One of the lead authors of the new book: Understanding Sea-level Rise and Variability, CSIRO’s Dr John Church. (CSIRO)
On the front line of rising sea levels
The authors of a new book have called for the development of more robust international ocean and ice sheet monitoring and modelling programs designed to help community adaptation planning keep pace with the threat of rising sea levels.
Although science is improving our insight into ocean and ice dynamics, and the impact of sea-level rise, billions of dollars worth of coastal development is still being constructed under the assumption that the stable sea levels of the past several millennia will continue.
To make the science of sea-level rise clear, a group of international scientists have written a book called Understanding Sea-level Rise and Variability, a comprehensive overview of current knowledge on the science of sea-level rise.
The 420-page book is the work of more than 90 scientists from 13 nations, led by CSIRO’s Dr John Church, Dr Philip Woodworth from the Proudman Oceanographic Laboratory UK, Dr Thorkild Aarup from the Intergovernmental Oceanographic Commission (IOC), and Dr Stan Wilson from the US National Oceanic and Atmospheric Administration.
In this podcast, Dr Church from CSIRO Marine and Atmospheric Research explains sea-level rise and the projections for the future.
Interviewer: G’day, and welcome to CSIROpod. I’m Glen Paul. Anyone who’s ever paid attention to the warnings of climate change is aware that sea level rise is one of the consequences. And even though science is improving our insight into ocean and ice dynamics, and the scientific measurement of the rate of sea level rise, billions of dollars worth of coastal development is still being constructed under the assumption that the stable sea levels of the past several millennia will continue.
That’s why a group of international scientists have written a new book called Understanding Sea-Level Rise and Variability, a comprehensive overview of current knowledge on the science of sea level rise. One of the lead authors is CSIRO Marine and Atmospheric Research Scientist, Dr John Church. John thanks for talking to me again. Last time we spoke it was for the Vodcast, Climate Change Threatening the Southern Ocean, and in that you said projections had sea level rising by 18 to 59 centimetres by 2100. Now, do those figures still stand?
Dr John Church: Yes they do, except that in addition to the 18 to 59 centimetres, there’s a contribution from the dynamic response of the ice sheet, which is not very well understood. So this is a response of the ice sheet to particularly ocean warming, and the sliding of glaciers into the ocean more rapidly.
The IPCC estimated that it’s perhaps up to 20 centimetres, so making a full range of those predictions really 18 to 79 centimetres. But they recognised that we didn’t understand ice sheets very well, so it actually could be a larger dynamic response, but our understanding was so poor that they couldn’t really constrain that upper limit.
Interviewer: So a lot of data has been collected for this book, but just how well does it cover the topic?
Dr John Church: The book is comprehensive in that it covers all aspects of sea level change. That includes people who are looking at the impacts of sea level rise, estimating coastal populations. People looking at the longer time scale associated with sea level change, so looking at sea levels recorded in corals, in sediments around the world. People like myself who actually measure sea level with coastal tide gauges, or satellite instruments, which measure the height of the sea surface relative to the centre of the earth. People who measure the temperatures of the ocean, and of course as the ocean’s warm, they expand and sea level rises, just like a thermometer. People who look at glaciers and ice sheets for measuring the thickness of glaciers, the movement of ice sheets into the ocean, and the changes in snowfall on the ice sheets.
And of course the land itself is also moving, so we need to have measurements of that land motion, and models of that. And of course there’s the impacts of sea level rise from extreme events, major coastal flooding events, such as Hurricane Katrina in New Orleans, and many other examples around the world. And we bring it all together with well, what are the observations that we require into the future, and synthesis of the various components.
Interviewer: OK. Now, that’s fairly comprehensive, and you did mention there the ice dynamics aspect of it all, but what are some of the conclusions drawn in the book that we may not have heard before?
Dr John Church: Well one of the things I think we need to think about in planning for the future is we know that over the period of development of our modern coastal society the rates of sea level rise have been relatively small. That’s changed. The rate of rise has increased from the 18th to the 19th Century, and during the 19th Century. It will continue to rise during the 21st Century, and it will continue to rise beyond the 21st Century. So we’d need to change our mindset from a period of stable sea levels, which have dominated our past thinking about coastal development, to a period of changing sea levels, and changing sea levels on the longer term.
Interviewer: Now even with the world’s best scientific minds behind this book, specialists in their fields, there are still the detractors of climate change and sea level rise. Why do you think that is?
Dr John Church: I think there’s a significant component of vested interest, people who don’t want to hear the story for whatever reason, but the geological evidence is clear that sea level has changed in the past, and it will continue to change into the future.
The difference to the past to now is that we have a huge investment in the coastal zone. And why do people really not want to understand and to plan for the future? I guess I don’t really know the answer to that, but we are going to have to adapt to coastal sea levels, and we’re much better to plan that adaptation, rather than have that adaptation forced onto us through events like extreme events impacting coastal cities.
Interviewer: I see. So then who should read this book?
Dr John Church: The book was originally aimed at both scientists in the field, because it is a very an interdisciplinary field, and scientists need to have a view across the many different disciplines involved. But also for people like coastal planners, policy-makers, who need to understand what the issues are, and need to make decisions about both mitigation of climate change, what are the thresholds that might be approaching, and people who need to plan adaptation, planning cities, planning coastal developments, and how should we allow for changing sea levels. The general public will have some interest, but mostly it’s more the specialist audience.
Interviewer: OK. So, Understanding Sea-Level Rise and Variability, a comprehensive overview of current knowledge on the science of sea-level rise – that’s available in bookshops?
Dr John Church: Yes, it’s available in bookshops. It’s published by Wiley-Blackwell, so probably more technical bookshops in general. But I know some general bookshops also have it, and in fact are selling it.
Interviewer: OK. Great. Well, hopefully the message gets through. Nice talking to you once again, John.
Dr John Church: OK. Thank you.
Interviewer: Dr John Church from CSIRO Marine and Atmospheric Research. For more information visit www.csiro.au.