Short note: Human induced climate change

Human-induced (anthropogenic) climate change is the long-term change in the Earth's climate caused by human activities that increase the concentration of greenhouse gases (GHGs) and change land surfaces, beyond natural climate variability. According to the IPCC it is unequivocal that human influence has warmed the planet – by about 1.1 °C since pre-industrial times.

Mechanism

GHGs (CO₂, CH₄, N₂O, CFCs) let sunlight through but absorb the heat radiated from the Earth, warming the lower atmosphere. Human activities strengthen this natural effect – the enhanced greenhouse effect. Atmospheric CO₂ has risen from about 280 ppm before industrialisation to over 420 ppm today.

Human causes

1. Burning fossil fuels for electricity, industry and transport – the largest source of CO₂.
2. Deforestation and land-use change – releases stored carbon and removes sinks.
3. Agriculture – methane from livestock and paddy fields; N₂O from fertilisers.
4. Industry – cement, steel, chemicals; HFCs from cooling.
5. Waste – methane from landfills and sewage.
6. Black carbon from diesel, brick kilns, cook stoves.
7. Urbanisation – heat islands, high energy use.

Impacts

Global warming, glacier melt and GLOF risk in the Himalaya, sea-level rise, irregular monsoon, floods and droughts, food insecurity, spread of diseases and loss of biodiversity.

Control

Renewable energy, energy efficiency, forest conservation, sustainable agriculture, and international agreements such as the Paris Agreement.