The Biggest Danger
This effect moderated temperature on the Earth long before humans began changing the chemistry of the atmosphere. Like a well managed greenhouse, the Earth’s surface remained warm, but not too hot, and thus allowed the growth of the lush ecosystems we have inherited. The increase in heat-trapping gases in the Earth’s atmosphere caused by human activity means the greenhouse effect could, like a poorly managed greenhouse that is left closed up on a hot summer day, overheat and do great damage to all the living creatures on the Earth.
The Main Causes: Human Emissions
The primary greenhouse gases include:
- carbon dioxide
- nitrogen oxides, and
- fluorinated gases
These make up only one percent or less of the Earth’s atmosphere, but they are almost entirely responsible for all of it’s heat trapping capacity.
Greenhouse gas levels have increased dramatically since the start of the industrial revolution. Based on scientific study of the Earth’s past, it is believed that the atmosphere of the Earth contained about 280 parts per million (ppm) of carbon dioxide before the industrial revolution began, and about .72 ppm of methane. Now the Earth’s atmosphere has about 385 ppm of carbon dioxide and about 1.8 ppm of methane.
Impacts of Different Greenhouse Gases
Carbon dioxide is the largest contributor to global warming, and occurs in relatively high concentrations. On the other hand, methane occurs in low concentrations, but it has a much higher heat-trapping capacity than carbon dioxide per unit volume. In fact, methane is 20 times more potent per unit as a greenhouse gas than carbon dioxide measured on a 100 year scale, and 100 times more potent measured on a 10 year scale. (Methane breaks down relatively quickly in the atmosphere to simpler molecules.)
Other trace gases, like nitrogen oxides, and other human-created fluorinated gases have heat trapping capacities 200-300 times more potent than carbon dioxide.
Humans Are Enhancing the Effect
We have initiated a new geological age: the Anthropocene — the age created by humans. We are brining this new geological era into being by radically increasing the impact of the greenhouse effect.
Carbon levels have increased in the atmosphere as a result of our burning large volumes of fossil fuels that have been trapped underground for millions of years. We have cut down millions of acres of forest and every tree contains carbon, and as a tree is burned or decomposes, that carbon is released into the atmosphere.
We have dangerously increased methane levels in the atmosphere as well. Methane leaks from natural gas wells and coal mines. It is also created anytime organic matter decays under oxygen-staved conditions. This occurs in rice paddies, and in the guts of herbivorous animals. As humans have cleared forests to make farms and expanded the number of cows, sheep, and goats, we have increased the amount of methane in the atmosphere. The arctic tundra is also now melting, and releasing enormous volumes of methane and carbon dioxide.
We Are Creating New Greenhouse Gases
Humans are now synthesizing more artificial nitrogen, for use as fertilizer, than all of the natural nitrogen fixing process of all of the plants on Earth. In nature, nitrogen is pulled from plants out of the atmosphere in a process called nitrogen fixation. But when this artificial nitrogen is applied to farmland, some of it is released into the atmosphere as nitrogen oxide, a powerful greenhouse gas that is several hundred times more potent per unit volume than either carbon dioxide or methane.
Another set of highly potent gases are fluorinated gases. These are accumulating in our atmosphere. Fluorinated gases are a set of chemicals used as refrigerants, for insulation, and for other industrial purposes.
Abrupt Climate Change Is Unpredictable
Dramatic weather changes aren’t gradual, according to a growing body of evidence. Rather, the Earth’s climate maintains a specific range of temperature and weather behavior for extended periods. Over time, pressure builds up from changes in the chemistry of the atmosphere, or changes in solar radiation. Once enough pressure has built, then the Earth enters a period of abrupt climate change.
Temperature increases will be extreme in some places and unnoticeable in others. The human enhancement of the greenhouse effect on the planet Earth does not mean that there will be an even heating of the continents and oceans. The net effect, however, will be a potentially devastating disruption of weather, rainfall patterns, storms, and sea level rise. If we do not stop adding greenhouse gases to the atmosphere, we may face unfathomable consequences.
Author: Brown, Nathan. A Cooler Climate, 2008.