Climatic

The causes of climate change

Climate change is caused by factors such as oceanic processes (e.g., ocean circulation), biotic processes (e.g., plants), variations in the amount of sunlight reaching the Earth, plate tectonics and volcanic eruptions, and human-induced changes in the natural world. The latter effect is currently causing global warming, and the term "climate change" is often used to describe the human-made effects.

The biggest driver of warming is the emission of gases that create a greenhouse effect, of which more than 90% are carbon dioxide (CO2) and methane. The burning of fossil fuels (coal, oil and natural gas) for energy consumption is the main source of these emissions, with additional contributions from agriculture, deforestation and manufacturing.

The human cause of climate change is not disputed by any scientific body of national or international standing. Temperature increases are accelerated or mitigated by climate feedbacks, such as loss of sunlight-reflecting snow and ice cover, increases in water vapour (itself a greenhouse gas), and changes in land and ocean carbon sinks.

The temperature increase on land is about twice the global average, leading to expanding deserts and more frequent heatwaves and forest fires. Temperature increases are also amplified in the Arctic, where they have contributed to melting permafrost, retreating glaciers, and loss of sea ice.

Warmer temperatures increase evaporation rates, leading to more intense storms and weather extremes. Impacts on ecosystems include the relocation or extinction of many species as their environments change, most directly in coral reefs, mountains, and the Arctic.

Climate change threatens people with food insecurity, water scarcity, flooding, infectious diseases, extreme heat, economic loss, and displacement. These impacts have led the World Health Organisation to name climate change as the greatest threat to global health in the 21st century. Even if efforts to minimise future warming are successful, some impacts will persist for centuries, including rising sea levels, rising ocean temperatures, and ocean acidification.