Global climate change (AQA GCSE Chemistry Combined Science): Revision Notes
Global climate change
What causes global climate change?
Rising average temperatures around the world are the main reason climate change happens. When Earth's temperature gets warmer overall, it changes weather patterns and affects life on our planet.
Climate change is a complex global phenomenon that involves interconnected systems including the atmosphere, oceans, ice caps, and living ecosystems. While temperature is the primary driver, the effects create feedback loops that can accelerate or modify the changes.
Potential effects of climate change
Climate change can cause six major problems around the world:
These six effects of climate change are interconnected - one effect often makes the others worse. For example, rising sea levels can increase storm damage, while changing rain patterns affect both food production and wildlife habitats.
1. Sea levels rise
When temperatures get warmer, ice melts and water expands. This makes sea levels go up, which causes:
- Flooding of coastal areas
- Increased coastal erosion where the sea wears away the land
2. Storms become more frequent
Climate change can make storms happen more often. These storms may also be more severe than before, causing greater damage.
3. Rain patterns change
Different parts of the world might get more or less rain than usual. The pattern of rain each month becomes different from what it used to be. This affects farming and water supplies.
4. Temperature and water stress affects living things
Humans and wildlife struggle to cope when temperatures change or when there are different amounts of water available. Animals and plants may not survive in their usual habitats.
5. Food production problems
Changes in temperature and rainfall make it harder to grow crops. This can lead to food shortages in many parts of the world.
6. Wildlife distribution changes
Animals have to move to new areas to find suitable conditions. For example, polar bears need ice to hunt, but warming temperatures melt their icy habitat.
Evidence for climate change
Scientists have strong evidence that human activities cause global warming:
The correlation between CO₂ and temperature
Graphs show that as carbon dioxide levels in the atmosphere have increased, so has the average global temperature. This correlation suggests the two are linked.
Evidence Example: CO₂ and Temperature Correlation
Scientists have measured atmospheric CO₂ levels since 1958:
- 1958: CO₂ levels were approximately 315 ppm (parts per million)
- 2023: CO₂ levels reached over 420 ppm
- During this same period, global average temperature increased by approximately 1.1°C
This clear correlation provides strong evidence for the relationship between human CO₂ emissions and global warming.
Human activities like burning fossil fuels release carbon dioxide into the atmosphere. The evidence shows this increase in CO₂ matches the increase in global temperatures.
Scientific models and peer review
Scientists have created a model to explain how:
- Human activities release carbon dioxide
- Carbon dioxide acts as a greenhouse gas
- The increase in average global temperature correlates with the amount of carbon dioxide
Even though Earth's climate is complex and difficult to model, scientists have peer reviewed their work. This means other scientists check that the research is correct before accepting the conclusions. This peer review process ensures the reliability and accuracy of climate science findings.
Key Points to Remember:
- Rising global temperatures are the main cause of climate change
- Climate change has six major effects: rising sea levels, more frequent storms, changing rain patterns, stress on living things, food production problems, and changes in wildlife distribution
- Human activities that release CO₂ correlate with increasing global temperatures
- Scientific evidence has been peer reviewed, making it reliable
- Correlation between CO₂ levels and temperature provides strong evidence for human-caused climate change