Climate change refers to a large-scale, long-term change in weather patterns and average temperatures on the planet.
Climate change is the long-term change in average weather patterns around the world. Since the mid-19th century, humans have contributed to the release of carbon dioxide and other greenhouse gases into the air. This causes global temperatures to rise, causing long-term changes in the climate.
Evidence of climate change
How is man changing the climate?
In the 11,000 years prior to the Industrial Revolution, the average temperature around the world remained stable at around 14ºC. The Industrial Revolution began in the mid-1800s, when humans began burning fossil fuels such as coal, oil, and gas.
Burning fossil fuels produces energy, but it also releases greenhouse gases such as carbon dioxide, methane, and nitrous monoxide into the air . Over time, large amounts of these gases have accumulated in the atmosphere.
For example, the level of carbon dioxide in the atmosphere increased by 40% during the 20th and 21st centuries and currently exceeds 400ppm (parts per million). This level of carbon dioxide is higher than at any other time in the last 800,000 years.
Once in the atmosphere, greenhouse gases, such as carbon dioxide, form a “blanket” around the planet. This blanket traps the heat from the sun and makes the Earth warm .
This effect was already observed in the 1980s. In 1988, the Intergovernmental Panel on Climate Change (IPCC) was created to provide governments with information to address climate change .
Tests have shown that high levels of greenhouse gases in the atmosphere are the main cause of rising global temperatures.
Scientists have been able to rule out natural events as causes of climate change, such as volcanic activity, changes in solar activity, or natural sources of CO2. However, these may have a small effect, in addition to human contributions.
In its most recent report, the IPCC states that it is “very likely” that human activity is the main cause of climate change .
How fast does the temperature increase?
Since the Industrial Revolution, the average temperature of the planet has increased by around 1 ° C. This is a rapid change in terms of our global climate system. Previously, natural global changes are understood to have occurred over much longer periods of time. It is also important to remember that the world is not warming evenly, so the temperature rise is greater than 1 ° C in some countries.
What Causes Climate Change?
What is the greenhouse effect?
When greenhouse gases, such as carbon dioxide , build up in the atmosphere, they act like a blanket around the Earth. When sunlight (short-wave radiation) hits this blanket, it passes directly through it and continues until it reaches the planet’s surface.
The Earth then absorbs this sunlight and emits a different type of light, infrared radiation, into space. As it leaves the atmosphere, infrared radiation also hits the greenhouse gas blanket. Most of it passes through it, but other part is absorbed and returns to earth. This traps infrared radiation and causes the surface to heat up, a process we call the “greenhouse effect.”
It is very important to understand that the greenhouse effect is fundamental for life on Earth. Without a blanket of greenhouse gases to trap heat, the temperature would be terribly cold and humans would not be able to survive. However, by adding more greenhouse gases to the atmosphere, humans have created a reinforced greenhouse effect.
The greenhouse gas blanket is now thicker and absorbs more infrared radiation than before. In other words, the greenhouse effect is stronger, and instead of keeping the Earth at a stable temperature, it is causing the planet to heat up.
What are the sources of greenhouse gases?
A quarter of man-made greenhouse gas emissions come from burning fossil fuels for the production of electricity and heat.
Another quarter of man-made greenhouse gas emissions come from agriculture, forestry and other land uses (AFOLU).
To feed ourselves and our livestock, people have cut down large areas of forest and used the land for farming. Forests are very good at removing carbon dioxide from the atmosphere, so cutting down trees allows carbon dioxide to build up even more in the atmosphere.
The land can also be used to raise livestock, such as for meat and milk. These animals produce other gases, such as methane. Crops that humans would have otherwise needed are also eaten, which means even more land is needed.
In addition to fossil fuels , deforestation and land use, airplanes and cement production also contribute to carbon dioxide emissions.
How much warming could we see?
Greenhouse gases can live in our atmosphere for tens or hundreds of years. The gases that are already in our atmosphere are effectively blocked and will contribute to the increase in temperatures.
Even if we stop all emissions today, we will not be able to avoid a certain level of warming. The amount of warming we will see, beyond what we have already caused, depends on the changes we make.
The Paris Agreement and global temperature targets
In 2015, almost every country in the world signed a document pledging to reduce greenhouse gas emissions. The goal was to limit the global average temperature to 2 ° C above pre-industrial temperatures. If possible, countries committed to aiming for a limit of 1.5 ° C.
Since then, the Intergovernmental Panel on Climate Change (IPCC) has published a report explaining the different impacts between a 1.5 or 2 ° C increase in temperature. It showed that limiting temperatures to 1.5 ° C has many benefits for people around the world. However, achieving this goal requires large and rapid reductions in global greenhouse gas emissions .
If we want to avoid a significant increase in average surface temperature, we must reduce greenhouse gas emissions and switch to renewable energy sources . We must also make more sustainable use of the land and may have to use techniques to remove carbon dioxide from the air.
If we continue to burn fossil fuels and cut down forests at the same rate, the planet could warm by more than 4ºC by 2100. This warming could fundamentally change life on Earth, with potentially drastic consequences.
Impacts of climate change
Human activity – from the emission of greenhouse gases and aerosols into the atmosphere to the change in land use – is the main driver of climate change . This has a number of impacts on the climate system, ecosystems and people.
Changes in the climate system include:
- Rise in the level of the oceans : Rising temperatures cause glaciers and ice sheets to melt, adding more water to the oceans and causing their level to rise. The oceans absorb 90% of the extra heat from global warming : warmer water expands, so our oceans are taking up more space.
- Acidification of the oceans : Acidification of the oceans occurs when they absorb carbon dioxide and become more acidic. It is often called the “evil twin” of climate change.
- Extreme weather events: Climate change is causing many extreme weather events to be more intense and frequent, such as heat waves, droughts and floods.
The climate change can also affect people and ecosystems. For instance:
- Flooding of coastal regions: Coastal cities are at risk of flooding as sea levels continue to rise.
- Food insecurity: High temperatures, extreme weather events, floods and droughts can damage farmland. This makes it difficult for farmers to grow crops and makes the yield of each year’s crops uncertain.
- Climate conflicts and migrants: Climate change is a stress multiplier: it can take existing problems, such as lack of food or shelter, and make them worse. This can cause people to fight over resources (food, water and shelter) or to migrate.
- Damage to marine ecosystems : Increased ocean temperatures, ocean acidification, and anoxia (lack of oxygen) are detrimental to marine life, such as fish and coral reefs.
How can we stop climate change?
Reduce global greenhouse gas emissions
The most crucial step in limiting climate change is to significantly and rapidly reduce global greenhouse gas emissions. There are many different ways to do this, and governments, businesses, organizations and individuals around the world can contribute.