Sea level rises could leave us all in deep water

Back in 1996 while speaking in the Senate in support of a motion condemning the government for not taking climate change seriously, Bob Brown mentioned the possibility of catastrophic sea level rises. He cited the evidence of a massive ice sheet that collapsed 120,000 years ago causing a rapid 6 metre rise in the sea level.

Senators from both the government and opposition rolled about laughing thinking that Bob had stumbled on his words and that he meant 6 centimetres. The debate was guillotined at that point but Bob sometimes recalls the stunned looks on Senators’ faces when he told them that it was no mistake. It really was a 6 metre sea level rise.

We can look back with amazement and regret at the lost decade during which Australia and the United States lead a denial campaign on global warming, only to finally be outed by undeniable evidence of serious impacts that are already happening.
But what about sea level rises? Occasionally I have suggested that there may be beach front property on Ghost Hill one day, but how likely is this in reality?

The current best estimates for sea level rises by 2100 are less than a metre. It doesn’t seem all that much. But many properties are built less than a metre above the high water mark and these must be considered at risk sometime this century, especially in combination with storm surges.
But here’s the catch. The current estimates are based predominantly on expansion of the oceans due to warming with smaller contributions from melting glaciers and icecaps. If some major icecaps collapse, all bets are off.

NASA’s Dr. James Hansen is one of a growing number of climatologists who think we may be getting into deep water – literally. We are now observing disturbing quantities of ice sliding into the ocean from Greenland and Antarctica. He thinks that the temperature rises now being predicted could cause these ice sheets to substantially collapse with the sea level rising as much as 5 metres by 2100. After all, we know that 3 million years ago the sea was 25 metres higher than today even though the average temperature was only about 3 degrees warmer. In the Jurassic period the sea level was a massive 200 metres higher than now.

The trouble is that nobody can predict how quickly the sea level might really change this century.

This was originally published in the Fraser Coast Chronicle on 14 August 2007.