Earth's climate has changed naturally over millions of years. Could the current cycle of warming simply be part of this natural cycle?
- The Medieval Warm Period occurred 1000 years ago.
- Climate proxies are used to estimate historical temperatures.
- The hockey stick graph shows a temperature rise across the 20th century.
- Graphs show that the last half of the 20th century is the warmest it's been for the past 1000 years.
The Earth's climate has changed naturally over millions of years, going through phases of warming and cooling.
These periods are central to the global warming debate - with some scientists arguing that the current rise in temperature is just another natural cycle in the planet's long-term climate.
Historical records suggest another period ...
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