Climate change: in it for the long haul

Credit: pixabay

How does the climate vary naturally over millennial time scales?
Can contemporary climate change be explained by natural variations?
What is the evidence for climate change? 

1) Put simply, the climate gets warmer and cooler again, in its natural and delicate balancing act. The most obvious example of a climate feedback is the ice albedo feedback: larger ice cover reflects more radiation back to space, keeping it cooler. As ice cover decreases, more radiation is absorbed by the darker coloured water, and the temperature rises. Part of the reason for the Earth's changing climate over millennia are slight changes in the Earth's orbit around the sun.

2) The evidence for contemporary climate change exceeds the temperature ranges previously seen in natural variations, suggesting there must be another factor at play to explain the extremes we are seeing now. Data also suggest that the climate is changing at a much greater speed than previously seen in natural variations. The US Forest Service explains it succinctly:

"Climate varies without human influence, and this natural variation is a backdrop for the human-caused climate change occurring now" 

3) Some climate deniers would have you believe that the evidence for climate change is largely disputed, anecdotal and insubstantial. It isn't:

• rising sea levels
• decreasing ice cover
• rising levels of CO2 and other GHGs
• rising global average temperatures on land and sea

Sources: The Royal Society; Nasa; Inside Climate News