Natural greenhouse effect
The atmosphere is a layer of gases around the Earth which is made up of several gases commonly referred to as ‘greenhouse gases’. These include water vapour, carbon dioxide, methane, and nitrous oxide. These gases help warm the Earth by a natural process called the greenhouse effect. The sun’s rays enter the Earth’s atmosphere and the Earth’s surface absorbs the heat energy, warming it. Heat is then radiated from the surface. Some of the energy escapes back into space, but much of it remains in the atmosphere. Greenhouse gases are responsible for trapping this energy in the atmosphere and warming the planet sufficiently to support life.
Human activities are adding to the natural greenhouse effect by increasing the quantity of greenhouse gases in the atmosphere. Most notably, carbon dioxide concentrations have grown as a result of burning fossil fuels such as coal, oil, and gas. Deforestation (the clearing of large areas of trees), has also had a significant impact, as trees absorb carbon dioxide from the atmosphere. If the trees are burned or left to rot, additional carbon dioxide is released. The atmospheric concentration of other harmful greenhouse gases like methane and nitrous oxide are also increasing due to human activity.
With higher levels of greenhouse gases in the atmosphere, more heat energy is trapped and the Earth becomes hotter. This process is known as ‘global warming’. Global average surface temperatures have reached around 1°C above pre-industrial levels (around mid-1800s).
Several other factors can change the Earth’s temperature such as the strength of the sun or volcanic activity. However, scientists agree that human activities have caused 95-100% of the warming observed since 1950 (IPCC, 2013). Global warming is the main cause of what today we call ‘climate change’.
Climate change refers to a large-scale, long-term shift in the planet’s weather patterns, including temperature, humidity, rainfall, and wind speed. While a rise of 1°C may not sound like a lot, it is enough to cause a substantial shift in our global climate.
Scotland was already 0.67°C warmer and 25% wetter in the last decade (2009-2018) compared to the 1961-1990 average (Met Office, 2018). In the next coming years, we are expected to have warmer and drier summers, and warmer and wetter winters. This will have a significant impact on Scotland – increasing the risk of flooding, degrading peat bogs, and putting several species at risk of extinction.
The importance of 1.5 degrees
In 2015, almost every country signed an international agreement to reduce global greenhouse gas emissions. Known as the Paris Agreement, it aims to keep global warming to a maximum of 2°C above pre-industrial temperatures, with the ambition of limiting it to 1.5°C if possible.
Mitigation and adaptation
There are two main responses to climate change, mitigation and adaptation. Both approaches are necessary if we wish to create a greener, more resilient future.
1) Mitigation is reducing emissions and stabilising the levels of heat-trapping greenhouse gases in the atmosphere.
Mitigation aims to address the root cause of climate change, limiting global warming by reducing emissions. This means we must rethink energy, land use, infrastructure, travel, what we eat, and much more. There are many different ways this can be done and governments, businesses, organisations, and individuals all have a role to play. In 2019, the Scottish Parliament passed the Climate Change Act, making a legislative commitment to reduce emissions by 75% by 2030 and 90% (compared to 1990 levels) by 2040, and reach ‘net-zero’ emissions by 2045. Net-zero means that the volume of greenhouse gases being emitted is equal to the volume being absorbed through offsetting techniques, like tree planting or carbon capture (both of which remove carbon dioxide from the atmosphere).
2) Adaptation is adjusting to the effects of climate change that are already occurring and preparing for future expected changes.
Greenhouse gases can stay in the atmosphere for over a hundred years. This means that we are already committed to some level of climate change because our historic emissions will continue to have an effect. Adaptation aims to reduce our vulnerability to stressors, such as flooding, but also make the most of new opportunities, for example increased crop yields from longer growing seasons.