Warning signals loud and clear

The climate stripes (shown here for Dunedin) are a compelling way to look at how temperature has changed over the past 100 years or so. They show how average annual temperature has changed, with darker blue colours indicating cooler conditions, and red for warmer years. The story is similar around the world: decades of variation around a relatively stable average, followed by irregular — but sustained — warming.

The warming trend for Dunedin has actually been slightly lower than many parts of the world, at least until recent years. The moderating influence of the surrounding seas is important here, compared with inland areas that warm up more rapidly. Unfortunately, that’s no reason for us to relax. For instance, research indicates that climate change made the June 2015 floods in Dunedin worse than they would otherwise have been. Climate change impacts elsewhere in the world affect us too, such as through food production and distribution networks.

Motivated by these clear warming signals, a ‘‘climate emergency’’ was declared by the New Zealand government back in December 2020, with many other governments making similar judgements around that time. However, our actions since then have not often matched the urgency of the situation. Carbon dioxide levels in the atmosphere have continued to rise, from 413ppm in December 2020 to 429ppm now, compared with a pre-industrial background level of around 280ppm.

Correspondingly, the past three years have been the warmest in the global instrumental record, which stretches back to the mid-1800s. In fact, the recent World Meteorological Organisation report on the state of the climate in 2025 shows that the past 11 years are the warmest in this record, with the Earth system increasingly storing more energy than it loses.

In other words, despite some great initiatives around the world at cutting our emissions, collectively we are not doing enough. In fact, we are perilously close to exceeding the 1.5°C warming threshold, with 2024 slightly above this point, and 2023 and 2025 hovering just below.

By itself, three years in the vicinity of this threshold does not mean it has been breached — we are more concerned with longer-term averages in terms of recognising major changes to the climate system. However, recent research suggests that we are on the cusp of breaching. Analyses of when lower thresholds of warming were breached show that they start similarly: some years alternating just above or below the threshold, followed by most, then all, years above it. Time will tell exactly what happens, but for now, the warning signals are loud and clear.

Why does it matter whether we pass 1.5°C of warming? Well, the situation doesn’t suddenly switch from benign to dangerous. However, the likelihood of major impacts increase substantially the further and longer we go above 1.5°C. Critically, these include ‘‘tipping points’’ beyond which recovery may not be possible for generations — such as loss of whole ecosystems, changes to ocean circulation or polar ice loss.

If, as looks increasingly likely, we do exceed 1.5°C warming, then what next? Really, this depends on what we do in the years to come ... what our ‘‘overshoot’’ pathway looks like. Do we rapidly reduce emissions to stabilise climate at (or even below) 1.5°C? Or do we continue with our current patchwork of efforts that come and go with changing governments?

There is no easy option here — changing behaviour is not simple, neither are root-and-branch reforms of agricultural emissions or how we generate and use energy. However, the implications of these choices for the planet are increasingly clear. We are indeed facing a climate emergency, and one that will only become more dramatic without urgent further action. As the current oil crisis demonstrates, greater movement towards renewable energy and electrification brings widespread benefits beyond just our climate. Fossil fuels are increasingly neither a cheap nor a reliable option any more.

• Daniel Kingston is an associate professor at the University of Otago School of Geography working in the field of hydroclimatology — the inter-relationships between the climate system and hydrological cycle — and a member of He Kaupapa Hononga, Otago’s Climate Change Research Network .