There has been quite a lot of interest in the speed and timing of sea level rise recently, brought about by the publication of new research and the sudden jump in world surface temperatures. The last IPCC report estimated a range of between 0.7 metres and 0.9 metres by the end of the century but there was a clause that specifically excluded Antarctica and Greenland’s melting ice sheets because not enough was known about them to quantify it. Most of the ice melting in Antarctica is from ice that is already in the sea and therefore does not contribute to sea level rise but the ice shelves hold the land glaciers in position and if the ice shelves go the land based glaciers slip quickly into the sea.
The results of the massive research effort to clarify the situation are now coming in thick and fast and they are all bad. James Hansen has sounded the alarm.
The results of the massive research effort to clarify the situation are now coming in thick and fast and they are all bad. James Hansen has sounded the alarm.
Just a quick note on what I believe are the important parameters. Firstly, just one metre is enough to bankrupt most economies and will displace two hundred million people causing a huge refugee problem if not world wars. Secondly we want to know the timing, if it will happen in our families’ lifetime so that it becomes of personal interest. So, all we want to know is, when are we going to get a one metre sea level rise?
The interesting part is that almost all the science on sea level rise shows that it rises very slowly under natural circumstances. But we are not in a natural situation. We have raised the level of CO2 in the atmosphere to 400 ppm instantaneously in paleological terms and we have raised the temperature by 1.5 C in a nanosecond in Earth’s history terms and there is no precedent for that.
The interesting part is that almost all the science on sea level rise shows that it rises very slowly under natural circumstances. But we are not in a natural situation. We have raised the level of CO2 in the atmosphere to 400 ppm instantaneously in paleological terms and we have raised the temperature by 1.5 C in a nanosecond in Earth’s history terms and there is no precedent for that.
So what do we have? There are three regions of the planet that hold enough ice to raise sea levels quickly and these are Greenland, West Antarctica and East Antarctica and they are all very different.
Firstly, it should be mentioned that the atmosphere is not a good conductor of heat and will not melt ice quickly and so this somewhat rules out Greenland because it does not have much ice sitting in the ocean. It is melting fast and will be a contributor and it pays to listen to Greenland specialist Jason Box.
Greenland's meltwater is upsetting the Gulf Stream and may give Europe some very bad weather but it is melting at the rate that could give a 100 to 300 mm of sea level rise quickly. It is part of the picture.
Firstly, it should be mentioned that the atmosphere is not a good conductor of heat and will not melt ice quickly and so this somewhat rules out Greenland because it does not have much ice sitting in the ocean. It is melting fast and will be a contributor and it pays to listen to Greenland specialist Jason Box.
Greenland's meltwater is upsetting the Gulf Stream and may give Europe some very bad weather but it is melting at the rate that could give a 100 to 300 mm of sea level rise quickly. It is part of the picture.
Second is that East Antarctica has by far the biggest amount of ice but it is remote and poorly observed so that apart from the knowledge that the Totton glacier is losing mass from the bottom of its glacier tail sitting in the sea, not all that much is known. It is certainly melting around the edges but lack of access is hindering research.
I strongly recommend watching this half hour lecture video of Eric Rignot at the American Geophysical Union meeting.
This leaves West Antarctica which is a series of islands holding in position a massive sheet of ice around 1000 metres thick and resting on the bed of the ocean.
What is happening here is that the temperature differential between the high cold Antarctic and the warming equator is increasing and the winds flowing from the cold to the warm are blowing faster.
This is causing a turnover of the water at the edge of the ice so that the very cold surface water (-2 C) is being blown out to sea (as evidenced by the increasing winter ice) and is drawing the warmer deep water (4 C) nearer the surface. This warmer water has now reached the grounded ice shelves of West Antarctica and melting them from the bottom and it is doing so at a furious rate.
What is happening here is that the temperature differential between the high cold Antarctic and the warming equator is increasing and the winds flowing from the cold to the warm are blowing faster.
This is causing a turnover of the water at the edge of the ice so that the very cold surface water (-2 C) is being blown out to sea (as evidenced by the increasing winter ice) and is drawing the warmer deep water (4 C) nearer the surface. This warmer water has now reached the grounded ice shelves of West Antarctica and melting them from the bottom and it is doing so at a furious rate.
There are other minor regions of glaciers in Alaska and the Himalaya's which are also steady contributors.
Nobody has ever seen and recorded a massive ice shelf disintegrate before and so it is not researched. The ice shelves named Larsons A and B disintegrated suddenly from 1995 onwards and it was photographed from space but nobody was expecting it to happen and so there were no instruments in place to research how it happened. That is not the case now and millions have been spent on observing and researching various ice shelves to work out what is happening. This research is where the new warnings are originating but much of the research is not completed yet and will take years before it is published and then many more years before it becomes government policy.
We therefore have to get the honest opinions of five or six leading scientists who are working on the ice and can interpret the results of the research so far and where we are headed.
A quote from The Royal Society of New Zealand emphasises the urgency.
“Experience shows that uncertainties around climate changes can result in decision-making being postponed until changes are clearer. This ‘wait and see’ approach is in itself risky, since the direction and rough magnitude of climate changes, and the associated increases in key risks, are well understood.”
The distilled consensus of opinion appears to be that we can expect the additional 800 mm of sea level rise to make the one metre in around forty to fifty years. Close enough to affect the lives of most people alive today.
The New Zealand governments recommendation to councils is to plan for 500 mm by 2100 which is clearly inadequate.
Here is an even more pessimistic report by people better qualified than me. https://www.kcet.org/redefine/sea-level-rise-could-come-much-sooner-than-you-think
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