Effects of Climate Change in North America : An Overview

As forecast by many researchers, climate change can be expected to impact regions through direct effects (e.g., temperature shifts, changes in sea level, extreme weather events, and precipitation changes) and indirect effects (e.g., migrations of species and changes in ecosystems). Previous studies have reported how various regions will face challenges as to adaptations and vulnerabilities brought on by climate change differently according to their wealth. Interrelated impacts have been forecast to occur in North America stemming from variations due to climate change, including economic, ecological, environmental, and social impacts. This study overviews the effects (direct and indirect) of climate change on various sectors in North America. It concludes, along with the suggestions of the Intergovernmental Panel on Climate Change’s (IPCC) Fourth Assessment Report (AR4), that future studies should focus on regional studies of climate change, impacts of extreme weather events, and in-depth integrated models for mitigation, adaptation, and impact based on future simulations of climate change.


Introduction
As forecast by many researchers, climate change can be expected to impact regions through direct effects (e.g., temperature shifts, changes in sea level, extreme weather events, and precipitation changes) and indirect effects (e.g., migrations of species and changes in ecosystems).Previous studies (Parson, 2003;Smith et al., 2005;Thomson, 2005aThomson, , 2005bThomson, , 2005c;;Füssel, 2009) have reported how various regions will face challenges as to adaptations and vulnerabilities brought on by climate change differently according to their wealth.
The increase in the frequency and intensity of extreme weather events over the past decades has been notable and well documented (Meehl & Tebaldi, 2004;Christensen et al., 2007;Meehl et al., 2007;Emanuel et al., 2008).The productivity of agriculture, forestry and tourism industries is sensitive to the climate.Public and private sectors related to waterfront properties (utilities, infrastructure, transportation, and resorts, etc.) are vulnerable during and after extreme weather events (Statistics Canada, 2006;Bureau of Transportation Statistics, 2006).Aging populations are also sensitive to climate change.Weather-related diseases cause an increase in urgent hospital admissions resulting in increased health care costs (Burleton, 2002).Extreme weather events have quite severe impacts on transportation systems (Lonergan et al., 1993), energy supplies, and other industries in North America.For example, major hurricanes in 2004 and 2005 in the US impacted oil and natural gas platforms and pipelines and caused high restoration costs in the billions of dollars for public utilities and transportation networks on the regional and national level (EEI, 2005).
Communities that rely on natural and water resources are sensitive to extreme weather events.Heavy rainfall, hurricanes, and ice storms affect quality of life and constrain economic activity.Community infrastructures are exposed to damage from tree insects, coastal erosion, rising sea levels, flooding, and storm waters.Fishing, hunting, whaling, travel, and various recreational activities have been affected by weather threats that have limited economic activities in these natural resource-dependent communities (NAST, 2001;CCME, 2003).
More frequent and intense extreme weather events have placed stresses on coastal communities, impacted ecosystems, increased coastal damage, and affected greater numbers of people during and after extreme weather events.For example, Alaskan villages, the Great Lakes area, the Gulf of St. Lawrence, and many other coastal communities that are within exposure range of tropical storms or winter storms have demonstrated their vulnerability and limited adaptive capacities (Clark et al., 1998;Parson et al., 2001;West et al., 2001;Scavia et al., 2002;Burkett et al., 2005).
Because of changes to ecosystems caused by climate change, commercial and recreational fisheries and plants must adjust to new spatial distribution of species.The uncertain productivity of forests will determine levels of carbon stock.The increase in length and scale of forest fires, loss of coastal and inland wetlands, and changes in high alpine areas and cold waters are all due to changes in forest and water ecosystems.For populations facing possible water availability issues in the western snowmelt-dominated region, some strategic adaptations may involve shifting seasonal runoff.Experts and climate-change-related centers have urged enhanced adaptation strategies, including more solid infrastructure plans (e.g., improving building codes and enhancing disaster preparedness), in order to prevent disasters that may be caused by extreme weather events associated with climate change.
More cities are forecast to experience extreme heat waves, increasing sea levels, increased numbers of dangerous storm surges, water shortages, droughts, and increased flooding.Stressors (severe heat waves, extreme weather events, and air pollution) generated by climate change may cause social disruption and increased human losses and injuries, as well as vector-borne and tick-borne diseases.This study overviews the effects (direct and indirect) of climate change on various sectors in North America.

