Anthropogenic Climate Change: How Human Activity is Warming the Planet and Altering Our Oceans

Climate change is not a one-time phenomenon. Throughout the 4.5 billion years of the Earth’s history the climate has changed repeatedly. For example, the early Earth was so hot that it was molten at the outset, cooling over time. The Carboniferous Period was also very warm, permitting Earth to burst forth with luxuriant plant growth. Insects were abundant as well. The era of the dinosaur was also warmer than what we experience today. Climate change, therefore, is not a new state of affairs. What may be new, however, is the strong likelihood that humans are responsible for the current regime of global warming and climate change. Many factors are involved in the changing climate.

Industrial Roots.The current situation appears to have derived from the Industrial Revolution. Industrial production emerged around 1750 in England, which was in the process of mechanizing the production of textiles. The use of fossil fuels, coal initially, to power the steam engine came at a terrible cost in retrospect. The coal was nothing more than fossilized plants. When alive, these plants had been photosynthetic factories.

The key point is that they absorbed enormous amounts of carbon dioxide. Now, by burning these fossilized plants, industrialists liberated tremendous amounts of carbon dioxide into the atmosphere. The burning of petroleum and natural gas has had the same effect.

This process, repeated daily over centuries, has increased the concentration of carbon dioxide in the atmosphere. This may seem trivial until one realizes that carbon dioxide has the ability to trap heat in the atmosphere. That is, long-wave radiation (light tending toward the ultraviolet spectrum) from the sun passes easily through the atmosphere to strike Earth. Plants capture some of this radiation to supply almost all other life with sustenance. That light then bounces back into the atmosphere as short-wave radiation (light that tends toward the infrared spectrum). This light does not escape back into space because carbon dioxide captures this light. Because light is heat, carbon dioxide heats as it captures light.

The result is a hotter Earth. Almost every year in the twenty-first century has been hotter than previous years, with 2015 being the hottest on record. Note that this is not a claim that 2015 was the hottest year in the history of the Earth. Because humans have kept meteorological data since only about 1880, scientists cannot speak authoritatively about earlier years. Nevertheless, the trend toward warming is well established. Because we are at the core of climate change, it is fair to pinpoint us as the principal cause, giving rise to the phrase “anthropogenic change.” We appear to have entered what some have called the “Anthropocene,” a period in which humans are the primary agents of change to Earth and its biota.

Agriculture and Natural Resources.The situation with agriculture is difficult because, like the industrial world, it depends almost wholly on the burning of fossil fuels. True, some farmers have made important adjustments by plowing the land less or even not at all. This phenomenon is known as no-till. As more people seek an American diet of meat, livestock raising has become ever more important. Unfortunately, cows release methane into the atmosphere as flatulence. The actual cropping systems of the world are less easy to judge. The planting of crops, soybeans, for example, should put in place a large number of photosynthetic factories. But in the subtropics and tropics, the cutting down of forests for farming may cause a net loss in overall photosynthesis. Remember that photosynthesis is necessary to draw down carbon dioxide levels. In Southeast Asia—Indonesia, for example—the rise of mixed plantations of oil palm trees, cacao, and rubber appears to create new forests that are efficient at drawing down carbon dioxide. World agriculture, then, is a series of systems, some of which appear to exacerbate global warming and climate change and others that may improve conditions over the long run.

What cannot be denied is the threat to our land, the most basic natural resource. Drought has crippled areas, like parts of California, that were prime farmland and that are being sustained through irrigation that is not itself sustainable. The great Ogallala Aquifer of the American West is being depleted to make up for the lack of rainfall. Other places, parts of India, for example, have in recent years suffered from floods due to excessive rain. Clearly, the problems that face people in certain parts of the world do not seem to affect others. The only connection is that all people, to greater or lesser degrees, are beginning to suffer the effects of climate change.

The Oceans.If Earth is warming, it seems reasonable to ask how this trend affects our world. It is important to direct our questioning toward the oceans because water, gram for gram, is among the most efficient holders of heat in the world. That is, the oceans hold vast quantities of heat. The current state of affairs is adding still more heat to the oceans. It may seem counterintuitive, but the oceans appear to be warming most rapidly at higher latitudes, with fewer changes at the equator. Again, this is not a trivial observation. Heating at high latitudes is dangerous because it is causing polar ice sheets to melt. This is the conversion of water from solid to liquid.

The liquid water simply joins the rest of the ocean. Consider a thought experiment. Allow a chunk of ice to melt in a container. When it has all melted, the liquid water will fill some portion of the container. The melted ice therefore causes the rest of the ocean to become even more engorged with liquid water so that the total volume of water increases, causing the sea levels to rise. Many hazards flow from this realization. Small islands are in danger of being submerged, wiping out the culture that had flourished there. The United States will not be immune to such catastrophes. Miami, Florida, and all of south Florida are susceptible to floods that undermine public transportation and other facets of life. New York City faces similar perils. In Italy, the city of Venice appears to be sinking into the Adriatic Sea. Should we allow such tragedies to occur? As the oceans warm, they appear poised to release other greenhouse gases, methane, for example, into the atmosphere, worsening the trend toward warming.

On the positive side, oceans absorb both heat and carbon dioxide, slowing down climate change in the atmosphere and on land. However, this short-term positive effect comes at a steep price. Besides the above-discussed rising sea levels, climate change also affects the circulation of ocean currents. Melting polar ice caps will significantly reduce the salinity of the water, which then combines with increasing heating of ocean surfaces to redirect ocean currents. Changing currents will, in turn, have a more significant impact on the climates experienced on land. Likewise, the increasing absorption of carbon dioxide, estimated at close to 30 percent, will increase the acidification of global oceans. This will affect the buildup of coral reefs and food webs already under siege from overfishing. Another issue resulting from climate change is ocean deoxygenation.

The increasing warming of the ocean’s surface leads to decreasing oxygen levels in the waters, further disrupting marine life habitats. Recent research has linked these phenomena to algae blooms that may cause extreme lack of oxygen and the emergence of literal coastal dead zones. Lastly, warm surface waters are increasingly connected to extreme events such as the increasing intensity of hurricanes. Some scientific institutions now suggest increasing the Saffir-Simpson scale measuring hurricane intensity. The scale currently maxes out at category five, or hurricanes with sustained wind speeds exceeding 156 miles an hour. Proposals would like to expand to a sixth category encompassing increasing hurricane activity that exceeds 192 miles an hour. Christopher Cumo

FURTHER READING:Gore, Al. 2007. An Inconvenient Truth. New York: Viking.

Hidore, J., J. Oliver, M. Snow, and R. Snow. 2010. Climatology: An Atmospheric Science. Upper Saddle River, NJ: Pearson.

Mann, E. F. and L. R. Kump. 2009. Dire Predictions: Understanding Global Warming. Upper Saddle River, NJ: Pearson.