Climate Change refers to a range of changes in the Earth’s climate from local to global scales that have a broad range of impacts on human society and natural ecosystems. These impacts include heat waves, drought, famine, extreme weather events and flooding.
The climate is driven by energy from the Sun, aerosols (tiny particles in the air, some of which are coming from human activities), and long-lasting, heat-trapping gases called greenhouse gases. These greenhouse gases trap infrared light energy from the Sun, preventing it from escaping back to space and making the Earth warmer than it would otherwise be.
Some of these greenhouse gases are produced by humans, such as carbon dioxide, but the vast majority is released by natural processes and changes in land use. The amount of CO2 in the atmosphere has increased since the pre-industrial era due to industrialization, deforestation, agriculture and other human activities.
As a result of these changes, the climate has become warmer, and is continuing to warm at an unprecedented rate. The rate of warming depends on the amount of CO2 in the atmosphere, as well as feedback processes that amplify or dampen disturbances to the climate system.
For example, changes in sea level and the melting of polar ice sheets are altering coastal communities by affecting their water supply, infrastructure and livelihoods. These changes will also increase the risk of coastal erosion, flooding and storm surges.
The most important factor driving current climate change is the warming of the planet’s surface temperature. This is caused by the greenhouse effect, where some gases in the Earth’s atmosphere act like the glass in a greenhouse to trap heat from the sun.
Other factors, such as ocean circulation changes and volcanic eruptions, can cause climate to change in other ways. Those changes can affect the rate at which heat is absorbed and re-radiated, as well as the extent of ice and water vapour in the atmosphere.
Some of the most significant and rapid environmental change has occurred in recent decades, with average global temperatures up by around 1degC in just 100 years. Some of the largest temperature increases have been in the Arctic, where summer sea ice has shrunk dramatically.
These changes can have major effects on the world’s biodiversity, including by affecting the geographical ranges and life cycles of plants and animals. Some species could become extinct, while others may suffer damage to their habitats and their ability to reproduce.
Another threat is the impact on human health. Some diseases are more likely to develop during periods of high heat and other changes in climate. Smoke inhalation, for instance, has been linked to respiratory problems and heart disease. People with mental illness are especially vulnerable to heat waves, because they find it difficult to regulate their body temperatures.
There is a growing body of evidence that shows that human activities have altered the Earth’s climate over the last century and that these changes are permanent. The climate is now warmer than at any point in the past thousand years, and will continue to warm unless we reduce greenhouse gas emissions.