31 January 2013

Australia’s sea-level risk assessment out of date as US authorities say possible  2-metre rise by 2100

by David Spratt

In assessing risks, it’s pretty basic that you assess the full range of possible future events, and the costs and benefits associated with each outcome. The more extreme outcomes at the edges of the range of possibilities may be considered less likely, but are often associated with very high costs and – in the case of climate change – catastrophic outcomes.
    On rising sea levels and coastal inundation due to global warming, that’s precisely what the Australian government is NOT doing.  While the science has for years projected sea-level rises in the range of 0.8 to 2 metres by 2100, the Australian government plods along spending tens of millions of dollars on consultants and adaptation research on the assumption that the rise will not exceed 1.1. metres.
   This madness is the subject of a submission authored by LIVE and myself to the current Senate Standing Committees on Environment and Communications Inquiry into Recent trends in and preparedness for extreme weather events (It is #10 here).
    The submission explains how the Australian government —having recognised that 2 metres was about the upper limit for sea-level risk assessments — then engaged in verbal gymnastics, flipping from “worse case scenarios” to “mid-range” to “plausible range of sea-level rise values” without a coherent explanation.
    So Climate Minister Wong told ABC “Insiders” on 15 November 2009 that:
1.1-metre ….is about the upper end of the risk. (Wong 2009)
And in June 2011 Climate Change Minister Combet told ABC News that:
The sea level rise of up to 1.1 metre…. is at the high end of the scenarios.
Trouble isn’t, neither statement was true.
   And whilst Australia’s “high scenario” stands at just 1.1 metres, others including the United States’ government and the European Union are taking a different approach in recognising that more extreme events are possible, and need to be assessed.   
     A new report published last month by the US Department of Commerce and the National Oceanic and Atmospheric Administration notes that:
Scientists have very high confidence (greater than 90% chance) that global mean sea level will rise at least 8 inches (0.2 meter) and no more than 6.6 feet (2.0 meters) by 2100.
The report says that “identifying global mean SLR estimates is a critical step in assessing coastal impacts and vulnerabilities” and recommends four scenarios:
  •  The lowest sea level change scenario (8 inch rise) is based on historic rates of observed sea level change. This scenario should be considered where there is a high tolerance for risk (e.g. projects with a short lifespan or flexibility to adapt within the near-term)
  • The intermediate-low scenario (1.6 feet) is based on projected ocean warming
  • The intermediate-high scenario (3.9 feet) is based on projected ocean warming and recent ice sheet loss
  •  The highest sea level change scenario (6.6 foot rise) [2 metres] reflects ocean warming and the maximum plausible contribution of ice sheet loss and glacial melting. This highest scenario should be considered in situations where there is little tolerance for risk. (emphasis added) 
US Department of Commerce/NOAA 2012 sea level rise scenarios
And since submitting to the Senate inquiry, another gem has come across my desk, this time from the U.S. Army Corps of Engineers.    In November 2011, the U.S. Army Corps of Engineers released updated guidance to Engineer Circular (EC) 1165-2-211 (2009) “Incorporating Sea-Level Change Considerations in Civil Works Programs.” The guidance series has a two-year lifespan, leading to the new 2011 release. This 2011 update includes:
...additional references and discussion reflecting recent advances and understanding of sea-level change since 2008-2009, including a statement that a credible upper bound for 21st century sea-level rise would not exceed 2 meters. This statement is based upon recent peer-reviewed articles by several authors using different methods but arriving at similar conclusions.
And where is Australia?  Hoping that the worst-case scenarios just won’t happen? That is certainly something this nation does not do when it comes to bushfire preparation.

Our propositions to the Senate Inquiry are:
  • Prudent risk management demands an analysis of the full range of possible future events, and the costs and benefits associated with each outcome.
  • The more extreme outcomes at the edges of the range of possibilities may be considered less likely, but are often associated with very high costs and – in the case of climate change – catastrophic outcomes.
  • Our coasts and coastal assets are vulnerable to storm surges. As a result of rising sea levels caused by global warming, the risk of severe flooding and storm damage to property will increase, beaches and bluffs will suffer increased erosion, low-lying areas will be inundated, with potential for saltwater to infiltrate into surface waters and aquifers, and  sewage and septic systems, transportation and water treatment infrastructure will be at risk from flooding and erosion.
  • There is a broad body of scientific work which estimates that sea-level could rise this century by as much as 2 metres. But the government’s work is based on three scenarios, none of which exceed 1.1 metres.
  • Small increases in the sea level can have devastating impact when combined with storm surges and high tides. The difference between a 1-metre and a 2-metre sea-level rise on such events will be in the tens to hundreds of billions of dollars for Australia, but we cannot quantify the cost because the assessment work has not been done.
  • The Australian Government has ignored basic, sound risk management practices in assessing future sea-level rises and the impacts of extreme storm surge events by discounting the more recent, upper-range, scientific projections.
  • The Australian people have a right to know how extreme coastal impacts could affect their lives, so that they can make fully-informed choices.
Let’s hope that the Inquiry holds public hearings and these issues get a proper airing.





  1. Thanks David. consistent with and corroborating all you've been saying on sea level rise for some years.

    Beyond that, ha ha. If you're over-goldplating poles and wires for guaranteed profit in an era of reducing electricity demand no non-risk should not be i sured against. Real risks though?

  2. From my understanding most of the sea level rise scientific modelling is based upon linear modelling to estimate sea level rise, with components from thermal expansion, mountain glacier melting and ice sheet collapse. (eg Vermeer & Rahmstorf 2009)

    But NASA climatologist James Hansen continues to propose that an exponential rate of sea level rise is possible this century with the impetus of climate feedback mechanisms such as increasing sea ice loss, methane release from Arctic permafrost, and release of methane from undersea clath hydrate deposits. Such positive climate feedback mechanisms will accelerate global warming and collapse of Greenland and West Antarctic Ice sheets which may result in a multi-metre rise in sea levels by the end of the century.

    Unfortunately we don't yet have a long enough period of accurate data measurement of ice mass loss from Greenland and West Antarctic Ice sheets to predict whether the rate of mass loss will be a linear or exponential trend. But measurements do show the rate of mass loss is accelerating.

    From paleoclimate studies we know that rates of sea level rise of 5 metres or so per century have ocurred naturally. We are much more rapidly changing the climate and the earth's energy imbalance, than in previous geological epochs, so sea level rise might start out very slow due to the inertia involved in ice sheet collapse but increase quite rapidly once climate feedback mechanisms kick in.

    So, 2 metres of sea level rise may be the worst case in terms of current peer reviewed science, but science cannot rule out at the moment, the possibility of even higher levels this century.

    See my review of James Hansen's discussion paper released late December 2012:

    Interview with James Hansen on Arctic Methane Feedback amplifying warming

    Arctic News: Dramatic increase in methane in the Arctic in January 2013

    From 2007: NASA Climatologist Predicts Disastrous Sea Level Rise