Sustainability & Environmental Governance
What Is Climate Change?
A clear summary of what is driving climate change, what the latest scientific assessments say, and what international agreements aim to do about it.
Climate change refers to long-term shifts in temperatures and weather patterns. Natural factors have always influenced the climate, but since the 19th century human activities have become the main driver, above all through the burning of fossil fuels.
What is causing it
Certain gases in the atmosphere trap heat that would otherwise escape into space. The most important of these greenhouse gases released by human activity are:
- Carbon dioxide (CO₂), from burning coal, oil and gas, and from deforestation. It is the largest contributor to warming.
- Methane (CH₄), from agriculture and livestock, landfills and fossil fuel production. It is shorter-lived than CO₂ but far more potent.
- Nitrous oxide (N₂O), mainly from fertilizer use.
- Fluorinated gases, used in refrigeration and industry.
Chlorofluorocarbons (CFCs), once used in refrigerators and aerosols, are also powerful greenhouse gases. They have been largely phased out under the Montreal Protocol (1987) because they damaged the ozone layer, a success that has also avoided a significant amount of warming. Their replacements, HFCs, are now being phased down under the Protocol’s Kigali Amendment.
What the science says
The Intergovernmental Panel on Climate Change (IPCC) concluded in its Sixth Assessment Report that human influence has unequivocally warmed the planet. Global surface temperature in 2011–2020 was about 1.1°C above pre-industrial levels, and 2024 was the first calendar year on record above 1.5°C.
The effects are already visible: more frequent and intense heatwaves, heavy rainfall and droughts, melting ice and rising sea levels. Climate change also adds pressure on nature: the 2019 global assessment by IPBES estimated that around one million species are threatened with extinction, with land-use change, exploitation and climate change among the main causes.
Where current policies lead
The UN Environment Programme’s annual Emissions Gap Report compares countries’ policies and pledges with what is needed. Its 2025 edition projects warming of about 2.3–2.5°C this century if countries fully implement their national pledges, and about 2.8°C under current policies, far above the goals of the Paris Agreement. It also warns that exceeding 1.5°C is very likely within the next decade.
What is being done
Under the Paris Agreement (2015), countries committed to keep warming well below 2°C and to pursue efforts to limit it to 1.5°C, submitting national plans that are meant to become more ambitious over time. The main levers are:
- shifting energy systems to clean sources and using energy more efficiently;
- protecting and restoring forests and other ecosystems that store carbon;
- reducing methane from agriculture, waste and fossil fuels;
- adapting cities, infrastructure and agriculture to the changes already under way.
Conclusion
Climate change is driven by human activity, and so are its solutions. Reducing emissions quickly, protecting the ecosystems that store carbon and preparing for the impacts already locked in are tasks for governments, companies and communities alike.
This article is for general information and education, based on the scientific assessments listed below.
Sources and further reading
This article is for general information and education. It is not legal, financial, investment or engineering advice.