitation.

• The average annual temperatures and precipitation will likely continue to increase across the state, leading to more frequent summer droughts, spring floods, disruptive winter storms, and more frequent and severe thunderstorms.

• North Carolina is expected to experience more frequent destructive hurricanes (category 3+) with an associated increase in loss of life and property.

• Tornados are becoming more numerous throughout the state and are expected to further increase as the frequency of severe thunderstorms and more intense hurricanes increases.

• Sea levels along the coast of North Carolina could rise more than three feet by the end of the century, flooding large areas of land, and exacerbating the effects of storm damage.

• Even at the lower end of warming projections, weather related economic impacts will likely be severe as more intense droughts exacerbate water shortages, increase wildfires, and disrupt agriculture. Warming will likely cause changes in vegetation patterns that will impact the timber industry. Flood and storm damage is likely to increase with associated insurance costs.

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In addition, Paleoclimatic records indicate that the Gulf Stream fluctuates with natural cycles and has shut down on numerous occasions in the past. Researchers at the University of Illinois believe there is almost a fifty percent chance that the Gulf Stream will shut down by the end of this century. This would lead to an abrupt shift in global climate in the space of a decade or even a few years, and cause much more severe winters in North Carolina and throughout the eastern United States

1.2 Introduction This report examines the projected impacts of human exacerbated global climate change to the climate of North Carolina. The report examines the effect of rising temperatures due to global warming, and the subsequent effects on precipitation, extreme weather events, and macro climate patterns that influence weather in the state. The report uses published peer reviewed scientific papers as its source material. A list of referenced scientific papers and other source material is included at the end of this report. The report contains the following sections:

• Background to Global Warming – Examines the evidence and science behind global warming and briefly discusses observed trends around the world and the projected global impacts and impacts to the southeast United States region

• Background to State Climate – General discussion of the climate of North Carolina and observed normal conditions including average temperatures, precipitation, and extreme weather events

• Temperature Effects of Global Warming on North Carolina – Observed trends and predicted effects of rising temperatures

• Precipitation Effects of Global Warming on North Carolina – Observed and predicted effects of changing precipitation patterns

• Effect of Global Warming on Other Weather-influencing Factors – Including El Nino, the Gulf Stream, and rising sea levels

• Effect of Global Warming on Hurricanes, Severe Thunderstorms, Tornados and Winter Storms • Economic Consequences of Extreme Weather Influenced by Global Warming • Conclusions outlining best and worst case scenarios

1.3 Background to Global Warming Temperature records around the world indicate a steep rise in the average global surface temperature since 1970. Records indicate that the earth’s average surface temperature has risen by 1oF since 1900, with the sharpest rise in temperature occurring in the last ten years. Paleoclimate temperature data obtained from ice cores, tree rings, and sediments have shown that the 1990’s was the warmest

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decade in the last one thousand years. The overwhelming scientific consensus attributes this abnormal warming to rapidly increasing concentrations of atmospheric greenhouse gases (GHG) resulting from human activities. Carbon dioxide accounts for about two thirds of the warming effect with methane (CH4), nitrous oxides (N2O), ozone (O3), halocarbons, and particulates contributing the bulk of the remaining warming. Current atmospheric CO2 concentrations are at their highest level in 420,000 years. The United Nations Intergovernmental Panel on Climate Change (IPCC) predicted in 2001 that the earth’s average surface temperature could rise as much as 10.5oF by 2100. More recent computer modeling by Britain’s Open University predicts that the earth’s average temperature could rise by 17oF by the end of the century, leaving many areas of the globe uninhabitable.

Heat is the primary driver of the global climate system, and increasing temperatures affect weather patterns at all levels and in all regions. As higher temperatures drive evaporation, precipitation increases and rainfall patterns shift, leaving once fertile areas dry, while increasing rainfall in already flood prone regions. The effects of global warming are already manifesting as severe droughts in Africa and Asia, and increasing precipitation in northern and polar latitudes. The more ominous effects of global warming are evident in disappearing mountain glaciers, melting ice sheets, rising sea levels, and the slowing down of the Gulf Stream.

