Effects of Climate Change

The effects of climate change have already been observed around the planet and are expected to become more severe as global temperatures increase. Ice sheets and glaciers are rapidly melting as sea levels continue to rise, forcing the relocation of low-lying populations and threatening water supplies for millions of people. Ancient permafrost is thawing, weakening the foundations of roads and buildings and possibly triggering the release of vast amounts of trapped methane gas.

Droughts, desertification, and floods are on the increase, all of which have a detrimental impact on agriculture. Biomes from grasslands to forests are in a constant state of flux as various species of vegetation attempt to adjust to the unprecedented changes in plant distribution associated with accelerated changes in climate. The global transportation infrastructure is in jeopardy as extreme weather events buckle railroads, inundate roadways, and force the cancellation of travel plans. Heat waves are contributing to the deaths of thousands and warmer temperatures are hastening the expansion of tropical diseases. The negative effects of climate change will affect all aspects of society and the natural environment.

Ice Sheets, Glaciers, and Permafrost

In the Arctic, nearly all of the ice covering Greenland is in the form of glaciers, which are rapidly melting. On the west coast of Greenland, the average temperature in winter has increased 9 degrees F (5 degrees C) in just the past two decades. There is increasing calving of ice around the edges of the Greenland Ice Sheet as it becomes more porous because of the development of moulins, which are holes or crevasses through which melt water enters a glacier from the surface. The water pouring into the moulin can melt through the ice until it makes contact with the rock base below, causing the glacier to advance more rapidly and perhaps even slide off its base into the sea. 

While it is unlikely that the Greenland Ice Sheet will disappear altogether, continued melting could reduce it to one-third its normal size. In the Arctic basin, sea ice is on the decline, with the ice pack getting thinner and thawing farther from shore. Since the early 1900s, the ice pack has been melting faster during the summer; since the 1950s, the area of summer ice pack has declined by 40 percent. The current rate of sea ice loss during the summer is about 10 percent per decade. Forecasts had originally suggested that the Arctic Ocean could be ice free in summer by 2030. However, the Northwest Passage from the Atlantic to the Pacific was free of ice and open in the summer of 2007, and at the current rate of melting, the Arctic Ocean could be completely ice free by the end of the 21st century.

Antarctica contains the largest continental ice sheets on the planet, and they are showing signs of rapid melting and movement. The average temperature of the west antarctic peninsula has increased by more than 3.6 degrees C (2 degrees C) since the 1950s, and the midwinter temperatures have warmed by as much as 9 degrees F (5 degrees C) during the same time period. Ice shelves consist of huge areas of ice frozen onto the Antarctic land mass and play an important role in Antarctic glacial retreat. Large chunks of ice occasionally break off the edges of these floating ice masses and drift away. The second-largest iceberg ever measured broke free from the Ross Ice Shelf in March 2000. A week later, three more large pieces broke free from the same ice shelf.

In 2002, the Larsen Ice Shelf lost a 1,200 sq. mi. (3,107 sq. km) chunk of ice. While the breakup of these ice shelves may not have a major effect on sea level because they are already floating in water, many of these ice shelves hold back glaciers in the ice sheet, preventing them from advancing seaward. If the ice shelves melt, it will allow the glaciers to move forward, adding ice to the sea and raising sea level.

The Arctic and Antarctica are not the only regions where ice is melting. The Himalayan Mountains and the Tibetan Plateau are home to many of the world’s great glaciers, covering more than 70,000 sq. mi. The glaciers are the source of water for the main rivers of India, including the sacred Ganges and the Indus. During the summer, the slowly melting glaciers provide water for drinking and irrigation, and during the winter, snowfall replenishes the ice for the next summer.

However, warmer temperatures are causing the glaciers to melt faster during the summer, causing major flooding in the lowlands, while the lack of snowfall at higher elevations during the warmer winters is causing drought. The same is true of the glaciers along the equator in Africa. Mount Kenya has had glaciers throughout recorded history, but now only 20 percent of these glaciers remain. The farmers in the surrounding valleys have always depended on the glaciers for their water, but the rivers are drying up and people are starving.

The snows of Mount Kilimanjaro are world famous and have been a mainstay of the people of equatorial Africa for centuries. The glaciers on the mountain are nearly gone and will soon vanish completely, leaving the locals to fight over the limited remaining water supplies. Likewise, in the mountains of Uganda, the glaciers are disappearing at an alarming rate, with 80 percent of the glacial ice melting since 1850 and all of the glaciers expected to be gone within the next 40 years. The glaciers in the European Alps have decreased by 50 percent since the 1900s and are predicted to disappear by the middle of the 21st century. During the devastating summer heat wave of 2003, which killed at least 30,000 Europeans, the glaciers in the Alps lost 7 ft. of ice. Switzerland suffered major flooding in 2005 as a result of rapidly melting glaciers and the resultant runoff. Glacier National Park in the United States has lost 80 percent of its glacial ice since 1850 and is expected to be glacier free within 30 years.

