The time is fast approaching when we will have to acknowledge that scientist’s projections of the rate at which climate change is impacting the environment is simply too conservative. It may be that the rate of climate change is faster or the impacts are greater. Or both.

I mentioned the fast rate of Antarctic ice melt and its impact on sea level in a previous blog. Now the British Antarctic Survey    reports the faster-than-expected impact of warming on the Wilkins Ice Shelf, a 16,000 sq. km  area of ice (the size of Northern Ireland) on the western side of the long tendril known as the Antarctic Peninsula, approximately 1000 kms south of South America. Image courtesy British Antarctic Survey

While monitoring satellite images of the shelf, glaciologist Ted Scambos, of the University of Colorado noticed a 41 km x 2.5 km (25.5 by 1.5 miles) iceberg had broken away from the Wilkins Ice Shelf at the end of February 2008. He alerted the British Antarctic Survey (BAS) team who investigated the ice shelf first hand.

The BAS reports that the edge of the shelf proceeded to crumble and disintegrate in a pattern that has become characteristic of climate-caused ice shelf retreats throughout the northern Peninsula, leaving a sky-blue patch spreading across the ocean surface compose of hundreds of large blocks of exposed old glacier ice.

By 8 March 2008, the ice shelf had lost just over 570 km2  (220 sq. miles), and the patch of disintegrated Antarctic ice had spread over 1400km2. As of mid-March, only a narrow 6km (3.7 miles)wide thread of shelf ice between two small islands that support part of the shelf was protecting several thousand kilometres of potential further break-up.

Scambos said that it’s not just  ice breaking off the shelf, but rather massive sections shattering, and that if the thread of ice collapses, half of the ice shelf could be lost within a few years.

In 1993, Professor David Vaughan of the BAS predicted that the Wilkins Ice Shelf would likely disappear within 30 years if climate change continued at the same rate as in 1993.

There’s now a good chance the Wilkins Ice Shelf will dissappear long before 2023, which will come as no surprise for those who are following closely the recent evidence of the impact of climate change. This discovery follows the recent UNEP report that the world’s glaciers are continuing to melt away. Data from 30 reference glaciers in nine mountain ranges show that between the years 2004-2005 and 2005-2006 the average rate of melting and thinning has more than doubled.

Professor Vaughan said: “Wilkins is the largest ice shelf on the Antarctic Peninsula yet to be threatened. I didn’t expect to see things happen this quickly. The ice shelf is hanging by a thread – we’ll know in the next few days or weeks what its fate will be.

“Climate warming in the Antarctic Peninsula has pushed the limit of viability for ice shelves further south – setting some of them that used to be stable on a course of retreat and eventual loss. The Wilkins breakout won’t have any effect on sea-level because it is floating already, but it is another indication of the impact that climate change is having on the region.”

Ice shelves float in the sea and already displace water volume. When they break up and melt, they do not raise sea level. However, ice shelves restrain the flow of glaciers behind them from sliding into the sea. When the ice shelves disintegrate, glaciers can slide quicker towards the sea, melt and raise the sea level. The collapse of ice shelves can therefore precede a faster rise in sea level. Melting sheets also increase feedback in the climate system by reducing the reflectivity of that part of the earth’s surface, enabling sunlight to be converted to ocean heat which in turn accelerates melting of the floating ice.

Fortunately, few glaciers flow into Wilkins Ice Sheet, but if the trend continues and other sheets are affected, sea levels will eventually be impacted.

The Antarctic has warmed at three times the global average – and, along with Alaska,  faster than any other region on the planet – over the past half century and six Antarctic ice shelves have already disappeared over recent decades, including  Prince Gustav Channel, Larsen Inlet, Larsen A, Wordie, Muller, Jones and the 3,250 sq. km, 220 metres thick  Larsen B Ice Shelf, which fell apart   over several months in 2002 –  720 billion tonnes of ice gone. Again, an unexpected event.

Science magazine  reported that the Ross and Ronne ice shelves may be instrumental in retaining the glaciers behind them and that if those two shelves were to collapse, the entire land-based western ice sheet could flow into the ocean, with the potential to raise sea levels by 5 metres. 

And still we keep pumping out more and more greenhouse gases and argue over what action to take, when the solutions are already available.

For more Antarctic images see Polar View

Note: Ice sheet – is the huge mass of ice, up to 4 km thick, that covers Antarctica’s bedrock. It flows from the centre of the continent towards the coast where it feeds ice shelves.

Ice shelf – is the floating extension of the grounded ice sheet. It is composed of freshwater ice that originally fell as snow, either in situ or inland and brought to the ice shelf by glaciers. As they are already floating any disintegration (like Larsen B) will have no impact on sea level. Sea level will rise only if the ice held back by the ice shelf flows into the sea. By Christo Norden-Powers            © 2008 Spandah

posing bigger risks for coastal businesses and communities

Two recent studies (published in January 2008) have sounded warning bells about the rate of ice melt in Greenland and Antarctica that suggests sea levels could rise higher and faster than the 0.18 to 0.59 metres by the end of this century estimated by the Intergovernmental Panel on Climate Change (IPCC) in its 2007 Fourth Assessment Report, posing increased risks for businesses and communities located in coastal regions.