Mt. Hood, Oregon * Global weather is a vastly complex system dependent on a multitude of interactive variables and unforeseeable events, such as the way greenhouse gas emissions may change in the future. As such, it is difficult to predict exactly what the future effects of global warming will be on regional weather patterns. Most predictions rely on historical evidence, identified trends, and more recently on advanced computer climate models. The most advanced computer models can now replicate current and past climates with enough accuracy that the vast majority in the scientific community trusts these models to predict future climate scenarios with a high degree of probability. Based on these advanced computer model simulations and observed trends, the following predictions of future climate conditions have been made:

• Average global temperature will rise 2.5-10.5oF by 2100 with higher regional variations • Overall global precipitation will increase 5-25% by the end of the century • Precipitation patterns will shift, causing rain and snowfall to increase in some regions and

decrease in others • Frequency, duration, and intensity of heat waves, droughts, and floods will likely increase • Maximum wind and precipitation intensity of tropical cyclones is likely to increase in some

areas with more frequent destructive (category 3+) hurricanes impacting North Carolina • El Nino conditions are likely to become more frequent in the eastern tropical Pacific ocean,

with corresponding global effects • The Gulf stream is likely to continue to weaken due to melting polar ice, leading to a possible

shutdown by the end of the century, thus creating an abrupt shift to much colder winters in the North Atlantic region along with other adverse effects around the globe, including droughts in some regions

1.4 Background to North Carolina Climate North Carolina has the most complex climate of any state on the east coast of the United States due

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to its latitude and topography. The key elements that influence the weather in the state are the interaction between warm and cold waters off the coast, the large variation in altitude from east to west, and a location that puts it under the influence of tropical cyclonic storms (including hurricanes) that form in the eastern Atlantic. The Gulf Stream that carries warm water north from the tropics lies approximately fifty miles off the coast of North Carolina and moderates winter temperatures in the coastal areas of the state. The state also lies at the southern extremity of the Labrador current which brings cold Arctic water south and reduces the warming effect of the Gulf stream. Low pressure systems often form where the two currents meet, causing frequent storms along the coast. Elevation climbs from sea level at the coast to over 7,000 feet in the Great Smokey mountains. This difference in elevation accounts for the greatest variation in temperatures across the state. Average temperatures in the higher western areas can be as much as 20oF lower than the southeast coast, where conditions are more similar to northern Florida. The Appalachian mountains moderate winter temperatures by acting as a barrier to cold air masses migrating south from Canada across the great plains. Average temperatures range from a winter low of 0oF in higher mountain elevations to a summer daily highs of 100oF in the southern Piedmont. Precipitation varies across the state due to topography and prevailing winds. There are no distinct wet and dry seasons but precipitation tends to be higher in summer due to thunderstorms and tropical cyclonic storms. Precipitation in spring and winter occurs mainly from low-pressure systems migrating from the south and west. The Piedmont and coastal areas average between 40 to 55 inches of precipitation per year. Topography influences rainfall in the mountains, and precipitation can vary from 37 inches in local rain shadows to 90 inches on southwest facing slopes. Winter storms bring a combination of rain, snow, sleet (mixture of snow and rain), and freezing rain to North Carolina every winter. The frequency and severity of winter storms increases further to the north and west. The northwestern Great Smokey mountains experience an average of 14 winter storms each season, the central Piedmont experiences between six and 12, and the southeast coast experiences less than four winter storm events a year. Snow and freezing rain can occur at any place in the state throughout the winter although snow storms are most common in the mountains and freezing rain is experienced most often in the northern Piedmont. Sleet-dominant storms occur much less frequently in North Carolina, although when they do, they are most likely to be experienced in the central Piedmont. The coastal region occasionally experiences Nor’ Easters that can cause damage and beach erosion from high winds. Severe thunderstorms occur at any time of the year in North Carolina but are most common during summer, when storm-bearing fronts form from hot continental air masses that meet moist air moving into the state from the Gulf of Mexico and Atlantic ocean. Severe thunder storms can cause severe localized damage from high winds, tornados, and flash floods. Most locations in the state experience 40 to 50 thunderstorms a year. Tropical cyclonic storms bring damaging wind, rain, and tornados to the state on average twice a year. North Carolina ranks number two in the nation for direct land falling hurricanes. On average, over a hundred year period, a hurricane makes direct landfall in the state once every ten years, causing extensive damage inland. However, the frequency varies from decade to decade so the state can experience multiple direct hits in the space of a few years. The moderate climate, abundant moisture, and favorable soil conditions contrive to make North Carolina a very productive agricultural state. Diverse micro-climates enable a wide variety of crop production, from citrus fruits along the south coast to apple orchards in the mountains. Tobacco, cotton, and a variety of grains, cereals, and beans are the key cash crops. The fairly moderate summers allow for economical hog, turkey, and chicken production without the need for expensive air conditioning.

