CO Who? Nations Shift Focus Away From Number One Greenhouse Gas

2.19.13

Jessica Kennedy, Energy Consultant, Energy Curtailment Specialists

The UN climate change negotiations in Doha, Qatar last week did not result in any strong international treaties to curb carbon dioxide (CO2) emissions or reform the way the world generates and uses energy, but some minor progress was made that can impact climate change. Most notably, the 25 members of the Climate and Clean Air Coalition agreed to reduce the emissions of three other greenhouse gasses: black carbon, ozone (O3) and methane (CH4). These pollutants are known as short lived climate forcers (SLCF) because they only last in the atmosphere for a short period of time. CO2 has a lifespan in the atmosphere of about 100 years, whereas SLCFs live in the atmosphere anywhere from a few days to a maximum of only a few years. This means that the world could potentially see a decrease in climate change in a shorter period of time by decreasing emissions of SLCFs in addition to CO2. Greenhouse gasses other than carbon dioxide have gained little attention over the years, even with greater awareness on climate change and global warming. Because so much depends on the outcome of the world's efforts to slow or even stop climate change, it is important to understand all components that contribute to global warming.

Methane (CH4) is considered to be the most important greenhouse gas behind CO2. CH4 is emitted primarily by industry, agriculture, and waste management operations, as well as several natural processes. Even more alarming is that the impact of CH4 gas is about 20 times greater than an equal quantity of CO2. In the United States, CH4 emissions have remained relatively steady over the past 10 years, accounting for roughly 10% of all human generated greenhouse gas emissions. According to EPA projections, CH4 emissions are actually expected to increase by just under 10% by 2020. Perhaps, with new restrictions on the release of CH4 into the atmosphere, the emission trend will decrease while global temperatures rise.

Ozone (O3) is also a major, but short lived, greenhouse gas and a primary component of smog. This may come as a surprise to many since we all know the ozone layer is essential to protect life on earth. Whether or not the O3 is beneficial or harmful depends on where it is located in the atmosphere. The ozone that acts as a harmful greenhouse gas is located in the atmospheric layer known as the troposphere. This layer is the one closest to Earth's surface and traps all greenhouse gasses that are emitted from Earth's surface. This type of ozone is known as "tropospheric ozone" or "ground level ozone." The ozone layer that protects the earth from solar radiation is located in the stratosphere, which is the layer of the atmosphere directly above the troposphere. This layering explains why ozone can't simply be replenished to the ozone layer by releasing it into the atmosphere. O3 emitted from Earth cannot reach the stratosphere because it is trapped as a greenhouse gas in the tropospheric layer. Because they don't last long, there is no opportunity for O3 molecules to migrate from the troposphere to the stratosphere. Therefore, ground level O3 remains a harmful greenhouse gas to humans, plants and animals.

Black carbon, otherwise known as soot, is particulate matter released by the burning of fossil fuels, mainly coal. The reason black carbon is a problem is mainly because it is a dark material, and absorbs sunlight in the atmosphere resulting in a warming effect. Black carbon that falls to the ground and blankets the arctic reduces the ability of the snow and ice to reflect sunlight, a property known as albedo, which causes the surface to absorb more sunlight and grow warmer. The temperature of the surrounding air also goes up due to radiant heat. It is estimated that Arctic temperatures have already risen due to the decreased albedo from black carbon deposit and melting of reflective snow and ice cover.

The recent 2012 World Energy Outlook released by the International Energy Agency is skeptical that the world can curb CO2 emissions enough to keep climate change at bay, but does not take into account the role of SLCFs. According to scientists, it may be possible to "buy some time" to curb CO2 emissions by drastically reducing emissions of short lived greenhouse gasses. The warming contribution of black carbon alone is estimated to be about 100 to 2,000 times higher than that of CO2. It is clear that reducing, or even better, eliminating this pollutant from the atmosphere will have a very positive effect on climate and human health. Black carbon is a primary component of the smog that contributes to respiratory illness and even shortened life expectancy among those who live in smog-polluted areas.

Cutting emissions of these short-lived climate forcers has the potential to cut global warming by 0.5°C by 2050. This may not put us entirely on track to meet the 2°C goal previously agreed on by the UN Copenhagen Accord in 2009, but it would improve current warming projections that range from 4°C to 6°C by the end of the century. In conjunction with cutting CO2 emissions, the plan to slash emissions of SLCFs may be a wise course of action for developed countries. Because there is no solid agreement among the UN on how to effectively reduce CO2, the agreement to reduce these other greenhouse gasses is at least a step forward in the fight against climate change. A very small step perhaps, but it may prove to be an important one.

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