What Are Greenhouse Gases, Main Sources and Climate Impact
For the past few years, the terms “greenhouse gasses” and “greenhouse effect” have been thrown around by the media to the extent that they no longer have any meaning. But what are greenhouse gases and how do they threaten our lifestyle on Earth?
Greenhouse gases are a category of compounds that can trap heat in the atmosphere. Instead of letting this long-wave radiation escape, they cause the planet’s surface to become warmer than it would be if they were not present.
This group of gases is the main cause of the greenhouse effect. When there is an increase in the amount of greenhouse gases in the atmosphere, then the greenhouse effect also increases. As a result, global warming ensues and further climate change.
What Is the Greenhouse Effect?
Greenhouse gases allow sunlight to pass through the atmosphere freely, where the Earth’s surface then partially absorbs it. However, some of this energy then bounces back out into space as heat. The greenhouse gasses in the atmosphere intercept and absorb some of the heat emitted into space.
Greenhouse gasses are made of three or more atoms – a molecular structure which allows them to absorb some of the escaping heat. When they re-emit it back towards the Earth, global temperatures increase.
The trapped heat causes the greenhouse effect. Therefore, the more greenhouse gases are in the atmosphere, the more heat remains on Earth. The process has been named after the way a greenhouse works. Read “What Is the Greenhouse Effect and How It Happens” for a deeper understanding of how this process occurs and how it affects all life on Earth.
What Are Greenhouse Gases?
The group of greenhouse gasses (often referred to as GHG) is rather extensive. Today, we will mention only the main contributors to climate change, according to the U.S. Environmental Protection Agency (EPA).
- Carbon dioxide (CO2) is the leading GHG that enters the atmosphere through the burning of fossil fuels (coal, oil, and natural gas). However, many other human activities contribute to the release of CO2 in the atmosphere, such as trees and wood products, solid waste, as well as certain chemical reactions (such as the manufacture of cement). CO2 is removed from the atmosphere with the help of plants, which absorb it as part of the biological carbon cycle.
- Methane (CH4) is emitted in the atmosphere during the production and transport of coal, oil, and natural gas. Moreover, agricultural practices and livestock also cause methane emissions, as well as the decay of garbage in solid waste landfills.
- Nitrous oxide (N2O) emissions are high in areas with intensive agricultural and industrial activities. The combustion of fossil fuels and solid waste are also to blame.
- Fluorinated gases – such as perfluorocarbons, hydrofluorocarbons, nitrogen trifluoride, and sulfur hexafluoride – are powerful, synthetic greenhouse gases. They end up trapping heat in the atmosphere due to a variety of industrial processes. Even though this kind of gas emissions is typically smaller in quantity, they are extremely potent greenhouse gases. Therefore, some scientists refer to them as High Global Warming Potential gases (“High GWP gases”).
Leading Sources of Greenhouse Gasses
We already mentioned some of the sources that increase the amount of GHG in the atmosphere. According to EPA, These are the primary sources of greenhouse gas emissions in the United States:
- Electricity production (30 percent of 2014 GHG emissions) generates the single largest amount of greenhouse gas emissions. Until solar power becomes more prominent, we are stuck with almost 67 percent of our electricity coming from burning fossil fuels.
- Transportation (26 percent) greenhouse gasses come from burning fossil fuel for our cars, trucks, trains, ships, and planes. More than 90 percent of the fuel burned for transportation is petroleum-based, including diesel and gasoline.
- Industry (21 percent) burns fossil fuels for energy, releasing greenhouse gas emissions into the atmosphere. Certain chemical reactions needed to produce goods from raw materials also contribute greatly.
- Commercial and Residential (12 percent) GHG emissions come from homes and businesses that burn fossil fuels for heat. The handling of waste, as well as the use of certain products that contain GHG, are also to blame.
- Agriculture (9 percent) contributes to the total GHG emissions due to agricultural soils, livestock such as cows, and intensive rice production.
- Land Use and Forestry (offset of 11 percent) – Land areas can either act as a carbon sink (by absorbing it from the atmosphere) or as a source of GHG emissions. In the U.S., since 1990, managed forests have absorbed more CO2 than they emitted.
U.S. Emission Trends
Since the 90s, U.S. greenhouse gas emissions have seen a disturbing and gradual increase. From year to year, factors like changes in the economy or the price of fuel influence the rise or fall of gas emissions.
In 2014, U.S. greenhouse gas emissions had increased significantly compared to 2013 levels. A number of factors played a role, including the extreme winter conditions which resulted in an increase in fuel demand, particularly in commercial and residential sectors. At the same time, the increase in vehicle miles traveled caused transportation emissions to spike, while the progress in industrial production also caused industrial sector emissions to rise.
GHG & Climate Change
According to EPA, many factors – both natural and human – are responsible for the changes in Earth’s atmosphere and surface temperature. The agency named alterations in the reflectivity of Earth’s surface; variations in the Sun’s energy reaching Earth; and changes in the greenhouse effect.
Scientific estimates going as far back as thousands of years show that the climate system experiences natural variations during time scales. Scientists explain climate changes which occurred prior to the Industrial Revolution in the 1700s by natural causes, including volcanic eruptions, changes in solar energy, and natural changes in greenhouse gas concentrations.
On the other hand, more recent climate changes could not have been caused by natural causes alone. Most observed warming could not be explained by natural causes, particularly since the mid-20th century. Rather, more and more research points to human activities as the dominant cause of that warming.
Humans have contributed substantially to climate change by adding heat-trapping gases like CO2 to the atmosphere. Seeing that burning fossil fuels is the primary human activity influencing climate change, maybe we should start altering our lifestyle to preserve the Earth.