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1.5 Temperature Effects of Global Warming on North Carolina State records indicate that the average temperature in Chapel Hill has risen by 1.2oF over the last one hundred years. This is slightly higher than the global average rise of 1oF and consistent with computer model projections. There is no clear trend showing a rise in extreme temperatures although the highest and lowest readings both occurred in the 1980s (highest 110oF at Fayetteville in 1983, lowest –34o at the summit of Mt. Mitchell in 1985). Current projections of global warming predict an increase in the global average temperature of between 2.5oF and 10.5oF. Models predict that the southeastern United States will experience greater temperature increases than the global average, possibly by as much as 30% above the average. North Carolina will likely see average temperatures rise by as much as 3oF in the next thirty years and possibly as much as 13oF by the end of the century. Warming will continue by 2-3 degrees even if greenhouse gas emissions could be halted immediately, due to a delay in temperature response to atmospheric greenhouse gas concentrations. Increases in winter and nighttime temperatures are predicted to be higher than summer and daytime temperatures. Even the most conservative forecasts suggest that the state could have a climate similar to that of central Florida in just a few decades. Higher temperatures will adversely impact the state in the following ways:

• More frequent and extended summer droughts, further impacting water supplies • Increase in heat-related deaths and other heat-related health problems including increases in

the outbreak of tropical diseases such as malaria and west Nile virus • Poorer air quality as higher temperatures encourage formation of low level ozone • Changes in vegetation patterns towards more heat-favoring southern plant species and

possibly replacing forested areas with grassland and savanna • Impact to timber industry due to tree loss and/or change in predominant timber species • Impact to farming due to water shortages, changes in crop patterns, and the possible need for

summer air conditioning in hog farms • Increased summer wildfire risk with associated impact to life, property, and insurance costs

1.6 Precipitation Effects of Global Warming on North Carolina Model predictions and observations around the world indicate that precipitation is increasing, and will continue to do so as the world becomes warmer. It is also likely that precipitation patterns will alter so that summer rainfall will occur in less frequent but heavier bursts, increasing risks of flash flooding. In North Carolina, state climate records indicate that total annual precipitation has increased across the state since 1950. Records also indicate that precipitation patterns are shifting towards drier

summers and wetter winters. Summer droughts are likely to become more frequent, longer in duration, and more intense due to lower overall summer rainfall, increased duration of time between rain showers, and lower aquifer recharge rates due to increased runoff and faster evaporation. The five-year drought peaking in 2002, which saw the driest July-August period on record, may become a regular annual event. Drought and flash flooding effects could be further enhanced if vegetation growth patterns change, creating less forested area and more grassland. Greater winter

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precipitation would lead to increased springtime flooding due to saturated soil and increased snowmelt. There is no clear trend to show that extreme precipitation events are increasing in frequency, although state records indicate that the greatest single snowstorm and 24-hour snowfall event occurred in 1993 on Mount Mitchell.

1.7 Effect of Global Warming on Other Weather Related Factors The El Nino Southern Oscillation (ENSO), the Gulf Stream, and rising sea levels influence weather and weather effects in North Carolina. It is known that the ENSO and the Gulf Stream influence tropical cyclone activity in the Atlantic. These effects are described in Section 1.8. A brief discussion on the projected impacts of global warming to the ENSO, Gulf Stream, rising sea levels, and their corresponding effects on weather in North Carolina follows below.

