There are a number of ways we can measure the change in the Earth’s air temperature. Some of these measures help us look at evidence of climate change in the past, whilst other measures enable us to look at more recent climatic change.
Evidence of climate change in the past
- Geological fossil evidence
Plants and animals adapt to living in certain climates. Evidence of climate change can be seen when the fossils of a plant/animal are found in an area that the plant/animal could not survive in today. For instance, fossils of the thick-furred Mastodon have been found from Alaska to Florida.
- Ice cores
When snow falls in Antarctica and Greenland it builds up (because it’s cold). The snow turns to ice and traps air molecules inside.
An ice core drills into the deep ice and can show ice build up over many thousands of years. The air molecules can be analysed to calculate the air temperature.
- Ocean sediments
Similar to the way snow builds up over thousands of years, so do sediments on the sea bed. Scientists can analyse ocean sediments and calculate global air temperature.
- Historical records
Cave paintings on the French-Spanish border depict animals around when the paintings were drawn (over 10,000 years ago). The paintings are of animals adapted to a much colder climate than currently found in the area. Diaries and personal records can also provide evidence of climate change.
Recent evidence of climate change
- Global temperature data
This map shows variations in global air temperature (2017). The dark red areas show where
temperatures are much higher than normal. It highlights where the global temperature is
Overall it shows that average global temperatures have increased by 0.85°C.
- Sea ice and glaciers
Valley glaciers and ice sheets have been closely monitored over the last 100 years with relatively accurate equipment and more recently with satellite imagery. Glaciers and ice sheets around the world appear to be shrinking; the volume of Arctic sea ice has decreased 10% in the last 30 years, in the early 2000’s the Columbia Glacier in Alaska was retreating at an alarming 30m a day.
Reliability of ‘evidence’
- Cave paintings – It is difficult to date them accurately.
- Diaries and personal records – Personal accounts can lack objective accuracy.
- Global temperature data – Some areas of the world lack weather stations, notably in Africa, meaning that global maps are not absolutely accurate and reliable.
- Ice cores – Using scientific equipment means that the data is accurate and reliable.