Changes in Temperature
Previous studies have thoroughly documented the increase in annual mean air temperature in North America over the past forty years .For example, night-time temperatures have increased more than day-time temperatures, while spring and winter have demonstrated more warming than other seasons (Karl et al., 1996;Brown & Hunt, 2007;Füssel, 2009;Pederson, et al., 2010).Geographically, Alaska and northwestern Canada have shown the most significant warming, followed by the continental interior, the southeastern US, and eastern Canada.Because of the combination of greenhouse gas effects and sulphate aerosols (Karoly et al., 2003;Stott, 2003;Zwiers & Zhang, 2003), spring warming has extended the growing season an average of 2 days per decade (Bonsal et al., 2001;Easterling, 2002;Bonsal & Prowse, 2003;Feng & Hu, 2004).Temperature-specific terms relevant to the selected articles as to temperature changes between seasons and geographical locations due to climate change, study methods, and suggestions for future studies are presented in Table 1.
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Rising Sea Levels
Aggressive coastal investment plans, increasing coastal populations (both local and non-local), extended urbanization, and rising property values are adding stress to the ecosystems of coastal regions and revealing vulnerabilities to rising sea levels and severe storms resulting from climate change (Kleinosky et al., 2007;Füssel, 2009).Sea levels are forecast to rise at an accelerating pace over time, especially in eastern North America and western Alaska (Zhang et al., 2000;Church et al., 2004;Meehl et al., 2007;Cooper et at., 2008;Wu, et al., 2009).
Many previous studies have documented the correlations between rising sea levels, coastal and inland erosion, and more frequent and intense storms in the US (Meehl et al., 2007;Travis, 2010).Economic damage, unstable coastlines, and affected populations during and after extreme weather events (hurricanes, storms, wind, waves, ice encroachment) have been forecast to increase continuously in the coming decade (Zhang et al., 2000;Scavia et al., 2002;Emanuel, 2005).Increasing sea levels along with strong windstorms have already been reported to cause increasing damage on the Gulf and Atlantic coasts.Additionally, Wu et al. (2009) estimated that nearly 510,000 people and 1,000 km of roads will be impacted by rising sea levels due to inundation in the coastal portion of the Mid and Upper Atlantic Regions of the US by 2100.Rising sea levels relevant to the assessment of impacts of climate change on various sectors along with the studied regions, research methods, brief findings, and suggestions for future study are shown in Table 2.
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Extreme Weather Events
Storms.As mentioned above, the impacts of rising sea levels on the coastal regions of North America have been heavily documented (Travis, 2010).Many coastal communities and waterfront properties have been facing the dangers associated with storm surges and disruptive flooding over the years (Pielke et al., 2008;Kossin& Camargo 2009).For example, hurricanes Ivan in 2004 and Katrina, Rita and Wilma in 2005 had an enormous impact on infrastructure (Select Bipartisan Committee, 2006).In 2005 Hurricane Katrina flooded New Orleans, due to inadequate public evacuation plans and strategically sound emergency services, the impact of Hurricane Katrina in particular on the total affected population was disastrous (Balling & Cerveny, 2003).In 2006 storm surges battered Delta, British Columbia, and winter storms caused severe flooding and coastal erosion in San Francisco and along the Pacific coast (Bromirski et al., 2003;Edmiston et al., 2008).Settlements with high population density along the coasts, aging infrastructures, outdated building codes, urbanization, and ineffective and untimely warning systems have amplified the damage caused by these extreme weather events (Easterling et al., 2000;Balling & Cerveny, 2003;Changnon, 2003Changnon, , 2005)).Extreme-weather-specific terms relevant to the impacts of extreme weather events and natural disasters on various social-economic sectors are presented in Table 3.It also summarizes studied regions, research methods, brief findings, and suggestions for future study.
[insert Table 3 about here] Economic damage.Over the last 10 years (2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009), storms, floods, hurricanes, and wildfires, have caused most of the major economic damage (USAID, 2009).Approximately 95% of the affected populations were impacted by floods, storms, droughts, and wildfires, while floods, extreme temperatures, and storms caused 93% of human loss in North America in the past decade (BC Stats, 2003;USAID, 2009;Chen, 2011).Looking ahead, coastal areas and ski resorts have been forecast to receive significant negative impacts brought about by climate change.For example, because of increasing sea levels along the beaches in the state of Florida, billions of dollars will be spent for sand replenishment (Jones & Scott, 2006).Losses of ski zones at lower elevations are forecast to result in shortened snow seasons (7-10 weeks), decreased visitation, and diminished tourism receipts.Western North America is forecast to have its non-artificial-snow ski season shortened by 3 to 6 weeks (Hayhoe et al., 2004;Scott & Jones, 2005).
From 1998 to 2008, major storms cost an average of USD $50 million/storm, with the highest single storm (Katrina in 2005) having an impact of USD $2 billion (Business Week, 2005).Warmer weather triggered regional power outages resulting in millions in insured losses as well as total losses due to business interruptions in the billions (LaCommare & Eto, 2004;USAID, 2009).
Diseases.Extreme weather events (e.g., heat waves, air pollution, heavy precipitation, and droughts) endanger human health, having been documented to be correlated with increased urgent hospital admissions and mortality rates (Kolivras & Comrie, 2003;Patz et al., 2005;Thomas et al., 2006;Gosling, et al., 2009).For example, respiratory and cardiovascular illnesses are sensitive to air pollution and heat waves.Heavy precipitation has caused water-borne disease outbreaks, while heavy runoff can contaminate watersheds and increase bacterial counts.Statistics show that West Nile virus, vector-borne illness, and Lyme disease have been associated with warming temperatures in North America (McCabe & Bunnell, 2004).The impacts of extreme weather events on diseases are presented in Table 4.
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Variations in Stream Flow
Many factors (such as increased population; demand for water resources due to industrial, agricultural, and municipal needs; and changes in water quality and ecosystems) have affected the allocation of water resources and may have resulted in extended droughts in North America (Dupigny-Giroux, 2001;Wheaton et al., 2005;Kunkel & Pierce, 2010).For example, in the central Rocky Mountain region, stream flows have decreased nearly two percent per decade since 1910 (Rood et al., 2005) while there has been a 25% increase in stream flows in the eastern US over the past three decades (Groisman et al., 2005).According to Knowles et al. (2006), 74% of weather stations have documented an increase in precipitation (as rain not snow) in the western mountains of the US.On the other hand, because of regional warming, in the western mountains of North America, there has been a decrease in water from snow ranging from between 15 to 30% since the 60s (Groisman et al., 2005;Mote et al., 2005;Lemke et al., 2007), while Canada has experienced a decrease in both precipitation and snowfall in the west and Prairies (Vincent & Mekis, 2006).However, trends in the moisture index show various divisions in levels of wetness due to variations in precipitation and evapotranspiration.An increase in precipitation and a decrease in evapotranspiration (a reflection of higher air temperatures) would lead to a wetter outcome, for example, in the southern region of the US (Grundstein, 2009).