1.7.1 El Nino Southern Oscillation Under normal conditions in the tropical Pacific ocean, westward flowing trade winds cause warm tropical surface water to migrate west and form a vast area of warm ocean stretching from western Indonesia to the mid-Pacific. The westward migration of surface water causes colder deep water to well up in the eastern Pacific and form a band of cooler surface water from the mid-Pacific to the west coast of South and Central America. This difference in ocean surface temperature along the equatorial Pacific is responsible for vastly differing climates in the western and eastern tropical Pacific. When the Pacific trade winds weaken, warmer water migrates east and the upwelling of cool water in the eastern Pacific is hindered, raising ocean surface temperatures off the coast of Central and South America. An opposite situation occurs when the trade winds intensify, causing warm water to migrate further west resulting in even cooler ocean surface temperatures in the eastern Pacific. Warming of the eastern Pacific is known as El Nino and the reverse cooling is referred to as La Nina. The periodic cycle between an abnormally warm and abnormally cool eastern Pacific ocean is known as the El Nino Southern Oscillation (ENSO). El Nino and La Nina events typically occur every three to seven years and influence weather patterns worldwide. El Ninos bring adverse weather conditions to many areas of the world, including drought to parts of North America, South Asia and Africa, and flooding to South America. Studies conducted by the State Climate Office of North Carolina found that summers in the state became drier and winters wetter during El Nino years. Global warming models predict that as surface water temperatures increase in the eastern Pacific, El Nino events will become more common, prolonged and severe, setting the stage for more intense droughts and floods worldwide. In North Carolina the global warming-induced trend towards drier summers and wetter winters could become even more pronounced as El Nino events become more common, furthering the risk of severe summer droughts and winter floods across the state.

1.7.2 The Gulf Stream The Gulf Stream current carries warm surface water and mild humid air from the tropics to the North Atlantic and is part of the great ocean conveyor system that influences climate worldwide. The Gulf Stream has the greatest effect on northwest Europe, where winter temperatures are typically 10oF warmer than they otherwise would

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be. The Gulf Stream also has a significant effect on moderating winter temperatures in the eastern United States. Paleoclimatic records indicate that the Gulf Stream fluctuates with natural cycles and has shut down on numerous occasions in the past. Even minor fluctuations in the current can cause major cascading effects to weather around the world. The same records indicate that the current can stop in a short span of time, ushering in very rapid and severe changes to global climate. The most recent shutdown occurred about 12,000 years ago during a period known as the “Younger Dryas” when average temperatures in the North Atlantic plummeted 10oF in as little as a decade and remained that way for 1,300 years. A minor disruption in the Gulf Stream around 700 years ago ushered in a ‘little ice age’ in Europe that lasted more than 500 years and had profound impacts on the agriculture, economies, and politics of the region at that time. Global warming is causing temperatures to rise most rapidly in the Arctic region. The result has been a massive influx of fresh water from melting glaciers and increased precipitation entering the North Atlantic, and reducing ocean surface water salinity. This buoyant cold surface water hinders the northward flow of warm tropical water with the effect of slowing, or possibly even stopping, the Gulf Stream. Present warming and subsequent ice melting has caused ocean salinity in sub-polar seas bordering the North Atlantic to drop rapidly since 1950, with the sharpest drop occurring in the last ten years. These alarming observations have deepened fears that this will initiate a slowing or possible complete shut-down of the Gulf Stream. The chance of the Gulf Stream stopping was until recently considered to be remote. Now however, some prominent climate scientists believe that there is a much greater chance that this will happen sooner rather than later in light of new data and results from more advanced computer climate models. Professor Mike Schlesinger of the Climate Research Group at the University of Illinois believes that there is almost a fifty percent chance that the Gulf Stream will shut down completely by the end of the century if greenhouse gas emissions continue unabated. If the Gulf Stream does shut down, the consequences to the North Atlantic region, including North Carolina, would be severe. Computer models simulating Gulf Stream effects indicate that average temperatures in the North Atlantic region would plunge by as much as 10oF, creating a climate in North Carolina similar to current-day Pennsylvania. Robert Gagosian of the Woods Hole Oceanic Institution states that, “Winters on the east coast of the US would become twice as cold as the worst winters on record in the last century”. Historical records indicate that the transition to more severe winters would not be gradual but would occur abruptly in the space of a decade or even a few years and could remain that way for centuries even as the earth continues to warm.

