1.4 Reduction of Greenhouse Gas (GHG) Emission
There is a scientific consensus that greenhouse gas (GHG) production is increasing, which has led to climate change and several other environmental concerns. Despite efforts to make us believe otherwise, much of the severe weather occurring worldwide is indeed due to climate change. There is a significant amount of evidence to substantiate the existence of climate change and the overall warming of the earth. Climate change is due to the Greenhouse Effect; it is a natural effect, caused by CO2 and water vapor naturally present in the atmosphere. The focus of debate (scientific and political) has been on whether there is also an anthropogenic greenhouse effect, causing further climate change. Carbon dioxide (CO2) is not the only greenhouse gas (methane, CH4 is another potent GHG; this will be discussed further in upcoming sections), but most of the debate focuses on it. It is thought that the dramatic increase in CO2 in the atmosphere is due to the burning of fossil fuels.
The world is highly dependent on fossil fuels; the US is also highly dependent on fossil fuels. As we saw in the charts in Lesson 1.3, global energy consumption will continue to increase over the next 30 years. Fossil-based sources such as coal, natural gas, and petroleum are expected to be the dominant energy source in 2050.
There is a mountain of evidence indicating that the planet is warming. The figure below shows global average surface temperature levels plotted from 1880-2020. The change has been most dramatic in the last 30 years. Yearly global temperatures from 1880 to 2023 relative to the 20th-century average show that Earth's surface temperature has increased by 0.14 degrees Fahrenheit per decade since 1880. The pace of warming has more than doubled since 1981.
The 2023 Global Climate Report from NOAA's National Centers for Environmental Information reveals that every month in 2023 was among the seven warmest on record for that particular month. Additionally, each month from June to December marked the hottest ever recorded for those months. In July, August, and September, global temperatures exceeded the long-term average by more than 1.0°C (1.8°F)—the first time any month in NOAA's records has surpassed this threshold.
The impacts of climate change on our planet can be observed from pole to pole. NOAA tracks global climate data, and here are some notable changes they've recorded, with more details available on the Global Climate Dashboard.
- Global temperatures have increased by about 1.8°F (1°C) from 1901 to 2020.
- Sea level rise has accelerated from 1.7 mm/year during most of the 20th century to 3.2 mm/year since 1993.
- Glaciers are retreating: the average thickness of 30 well-studied glaciers has reduced by over 60 feet since 1980.
- The summer sea ice coverage in the Arctic has diminished by approximately 40% since 1979.
- Atmospheric carbon dioxide levels have risen by 25% since 1958 and by about 40% since the Industrial Revolution.
- Snow is melting earlier than long-term averages indicate.
In the Arctic and Antarctic regions, the ice pack and glaciers are melting, and at an even faster rate than originally anticipated. Scientists have found that increasing atmospheric temperatures are not the only cause of this; the melting is causing water currents to shift and move warmer water around the poles, so melting is happening underneath the ice pack. The figure below shows that the total area of the Arctic Ocean with at least 15% ice coverage each September from 1979 to 2023 shows that, since 1980, the extent of ice surviving the summer has decreased by 13.1% per decade. The figure related to Sea Ice Concentration demonstrates that the sea ice concentration on September 19, 2023, compared to the 1981-2010 average extent for that date (indicated by the gold line), marked the sixth smallest summer minimum ever recorded. The sea levels have also risen by 8-9 inches since 1880, with the rate of increase accelerating during the satellite era.
Another problem could stem from the increased production of natural gas. Natural gas consists primarily of methane. Sources include petroleum and natural gas production systems, landfills, coal mining, animal manure, and fermentation of natural systems. Methane has 25 times the global warming potential of CO2. The figure below shows the total GHG percentages from various economic sectors. The transportation sector is the largest contributor of greenhouse gas emissions. Greenhouse gas emissions from transportation mainly result from burning fossil fuels in cars, trucks, ships, trains, and planes. Over 94% of transportation fuel is petroleum-based, including primarily gasoline and diesel, which leads to direct emissions. The transportation sector is the largest source of direct greenhouse gas emissions and ranks second when considering indirect emissions from electricity use across all sectors. Although transportation is an end-use sector for electricity, it currently accounts for a relatively small portion of total electricity consumption. Indirect emissions from electricity make up less than 1% of direct emissions in this sector. The next figure shows the emissions of various GHG emissions from 1990-2021. The EPA points out that overall emissions of CH4 have been reduced by 11% from 1990-2021. However, an article published in Nature (Yvon-Durocher, March 2014) suggests that there may be an unexpected consequence of warming temperatures; global warming can increase the amount of methane evolved from natural ecosystems. So, it remains to be seen what impacts can happen that have not been included in climate change models.
There are several possible responses to abate CO2 and CH4: 1) do nothing; 2) reduce CO2 and CH4 prudently; 3) drastically reduce energy use; and 4) move to a carbon-free society. The easiest, but quite possibly the most damaging in the long run, is to do nothing - currently, some nations are pushing to at least increase conservation. The use of hybrids has decreased our use of gasoline, as the increase in Corporate Average Fuel Economy (CAFE) standards has had an impact. However, prudent measures to reduce GHG will most likely not be enough to make a huge impact. Therefore, the use of biofuels could have great potential for reducing the impact of CO2 and CH4, if done well. However, some actions in South America have shown that if switching to biofuel growth is not handled well, a greater problem can be created. Some rainforest areas were removed from South America to clear land for producing biofuels, but the rainforests that were removed were burned, putting an excessive amount of CO2 in the atmosphere. Rainforests have grown over long periods, so there was a lot of carbon stored in them - they were also places where exotic animals, plants, and insects lived, so the burning endangered the wildlife species in the rainforests. One thing to always keep in mind: whenever an action is taken in our atmosphere, there is the possibility of a negative consequence that one cannot foresee.