The idea
No single measurement proves climate change. What convinces scientists is that many independent measurements agree.
| Indicator | What is measured | Direction |
|---|---|---|
| Global mean surface temperature | Thermometers, satellites | Rising |
| Atmospheric | Air samples, ice cores | Rising |
| Sea level | Tide gauges, satellite altimetry | Rising |
| Arctic sea ice extent | Satellite imagery | Falling |
| Glacier mass balance | Repeat surveys | Falling |
| Ocean pH | Water sampling | Falling (acidifying) |
| Spring events (first bloom, ice-out) | Records kept for centuries | Earlier |
Independent lines of evidence
Tide gauges know nothing about ice cores. Cherry blossom records in Kyoto — kept since the 800s — know nothing about satellites. When methods with completely different sources of error point the same way, that agreement is the evidence.
Weather is not climate
A cold week says nothing about climate, and neither does a hot one. Climate is the statistics of weather over decades.
The dog-walk analogy
Weather is the dog, running back and forth on its leash. Climate is the person holding it. Watch the dog for a minute and you learn nothing about where the walk is going.
Curriculum connection
B2.6
identify and use various indicators of climate change to describe the impacts of climate change on local and global ecosystems, and analyse how human activities contribute to climate change
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B1.1
assess impacts of climate change on the sustainability of local and global ecosystems, describe local or global initiatives for combatting climate change, and identify solutions to address some of the impacts
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