Climate change: Sea level rise inevitable

Prime Minister Jacinda Ardern says climate change is "my generation's nuclear-free moment," but new research shows the damage to New Zealand could be as bad as an actual nuclear attack.

Multiple reports in recent months have painted a worrying picture of the future for New Zealand's climate and sea levels.

The UN World Meteorological Organisation (WMO) said in its Greenhouse Gas Bulletin this week that atmospheric concentrations of carbon dioxide grew at record rate in 2016.

Atmospheric concentrations of carbon dioxide (CO2), the main man-made greenhouse gas, hit 403.3 parts per million (ppm) in 2016.

The last time carbon dioxide levels reached 400 ppm was 3-5 million years ago, in the mid-Pliocene era, and the WMO warns this could potentially add 3degC to temperatures and fuel a 20-metre rise in sea levels.

NIWA's Chief Scientist for Climate, Atmosphere and Hazards, Dr Sam Dean, warns the rise could be even higher - as much as 40-metres.

"Under such a scenario records from the Earth's history suggest sea levels could ultimately rise from between 10-40 m," he says.

"Scientists currently believe if we can keep the warming of the Earth's atmosphere to below 2 degrees then we are likely to avoid such an outcome."

Dr Dean says this is based upon a number of techniques in paleoclimate research, the primary one being the identification of raised beaches and undersea deposits on land that is currently above sea level and in a geologically stable location.

The water for the rise is mostly expected to come from melting ice sheets in Greenland and Antarctica, and would have a "quite significant" effect on New Zealand.

But there is some comfort. 

"It is expected that this will take 1000 years to occur," Dr Dean says.

New Zealand has played its part in causing the damage. The country's gross greenhouse gas emissions have increased by 24 percent since 1990, half of which come from agriculture, according to the Ministry for the Environment and Statistics New Zealand report released earlier in October.

It's already taking a significant toll. The country's glaciers have lost a quarter of their volume since 1977, and sea levels have risen by up to 22cm in the past century throughout our main ports.

A Ministry for the Environment report was delivered to the Government in April, warning sea levels could rise 30cm-40cm by 2050.

This would mean 133,000 people were at risk of "higher levels of coastal erosion".

Insurance Council chief executive Tim Grafton says almost 70,000 properties may be uninsurable within 20 to 30 years.

"If nothing is done to reduce risk that will almost be a certainty in some parts of New Zealand," he says.

"The whole point of this is not to scaremonger, but actually to say, reality check everybody - we need to address this issue with some seriousness so that in a few decades time we're not in that position."

He says there are already pockets of New Zealand where it is difficult to get insurance due to rising sea levels.

"People seem to think that these things won't affect them in their lifetime because they believe the extreme events from climate change lie decades away."

And the damage is already beginning. This year has already seen devastating weather events cause havoc in Edgecumbe and Otago.

Figures show weather-related claims are now at the highest since records began, with more than $230 million paid out this year.

In March, the Auckland suburb of New Lynn flooded after a massive deluge swamped streets and storm water systems were overwhelmed.

And the research shows water networks like these will soon be under even more pressure. The new Deep South report found we can soon expect higher sea levels leading to increased sewage overflows and salt water corrosion in pipes.

More frequent coastal storms will cause inundation, physical damage and treatment plant failures - as well as extreme rainfall and droughts.

"We need to start to transition our infrastructure to a model that's more appropriate for the weather patterns and sea level rise that we can expect," says University of Waikato Professor of Environmental Planning Iain White.

It is also likely to exacerbate socio-economic and ethnic health inequalities, according to a report from Royal Society Te Aparangi released in October.

"If we think of the basic building blocks of health, such as our shelter, the air we breathe, water we drink and the food we eat, all will be affected by climate change," society president Professor Richard Bedford said.

He said New Zealand could expect:

  • More particulates and pollen causing increased respiratory problems
  • Contamination of drinking water supplies and increased toxic algal blooms
  • Increased food spoilage or crop failures

There could also be social and mental disruption if people had to relocate and repeated stresses could take a toll on mental health.

However it may already be too late to stop runaway global warning.  The Ministry for the Environment and Statistics New Zealand report warns that even if we took all possible precautions now, it would take "centuries" before some aspects of climate change levelled off.

"New Zealand's climate will continue to warm in the short term due to the cumulative effect of past emissions of greenhouse gases, such as carbon dioxide, which can persist in the atmosphere for thousands of years."

Dr Dean echoes this warning.

"We can expect 20-30cm of sea level rise by 2050 with reasonable certainty. However the amount of sea level rise we get at the end of the century is very much dependant on human emissions of greenhouse gases in the years ahead," he says.

"It is too late to prevent another 20cm of sea level rise."