If you asked most New Zealanders how they think climate change will affect them personally, my guess is not many would mention needing to boil their drinking water. But 1.5 million Aucklanders are currently on the cusp of a boil water notice which can be systemically linked back to human greenhouse gas emissions.
This is a revealing example of how climate change will hit us in ways we mightn’t expect – in fact, it already is. The impacts on our lives will be pervasive, cascading and sometimes difficult to attribute. And even for those of us fortunate enough to live in a wealthy developed country, we are less resilient to those impacts than we might like to believe.
Water, water, everywhere
Last week’s “Tasman Tempest” storm dumped enormous amounts of rain over several days throughout Northland, Auckland and Waikato. Auckland had its wettest day since 1959 on Friday.
Most significantly, the Upper Hunua above the city’s largest water catchment was hit by a one-in-100-year rainfall which caused landslips and erosion. The dams were contaminated with silt, leading to a 50% drop in the output from the Ardmore Water Treatment Plant. Aucklanders have been asked to reduce their daily water consumption by 20 litres until the end of March to avoid triggering a boil water notice.
While our thoughts are with Auckland, spare a thought for the residents of Levin, who had the exact same problem in early February and did need to boil their water for several days.
How are these situations connected to greenhouse gas emissions? Let’s step through the evidence.
The chain of causality
Greenhouse gases have that name because they trap heat radiating from the Earth’s surface and slow the rate it is lost to space, causing the planet to heat up. That much is basic physics. Since the industrial revolution, humans have been dumping more greenhouse gases into the atmosphere each year through burning of coal, oil and gas, and other activities. The scientific evidence has shown beyond reasonable doubt that the increase in greenhouse gases is the dominant cause of the global warming we have experienced.
All this is beyond serious dispute. Well, unless you are the person Donald Trump has picked to run the Environmental Protection Agency.
Last year was the hottest on record, again, and global average temperatures have increased by around 1°C since 1900. New Zealand has warmed by a similar amount.
Global warming affects rainfall patterns. As our Ministry for the Environment explains, rising temperatures lead to an increase in flood events:
“A warmer atmosphere increases the water-holding capacity of the air. This means that, assuming other factors remain the same, rainfall is likely to be more intense. The expected percentage increase in extreme rainfall is around 8 per cent per degree Celsius of temperature increase.”
Observations affirm the predictions: the intensity of extreme rainfall events has increased across most of the world at a rate similar to that predicted.
Framing the question right
So, did human-induced climate change cause the problem with Auckland’s water supply? Let’s look at that question another way. Every weather event is now happening against the backdrop of one degree of global warming. As NIWA meteorologist Ben Noll put it:
“While no one weather event is caused by climate change, all events are influenced by climate change since the atmosphere is now warmer and wetter than it was in the past. Climate change increases the likelihood of extreme rainfall, given the appropriate weather setup.”
It’s like if we knew someone who lived with a smoker and developed lung cancer, we would be wrong to assert with certainty that the smoking caused their illness. But we are absolutely correct to say that ‘second-hand smoke causes lung cancer’.
Similarly, greenhouse gas emissions cause climate change, which causes an increase in extreme rainfall events, which can cause contamination of water supplies. At risk of oversimplifying, dirty energy causes dirty weather, which can cause dirty water.
Preparing for cascading impacts
Climate change is already impacting our lives, and what Auckland is currently experiencing is an example of how the impacts can cascade. This will make adapting to climate change more difficult and costlier than we might think.
The complex interactions within and between the physical world, societies and economies will mean there are impacts we have not even imagined yet. Our interconnected world also means that impacts in far flung locations can and will affect us. Examples include droughts leading to spiking global wheat prices, or creating conditions for civil unrest as we have seen in Syria, leading to a humanitarian crisis which continues to reverberate throughout global politics.
We need to understand these risks better, so it is positive to see a new research project from the New Zealand Climate Change Research Institute aimed at doing exactly that. But frankly, in New Zealand we are only just beginning to grapple with the more certain and easier to understand impacts – such as sea level rise. The Auckland floods, the devastating Port Hills fires in Christchurch, and the looming threat to low-lying communities like South Dunedin ought to shake us out of our complacency. They should prompt central and local governments to act with more urgency on developing national and local plans to increase our resilience.
An ounce of prevention is worth a pound of cure
Of course, while we get to work on managing the unavoidable, the greatest issue we face with climate change is to avoid the unmanageable. We are looking forward to the release next week of a groundbreaking new report showing pathways for New Zealand to achieve zero net emissions in the second half of the century. If the world as a whole can achieve this, we might just have a chance of limiting global warming to a tolerable level. Stay tuned for coverage of this important report next week.