Underground and surface water resources are needed for agriculture and ecological systems.Climate change impacts the capacities of freshwater resources across regions, and exposes their vulnerability (Loukas et al., 2002;Branfireun & Macrae, 2009).Examples have included increased winter snow-melts and earlier spring flows and decreased flows in summer (Christensen et al., 2007;Merritt et al., 2006;Miller et al., 2003).Evaporation and precipitation rates are related to the warming weather.Warming temperatures impact the timing of snow-melting and water flows across seasons.Expanding dry seasons and water levels that vary from region to region impact the availability of watersheds and influence water quality (Lemmen & Warren, 2004).
Decreased or ceased water flows from springs, water shortages, and decreased ground water recharge are forecast for the southwestern US due to climate change (Loáiciga et al., 2000), while river stages are forecast to change in south-central British Columbia (Allen et al., 2004).Decreased agricultural productivity, shifted water allocations, and water reduction have caused millions of dollars in losses (Chen et al., 2001).Extended warming in the summer has contributed to higher temperatures (an increase of from 2 to 7°C) of streams, rivers, lakes, and reservoirs (Gooseff et al., 2005), causing lower oxygen levels and decreased flows (Fang & Stefan, 1999), and affecting fish allocations and growth rates (Morrison et al., 2002).Expanded erosion seasons have impacted the quality of soil and water resulting in changing agricultural yields and challenges to ecosystems (Füssel, 2009).Stream-flow-specific terms relevant to the assessment of inter-relationships between precipitation, snow water, and water resource allocations are presented in Table 5.The selected articles, study methods, findings, and suggestions for further study are also provided.
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Ecosystems
Due to regional differences, trends of increasing temperatures and changing precipitation rates have been documented with no uniform ecosystem impacts across the continent of North America (Millett et al., 2009).Climate change has caused ecosystem disturbances resulting in losses in both native and exotic species (Sala et al., 2000).For example, warming temperatures and fluctuating water supplies have impacted sustainable productivity and rates of mortality among recreational inland fisheries and commercial fisheries, for salmonid species and walleye in North America (Babaluk et al., 2000;Chapin et al., 2000;Schindler, 2001;O'Neal, 2002;Chu et al., 2003;Gallagher & Wood, 2003;Baldocchi & Valentini, 2004;Lester et al., 2004;Chu et al., 2005;Reed & Czech, 2005;Rose, 2005).The warming climate has extended growing seasons and increased evaporation rates (Gerber et al., 2004;Woodward & Lomas, 2004;Pederson et al., 2010).Biological invasions (Zavaleta & Hulvey, 2004), wildfires (Smit et al., 2000), and climate change have resulted in changes in plant species, shifts in tree species (Morgan et al., 2001), changes in the production of amphibian eggs (Beebee, 1995), and shifts in breeding migrations.According to Thomas et al. (2004), one to twenty nine percent of animal and plant species globally will become extinct by the year 2050.
Biogeographical distribution, primary production, and phenology are the three main linking factors related to climate and terrestrial ecosystems.Competition, herbivores, disease, wildfire, hurricanes, droughts, and human activities have direct and indirect impacts on organisms.These effects may cause plant species to flower earlier, perhaps resulting in such things as earlier first flights of butterflies (Forister & Shapiro, 2003), or changes in the color of fall leaves (Beaubien & Freeland, 2000;Schwartz & Reiter, 2000;Cayan et al., 2001;Hicke & Lobell, 2004;Wolfe et al., 2005;Boisvenue & Running, 2006).
Along the east coast of the US, 28 migrating bird species have shown earlier nesting behavior, while tree swallows and Mexican jays have been observed in earlier egg laying due to warmer springs (Brown et al., 1999;Butler, 2003).Species that have demonstrated earlier breeding include frogs (Gibbs & Breisch, 2001) and red squirrels in Canada (Reale et al., 2003), while some other species have experienced higher mortality rates (for example, fungal parasites) and changes of habitation northward (for example, red wolves) (Hersteinsson & Macdonald, 1992;Kiesecker et al., 2001;Pounds, 2001).
Forest fires.Commercial forestry is sensitive to wildfires, insects, diseases, and climate change (Flannigan et al., 2004;Gan, 2004;Woods et al., 2005).The increase in summer temperatures has been forecast to increase the risk of forest fires.The range of emissions scenarios (from low to high) has also been forecast to impact harvest volumes and revenues (Perez-Garcia et al., 2002;Sohngen & Sedjo, 2005).Various factors triggering wildfires include droughts, snowmelting, the warming climate, and dead trees from insect outbreaks and diseases (Volney & Fleming, 2000;Williams & Liebhold, 2002;Logan et al., 2003;Kunkel & Pierce, 2010).In North America, areas burned by wildfires increased from 2 to 6 times and the length of fire durations increased from 7 days to 40 days compared to previous decades, resulting in increased property and human losses (Schoennagel et al., 2004;Westerling et al., 2006;Running, 2006).Additionally, three correlated factors (drought, warming weather, and water shortages) have negatively impacted growth rates and yield performances for forests in North America (Barber et al., 2000;Caspersen et al., 2000;McKenzie et al., 2001;Joos et al., 2002;Peterson et al., 2002;Boisvenue & Running, 2006).Agricultural yields.Crop yields are sensitive to weather, water resources, pest invasions, and sustainable land-use practices (Lobell & Asner, 2003).Studies have shown that various crops (corn, rice, sorghum, soybean, wheat, common forages, cotton, and some fruits) (Adams et al., 2003;Rosenberg et al., 2003;Tsvetsinskaya et al., 2003;Antle et al., 2004;Thomson et al., 2005c), and irrigated grains (Thomson et al., 2005c) may benefit from the warming weather.The southeastern US and the corn-belt are more sensitive to weather changes than the Great Plains (Carbone et al., 2003;Mearns et al., 2003).Nevertheless, controversy as to how CO2 has impacted crop growth rates exists in the literature (Long et al., 2005;Durandeau, et al., 2010).Other weather-related factors (frost, an earlier spring, and disastrous winter thaws) and market competition have also impacted economic gains from crop yields (Bélanger et al., 2002;Mearns et al., 2003).
The vulnerability of the agricultural sector has increased because of its exposure to various severe weather events along with changes in market values (Tarnoczi & Berkes, 2010).Improved water conservation and crop diversity, changes to public policies, and strategic soil adaptations have been utilized to enhance the capacity of the agricultural sector to cope with challenges stemming from climate change (Smit & Skinner, 2002;Easterling et al., 2003;Senate of Canada, 2003;Wall & Smit, 2005;Wheaton et al., 2005).Over the past 20 years, heavy rainfall and climate fluctuations have had mildly positive impacts on the yields of corn and soybeans, and have been positive factors for the growth of walnuts and oranges, but have been negative for cotton and avocados (Lobell et al., 2007).

