Tiago
Climate Change
Present-day climate change includes both global warming—the ongoing increase in global average temperature—and its wider effects on Earth’s climate system. Climate change in a broader sense also includes previous long-term changes to Earth’s climate. The modern-day rise in global temperatures is driven by human activities, especially fossil fuel burning since the Industrial Revolution.
Earth’s average surface air temperature has increased almost 1.5 °C (about 2.5 °F) since the Industrial Revolution. Fossil fuel use, deforestation, and some agricultural and industrial practices release greenhouse gases. These gases absorb some of the heat that the Earth radiates after it warms from sunlight, warming the lower atmosphere.
Contents
- 1 Terminology
- 2 Global temperature rise
- 2.1 Temperatures prior to present-day global warming
- 2.2 Warming since the Industrial Revolution
- 2.2.1 Differences by region
- 2.3 Future global temperatures
- 3 Causes of recent global temperature rise
- 4 Modelling
- 5 Impacts
- 6 Reducing and recapturing emissions
- 7 Adaptation
- 8 Policies and politics
- 9 Society and culture
- 10 History
- 11 References
Terminology
Before the 1980s, scientists used the term inadvertent climate modification to refer to human impacts on the climate. In the 1980s, the terms global warming and climate change became more common. Scientifically, global warming refers only to increased global average surface temperature, while climate change describes both global warming and its effects on Earth’s climate system, such as precipitation changes.
Key distinction: Climate change encompasses global warming plus broader impacts like extreme weather and sea level rise.
Global temperature rise
Temperatures prior to present-day global warming
Over the last few million years, the climate cycled through ice ages. The most recent glacial maximum 20,000 years ago was 5–7 °C colder, with sea levels over 125 metres lower than today.
Warming since the Industrial Revolution
Around 1850, thermometer records began. Multiple datasets show worldwide increases in surface temperature at ~0.2 °C per decade. The 2014–2023 decade warmed to an average 1.19 °C compared to pre-industrial baseline. 2024 was the warmest on record at +1.60 °C.
Differences by region
The Arctic has warmed 3-4 times faster than the global average. Land regions have warmed nearly twice as fast as oceans. Over 90% of excess energy has been stored in the ocean.
Future global temperatures
| Scenario | Projected warming by 2100 |
|---|---|
| Very low emissions | 1.0–1.8 °C |
| Intermediate emissions | 2.1–3.5 °C |
| Very high emissions | 3.3–5.7 °C |
Causes of recent global temperature rise
The primary driver is greenhouse gases: CO₂ (50% increase since 1750), methane (164% increase). In 2019, global emissions were equivalent to 59 billion tonnes CO₂.
- CO₂ sources: Fossil fuels (75%), deforestation, cement production
- Methane sources: Livestock, rice, landfills, fossil fuel extraction
Impacts
2024 was the warmest year on record at +1.60 °C. Climate change threatens increased flooding, heat, food scarcity, disease, and economic loss.
| Environmental Impact | Example |
|---|---|
| Wildfires | Intensified by heat and drought |
| Coral bleaching | Due to marine heatwaves |
| Droughts | Compromising water supplies |
Reducing and recapturing emissions
To limit warming to 2 °C, emissions need to reach net-zero by 2070. Key strategies:
- Clean energy: Renewables (86% of new electricity in 2023)
- Energy conservation
- Carbon dioxide removal: Reforestation, direct air capture
Adaptation
Adaptation involves flood controls, drought-resistant crops, and ecosystem restoration. However, some limits to adaptation have been reached in tropical and polar regions.
Policies and politics
The Paris Agreement aims to keep warming “well under 2 °C”. Current pledges project 2.8 °C warming by century’s end.
Society and culture
89% of global population demands intensified climate action (2024 survey). Climate denial originated from fossil fuel interests but consensus is >99% among scientists.
History
Key milestones: Joseph Fourier (1820s) proposed greenhouse effect; Svante Arrhenius (1896) calculated CO₂ doubling would cause 5-6 °C warming; James Hansen (1988) testified on human-caused warming.