1.7.3 Rising Sea Levels Sea levels around the globe are rising due to melting polar ice and thermal expansion from rising ocean temperatures. The IPCC estimates that the average global sea level could rise as much as three feet over the next century. Natural subsidence along coastlines in some areas will compound the effects of rising sea levels from global warming. The North Carolina coast is subsiding naturally due to glacial rebound, and by 2030 sea level along the state’s coastline could rise by as much as 12 inches. Given the low-lying nature of much of the coastal region, conservative forecasts Cape Hatteras, NC predict that rising sea levels would inundate over 700 square miles of coastal area by 2030 and more than 1,300 square miles by 2100. The Barrier Islands could virtually disappear by mid-century. Increasing sea levels will exacerbate the effect of storm damage from extreme weather events such as tropical cyclonic storms, and impact areas not currently under threat as the sea advances further 7

inland. Rising sea levels will in effect move the ocean closer to populated areas and expose them to greater risks from tropical cyclonic storms making direct landfall in the state.

1.8 Effect of Global Warming on Tropical Cyclones, Tornados, and Winter Storms Most climate models predict that rising temperatures will influence violent and disruptive weather events such as tropical cyclones, severe thunderstorms, tornados, and winter storms that frequently impact the state. The following section provides a more detailed analysis of how global warming may influence these extreme weather events and their potential further impacts on the state.

1.8.1 Tropical Cyclones Background Tropical cyclones (the generic term for tropical depressions, tropical cyclonic storms, hurricanes, and typhoons) are one of nature’s most powerful and destructive weather events. Each year tropical cyclones cause thousands of deaths and billions of dollars of damage worldwide. Cyclones occur in all regions of the tropical oceans except for (until recently thought) the South Atlantic. Tropical cyclones form when bands of thunderstorms over warm tropical ocean surface water encounter a low pressure system with sufficiently low enough pressure to cause the bands to begin to swirl around the center of the system. Thunderstorms generate large upward convection, creating high winds that swirl into the low pressure area to replace upward flowing air. Moisture in the air cools as it reaches upper altitudes, condenses, and precipitates out as rainfall. Condensing moisture releases latent heat, warms the surrounding atmosphere, and further intensifies upward convection and wind speeds. Rising air is propelled outward when it reaches the top of the storm structure, drawing yet more air in from below. Some of this upper level air descends into the center of the cyclone preventing cloud formation and forming the characteristic “eye” of the storm. Air pressure in the eye is so low that the sea level beneath the eye rises several feet due to the suction effect and exacerbates the effect of wind-driven storm surge when the cyclone makes landfall. As long as sufficient heat, moisture, and favorable atmospheric conditions persist to allow rapid heat transfer between the atmosphere and ocean to continue, the tropical cyclone becomes a self-sustaining heat engine with the ability to intensify into a fully developed hurricane. Such a hurricane can easily be 500 miles across and contain enough energy that, if harnessed, could power the entire United States for six months. A tropical cyclone with maximum sustained winds below 40 miles per hour (mph) is known as a tropical depression, between 40 and 74 mph a tropical cyclonic storm, and above 74 mph the tropical cyclone is classified as a hurricane (or typhoon in the Pacific ocean and severe tropical cyclone in the Indian ocean). Hurricanes in the Atlantic region are classified from category 1 to category 5 on the Saffir-Simpson scale depending on their peak wind speed. Peak wind speeds range from 74 mph in a category 1 storm to 155+ mph in a category 5 storm. The storm’s energy increases exponentially as the category increases, so that a category 5 hurricane has four times the energy (and destructive power) of a category 1 hurricane. Theoretically, wind speeds in a hurricane can reach the speed of sound, although the highest wind speed actually measured in a cyclone was about 200 mph. In order for a tropical cyclone to form and self-sustain, the following conditions must be present:

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1. Surface ocean temperatures must be greater than 80oF to provide a continuous supply of

sufficient energy to the storm system 2. A high variation in temperature from low to high altitude to generate sufficient condensation

and heat transfer to the upper atmosphere 3. High humidity in the mid-troposphere to provide sufficient moisture 4. A pre-existing low pressure system at least 300 miles north or south of the equator to initiate

sufficient convection 5. Low vertical wind shear (difference in low altitude and upper altitude wind speeds) so that the

