Global climate change: How does it happen, and is there hope?

The coming of the New Year often brings about feelings of nostalgia as we reminisce about the previous calendar year. Looking back at 2015, we as humans have quite a bit to be proud of: the granting of women’s voting rights in Saudi Arabia, the development of a new highly effective drug for the prevention of HIV infection, and of course, the new Star Wars film. However, arguably one of the most significant accomplishments of 2015 was the Paris Agreement – the first-ever universal, legally-binding global climate deal.

In December of 2015, nearly 200 nations united to develop pledges to curb global climate change. The deal requires any country that ratifies it to limit its greenhouse gas emissions in the coming century with the goal of keeping global temperatures from rising. In order to understand why lowering greenhouse gas emissions – as pledged by the Paris Agreement – is so crucial to the conservation of our planet, it is important to understand what these greenhouse gases are.

The term, greenhouse gas, stems from the notion that Earth is a giant greenhouse – a contained area in which the temperature is maintained within an ideal range in order to facilitate life and growth. This ideal temperature is achieved via a feedback mechanism between the Earth’s surface and the atmosphere; greenhouse gases within the atmosphere act as global insulators by trapping thermal energy reflected by the Earth’s surface when sunlight reaches it. This feedback mechanism, under ideal conditions, results in a life-supporting average surface temperature of 59 degrees Fahrenheit. However, when these greenhouse gases exist in excess in our atmosphere, as they do now, the greenhouse effect is enhanced, resulting in a global heating of the Earth’s surface. Since the beginning of the industrial revolution in the late 1700s and early 1800s, years and years of fossil fuel burning, domestication and manure management of animals, farming techniques, deforestation, and landfill waste build-up have led to an accumulation of greenhouse gases that has proved detrimental to our global climate. Listed below are 4 of the major greenhouse gases, where they come from, and how they contribute to global climate change.

1. Carbon Dioxide (CO₂): CO₂ is believed to be the main factor driving climate change. This compound is released through natural processes, such as breathing, as well as human activities, such as deforestation and fossil fuel combustion. The chemical structure of CO₂ renders it capable of absorbing infrared radiation reflected by the Earth’s surface. Energy from an infrared photon causes the CO₂ molecules to vibrate. Soon after, the CO₂ molecule releases this extra energy by emitting another infrared photon that may then be absorbed by another greenhouse gas molecule. This ability to absorb and re-emit infrared energy is what makes CO₂ an extremely effective heat-trapping greenhouse gas. Importantly, not all gas molecules can absorb infrared radiation like CO₂ can. For instance, N₂ and O₂, which make up most of the Earth’s atmosphere, do not absorb infrared light. Notably, Earth’s atmospheric CO₂ has reached its highest level in 650,000 years.                                                                                                                                                                  

2. Methane (CH₄): Methane is a hydrocarbon gas produced by agriculture, the decomposition of waste in landfills, and the management of livestock manure. Similar to CO₂, methane’s molecular structure causes radiation to be trapped within the atmosphere. Methane can be broken down or oxidized by radicals in the atmosphere to CO₂ and water vapor, each of which are greenhouse gases themselves. Furthermore, a molecule of methane lasts almost 10 years before it is broken down and removed from the atmosphere. 

3. Nitrous Oxide (N₂O): N₂O is produced through both natural sources such as nitrogen from soil, as well as human activities such as fossil fuel combustion and biomass burning. N₂O breaks down to form nitric oxide (NO) which can deplete the Earth’s protective ozone layer.

4. Fluorinated gases: Fluorinated gases are synthetic compounds

   

   with molecular structures so stable that they are resistant to chemical reactions. Fluorinated gases may result from industrial processes like aluminum and semiconductor manufacturing.There are no natural processes that remove these compounds from the lower atmosphere. Thus, over time, winds drive these compounds into the upper atmosphere, where they are broken down and release either atomic chlorine or bromine. One chlorine atom has the power to destroy over 100,000 ozone molecules, such that the ozone is destroyed by fluorinated gases faster that it can be produced.

Accompanying the attempts to limit greenhouse gas emissions within the Paris Agreement are goals to meet every 5 years to set more ambitious and focused targets, to report to each other and the public on how well each nation is achieving their targets, and to develop infrastructure such as solar and wind power to adapt to the effects of global climate change. Many climate experts agree that this pact, while not perfect, is an important milestone in the journey to curb climate change, stating, “If we’re focused, we can do this.” It appears that 2016 will be a great year for our beloved planet Earth.

Peer edited by Saidivya Komma

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This article was co-published on the TIBBS Bioscience Blog.