Antarctic
A study of the Antarctic continent by Eric Rignot and his colleagues at NASA’s Jet Propulsion Laboratory found that West Antarctic lost 132 billion tonnes of ice in 2006, and the Antarctic Peninsula, which is the section that stretches towards  the southern tip of South America, lost 60 billion tonnes.
The combined loss of 192 billion tonnes of ice raised global  sea levels by approximately 0.5mm, an increase of  nearly 70% over the Antarctic’s contribution of just 0.3mm to sea level rise ten years ago, in 1996.

When projecting sea level rise, the IPCC included estimates based on the then known 1993 – 2003 ice melt from Greenland and Antarctica,  but did not include uncertainties in climate-carbon cycle feedbacks, or the full effects of changes in ice sheet flow, as not enough is known about how those processes work. 

Rignot’s study shows that the actual contribution was at the upper end of the IPCC’s estimates.

IPPC’s projections are probably underestimated
If that’s not bad enough, the IPCC also stated that the  maximum figure for its worst scenario ‘are not to be considered upper bounds for sea level rise’ and acknowledged that feedback mechanisms in the climate system could cause greater sea level rises than those projected.

A team of scientists from Australia’s CSIRO, NASA’s Goddard Institute for Space Studies, Scripps Institution of Oceanography and the UK’s Hadley Centre – four of the leading climate research bodies in the world – recently wrote (Science journal Feb 2007) that observed actual sea levels have risen faster than the models had projected, and would be closer to 88cm rise between 1990 and 2100.

Alarmingly, that team scientists agreed that previous projections may have underestimated the rate of change. They found that carbon dioxide concentrations were reasonably accurately projected by scientific modelling, but that global mean surface temperatures were actually in the upper part of the range projected by the IPCC. 

So, it seems that we have a good grasp of the CO2 emissions, but we are underestimating the impact that those emissions have on temperature increases and sea level rise.

There is a higher risk to people, business, animal and plant species and societies in under-estimating impacts than in over-estimating impacts.  If we over-estimate impacts we are likely to over-compensate with mitigation and adaptation strategies. If we under-estimate, we may not act fast enough to mitigate emissions and prevent serious or catastrophic change; or we may leave action too late to adapt economies, health services, infrastructure, social systems etc in time to cope with the change.

Further acceleration of change?
The current figure of 70% decadal sea rise from Antarctic melt should be of considerable concern, because it has occurred with a fairly modest rise in atmospheric and sea temperatures in the Antarctic region.  Although we cannot be absolutely certain, we can probably expect the rate of melt to accelerate in the next few decades as emissions increase, temperatures rise further and faster, and positive climate feedback systems kick in.

A serious problem arises if the globe continues to heat up at present rates (or faster) and if the ice melts also accelerate. Then the sea level rise will follow a similar pattern to compound interest on investments with small increments adding up to large change over a human lifetime.

For example, assuming that the Antarctic contribution to sea level rise continues to accelerate by a steady (current rate) 70% per decade the sea rise from Antarctic melt alone will be

• 2.9 mm in 2040 
• 5.0 mm in 2050
• 14 mm on 2070
• 24 mm in 2080
• 41 mm in 2090
• 72 mm in 2100. 

At that rate, and purely from Antarctic melt, the IPCC’s minimum sea level rise of 18cm will have been achieved  by 2063 instead of 2100, and the IPCC’s maximum sea level rise of 59cm will be reached around 2085, i.e. 15 years ahead of the worst scenario schedule. By 2100 the sea level will have risen by over 1.3 metres just from the Antarctic melt alone, and that would still represent only about 2% of the ice currently covering Antarctica.

That would expose many vital areas of major cities to inundation from storm surges as storms intensify and become more frequent with more warming.

 If sea levels rose even slightly faster through thermal expansion and melts from other ice sources, such as Greenland, and sea levels rose just 2 metres, cities like New York, London, and large parts of Sydney would become uninhabitable.  Whenever I walk along the beach at the Kurnell Peninsula in southern Sydney I wonder whether the narrow barrier sand dunes on the ocean side will withstand even a 0.5 metre sea rise with increased storm surges.  The entire peninsula (plus the oil refinery and forthcoming desalination plant) could be at risk, not to mention the Toyota factory, golf course and high school.

And driving towards Sydney airport, located on Botany Bay, it’s easy to see that 1 to 2 metre sea level rise will put the airport and homes along the Bay and inland for 1 – 2 kms inland at risk, as well as the Port Botany shipping freight depot and many inner city suburbs with all their associated infrastructure.

2 metres rise would make Macquarie Bank’s commercial rights at Sydney airport worthless.

Global acceleration of ice melt
The acceleration of ice melt is a  global phenomenon, not just in Antarctica.