system remains organized Weather records indicate that the frequency and intensity of tropical cyclones vary over periods of decades and coincide with fluctuations in tropical ocean surface temperatures. Warmer surface ocean temperatures generally coincide with more frequent and powerful storms. In the Atlantic ocean these temperature and associated storm cycles occur every twenty to fifty years with the most active storm decades occurring in the 1950s, 1980s, and mid 1990s to the present. In addition, several other factors are known to influence tropical cyclone frequency and intensity around the world. The El Nino Southern Oscillation (ENSO) and the Gulf Stream play a major role in hurricane development in the Atlantic basin. During an El Nino year, hurricane formations in the Atlantic and northwestern Pacific are significantly reduced, whereas they are more frequent during La Nina periods. When the Gulf Stream current is stronger, more frequent and powerful hurricanes occur in the Atlantic. In an average season the Atlantic region experiences around ten named tropical cyclones of which six achieve hurricane strength, and two of those become major (category 3+) hurricanes. North Carolina normally experiences around two tropical cyclones per year and suffers a direct hit from a fully developed hurricane once every ten years. In a more active season such as that of 2004, the Atlantic can spawn more than ten hurricanes and six or more major hurricanes. The United States and North Carolina experience a correspondingly higher number of direct land falling hurricanes during these periods. Global Warming Effects Due to a lack of clear data, it is impossible to establish any clear trends that associate changes in tropical cyclone behavior to global warming. Hurricane records in the Atlantic and Pacific go back only one hundred years or so, and records in the rest of the world began as late as the 1960s when satellite technology enabled global coverage of the world’s oceans. As such, no clear trend can be established to link hurricane activity with rising global temperatures. However, as stated previously, ocean temperatures play a key role in tropical cyclone formation, and last year’s exceptionally active tropical cyclone season in the Atlantic and western Pacific oceans were influenced by unusually warm ocean surface temperatures. An area of the western Pacific ocean two degrees warmer than normal spawned twenty typhoons and caused a record ten typhoons to make landfall in Japan. Japanese meteorologists have openly blamed global warming for the unusually active season there. Six hurricanes, including three major hurricanes, made landfall in the United States last year. Four of these hurricanes made landfall in Florida, the first time in over a century that four storms have hit the same state in one season. It is now known beyond any doubt that global warming is causing ocean temperatures to rise worldwide. Although many factors influence tropical storm formation, a warmer ocean provides more energy for hurricane development. As such, global warming is changing the environment so that conditions are becoming more favorable for hurricane formation around the world. As Kevin Trenberth, head of the Climate Analysis Section of the National Center for Atmospheric Research and lead author of the upcoming 2007 IPCC report, states,

“The evidence strongly suggests more intense storms and risk of greater flooding events, so that the North Atlantic hurricane season of 2004 may well

be a harbinger of the future”.

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Another unusual cyclone event occurred last year that is consistent with global warming projections. In March 2004 a hurricane formed in the tropical south Atlantic and made landfall in Brazil, causing deaths and widespread damage. The storm, named hurricane Catarina, formed in the one region of the tropics where hurricane development was previously thought to be impossible due to unfavorable atmospheric conditions. Although there is no proof as yet to link this abnormal occurrence to global warming, climate models have predicted that this is an area where global warming would create more favorable conditions for hurricane formation. Hurricane Catarina developed and followed a path remarkably consistent with climate model predictions. At the very least, the storm did validate the accuracy of the computer climate models. Climate scientists are divided as to whether or not global warming will cause an increase in the frequency of hurricanes worldwide. Some computer models predict an increase and other models predict a decrease. Also as previously discussed, most scientists believe that global warming will create more frequent and longer duration El Nino conditions (see below) and this is known to suppress hurricane formation in the Atlantic. However, most climate scientists, backed up by advanced computer models, project that hurricane intensity will increase ,causing more frequent destructive (category 3+) hurricanes. One of the most comprehensive studies on the effects of global warming and simulated hurricane intensity was recently conducted by the NOAA Geophysical Fluid Dynamics Laboratory in Princeton, New Jersey. The study used nine leading climate computer models to simulate the effects of a doubling of atmospheric CO2 on hurricane formation in the north Atlantic basin. Although not conclusive, the simulation forecasted that the overall formation of Atlantic hurricanes could decrease slightly but the number of severe (category 4+) hurricanes would rise. Average hurricane peak wind speeds could increase by 16% and peak precipitation could increase by as much as 28%. James McCarthy of Harvard University and IPCC lead author states,

