Edexcel B GCSE Geography > Hazardous Earth > What is the evidence for human activity causing climate change?
Global warming is caused by the enhanced greenhouse effect, which has been worsened by increased carbon dioxide and other greenhouse gases in the earth’s atmosphere.
Growing evidence supports the view that human activity is responsible for causing climate change, including increased global temperatures, sea level rise and ocean warming, the decline of Arctic Sea ice, and increased levels of CO₂ in the atmosphere.
Increased global temperatures:
This graph shows the change in global surface temperature compared to the long-term average from 1951 to 1980. Earth’s average surface temperature in 2024 was the warmest on record since recordkeeping began in 1880.
Global land-ocean temperature index
Between 1880 and 2024, average global temperatures increased by 1.28°
The rise in global temperature is closely associated with increased carbon dioxide levels.
Increased levels of CO₂ in the atmosphere:
Since the 1950s, atmospheric carbon dioxide levels have rapidly increased from 280 to over 400 parts per million in 2025. This increase has been caused by humans burning fossil fuels.
Atmospheric CO2 levels measured by NOAA at Mauna Loa Observatory, Hawaii, since 1958
Sea level rise and warming oceans:
Since 1900, sea levels have risen globally by around 20cm. Since 1993, the sea level has increased by 102.8mm, around 3.2mm a year on average, although in some areas, this is higher.
Sea level variation 1993 – present
As the sea warms, thermal expansion occurs (insert definition: water expands as it heats), leading to rising sea levels. Globally, oceans have gotten warmer by 0.9°C on average since the late 19th
The melting of glaciers and ice sheets also contributes to rising sea levels.
Reduction in Arctic Sea ice and melting glaciers:
The thickest Arctic Sea ice has decreased by 90% between 1979 and 2024 due to warming global temperatures and continues to shrink by 12.2% every decade. This sharp decline cannot be linked to the yearly natural melting and freezing cycles in the Arctic, humans are to blame.
Annual September Arctic sea ice minimum extent
90% of global valley glaciers are shrinking.
Summary
Insolation drives the global atmospheric circulation system by heating the Earth unevenly, with stronger heating at the equator and weaker at the poles.
The Earth’s global atmospheric circulation is divided into three cells: the Hadley Cell, Ferrel Cell, and Polar Cell, which redistributes heat around the planet.
Hadley Cell: Warm air rises near the equator, moves poleward, then cools and sinks around 30° latitude, creating arid, high-pressure zones.
Ferrel Cell: Air flows from high-pressure zones toward low-pressure areas at 60° latitude, transferring heat between the Hadley and Polar cells.
Polar Cell: Cold air sinks at the poles and moves toward 60° latitude, rising again and forming low-pressure zones.
Ocean currents complement atmospheric circulation by transferring warm water from the tropics to higher latitudes and cold water towards the equator.
