Climate change has been debated for a while on whether it’s real or a myth. With the signing of the Paris climate agreement this month, it appears that everyone finally agrees it’s real and we need start working on it before the planet reaches the danger zone from where it can’t recover. But what is causing most of this climate change?

In a word: Humans, or more precisely, the human actions that increase greenhouse gas emissions. How does burning coal, driving our cars and cutting down trees for development result in melting glaciers, rising water levels and warmer water temperatures?

Greenhouse gases are gases in the Earth's atmosphere that produce the greenhouse effect. Changes in the concentration of certain greenhouse gases, from human activity (such as burning fossil fuels), increase the risk of global climate change. Greenhouse gases include water vapor, carbon dioxide (CO₂), methane, nitrous oxide, halogenated fluorocarbons, ozone, perfluorinated carbons, and hydro fluorocarbons. 

These gases surround and insulate the Earth like a blanket. They allow the sun to reach and warm the Earth’s surface then block the warmth from escaping back into space. Human activities, including those mentioned above, have continued to increase and have upset the balance of the natural system for several greenhouse gases: methane, nitrous oxide, fluorinated gases and especially carbon dioxide. As these gases continue to be emitted into the atmosphere, they form a thicker layer. And just like the blanket, the thicker it is, the more heat it holds.

The United States and China are the biggest contributors of these gases with the European Union coming in third. The major culprit of gas emissions is the burning of fossil fuels (coal, oil and natural gas). Other pollution activities include agriculture, deforestation and livestock breeding.

Carbon dioxide is the biggest contributor to the problem. It occurs naturally from a number of sources. In the natural system, CO₂ can be absorbed by oceans and plants taking it in during photosynthesis. The man made increases of CO₂ have tipped the balance and these natural intake sources cannot absorb these additional amounts. Some CO₂ can remain in the atmosphere for thousands of year.

Even if the oceans could absorb more CO₂ from the atmosphere_, it increases the acidity of the oceans and turns it into carbonic acid. This acid uses up the carbonate in the water so it’s not available for sea creatures who need it for skeleton and shell building and coral reefs.

Methane is the second largest culprit of the greenhouse gases. In addition to the same industrial sources that emit CO₂, landfills and rice cultivation are additional sources of methane gas. While methane does not last as long in the atmosphere as CO₂, it is much better at trapping heat.

Nitrous oxide (N₂O), another greenhouse gas, is part of the Earth’s nitrogen cycle. Unfortunately 40 percent of the nitrous oxide worldwide comes from human activities, including fossil fuel burning, agriculture and wastewater management. It can last in the atmosphere approximately 114 years before it is removed or destroyed by chemical reaction. According the U.S. EPA, “the impact of 1 pound of N₂O on warming the atmosphere is almost 300 times that of 1 pound of carbon dioxide.”

Since weather information has been accurately recorded, the temperature trend has been increasing. For example, the ten warmest years on record have occurred since 1998 and so far 2015 is the hottest year on record and with only a few weeks left in the year, it should end that way.

Unfortunately, it appears the blanket is doing its job.

For more information on the Paris agreement, see the Michigan State University Extension news article “Paris climate agreement”

For more information on greenhouse gases, visit the U.S. EPA website.