The greenhouse gases – carbon dioxide, methane, water vapour, nitrous oxide, etc. – are called so because they trap the Sun’s heat in Earth’s atmosphere and don’t allow it to be reflected into space. In effect, Earth’s atmosphere insulates the surface like the glass walls of a greenhouse, causing it to warm over time. The Swedish chemist Svante Arrhenius first described the effect in the late 19th century.
In the last two centuries, greenhouse gases have accumulated in the atmosphere, most of them put there by humans’ large-scale combustion of fossil fuels. As a result, Earth’s surface has been undergoing a warming surge, significant enough to overwhelm natural temperature fluctuation cycles.
Fossil fuels such as petroleum, coal, oil and natural gas are formed deep inside Earth’s crust organic matter buried there for millions of years. As fuels, they have played a critical role in powering the first industrial revolution and, over the decades since, have provided an unprecedented amount of energy used to operate machines. These fuels contain hydrocarbons of different types; when burnt, they release carbon dioxide (plus other byproducts depending on the type of fuel).
The atmosphere’s carbon dioxide content has increased commensurately with humans’ use of fossil fuels. Today, the gas is one of the major greenhouse gases, alongside the likes of methane. While methane is considered to be a trace gas in the atmosphere, its level has been increasing as well. Notably, methane is around 25-times as potent a greenhouse gas as carbon dioxide. It’s released from the burning of fossil fuels as well as by bacteria and some insects in water-logged regions and in the oceans.
A few years ago, meteorologists noted that the atmospheric concentration of carbon dioxide as detected by sensors installed in Hawaii had breached the 400 parts per million mark – the highest level in three million years. The ‘achievement’ highlighted the precarity of humankind’s current situation: we are increasingly incapable of tolerating even an occasional spike in emissions because it could tip us over the edge.
Also read: The Idea of Tipping Points Has Come to Dominate Climate Science
The countries that emit the most carbon dioxide are in Asia (over half the total), especially China, and North America (nearly a fifth), especially the US. India also features prominently in the list of top emitters, especially since its emissions, principally from use of fossil fuels and cement-manufacturing, have almost doubled in the last decade. Other similarly profligate emitters include countries in Europe and the Middle East.
The links between economic development and carbon dioxide emissions are plain. One of the most critical of these linkages is deforestation. In many countries, such as in Brazil, governments have been clearing forests to make way for agriculture, real estate, mines and dams. Deforestation accounts for about a tenth of all carbon dioxide emissions around the world, in two ways. Forests counter the greenhouse effect by consuming carbon dioxide for photosynthesis, so removing forests leaves more of the gas in the air. Second, clearing a forest releases carbon dioxide because the wood of the trees is often burnt.
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Earth’s surface warmed by about 1º C over the last century. This is a deceptively small change that represents 10x faster warming than the result of temperature changes over the last millennium.
As more governments plus the UN acknowledged the need to keep the world from warming further, they got together to draft and subsequently ratify the Paris Agreement, which comes into effect next year. One of the agreement’s goals is to limit the world’s average surface temperature from rising above 2º C above pre-industrial levels by 2011. However, as of today, most countries that signed the agreement – 197 in all – have failed to meet the corresponding targets.
One alternative way to stave off this impending disaster is to plant trees over vast tracts of land, although this option is accompanied by its own complications and limitations. Others include altogether reducing the use of machines that emit carbon dioxide and switching to alternative energy sources, such as solar and wind energy. These changes in turn require us to change our lifestyles and, of course, consume less.
Also read: Why Simply Planting More Trees Won’t Help Us Deal With Climate Change
Scientists and engineers have also devised supplementary technologies that capture the carbon already present in the air and soil, using physical and chemical techniques, and convert them to fuels or other material assets. For example, a company in Iceland has reportedly been manufacturing methanol from carbon dioxide (plus water and some energy), then used as an alternative fuel for specially designed cars.
However, this technology – and others like it, which convert carbon dioxide into substances useful in various industrial processes – don’t solve the problem as much as postpone it: if carbon is removed from the air and trapped in fuels, it is bound to be released into the air once again when the fuel is burnt. The supporters of this solution have defended that at least the gas is being recycled.
Scientists have also proposed converting the carbon dioxide into long-lasting materials not likely to reenter the environment soon. In January 2018, for example, a team in Canada had devised a way to convert carbon dioxide into ethylene, which is a building block for certain types of plastic. Since the conventional way to make plastic required the use of fossil fuels among the raw materials, using carbon from the air could also reduce the demand for fossil fuels for this purpose.
But even then, we are still only kicking the can down the road instead of solving the problem itself. If we don’t change our consumption patterns and continue to produce and discard plastic at the current rates, the world’s already alarming plastic pollution over its lands and in its water bodies will only get worse.
As things stand, reducing the amount of carbon dioxide in the atmosphere and soil remains a colossal challenge. A major stumbling block is the absence of any viable as well as economically feasible alternatives with a smaller carbon footprint and which can be deployed en masse. And while the Paris Agreement provides some guidance on what countries need to do, its recommendations are not legally binding, leaving governments and the people to commit as many resources as they can based on their perception and priorities.
Chitra Kannabiran leads research on molecular genetics at the L.V. Prasad Eye Institute, Hyderabad.