The IPCC estimated that between 1960 and 1990, global ice loss from glaciers and ice caps averaged 136Gt (136 billion tonnes) per year.

Over the next 13 years to 2003 that figure doubled to an average 280Gt per year.

The estimated annual average sea level rise between 1961 and 2003 from the combination of glaciers and ice caps, the Greenland ice sheet and the Antarctic ice sheet was 0.69mm.

In the last decade of that period, the sea level contribution from those sources increased 174% to 1.2mm per year.
 
And in the same week that Rignot’s study was published in Nature Geoscience,  Edward Hanna, of the UK’s University of Sheffield, reported in the Journal of Climate that the Greenland ice melt from 1998 – 2007 was the biggest decadal melt since records began in the 1950’s. The top 6 melt years for Greenland are all since 1995.

You can see the trend.

But that’s not all. An even bigger influence is at play that may dwarf the ice melts.

Thermal expansion
The figures given above for sea level rise from Antarctic ice melt do not include thermal expansion of oceans caused by rising ocean temperatures.

Water volume expands as the water is heated. Global average ocean temperatures rose 0.1 degrees Centigrade (upper 700 metres of ocean) from 1961 – 2003, but that incremental increase was sufficient to cause approximately 17.2mm  (22%) of the actual 77.4mm sea level rise during that period, simply by thermal expansion. That’s an average of average 0.4mm rise per year as a result of the oceans warming up.

The average annual sea level rise over that period was approximately 1.8mm.

However, in just  the last 11 years of that period – from 1993 to 2003 – the sea level rose by 34.1 mm, an annual average sea level rise of 3.1mm per year (172% up on the 1963 – 2003 average). Thermal expansion accounted for 17.6 mm of that rise in global sea level – an average 1.6mm per year, a substantial 400% increase in the average annual thermal expansion rate over the previous 43 year period. 

The percentage of sea level rise attributable to thermal expansion has more than doubled from 22% over the period 1963 – 2003, to 51% in the period 1993 – 2003.

Implications
No-one knows for certain what will happen with sea levels over the next decades and century. However, on current trends and emission trajectories, and with the slow pace of global policy development and additional climate feedbacks, it seems pretty certain that the IPCC’s upper estimates are likely to be substantially exceeded.

As climate science becomes more refined, and with improved data and understanding of climate change processes, the uncertainties that currently exist will be reduced to provide greater certainty.  However, recent improvements in data and understanding suggest that, if anything, we are underestimating the pace, power and extent of climate change and its impacts.

Is 2 metres sea level rise possible this century?
Is a 2 metre sea level rise this century  an outrageous suggestion?

No. There is precedent.

20,000 years ago the last ice age began to thaw. Over the next 10,000 years  the earth’s temperature warmed by 5 degrees C, or an average 1 degree C every 2,000 years. That is one of the quickest rises in the earth’s history – until now. 

Approximately 19,000 years ago, just after that thaw began, sea levels rose  by 10 – 15 metres over a period ranging from as little as 100 years to 500 years, as a result of the collapse of a large ice sheet. 

If business and lifestyles continue as usual, pumping out greenhouse gases at an ever increasing rate, there is little doubt that our planet will get hotter by at least 3 degrees C, and perhaps as much as 6 degrees C, by the end of this century (based on IPCC projections).

That is 60+ times faster than in previous history.

It is a recipe for substantial, unpredictable and uncontrollable, and very dangerous positive feedback triggers (enhancers) to begin firing.

And three of Nature’s big guns will be Greenland, Antarctica and thermal expansion of the oceans – and the consequent sea level rise.

I’ll look at the implications of sea rise on business, property, infrastructure and other factors in future blogs.

A note on underestimating climate change
In assessing the extent of risk to business, individuals and society from climate change, a number of factors must be considered in relation to ‘underestimating’, including

• Shortcomings in the models used to project climate change impacts. Climate change science is fairly new and evolving, and there are still many unknowns and uncertainties with climate change science. The climate system is massive and complex, and we have insufficient data on many aspects of climate and especially on feedback systems that can rapidly accelerate the change
• Scientists are generally fairly cautious, erring on the conservative side when expressing degrees of certainty about climate change, and how far they extrapolate the meaning of their findings, especially when their work is peer reviewed and possibly criticised; or when research funding comes under threat if certain strong views are expressed
• The language in the  IPCC’s fourth (2007) report was modified following intense pressure from various government representatives before the report was published. For instance, China, the USA and Saudi Arabia fought ferociously through the night (and succeeeded) to weaken some of the language in the Working Group 1 report. Each of those nations has a direct interest in continued oil or coal usage for economic growth.

The last point above is totally unacceptable in my view, because it runs the risk of slowing the global response to climate change and leaving the world, billions of people, the majority of species of animals and plants, and, of course the global economy exposed to higher risk through slower mitigation and adaptive responses on order to bolster a political agenda.

by Christo Norden-Powers     ©2008 Spandah Pty Ltd