"Global warming is not necessarily causing more hurricanes, but it may well be

causing bigger and more powerful ones". Even if fewer overall hurricanes were to occur, an increase in peak wind speeds, peak precipitation, and an increase in the number of Category 4+ hurricanes impacting the US is bad news for North Carolina and the Atlantic basin as a whole. Although statistically only one in five hurricanes that make landfall in the US is a category 3 or above, they account for more than 80% of the total storm damage in a typical season. A 16% increase in wind speed adds 30% more energy to a storm system and a third more rainfall would cause much more frequent flooding on a scale greater than what the western part of North Carolina experienced in the 2004 season. Clearly, stronger hurricanes have the potential to inflict greater damage and it can be expected that damage and loss to life and property from tropical cyclonic storms will increase in the state as temperatures rise.

1.8.2 Severe Thunderstorms, Tornados, and Winter Storms Climate models are not yet sophisticated enough to accurately determine if the frequency and intensity of ‘micro’ weather events such as isolated thunderstorms, tornados, and winter storms will increase as a result of global warming. However, these weather events are influenced by regional and global changes in temperature and humidity, therefore it is quite probable that global warming will have an effect.

Severe Thunderstorms

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enerate ent and severe summer thunderstorms. High winds and

flash flooding from severe isolated thunderstorms account for the

Thunderstorm frequency and severity is related to temperature and atmospheric moisture content, so it can be expected that warmer, wetter summer conditions resulting from global warming will gmore frequ

bulk of non-tropical cyclone weather damage in the state. It is logical to assume that as the

equency and intensity of severe thunderstorms increase, associated damage to life and

ornados ropical cyclones and severe thunderstorms spawn an average of

os a year in North Carolina. Records indicate that the

. al

inter Storms Winter storms are a regular feature of North Carolina weather. Severe winter

commonly experienced in northern and mountain states are s

n odels predict at winter precipitation will continue to increase, so it is logical to assume that the frequency and/or

at rain

then winter weather in North Carolina would lter dramatically. Winters would become much colder, last longer and bring much more frequent and

.9 Economic Consequences of Extreme Weather

er events primarily related to evere storms and hurricanes. In the 1990s North Carolina ranked fourth in the nation for weather

on

ssible to accurately estimate the potential cost of damage due to extreme weather vents caused by global warming, it can be expected that weather related loss of life and costs will

eather related economic costs due to global warming will be discussed an upcoming report.

frproperty will also increase. TTforty tornadoverall number of reported tornados in the state has doubled in the last one hundred years with an associated increase in related fatalities and property damage. This increase is consistent with a national trend towards more frequent and destructive tornadosAlthough global warming may cause the overall frequency of tropiccyclone impacts to decline slightly, North Carolina is likely to experience higher intensity cyclones which breed more violent and nuan increase in severe thunderstorms it is likely that tornados will be more common anmore destructive during the summer tropical cyclone and thunderstorm season.

merous tornados. Coupled with d potentially

W

There has been an i

storms on a scalerare in North Carolina although such events are often economically disruptive athe state lacks sufficient funds to adequately deal with them.

crease in winter precipitation over the last 100 years. Climate mthseverity of winter storms impacting the state will increase correspondingly. Average annual temperatures are expected to increase several degrees in the next decades with the highest increases occurring in winter. Higher winter temperatures could alter precipitation so thand freezing rain storms become more common. If global warming causes the Gulf Stream to shut, downasevere snow storms of the type more commonly experienced in New England. The winter storm of 2002-2003 that brought large parts of the state to a standstill would quite possibly become an annual event and seem mild in comparison.

1 North Carolina is particularly susceptible to damage from extreme weathsrelated insurance claims, and number two in 2000. On average, damage from extreme weather events such as thunderstorms, tornados, and tropical storms costs the state approximately $6.5 billidollars per year. Although it is impoeincrease substantially as the frequency and intensity of floods, winter storms, hurricanes, and severe thunderstorms increases. A more detailed analysis of w