Climate Model Simulations
Changes in atmospheric circulation affect climate extremes in North America.To better understand potential changes in weather and climate extremes, more extensive access to high temporal resolution data (daily, hourly) from climate model simulations is needed.According to the most recent climate combined simulations, the year-round temperature increase is forecast to range between 1 to 3ºC over the years 2010 to 2039 (Christensen et al., 2007).The greatest warming is forecast to occur in winter at high latitudes and in summer in the southwestern US, and the southwestern US is forecast to experience decreased mean precipitation annually while the rest of the US will experience an increase in annual mean precipitation.In the same period, annual mean precipitation is forecast to increase from between 20% to 30% in the winter in Canada.As measured by the Power Dissipation Index, there has been a strong statistical connection between tropical Atlantic sea surface temperatures and Atlantic hurricane activity over the past 50 years.However, the phenomenon is still under-documented in relation to accurate predictions of sea surface temperature in tropical cyclone formation regions (Meehl et al., 2007;Füssel, 2009).

Usages of energy.
Climate change has impacts on the usage of energy, water power, and transportation systems.Several studies have concluded that summer electricity consumption will increase while heating degree days will decrease in the winter peak season (Morrison & Mendelsohn, 1999;Mendelsohn, 2001;Sailor & Pavlova, 2003;Scott et al., 2005;Hadley et al., 2006).According to the United States Global Change Research Program (2009), rising temperatures will likely increase energy demand for cooling and reduce energy demand for heating.In the United States, since cooling in buildings is provided by electricity while heating is provided by natural gas and fuel, there will be an increase in the use of electricity and a decrease in the use of gas/fuel.Because half of the nation's electricity is generated from coal, the increase in demand for electricity will likely result in increased levels of carbon dioxide emissions.

