A Hard Rain’s A-Gonna Fall

There is insight in the stories that numbers can tell, and for some of us that insight offers a sense of calm in turbulent times. Which may be why in the midst of this year’s rains I started making graphs of the accumulated rainfall and how it stacked up against previous years.

Following the Anniversary Weekend floods in January, Cyclone Gabrielle a couple of weeks later and the “May 9 Auckland Storm Event” I put this one together and posted it to Twitter:


The specific data is for Auckland Airport and I snagged it from NIWA’s Cliflo site. The accumulated rainfall for each of the sixty previous years is in grey and 2023 is shown in blue, although it has no need for special labelling to stand out.

I updated it a couple of times over the course of the year and it has circulated to the point that people I don’t know have recently been asking me if we have cracked the annual record. And I can report that as of yesterday, 1489.8 mm of rain has fallen at the airport which beat the previous record by a couple of millimetres. So with two months still to go in the year the plot now looks like this:

Rainfall for the last 60 years, with 2023 (so far) in blue.

We are likely rolling into an El Nino summer, which is hotter and drier than normal so it is not clear how far over the record we will find ourselves by Christmas. However, for Aucklanders it will be certainly be “far enough”.

In fact, our current rainy spell didn’t start on January 1, but in mid 2022. If you plot the total rainfall over the previous year for each day in the last 60 years this is the result:

A plot of the accumulated 365 day rainfall, over the previous 60 years.

It is very clear that we have just lived through an unusual time. An average year in Auckland sees a bit more than a metre of rain but but we managed 2.1 metres of rain in a 365 day stretch, and that really is different from what we expect.

The subtext to this is of course “climate change”. That said, the attribution of single, unusual events to the changing climate is a complex and challenging task and all I am doing is taking some numbers and turning them into pictures. I am an astrophysicist* so I’ll stay in my lane and offer these plots as an interesting commentary on a soggy year and refrain from personally drawing deeper conclusions, although others certainly can.

But it has been a very odd year. Moreover, it is the sort of odd year that climate scientists predict will become increasingly normal for Auckland if the world continues to warm.

A graph is just one type of picture of what a lot of rain looks like and most of us will have other pictures that can be tied to specific moments on the plots. The day before the Auckland Anniversary weekend floods we had a visit from an old university friend and his family. It had been a while, but he is one of those people with whom you can pick up the threads as if only days had passed, even though it had been decades. They were in Auckland to see the Elton John concert but instead of an encore of Yellow Brick Road, they sent us a video shot from the bus carrying them back to their hotel from the canceled concert.

A phrase that circulates on social media is that “climate change will manifest as a series of disasters viewed through phones with footage that gets closer and closer to where you live until you’re the one filming it.” For me and for Auckland it is more than close enough.

* Astrophysicist, particle physicist and astronomer, depending on what day of the week it is.

Header image via MetService.