The climate is changing because of human activities.  It also varies naturally.  How do we sort out what is going on and why and use the information for better planning for the future?  Indeed, climate science is vital to New Zealand if the country is to have the information needed to adapt to climate change, but the necessary research and information is threatened.

I live in the Auckland area and experienced the January 27, 2023 rain bomb (we got 280 millimetres in one day in my area on the North Shore) – less than three weeks later came Cyclone Gabrielle.  It was evident to me that NZ was insufficiently prepared for the increasing climate extremes with climate change.  Globally, 2023 is the warmest year on record at about 1.4C above pre-industrial values.

But how much of an event such as Gabrielle is chance – random acts of weather – and how much is pre-determined by climate changes caused by humans? 

There is always a lot of natural variability occurring with weather and interactions of the atmosphere with the oceans, land, and cryosphere.  El Niño is a natural climate variation and is inherently a coupled ocean-atmosphere phenomenon: that is, the ocean and atmosphere working in tandem to cause fluctuations in the climate. El Niño is a warming of the tropical Pacific Ocean surface, so that there are above-average sea surface temperatures, while La Niña is a cooling of the same region with below-average temperatures. Both change the global atmospheric circulation, which influences patterns of weather systems and temperature and precipitation around the world.

As these phenomena set up, they help us predict (with some uncertainty) patterns of weather for up to a year in advance, but they are not predictable for longer times.  Other facets of climate are predictable for much longer, especially human-induced climate change.  Even so, all weather events are embedded in the changing environment, and consequently weather includes elements of both the random and pre-determined.  Decision makers need to understand this and plan in ways that accommodate both.

On March 20 this year, Newsroom featured an article about how local councils are stumbling forward in planning for the future, making use of completely inappropriate projections of the future climate.  These were not predictions but possible “what if” scenarios if humans continued to emit carbon dioxide and other pollutants into the atmosphere at various rates. As Newsroom reported, nine regional councils and eight district councils commissioned Niwa to prepare regional climate projections in the past few years. Some of those, like Auckland, are working those temperatures into their decision-making.

These scenarios, developed by the Intergovernmental Panel on Climate Change for planning purposes, represent possible emissions, as distinct from likely emissions. Many climate models have been used to make projections of future weather and all have uncertainties, as well as the uncertainties in the prescribed emissions that depend on unpredictable human behaviour. Which models are most credible (and useful) in the New Zealand context need to include assessments that are specific to our region.

In other words, if councils hope to plan for the future, they need access to long-term sound continuous research that is specific to New Zealand. Yet there is inadequate work in that area in New Zealand, including at Niwa.  Too much climate research funding is episodic, not continuous. As a climate change scientist, I see the urgent need for sustained funding to improve research and proper assessments of the best estimates of what will likely happen in the future, including the extremes. Translating what we are adapting to into useful information for councils and decision makers of all kinds is a major research task and should not (and cannot) be done by councils alone.

How big is the human component?

The changing flows of energy through the climate system suggest that it is less than 0.5 percent of the natural flow of energy from the Sun that ultimately radiates back to space. The energy imbalance arises from the increases in carbon dioxide and other greenhouse gases in the atmosphere that change atmospheric composition and interfere with the natural flows and produce heating.  However, the imbalance is very large compared with direct human heating from all sources and it accumulates. 

The main memory of the accumulated energy imbalance is the oceans, which are warmer by nearly 1C, and the atmosphere above the oceans is warmer and moister as a result; the atmospheric water vapour over the oceans has increased by about 10 percent since the 1970s.  As storms reach out about four times the radius of their precipitating area to grab moisture and bring it into the storm, it rains harder. 

There is always a drought somewhere, and the main cause of where large-scale droughts occur is El Niño cycles.  Water is the great air conditioner of the planet and if there is water on the surface of the land, extra heat will largely go into evaporation. But when the conditions on land are dry, the heat dries out soils and vegetation raising temperatures further, increasing risk of wildfire. In drought the effects accumulate. 

Human-induced climate change occurs on long time scales: 20 years is a reasonable estimate for noticeable significant changes, which is when it becomes clear that there is an underlying new normal of a warmer moister environment that all weather events are exposed to. A warming climate exacerbates natural events (storms and droughts), leading to greater extremes. It is essential to track and understand the extremes and the integrated effects on plants, forests, fisheries, water resources, farming, and cities. It means discerning the causes of the anomalous conditions, and the roles of climate change (and thus likely to continue), El Niño, random weather systems, and how these interact with each other. If we can model these in a computer then scientists are in a position to make better forecasts on multiple time scales and translate this into useful information for decision makers of all kinds, including councils. 

We don’t have that capability in New Zealand, and as I’ve argued in Nature magazine, developing it requires sustained funding and commitments to generating and developing products for dissemination.  Climate change is a major long-term threat that requires not only mitigation and adaptation, but information!  

This article is also published on Newsroom. illuminem Voices is a democratic space presenting the thoughts and opinions of leading Sustainability & Energy writers, their opinions do not necessarily represent those of illuminem.