Back to Basics: What is Climate Change?

07 November 2022

With the declaration of the climate emergency, the focus on net zero, and people campaigning for the environment, climate change became an everyday topic and a permanent item on the global political agenda. COP27 is starting today in Egypt and global leaders are debating solutions to the climate crisis. The answer to climate change is not an easy one and as with most complex issues ,it is worth taking a step back every once in a while to ensure understanding of the core issue. This article will take you back to the basics and lay out key concepts around climate change such as the greenhouse effect, the carbon cycle, greenhouse gasses and global warming.

The Greenhouse Effect

The first process to consider is the greenhouse effect, which is where heat is trapped inside the Earth’s atmosphere. This occurs due to the sun emitting short wave radiation to Earth, of which around half is reflected back into space or absorbed by the atmosphere, and the other half reaches Earth. Earth then reflects some of this back in the form of long wave radiation, however it is harder for long wave radiation to pass through the greenhouse gasses in the atmosphere than short wave radiation, so a large amount of this is trapped inside the atmosphere as heat. Normally this is a beneficial process, because it helps to regulate the Earth’s temperature to support life, however the amount of greenhouse gasses has risen to a point where the greenhouse effect is warming up our planet too much.

The Carbon Cycle

The carbon cycle is the way in which carbon is transferred through different states in a natural, self-sufficient process. Main places of storage for carbon (called carbon sinks) exist in the biosphere (living and dead organisms), carbon dioxide in the atmosphere, organic matter in soil, rocks, chalk and fossil fuels in the lithosphere (the outer layer of Earth’s structure) and in dissolved carbon dioxide, shells and organisms in the ocean. However, this process has been disrupted by humans taking carbon out of the lithosphere as fossil fuels and releasing them into the atmosphere as carbon dioxide. The amount of carbon in the Earth’s atmosphere in parts per million has spiked in a short period of time, due to human activities. Since carbon dioxide is a greenhouse gas, the excess amount in the atmosphere is amplifying the greenhouse effect.

Other Greenhouse Gasses

Although carbon dioxide is the most common greenhouse gas, there are others as well. These include methane, nitrous oxide, and small amounts of other gasses. The global warming potential (GWP) of gasses is measured over 100 years, and carbon dioxide has the base measurement of 1, meaning that other gasses are measured in terms of carbon dioxide equivalent. Methane has 25 GWP, nitrous oxide has 298 GWP and different types of hydrofluorocarbons have between 124 – 14,800 GWP. This means that methane has 25 times higher global warming potential than carbon dioxide over 100 years.

Global Warming

Global warming describes the average global temperature increase, which is a result of an amplified greenhouse effect. Although some fluctuation in temperatures is normal, the current global temperature rise is happening at an unprecedented pace that has not been seen in the past 10,000 years. In the 2015 Paris Agreement, a target of 1.5 degrees Celsius warming was set as the maximum safe threshold to support life on Earth. But it is likely that this will be passed, and the only way to keep this from happening is for a drastic reduction in global emissions.

Climate Change

Climate change is the average weather that we can expect to experience in a given place. This is changing, not only from global temperature rises, but also from other aspects such as sea level rises and extreme weather events.

Sea level rise is a major concern, and The Arctic is the place with the fastest temperature rise on Earth, meaning that arctic sea ice is melting. There are other areas of frozen freshwater in ice sheets in the Antarctic and Greenland, as well as glaciers around the world causing sea levels to rise. This is a threat to low lying areas which will become submerged by the ocean. Some countries are already experiencing this, such as areas of Kiribati, where people are forced to relocate.

Additionally, the frequency and intensity of extreme weather events is rising. Recently we have seen devastating floods in Pakistan, Hurricane Ian in Cuba and Florida, Super Typhoon Noru in the Philippines, Hurricane Fiona in the Caribbean, floods and fires in Australia, and fires across South Europe.

There are many other issues that could change the climate as we know it, such as ocean acidification, biodiversity loss, and problems that we may not know of yet. As we pass one threshold, we may trigger other processes to occur, so climate change is not necessarily linear.

To sum up, climate change is occurring at a dangerous level because of changes in the Earth’s natural processes. This includes the greenhouse effect, where greenhouse gases trap heat in the atmosphere. It also includes the way in which the carbon cycle has been affected to have more carbon dioxide in the atmosphere than it would naturally. These changes lead to global warming, an increase in average global temperatures, and this affects climate change, which in addition to temperature rise, also involves extreme weather events and sea level rise, as well as other changes to our environment.

For more information on climate change, see the Climate Change Committee's useful list of relevant resources here.