Antarctic ice is now melting faster than ever, raising sea levels. But the degree of risk to our coastline and economy is still a big unknown.

One of the most troubling lines in the recent reports from the Intergovernmental Panel on Climate Change was tucked away in a footnote. It stated that, of their various future sea-level scenarios, the estimate of the upper limit – a 1.1 metre rise by 2100 – was actually not the worst case. That is, the $226 billion value of Australian roads, rail, commercial buildings and homes spread over the coastal zone that may be underwater regularly by 2100 could be an underestimate. And they did not know by how much.

The potential source of that extra water? A destabilised West Antarctic Ice Sheet. The unknown that niggled at the authors was the possibility that West Antarctica would do what observations and theory say is possible – collapse, adding an extra five metres to sea levels. Recent observations suggest irreversible retreat has now commenced, and so the key question is not if, but how quickly? The IPCC did not know and the science community still does not know (guesses on timescales vary from 200 to 1000 years or more).

We now know that two huge areas of potential instability sit, almost unstudied by anyone, within the Australian Antarctic Territory.

But we are in a good position to begin to know. On Tuesday, April 21, I will deliver a lecture at the Royal Society in London describing remarkable progress in what we do know about Antarctica and its contribution to sea-level change. Thanks to international efforts coordinated by NASA and the European Space Agency we now know, for the first time in history and with great confidence, that the grounded ice of Antarctica is flowing into the ocean faster than snowfall replenishes it, hence raising sea levels. That imbalance is now 130 billion tonnes of ice each year.

And we know that this change is happening faster and faster – in both West Antarctica and Greenland. The big grounded ice sheets are now contributing to sea-level rises at double the rate they were in the 1990s. These changes have been observed in different ways, using different data, by different groups in different countries and the result is not disputed.

This success means scientists have never been better placed to address the future of Antarctica and how it will affect our own coastal sea levels. But their success, and the speed with which reliable information can be put in the hands of policymakers, depends on all the major Antarctic nations committing to long-term funded research tied with long-term logistical infrastructure. Inconveniently, the big unknowns are located away from our long-standing research stations – indeed, they are in some of the most remote regions on the planet.

It’s for this reason that the 20-year Australian Antarctic Strategic Plan report, submitted in October last year, called for long-range over-snow traversing capability and a funding cycle for both salaries and logistics that matched our identified 10-year national Antarctic strategic science goals. As the government considers that report, the prestigious Academy of Sciences and scientists internationally have urged us to retain our position as a major Antarctic scientific nation by adopting the recommendations of that plan.

Australia should not stand back and wait for other nations to do the work for us. Our Antarctic claim, frozen under the Antarctic Treaty, is to 44 per cent of the continent. That claim consists of about 30 metres of potential sea-level rise. Most of that sea level is safe for millennia, but perhaps not all of it. Indeed, we now know that two huge areas of potential instability sit, almost unstudied by anyone, within the Australian Antarctic Territory.

Last month an Australian and US collaboration revealed a significant chunk of one of those regions can be added to West Antarctica as potentially vulnerable to collapse – a further four metres of sea-level rise now comes into play. Again, we don’t know if this will occur, and if so, how fast. We know the hazard, we just do not know the degree of risk to us, our coastlines, our economy and our lifestyles. And for the same reasons, we don’t know the risk to our regional neighbours, many of whom are not as well equipped to adapt as we are.

The currency of the Antarctic Treaty is not occupation of land but science. We exercise influence over the future use of Antarctica by studying the full extent of the Australian Antarctic Territory – in the air, across the ground and at sea. For six decades or more Australia has been a linchpin in the international collaboration that have given us a first view of Antarctica. That science has led us to a point where we know much about this iconic continent. But it is what we do not know that should trouble us.