Other types of ice are melting as well. It is estimated that 20 to 25 percent of the Earth’s global landmass consists of permafrost (some of it below the Arctic Ocean), and some areas of permafrost are softening as the climate continues to warm. Across Siberia, the temperature of the permafrost has risen by more than 1.8 degrees F (1 degree C) since 1960, causing trees in the forests to lean and buildings to crack and crumble as the underlying frozen soil begins to thaw.

In some places around Fairbanks, Alaska, drier summers have warmed the permafrost by nearly 5.4 degrees F (3 degrees C), causing the same destruction seen in Siberia as well as a rash of fires and a northward migration of bark beetle infestations that are wiping out entire evergreen forests. Melting permafrost could also potentially free the billions of tons of methane that are currently locked in the frozen soil. Many fear that a sudden release of vast amounts of methane, which is 21 times more potent as a greenhouse gas (GHG) than carbon dioxide (CO2), would cause the worst-case projected global warming scenarios to happen.

Warming Oceans and Rising Seas

There is conclusive evidence gathered from millions of data points taken around the world that the temperature of the global ocean has increased dramatically in recent years. Since the mid-1950s, the mean temperature of the global ocean rose by more than 0.9 degree F (0.5 degree C) from the surface to a depth of 9,000 ft. Because of the high specific heat of water, which is five times greater than that of land, oceans have the capacity to store large amounts of heat energy that would otherwise be released into the atmosphere. 

However, the world’s oceans cannot continue to absorb this excess heat, and by the end of the 21st century it is estimated that enough heat will be released to the atmosphere by the oceans to raise global temperatures another 0.9 degrees F (0.5 degree C) in addition to the warming caused by the greenhouse effect. Because of thermal expansion and the addition of meltwater from ice caps and glaciers, sea levels are rising.

If global temperatures increase by 3.6 degrees F (2 degrees C), there could be a rapid melting of ice and sea levels could rise by as much as 6 ft. (1.8 m). If summer temperatures across the West Antarctic Ice Sheet were to rise above freezing, there could be a rapid melting event that would cause sea level to rise 20 ft. (6 m). If the entire Greenland Ice Sheet were to melt or to slide off its base into the ocean, sea level could be 30 ft. (9 m) higher. And in the highly unlikely, worstcase scenario, if the entire Antarctic Ice Sheet were to melt, sea levels worldwide would rise 230 ft. (70 m).

Agriculture, Drought, and Desertification

Global climate change is forecast to cause major shifts in the general circulation of the atmosphere, which will lead to variations in the length of the growing season and the alteration of precipitation patterns. These changes will, in turn, affect agricultural production. Some changes will be offsetting. An increased length of growing season may be offset by lower rainfall. Crop yields could be reduced, although the combined effects of climate and carbon dioxide will depend on the severity of climate change. In many regions of the United States, climate change and higher temperatures could result in considerable heat and water stress on crops, which could reduce corn, wheat, and soybean yields. In some northern areas, warmer temperatures and a longer growing season combined with rising CO2 levels may increase crop yields, provided there is adequate irrigation.

These projected agricultural shifts will affect not only the livelihood of farmers but also infrastructure

and other support services. During the last few decades, there has been a widespread drying trend over large sections of the Northern Hemisphere. Drought is more common in the tropical and subtropical regions of the world, and it is suspected that climate change is an underlying cause. The intensity and duration of droughts are on the increase, and nearly half of the planet is experiencing some form of prolonged drought. A warmer climate is forecast to generate wetter winters and drier summers across most of the middle and higher latitudes of the Northern Hemisphere, a scenario that would lead to a higher potential for summertime drought. Many scientists expect such extended extreme events to become more prevalent as the climate continues to change.

Agriculture is a critical component of local livelihoods in many countries around the world. This sector is particularly sensitive to land degradation, which results in the loss of productivity. The unwanted expansion of desert, or desertification, involves the loss of productivity of rain-fed cropland, range, pasture, woodlands, and forest from climate change. Contributing factors include drought, soil erosion, overgrazing, deforestation, warming temperatures, and changing precipitation patterns. Areas undergoing desertification are ranked as follows: a moderate-hazard area has an average 10 to 25 percent drop in agricultural productivity; a high-hazard area has a 25 to 50 percent drop; and a very high hazard area has a greater than 50 percent decline in agricultural output. Other natural resource challenges such as pests, crop diseases, poor soil fertility, and a lack of access to water are usually aggravated by periods of prolonged droughts. As of 2011, almost half of Africa’s land area was vulnerable to desertification.

