2023 was the warmest year since records began in 1850, beating the previous record of 2016, Europe’s Copernicus Climate Change Service (C3S) said last week. Temperatures in 2023 likely exceeded those of any year-long period in at least the last 100,000 years, the announcement added. As a result, last year was dotted with a large number of extreme weather events around the world — including heatwaves, floods, droughts, and wildfires. These are some of the implications of climate change. Although scientists unequivocally agree that climate change is real, there are still many myths and a lot of confusion around the subject. In this series of explainers, we will try to answer some of the most fundamental questions about climate change, the science behind it, and its impact. In the third instalment (you can scroll down to the end of this article for the first two parts), we try to answer the question: ‘As greenhouse gases occur naturally, why do emissions from human activities matter?’ But first, what are greenhouse gases? Greenhouse gases (GHGs) are those gases in the Earth’s atmosphere that trap heat. They allow sunlight to pass through the atmosphere but prevent the heat that sunlight brings from returning into space. Essentially, GHGs act like a blanket that envelopes our planet and insulates Earth from the cold of space. This process of maintaining a warmer temperature is called the greenhouse effect. The most notable GHGs are water vapour, carbon dioxide, methane, ozone, and nitrous oxide. These gases occur naturally and are a boon for the planet — in their absence, there wouldn’t be the greenhouse effect without which there wouldn’t be liquid water and any form of life. So if GHGs occur naturally, why do emissions from human activities matter? At the heart of the problem are not greenhouse gases but their concentration, meaning their amount in the atmosphere. For about a thousand years before the Industrial Revolution, the GHG concentration remained relatively constant. Since then, there has been a constant rise in the amount of some of the GHGs. For instance, carbon dioxide concentration in the atmosphere has spiked by around 48% since the pre-industrial era. The main driver behind the increase is human activities, like burning fossil fuels and deforestation. But how do we know humans are responsible for the rising GHG concentrations? Take the case of carbon dioxide. There are three types of carbon-containing material. Some consist of light carbon, or carbon-12. Some comprise heavy carbon or carbon-13 and others contain radioactive carbon-14. Over the past century or more, scientists have observed more carbon-12 in the atmosphere compared to carbon-13 and even less carbon-14 in recent decades, according to a report by the Associated Press. “Carbon-12 is essentially fossil carbon from long ago, as in fossil fuels. So the change in the ratio of carbon-12 to carbon-13 tells scientists the carbon in the air is more from burning fossil fuels than natural carbon,” the report added. To make matters worse, carbon dioxide emitted over the last century will remain in the atmosphere for centuries — will still be warming the planet and causing sea levels to rise. Susan Solomon, the Lee and Geraldine Martin Professor of Environmental Studies at MIT, told MIT News in an interview: “Some of our carbon dioxide will still be there in 1,000 years”. She added that for all practical purposes, on a human timescale, carbon dioxide emitted into the air leads to “the irreversibility of carbon dioxide-induced warming.” Humans have also added GHGs in the atmosphere that don’t occur naturally. This includes chlorofluorocarbons (CFCs) — once widely used as a refrigerant in air conditioners, freezers and refrigerators, these chemicals damage the ozone layer and are really potent GHGs. Compared to carbon dioxide, CFCs can produce more than 10,000 times as much warming, pound for pound, once they are in the air, according to the MIT News. Hydrofluorocarbons (HFCs), replacement of CFCs, don’t harm the ozone layer but are power GHGs. This unprecedented increase in GHG levels in the atmosphere is responsible for the rapid warming of Earth. In 2023, GHG concentrations reached the highest levels ever recorded in the atmosphere, according to the latest data by C3S and the Copernicus Atmosphere Monitoring Service (CAMS). It’s no coincidence that 2023 was also the warmest year on record. To read the first part of the series that addressed the question if the Earth is becoming warmer, click here. To read the second part of the series that addressed the question if humans are causing global warming, click here.