Conclusions and Suggestions
Interrelated impacts have been forecast to occur in North America stemming from variations due to climate change, including economic, ecological, environmental, and social impacts, as well as social and ecological changes.All the mentioned impacts will not exist in isolation at the regional, national, or international levels.For example, temperature changes will impact the quality of life of species, and may cause more frequent weather extremes, increased erosion, changes in biodiversity, increased numbers of invasive insects and diseases, changed moisture balances, and increased wildfires.Transformations of populations and urbanization are forecast to impact watershed resources and various kinds of power usage as well as emissions and air pollution.Types of recreation and tourism activities will be impacted because of the damage inflicted by severe natural disasters (Chen, 2011).
Reducing greenhouse gas emissions and adapting to the impacts of climate change have been the two major responses to the Kyoto Protocols.The IPCC's Second Assessment Report (SAR) raised awareness of the use and production of energy and CO2, and enhanced understanding of carbon sinks, but paid little attention to adaptation and greenhouse gas emissions.The Third Assessment Report (TAR) pointed out the importance of both adaptation and mitigation as actions for direct and indirect prevention.However, it failed to provide integrated strategies for assessment and strategic levels.The IPCC's Fourth Assessment Report (AR4) included many elements that emphasized the importance of conducting inter-relationship assessments for various sectors (Meehl et al., 2007).It concluded that research literature and findings lack guidance for integration as to adaptation and mitigation.
Suggestions regarding adaptive strategies from previous studies were based on past posted trends and experiences.Prevention and adaptation for future predictions are needed as a practical matter.The accountability of scientific research outcomes coupled with optimal practices regarding climate change will increase the efficiency of adaptive capacity (Meehl et al., 2007).This study concludes, along with the suggestions of the AR4, that future studies should focus on regional studies of climate change, impacts of extreme weather events, and in-depth integrated models for mitigation, adaptation, and impact based on future simulations of climate change.For example, future studies may consider exploring integrated relationships among mitigation, impacts, and adaptations as to private action, public arrangements, and inter/national policies at all levels.Providing more feasible implementation of impact preventions and risk controls will also ensure effective global governance in climate change policy.In order to accomplish the mission of the climate change policy and enhance the global social responsibility, an integrated system that can facilitate implementation of adaptation, mitigation, and sustainable development is needed in a timely manner.years (2003-2007) The coupling of hydrologic change with biogeochemical processes is essential to understand the impacts of a changing climate on water quality.
Progress in the area will accelerate with improved communication among the water disciplines.Branfireun & Macrae, (2009)

Table 1 .
Changes of Temperature

Table 2 .
Rising Sea Levels

Table 4 .
Diseases vs. Extreme Weather

Table 5 .
Water Resources vs. Climate Change