What Is Climate Change?
Climate change refers to long-term shifts in global temperatures and weather patterns. While natural factors have always influenced climate, human activities since the Industrial Revolution have been the primary driver of accelerated warming, mainly through the burning of fossil fuels like coal, oil, and natural gas.
The greenhouse effect is a natural process that warms the Earth. However, human activities have intensified this effect by increasing concentrations of greenhouse gases in the atmosphere, trapping more heat and raising global temperatures.
Key Greenhouse Gases
| Gas | Source | Global Warming Potential | Atmospheric Lifetime |
|---|---|---|---|
| Carbon Dioxide (CO2) | Fossil fuel combustion, deforestation | 1 (baseline) | 300-1000 years |
| Methane (CH4) | Agriculture, landfills, natural gas | 80x (20-year) | 12 years |
| Nitrous Oxide (N2O) | Agriculture, industrial processes | 273x (100-year) | 121 years |
| Fluorinated Gases | Industrial applications, refrigeration | 1000-23000x | Up to 50,000 years |
Observed Impacts
- Rising Temperatures: Global average temperature has increased by approximately 1.1 degrees Celsius since the late 1800s, with the last decade being the warmest on record.
- Sea Level Rise: Global mean sea level has risen about 20 cm since 1900, with the rate accelerating in recent decades due to thermal expansion and ice sheet melting.
- Extreme Weather: Heat waves, droughts, heavy rainfall, and tropical cyclones are becoming more frequent and intense.
- Arctic Ice Loss: Arctic sea ice extent has declined by about 13% per decade since satellite records began in 1979.
- Ocean Acidification: The ocean has absorbed about 30% of emitted CO2, causing a 26% increase in acidity since pre-industrial times.
- Glacier Retreat: Glaciers worldwide are losing mass at accelerating rates, threatening water supplies for billions of people.
The Paris Agreement
Key Goals
The 2015 Paris Agreement aims to limit global warming to well below 2 degrees Celsius above pre-industrial levels, with efforts to limit the increase to 1.5 degrees. To achieve this, countries submit Nationally Determined Contributions (NDCs) outlining their emission reduction targets.
Despite commitments, current policies put the world on track for approximately 2.7 degrees of warming by 2100. Closing this gap requires rapid transformation of energy systems, transportation, agriculture, and industry.
Climate Tipping Points
Scientists have identified several tipping points that, once crossed, could trigger cascading and irreversible changes:
- Collapse of the Greenland and West Antarctic ice sheets
- Widespread permafrost thaw releasing stored carbon
- Dieback of the Amazon rainforest
- Shutdown of the Atlantic Meridional Overturning Circulation
- Loss of coral reef ecosystems
- Boreal forest shift and dieback