An Intergovernmental Panel on Climate Change report claiming New Zealand will experience sea levels rises of one metre during the next century flies in the face of available scientific evidence, says a Waikato University scientist.
Dr Willem De Lange's own research suggests sea levels may actually be about to decrease, and any claims that sea levels will rise by one metre is “scientifically invalid”.
A Waikato University scientist is disputing IPCC claims New Zealand will experience sea levels rises of one metre during the next century.
Willem is senior lecturer in the university's department of Earth and Ocean Sciences with expertise in tsunami and storm surge prediction and mitigation; wave-induced sediment transport; dispersal studies; climate change; oceanography.
While sea levels have been rising around New Zealand for the last 120 years, the rate is slowing – and sea levels are still one to two metres lower than they were coming out of the little ice age in the 14th century, says Willem
“The problem is some of the work we have done shows that sea level rises in New Zealand seem to go in a step-like pattern.
“So it jumps up and stays fairly steady, and then after a while it jumps up again. The last time it jumped up was about 1998, and since that time it hasn't really done much at all.”
The IPCC projections cover a huge range of numbers, with a tendency for media in particular to pick either at the top end or above the top end, says Willem.
“So in their latest assessment they identified two main methods used to project what the sea level will be in one hundred years' time. My own research indicates we can't do any meaningful predictions beyond about 30 years.
“So these projects are based on ‘what if' scenarios, which may or may not happen. There is no probability associated with just how likely these numbers are.”
The IPCC consider IPCC Working Group 2 report, authored in part by Niwa scientists, is suggesting sea level – by the end of the century – will have risen by roughly twice what it rose by in the last century.
That prediction is 14-17 centimetres for New Zealand, says Willem.
“So if you double that you get 30-40cm. The report that's being released is claiming sea level rises of at least one metre. The problem is even with the doubling, the rate of sea level rise has been slowing progressively for New Zealand probably since the 1930s.
“When I first did this work in 1984 the rate that we had for New Zealand was 2.5 millimetres per year, and right now we are somewhere in the order of 1.7 millimetres.”
Willem published a prediction of the step in sea level that happened at the beginning of this century and predicts the next step is due in 2030 – plus or minus five years.
“I'm still predicting there will be a step, but I'm increasingly uncertain as to whether it will go up or down,” says Willem. “There's an increasing possibility that the step in sea levels will be downwards – which is not considered at all by the IPCC.
“The problem they are having with research that is increasingly coming out, is the rate in sea level rise in particular bares no correlation with temperature or green house gas emissions.
“The gas emissions have been accelerating rapidly over the last 30 years. The temperatures now are not much different to what they were when I was at high school.
“And so there hasn't been much in the way of a temperature rise for between 15 and 20 years, depending on what statistics you look at. This century there has been no effective temperature change and the sea level has been rising but at a slower rate.
In fact Willem says some of the more recent data indicates a global drop. “So taking the observations and pushing them forward is very difficult, but in my opinion I consider IPCC Working Group 2 is working with two numbers that are ridiculously high and they are overstating the problem.”
Work Willem's been doing on the Kapiti Coast and more recently on the Coromandel shows the future of coastal communities depends on their sediment budget; how much sand is on the beach.
“Most of our coastline has a positive sediment budget at present. So that means regardless of sea level rise those beaches are likely to be stable, or retreat. So I think it is unreasonable to go round telling people that our coastal communities are under dire threat.”
The IPCC predictions are based on projections which have failed to match observations, says Willem.
“And that's the problem they have. The bizarre thing is the further their projections track from the observations; the more certain they are humans are causing it to be worse than it should be.
“We identified back in the 1990s there was about a 60-year cycle in ocean behaviour and atmospheric behaviour, and that predicted at the time there would be 25-30 years of global warning followed by 25-30 years of global plateauing. Increasingly it is looking as though we are looking at 25-30 years of cooling.
“We are now 15 years into that 30-year period and data is suggesting that it's not warming – in line with predictions made by a number of people back in the 1990s.”
Willem raised those issues with the IPCC and now gets labelled a ‘denier'.
He's reassuring Omokoroa residents on Wednesday this week about the lack of ongoing issues regarding rising sea levels, or Port of Tauranga operations uncovered in the university's ongoing studies of Tauranga Harbour.
Willem is first speaker at the community meeting, to be held at the Omokoroa Settlers' Hall at 7pm.
“We've been invited to talk students working in the region on coastal erosion. The results so far show there is no relation to port issues and to climate change issues.”