Since the experiments of Irish physicist John Tyndall in 1859, we have understood that certain atmospheric gases are not transparent to radiation, but instead absorb long wave radiation and reemit that captured energy as heat (Pain 2009). These gases have kept our planet at the stable and inhabitable temperatures needed to support life, and their effect on earth’s temperature was termed the “greenhouse effect” by Svante Arrhenius in 1896. Arrhenius was among the first, if not the very first, to imagine that climate could be altered by human activity (Titus, Park et al. 1991).

The most abundant greenhouse gases include water vapor, carbon dioxide, methane, nitrous oxide, ozone and chlorofluorocarbons, and since the industrial revolution humans have measurably increased the concentrations of these gases. Today, thanks to Charles David Keeling, we have a record of atmospheric carbon dioxide concentrations on Mauna Loa, Hawaii dating back to 1958, which provide evidence of the recent increase in carbon dioxide, methane and nitrous oxide (Le Treut, Somerville et al. 2007). Moreover, the global record of carbon dioxide measurements shows that carbon dioxide concentrations in 2009 were higher than at any time in the last 800,000 years on earth, and the current carbon dioxide level of approximately 390 ppm is projected to increase by 2ppm per year (National Academy of Sciences 2010).

The  often politicized scientific conflict surrounding climate change does not call into question the existence of the greenhouse effect or the rising concentrations of GHGs, but rather the sensitivity of our climate to these anthropogenic changes. This debate is justified, as our climate is a complex system involving the atmosphere, oceans, and landscape. There are many natural feedbacks or reactions, which may limit or magnify changes to the climate system. Some of these feedback processes are not well understood and are difficult to model, such as cloud feedbacks. However, since the first report investigating the human impact on climate by the Intergovernmental Panel on Climate Change (IPCC) in 1990, there has been a surge of scientific research and climate data collection. The 2007 IPCC report stated unequivocally that the earth is warming due to human activity (2007). The impacts will be widespread and will directly and indirectly affect many aspects of human civilization, not least of which is business and commerce. The following seeks to detail the physical consequences of climate change and its bearing on business.

Higher Temperatures

Over the past 150 years, global temperatures have increased approximately 0.8˚C, and are anticipated to increase another 2˚C to 4.5˚C by 2100 with more dramatic warming corresponding to increases in latitude (Alley, Berntsen et al. 2007). Moreover, 2010 tied 2005 for the hottest year since 1880, when record keeping began. National Oceanic and Atmospheric Administration data shows that nine of the ten warmest years on record have occurred since 2001 (NOAA 2011).

Hotter temperatures affect the geographical range hospitable to many plant and animal species. This is particularly problematic for plant species, which can only migrate over long periods of time. In the United States, maple and beech tree varieties are contracting to the North, and several spruce and fir species have vanished. However, for young forests in the U.S., unrestricted by water and nutrient availability, warmer temperatures and higher CO2 levels may increase productivity (National Academy of Sciences 2010). Unfortunately, scientists anticipate that hotter summers will increase the probability of forest fires by 10% to 30% (Field 2007).

Ocean warming often reduces productivity by limiting mixing between warm and nutrient-rich cool waters, and in some areas, ocean warming causes upwelling of deep hypoxic water, which creates dead zones. This has occurred off the coasts of both Oregon and Washington. Additionally, increased ocean temperatures can cause massive coral bleaching by disrupting the symbiotic relationship between the coral and the algae upon which it depends for its nutrition.

Higher temperatures may benefit crops, such as melons and sweet potatoes, which do well in the heat, but additional heat can also put stress on agriculture; grains, soybeans and seed production are expected to decline. Climatologists predict that warmer temperatures will benefit agriculture in northern states, while the Midwest and Great Plains will experience decreased yields due to higher temperatures and precipitation decreases (National Academy of Sciences 2010). In all areas, higher temperatures have the potential to increase evapotranspiration rates although scientists have found a decline in this trend since 1998 as a result of limited soil moisture, prompting concerns about water availability (Jung, Reichstein et al. 2010).

Higher average temperatures and an increase in severe heat waves will have an impact on human infrastructure as well. The functionality of bridge joints, pavement and rail tracks can be compromised via thermal expansion, and airplane load limits can become restricted, since hot air reduces aerodynamic lift. In Alaska, thawing permafrost causes subsidence, which disrupts roads, buildings and pipelines.

Rising Sea Levels

Global warming leads to rising sea levels because of thermal expansion of ocean water and the release of freshwater previously stored in ice caps and glaciers. Scientists estimate that over the past fifty years approximately 85% of anthropogenic heating has been absorbed by the ocean. The resulting thermal expansion explains half of the recorded sea level rise observed over the past century (National Academy of Sciences 2010). The other half is explained by our arctic and mountain glacier melt. In 2010, Greenland’s melt period was a month longer than the average over the past 30 years, and the Canadian Arctic also experienced a significantly longer melt season. Last year was the third smallest Arctic sea ice coverage in the last 30 years (NOAA 2010).

