What are greenhouse gases?

Human activity on Earth has driven the climate crisis to where it is today, and the IPCC report from 2022 states that human activity is the reason for more intense heat waves, glaciers melting, and flooding. If we continue this path and global warming exceeds 1.5 degrees Celsius, many natural systems that humans depend on will be at risk. The human activity which is contributing the most to the increasing global warming is the release of several greenhouse gases.

Greenhouse gases are gases that trap heat in the atmosphere. They are usually referred to as GHGs, and the name comes from greenhouses because the gases behave in a similar way to greenhouses. GHGs let the sunlight in and heat the space by retaining some of that energy. A moderate level of GHGs in the atmosphere is necessary, since it keeps the planet's temperature at the right level for life on our planet (not too hot, not too cold). We are currently at a stage where the amounts of GHGs emitted are too high, leading to a likely scenario where irreversible global warming will make the planet uninhabitable.

The table below outlines the most common GHGs released into our atmosphere by human activity.

Carbon dioxide, methane, and nitrous oxides are "natural gases" and part of our ecosystem. However, they are now contributing to climate change due to their excessive release as a consequence of human activities. E.g., CO2 concentration has increased by over 50% since the industrial revolution due to the burning of fossil fuels and large-scale deforestation. It's also the most common GHG, which is why carbon dioxide is commonly used when referring to climate change.

The synthetic industrial GHGs, hydrofluorocarbon, chlorofluorocarbon, sulfur-hexafluoride, and nitrogen-trifluoride are found in small concentrations in the planet's atmosphere but heat effectively (See Global Warming Potential (GWP)).

GHG Protocol is the organization that introduced the scope terminology (scope 1, 2, and 3) and was launched in 1998 by the:

GHG Protocol Standard: A Corporate Accounting and Reporting Standard is the most used when measuring, managing, and reporting a company’s carbon footprint.

The “scope”-terminology is commonly used when calculating a company’s carbon footprint, distributing it depending on where it happens: in the company’s own activities or in the company’s value chain.

Scope 1 – direct emissions are emissions from the company’s owned or controlled sources, e.g., on-site energy natural gas, fuel, refrigerants, and emissions from combustion in owned or controlled boilers and furnaces, and emissions from fleet vehicles, e.g., cars, vans, and trucks.

Scope 2 - indirect emissions include purchased or acquired energy and occur at sources owned or controlled by another company, e.g., electricity, steam, heat, or cooling, generated off-site and consumed by the company.

Scope 3 – indirect value chain emissions include all the emissions in the value chain of a reporting company. Also known as “emission resulted from activities from assets not owned or controlled by the reporting organization, but that the company indirectly impacts in the value chain.” Scope 3 emissions can be divided into two categories: upstream emissions and downstream emissions.