11in

2

.0 Conclusions

to North Carolina’s climate, with associated impacts to extreme weather e extent of future greenhouse gas emissions. It is possible to estimate

oth the “best case” and “worst case” weather effects based on the IPCC emissions scenarios. In the

cts to

ide precipitation increases 5% by the end of the century, continuing the trend towards mmers and wetter winters

e effects of storm damage along the coast

amages

• re heat favoring plant species adversely impacting

Wo• se 13oF by 2100

e precipitation increases 25% by 2100, continuing the trend towards significantly drier and much wetter winters

reatly increasing effects of storm damage

cipitation to tropical storms affecting the state

ing industries

by gradual warming In t htemper alter the global,

nd hence state climate. One potential abrupt change relates to the Gulf Stream effect which is tential to

The impact of global warmingevents, largely depends on thbbest case scenario, the IPCC assumed a radical switch to clean technologies and stabilizing atmospheric carbon dioxide concentrations at 450ppm. In the high emissions scenario the IPCC assumed rapid global economic expansion sustained almost entirely by fossil fuels. In this scenario the IPCC assumed atmospheric CO2 would stabilize at around 1,000ppm. The projected impaNorth Carolina from each scenario are summarized below.

Best Case • Statewide average temperature rise 3oF by 2100 • Statew

drier su• Sea levels rise 10 inches by 2100, exacerbating th• More frequent and severe droughts, wildfires, floods, and storm damage with a moderate

increase in associated economic d• Small increase in average hurricane intensity by half a category, adding 10% more destructive

potential to tropical storms affecting the state Changes in vegetation patterns towards mothe farming and timber industries

rst Case Average state temperatures increa

• Statewidsummers

• Sea levels rise 27 inches by the end of the century, g• Severe droughts, water shortages, and flash flooding become common features of summer

weather • Much greater economic damage and loss of life from storms and wildfires • Large increase in average hurricane intensity adding 30% more destructive potential and 28%

more pre• Widespread loss of forest cover and severe impacts to the timber and farm• Fifty percent chance of Gulf Stream shutting down by the end of the century leading to much

more severe winters, although the effects may be offset

rut , it is much harder to predict the outcome of the worst case scenario because higher atures greatly enhance the chances of abrupt climate change that could rapidly

apreviously discussed. Two other potential abrupt climate change scenarios that have the porapidly alter global climate involve methane hydrates and the effect of vegetation die-off. Both effects would greatly enhance feedback into the warming cycle by rapidly contributing vast amounts of carbon to the atmosphere. The consequences of these effects to the climate of North Carolina, and the whole world, are potentially catastrophic. Photographs * Courtesy of Gary Braasch http://www.worldviewofglobalwarming.org/

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References

1. Alley, Richard B., Abrupt Climate Change, 2004 2. Environmental Protection Agency (EPA), Climate Change and North Carolina, September 1998

3. Fuhrman, Christopher M. and Konrad, Charles E., Dept. of Geography, University of North Carolina

at Chapel Hill, A Winter Weather Climatology for the Southeastern United States

4. Gagosion, Robert B., Woods Hole Oceanic Institute, Abrupt Climate Change, Should We Be Worried?, 2003

5. Gallagher, Patrick T., University of North Carolina at Wilmington, Changes in Climate Due to

Disruptions of the Gulf Stream Current and Thermohaline Circulation System, 2003

6. Knutson, Thomas R., Tuleya, Robert E., Impact of CO2 Induced Warming on Simulated Hurricane Intensity and Precipitation: Sensitivity to the Choice of Climate Model and Convective Parameterization, 2004

7. Lansea, Christopher W., Climate Variability of Tropical Cyclones: Past, Present, and Future, 2000

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Carolina, 2003

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12. National Oceanic and Atmospheric Administration, NOAA Reports Wet, Warm year for the US in

2004 – Hurricanes, Wildfires, Drought, Snowpack and Flooding All Notable, 2005

13. North Carolina Emergency Management Office, Hazard Mitigation in North Carolina, http://www.dem.dcc.state.nc.us/mitigation/index.htm, 2004

14. Philander, George S., Is the Temperature Rising? The Uncertain Science of Global Warming, 2000

15. State Climate Office of North Carolina, General Summary of North Carolina Climate, http://www.nc-

climate.ncsu.edu/climate/ncclimate.html

16. United Nations Intergovernmental Panel on Climate Change (IPCC) Climate Change 2001, Working Group I, The Scientific Basis

17. World Wildlife Fund International, Global Warming and Atlantic Hurricanes, 1999