Because of the fundamental interconnectedness of Earth’s natural processes, global climate change impacts not only the atmosphere, but also the hydrosphere, lithosphere, and biosphere.
Distribution of Water and Precipitation
In the upcoming Global Climate Change and Action section, you will learn about Africa‘s efforts to combat climate change in its Action Against Desertification program.
Glacier and snowpack reduction can also ultimately reduce river flows. In the Water Chapter, we read about the Ganges River, which originates in the Himalayas and is a major water source to most of India. Glacier and snow melt support summer flows in Asia’s major rivers, including the Ganges and Brahmaputra rivers of India, and the Yellow, Yangtze, and Mekong rivers in China. As glaciers diminish in size due to global warming, so does the source of water for these important rivers.
Droughts also diminish the availability of water for many in the world. For example, droughts reduce water flow in smaller rivers, causing nomadic herders such as those in Mongolia to move towards larger rivers. Unfortunately, the larger concentration of herders at bigger rivers destroys the vegetation in these riverside pastures, which are called riparian pastures. These pastures cannot sustain such high densities of grazing herds.
Long periods of drought in East Africa and Australia have resulted in the death of large numbers of domesticated animals and wildlife. In Russia’s wheat belt and the Western U.S., long droughts have spurred enormous wildfires, which destroy vegetation that stabilizes the soil (Figure 17). Areas that have experienced drought and wildfires are susceptible to mudslides, which are caused by intense rain storms that can follow drought and wildfires.
Intense rain storms are also becoming more frequent in general. Increased evaporation rates of surface ocean water due to warmer air and water temperatures provide more water vapor for rains, transforming gentle showers into more intense rainstorms, as the Mongolian herdsmen are experiencing.
More intense rains can overwhelm storm water drainage systems in cities. In more rural areas, intense rains can cause increased soil erosion and damage to farm crops, and can kill farm animals, wildlife, and people who are washed into flooding streams and rivers. For example, in 2012, an intense rain storm hovered over Beijing, China, resulting in almost 200 mm of rain during a ten hour period, which caused flooding in many areas of the city. Similar heavy rains have hit Central Europe, Greece, and the United States.
Another concern is the impact of warming ocean water on the global ocean circulation currents, or the ocean conveyor, which in turn will affect regional climate and precipitation patterns.
Extreme Weather Events
As the global average surface temperatures (especially ocean surface temperatures) become warmer, developing storms will contain more energy. According to IPCC (2013), tropical cyclones, such as Atlantic hurricanes and Pacific typhoons, have become more frequent and more intense— with stronger winds, heavier precipitation, and longer durations—since the late 1970s (Figure 18).
Learn more about Henry’s Law.
Another effect of global climate change is ocean acidification. Ocean acidification is caused when higher concentrations of carbon dioxide (CO2) in the atmosphere dissolve into ocean waters. When carbon dioxide dissolves, it combines with water to form carbonic acid (H2CO3), which causes an increase in the acidity of the water. This process, explained by Henry’s Law, is referred to as ocean acidification and it threatens the life of many animals and microscopic organisms. Recall again figure 24 in the Biodiversity Chapter which illustrates the tipping points for the nine threats to the planet. Climate change and ocean acidification are listed as two of these threats.
As we learned in the section about the evidence of climate change, sea levels have risen over the last century. The most intense sea level rises have occurred within the last two decades. Currently, it is projected that sea levels across the globe will continue to rise during the twenty-first century due to increased thermal expansion of the oceans and the increased melting of ice caps and glaciers.
This rise in sea levels puts people living in low elevation coastal regions (approximately 10% of the global population) at risk from seawater intrusion, inundation, and serious storm surges.
For many South Pacific islanders, sea level rise is causing frequent saltwater flooding that destroys their crops and contaminates their drinking water. As a result, many people have already abandoned their traditional island homelands. The inhabitants of the Carteret Islands in the South Pacific who will be discussed further in the Global Climate Change and Spirituality section of this chapter were the world’s first such “climate change refugees” (Figure 20).
Plants and Animals
In the upcoming Global Climate Change and Action section, you will learn how the U.S. Environmental Protection Agency is collaborating with Indigenous People to learn more about local changes in the relationship between climate and plant pollination.
Temperature and photoperiod play important roles in determining the timing of plant and animal life cycles. As the global climate becomes warmer, species are stressed by temperature, water, and food extremes.
In Northern Europe, Russia, and North America, for example, many plants now start “greening up” in spring a few days earlier than in the past in response to the warmer climate (Figure 21). However, in regions that occur further away from the equator, such as in Scandinavian countries at 60oN-70oN, the temperatures may warm earlier in spring, yet the seasonal photoperiod will not change. Therefore, temperature and photoperiod become asynchronous, occurring at different times. This timing mismatch affects crop pollination since the flowering of plants (which depends on the photoperiod) and the arrival of pollinators such as bees (which is dependent on the temperature) occur at different times. Decrease in crop pollination results in a marked reduction of food supply.
As noted above, oceanic microscopic organisms are threatened by the ocean acidification which is caused by increasing carbon dioxide levels in the atmosphere due to fossil fuel emissions. Many of these marine organisms build their protective external “shells” out of calcium carbonate (CaCO3), which easily dissolves in acidic water, putting an enormous stress on these tiny organisms (Figure 22). Since these microscopic organisms comprise the bottom of the food chain, the stress put on them by ocean acidification has cascading impacts up the entire chain to the top predators. Experiments suggest that coral reefs, mollusks, and sea urchins are particularly vulnerable to acidification. Additionally, reproduction of diatoms, a major group of algae and a primary producer of ocean biomass and atmospheric oxygen, is negatively affected.
Coral reefs are among the most biologically diverse communities of life on the planet. They are threatened not only by ocean acidification, but also by planetary warming which causes the corals to expel their endosymbionts or zooxanthellae, resulting in a white, bleached appearance. This can lead to the loss of a coral reef that would otherwise serve as a habitat for a rich diversity of coral reef fishes, and serve to protect many coastal island areas from storm surges.
Questions to Consider
Keep a record of the food items you eat every day at your main meal. Go to the Union of Concerned Scientists Climate Hot Map and see what impact global climate change may have on your food. How many of these food items could you afford to lose before your health would be at risk? What would you do to replace the food items of your main meal that could be lost to global climate change?
Science has advanced our understanding of global climate change. We understand what drives climate change and we understand the severe impacts climate change is having on environmental processes and human communities. However, as Dale Jamieson states:
. . . the problem we face is not a purely scientific problem that can be solved by the accumulation of scientific information. Science has alerted us to the problem, but the problem also concerns our values. It is about how we ought to live, and how human beings ought to relate to each other and to the rest of nature. These are problems of ethics . . .8
It is to these problems that we now turn.