For years, 1.5°C has been the number hovering over every climate crisis conversation. It's been used as a line in the sand, or a limit governments promised to fight for. It's a catchy number that, somehow, became shorthand for whether we were still doing enough.
Now, a new United Nations climate report says the world is likely to cross this temperature threshold around 2030. So… what happens next?
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Why does 1.5°C matter?
The 1.5°C climate target is about keeping climate damage as limited as possible (reducing climate-related displacement, droughts, rising sea levels etc). The Paris Agreement committed signed nations to holding warming “well below” 2°C while pursuing efforts to keep it to 1.5°C.
In essence, climate change doesn’t suddenly become catastrophic at 1.5°C. It gets progressively worse with every additional increment beyond it. According to last year's World Climate Report, we’re already sitting at roughly 1.4°C of warming compared with pre-industrial levels. And around the world, rivers are running dangerously low, oceans are reaching record temperatures, glaciers are retreating (as we've recently seen in Nepal) and extreme weather is becoming more destructive.
For our Pacific Island neighbours, the stakes are even higher, as rising seas threaten homes, land and entire ways of life.
Does crossing 1.5°C mean we’ve lost?
Not necessarily (and this is the part worth holding onto). Scientists increasingly talk about a potential “overshoot”: temperatures could temporarily rise above 1.5°C before falling again later this century.
If countries rapidly slash fossil fuel use, accelerate clean energy and remove significant amounts of carbon dioxide from the atmosphere, peak warming could potentially be limited to around 1.8°C before temperatures return towards 1.5°C.
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What happens if we keep warming?
Every tenth of a degree matters. Higher temperatures mean greater risks to food systems, ecosystems, coastlines and human health. Each increment also increase the possibility of triggering tipping points – changes such as major ice-sheet loss or shifts in ocean circulation that could be extremely difficult, if not impossible, to reverse on human timescales.
Fortunately, progress is happening. Solar power, electric vehicles and electrification have accelerated dramatically since the Paris Agreement. The world is no longer heading towards some of the most extreme warming scenarios once considered possible. But emissions still aren’t falling fast enough.
What can we actually do about it right now?
Perhaps the question is no longer whether we can “save” 1.5°C in the way we once imagined, but how much damage we can prevent.
That means finding ways to live more sustainably: moving faster on renewables, cutting fossil fuel use, protecting vulnerable communities and investing in carbon removal – while making sure developing countries aren’t left carrying the cost.
Australia will have a particularly interesting role to play as it leads international climate negotiations at COP31 later this year, too.