Sea levels have been accurately measured over the past hundred years, and the record shows that sea level rise has been accelerating, especially in the last couple decades. The 2007 IPCC report estimates rises of 0.6 to 1.9 feet depending on the severity of the warming during the 21st century, and levels are expected to rise twice as fast along the Northeastern U.S. coast (Science Daily 2009). If ice sheet dynamics were critically compromised and there was complete melting of Greenland and Antarctica, they would contribute 23 and 197 feet to sea level rise, respectively (National Academy of Sciences 2010).

In the United States, over half of the population lives in coastal counties, and the population is predicted to expand. Ten of the fifteen largest U.S. cities are located on the coast. Many of these coastal areas are hubs of economic activity which provide jobs and support recreation, waterborne commerce, fisheries, tourism and mineral production (Crossett 2004). Sea level rise directly threatens the infrastructure of these activities through flooding, beach erosion, wetlands converted to open water and higher salinity levels in estuaries. Studies in San Francisco are already reporting coastal erosion due to rising sea levels. Additionally, higher sea levels may increase the damage caused by storms and hurricanes. Cities located on deltas below sea level, such as New Orleans, are particularly vulnerable. Already several coastal Alaskan villages require relocation due to higher sea levels, which will cost an estimated $54 million (Field 2007).

Limited Water Availability

Global warming alters the water cycle: hotter temperatures lead to higher evaporation rates, which results in higher precipitation. This means that current water sources may be reallocated elsewhere.

Western regions of the United States reliant on snow melt for water will experience a change in the seasonality and amount of water availability, since snow pack is decreasing and melt is occurring on average four weeks earlier than it did fifty years ago. Since 1950, snowmelt from the Rockies has declined 15% to 30%. This reduces the amount of water available in the summer, and increases the likelihood of drought. Due to reduced snow melt and higher evaporation, water levels have gone down in both the Colorado and Columbia River basins (Field 2007). Moreover, humans are further altering the water cycle by changing the landscape in ways that increase surface runoff and decrease groundwater replenishment.

A restricted water supply will place a strain on agricultural, municipal, industrial and ecological users, potentially hindering economic development. There will be increased costs for managing, storing and conserving water. There will also be challenges for waterway navigation, hydropower and recreational water activities.

Altered and Increasingly Extreme Weather Patterns

Climate change has an effect on local and regional weather patterns and the frequency of extreme weather events. Research has shown that in the United States periods of cold have become less common and less extreme, while hot days and nights are becoming more intense, frequent and enduring. Intense precipitation events are also increasing. In the United States over the past century, the heaviest 1% of rain events increased 20%. The U.S. is also expected to experience more pronounced wet and dry seasons.  The summers in the Midwest, Pacific Northwest and California are predicted to be increasingly dry and prone to droughts (National Academy of Sciences 2010).

Global warming increases sea surface temperatures and humidity, since warmer air can carry more moisture. Both improve conditions for thunderstorm development. As a result, over the last four decades, scientists have observed an increase in the frequency, intensity and duration of cyclones in the North Atlantic (Climate Institute 2010).

Some areas of the United States are expected to become more vulnerable to flooding due to a hike in precipitation. In 2008, the Organization for Economic Cooperation and Development placed New York City, Alexandria, New Orleans and Miami among the ten cities in the world most at risk for flooding (Nicholls, Hanson et al. 2008). The impacts of severe flooding often include large population displacement and contamination of the water supply (Climate Institute 2010). Infrastructural damage is also common; in Miami an estimated $400 billion in assets are exposed to risk from flooding (Nicholls, Hanson et al. 2008).

Increase Disease and Pest Populations.

The climatic range hospitable to many diseases and their associated carriers (e.g., mosquitoes, ticks and rodents) is expected to expand with climate change as many areas get wetter and warmer. These diseases include: malaria, dengue malaria, dengue fever, West Nile virus, Saint Louis encephalitis virus, Rocky Mountain spotted fever, Lyme disease, encephalitis, hantavirus and leptospirosis. At elevated temperatures, several of these diseases exhibit faster replication rates (National Academy of Sciences 2010). High temperatures also put stress on human health increasing vulnerability to disease. Extreme heat increases respiratory illnesses, episodes of fainting and/or cramps, and exposure to pollen and ozone. Reliance on air conditioning and air quality management will be higher and more widespread in the future, creating higher demand for power (Field 2007; Climate Institute 2010). In areas that become wetter, the prevalence of gastrointestinal parasites and liver fluke will become greater, too (Food and Agricultural Organization 2008).

Plant and animal health will also be negatively affected by the spread of pests and disease, and some regions are already experiencing these impacts. Milder winters in the Pacific Northwest allowed the buildup of the mountain pine beetle and led to the decimation of many of the region’s pine forests (Food and Agricultural Organization 2008). A team of Stanford researchers have found evidence that longer growing seasons and milder winters are leading to the habitat expansion and population swell of the corn earworm and the corn borer. The corn borer costs the United States approximately $1 billion in damages per year and the corn earworm annually destroys 2% of the nation’s corn crop (Diffenbaugh, Krupke et al. 2008).

 
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