By Sarah-Jane O'Connor 16/02/2016


Though we are already locked into sea level rise of at least 20 centimetres by 2050, the window of opportunity to act has not yet closed on us, climate scientists say.

Victoria University professors James Renwick (Physical Geography) and Tim Naish (Antarctic Research Centre) presented a keynote address on Monday at the Pacific Climate Change conference, hosted by Vic Uni.

Renwick likened the increased carbon dioxide in the atmosphere to “putting a much thicker blanket on the Earth”.

The changes expected to be seen in the planet’s climate as a consequence were happening at such speed, “in Earth’s terms it’s happening almost overnight,” Renwick said.

“We are going to see climate change for quite a long time yet, regardless of what we do politically and technologically over the next century or so.”

With three-quarters of the Earth’s surface made up of oceans, the vast majority – over 93% – of the extra heat had been absorbed by the oceans, Renwick said.

“We really need to pay attention to what’s happening in the oceans.”

Renwick said it worried him that it seemed the rate was increasing, “as far as you can see at the moment, the oceans have been absorbing heat at a faster rate.”

Of course, water expands with heat, so hotter oceans mean sea level rise. But Renwick said there could also be changes to the frequency or severity of El Niño cycles and changes to the South Pacific Convergence Zone.

“Rainfall follows the warmest water because that’s where you get the most buoyant air.”

Scientists aren’t sure yet exactly which way things will go, but Renwick cautioned that in the future, places that tend to be dry in an El Niño will likely be drier and those that are wet, wetter.

Professor Naish said limiting global warming would require “very aggressive mitigation and potentially the extraction of carbon dioxide from the atmosphere”.

Though Paris’ COP21 meeting was about committing to a 2-degree warming, Naish said the emissions-reduction pledges made, if they were delivered upon, would still only manage to limit warming to about 2.5 degrees.

“So the pledges don’t get us there.”

Regardless, we are locked into sea level rise of 20 to 30 centimetres by 2050, just based on the amount of atmospheric warming we’ve already contributed to, Naish said.

By the end of the century, that’s expected to be at least half a metre, but as scientists learn more about what will happen to the ice shelves and their associated ice sheets, predictions are heading up to one-metre sea level rise by century-end.

“There is still time, though. We know what to expect in the next 20-30 years so we sort of know what we are up against. It’s not a lot of time but there is time to take action.” He suggested that window could be the next decade: a pressing timeframe considering the Pacific could see up to 10% more sea level rise than the global average.

The near future and the long term would be affected by the decisions made in the now and in the coming years, Naish said. Those Pacific nations that were the most at risk – like the Maldives, Kiribati, Tuvalu and the Marshall Islands – would be the first to bear the brunt of the cost of climate change.

It was an unjust cost, Naish said, since those countries were not the ones emitting high amounts of carbon dioxide into the atmosphere.

Professor Renwick will be part of a panel giving a media briefing through the Science Media Centre on Wednesday at 12.30pm on climate change science and the Pacific.

Featured image: Flickr CC, Millennium Atoll/Caroline Island. Part of the Republic of Kiribati, The TerraMar Project.