Other countries experiencing desertification include Asia, Australia, and North and South America. As land for agriculture becomes further degraded, the need for more food could likely be met by increasing yields per unit of land area, water, energy, and time. Increasing variability in hydrological characteristics will likely continue to affect grain supplies and food security in many nations.

Vegetation

For many species of vegetation, climatic changes resulting in a temperature difference of a few degrees or a slight variation in rainfall pattern may determine whether a particular species survives or becomes extinct. Because climate and vegetation are so strongly associated, it is assumed that rapid changes in climate will affect plant distributions and alter the makeup of natural communities. An intensive study was completed in 1992 by C. Russell and L. E. Morse in 1992 to determine the effect of climatic change on native vascular plant species found in North America. The analysis assumed that a doubling of CO2 would lead to a 5.4 degree F (3 degree C) increase in global temperatures, basing the study on the maximum and minimum mean annual temperature that each species experiences in its current distribution. The results suggest that with this increase in temperature, 10 percent of the species under investigation would be beyond their climatic envelope and at risk for extinction.

Rare species were especially at risk, with nearly 20 percent threatened with extinction. Because climate plays such an important role in the distribution of plant species, the predicted global and regional climatic changes will likely affect a variety of existing vegetation patterns. Some species will migrate and form new associations, while others will be lost completely.

Fire patterns are likely to be altered as well, which could affect a variety of plant species, even those that are fire resistant or require the presence of fire to regenerate. A study based on a doubling of CO2 levels reveals that wildfires in Canada would undergo a 46 percent increase in seasonal severity. There are unique species that have maintained their present locations for thousands of years despite substantial climatic change, indicating that some species have a high degree of physiological tolerance to climatic fluctuations. In fact, some stress-tolerant species could benefit from extreme climates if competitors are locally depleted or eliminated.

Transportation Infrastructure

As abnormally hot days become more frequent, the transportation infrastructure is directly affected. Railroads tend to warp and buckle during extreme heat waves, sometimes causing train derailments. Asphalt roadways are subjected to softening, while concrete highways undergo joint buckling, creating hazardous conditions for motorists. Climate change and the resultant increase in severe weather events affect aircraft operations. Airports experiencing higher temperatures undergo high-density altitude conditions, which affect aircraft performance in the form of reduced lift, longer takeoff rolls, and runway closures. This phenomenon is especially prevalent at high-altitude airports where the air is already less dense.

The vast majority of flight delays and cancellations can be attributed to bad weather. Aircraft are negatively affected by high winds, such as those accompanying severe thunderstorms. These storms are strengthened by unstable conditions, which often result from surface heating associated with higher temperatures. In more than 80 percent of accidents among commercial air carriers, turbulence and high winds were responsible.

Many scientists predict that climate change will cause more extreme weather events and therefore perpetuate this trend. Increasing temperatures also have numerous indirect impacts on transportation and associated infrastructure. With sea levels projected to continue rising at an accelerated pace accompanied by higher storm surges and flooding, more major seaports along with the connecting roadway and railway facilities will likely be inundated. Likewise, airports located along coasts are at risk of diminished operations because of rising waters and will require expensive protection measures in the near future.

Health Impacts

Human health will be significantly affected by climate change because of warmer and more extreme weather, which has a categorical influence on the distribution of certain diseases. Viruses, bacteria, and insects such as mosquitoes all tend to favor a warmer, wetter environment and are the carriers of numerous infectious diseases. The most widespread of all mosquito-borne diseases affecting humans is malaria, with more people suffering from this tropical disease today than at any time in history. It is estimated that as many as 300 to 500 million people are infected with malaria each year, and that 2.5 million will die of the disease.

Malaria is expanding its range as it moves to higher latitudes and altitudes as a result of rising temperatures, deforestation, and population growth. If global temperature increases by 3.6 degrees F (2 degrees C), the range of malaria could expand to cover 60 percent of the planet. Global warming leads to more rounds of the type of weather that creates more fertile breeding ground for mosquitoes. Some scientists claim a link between global warming and the prevalence of West Nile encephalitis virus, which is transmitted by birds that have been infected by mosquito carriers. The disease first appeared in the United States in 1999, killing seven people. After it was first detected in birds in the southeast, it took just two years for the virus to spread across the United States. According to the Centers for Disease Control (CDC), in 2010 (a year of extreme weather), the virus had infected over 800 people in the United States.

Not only do higher temperatures increase the spread of tropical diseases, they also cause increased death rates for the seriously ill, the elderly, and those with weakened immune systems. More than 30,000 people were killed during the European heat wave of 2003 as temperatures rose 9 degrees F (5 degrees C) higher than normal. Most of the deaths were among the elderly because of cardiovascular problems associated with heat stroke. As global temperatures continue to rise, more extreme summer heat waves are forecast to occur.