The number ‘1.5’ comes up a lot when talking about climate change.

One reason for this is the Paris Agreement.

Ratified ten years ago this year, the Paris Agreement is a legally binding international treaty in which more than 190 nations committed to take action to limit global warming.

Why 1.5°C?

The Paris Agreement aims to limit warming to well below 2°C while aiming for 1.5°C in order to avoid dangerous climate change. 

The difference in effects between the two limits is significant.  

The Intergovernmental Panel on Climate Change, the United Nations body for assessing climate change science, said in its most recent assessment report that ‘every increment of global warming will intensify multiple and concurrent hazards’. 

Compared to 1.5°C, they said, global warming of 2°C would lead to more extreme weather, greater extinction rates and damage to more ecosystems. 

Warming of 1.6°C or greater would probably reduce the amount of food many farms could grow, while warming of 1.7°C would likely result in more days where heat and humidity pose risks to human health.

In 2025, in response to a UN resolution spearheaded by Pacific island nation Vanuatu, the International Court of Justice advised that climate change was an ‘existential threat’ that will ‘escalate’ if global warming continues. 

What if the world overshoots 1.5°C of warming?

While each small increase in warming will intensify the effects of climate change, the opposite is also true. 

Every fraction of a degree matters.

Keeping global warming to 1.51°C is better for people on planet earth than 1.52°C, which is better than 1.53°C, and so forth. 

While the world is currently not on track to reach the Paris goals, rapid action could see warming return below 1.5°C by the end of the century, following an overshoot pathway as described at the start of this article.

By limiting how long temperatures overshoot 1.5°C and by how much, the world can still avoid the worst effects of climate change. 

What will it take to limit 1.5°C overshoot? 

The amount and duration of any 1.5°C overshoot will be decided by what humanity does next.

Limiting 1.5°C overshoot requires cutting greenhouse gas emissions and growing the amount of carbon dioxide removed from the atmosphere (through tree planting and marine ecosystem restoration, for example). 

Climateworks Centre has modelled least-cost pathways to significantly reduce Australia’s greenhouse gas emissions and identified what solutions are available in all sectors of the economy.

We have also identified how Indonesia, Vietnam and other ASEAN nations can reduce emissions from high-emitting industries such as steel, textiles and plastics manufacturing through renewable energy and electrification. 

And we have worked to leverage ocean-based solutions for both emissions reduction and carbon dioxide removal.

The solutions are known, the technology is ready.

The challenge now is for governments, businesses and investors to work together to implement these solutions quickly, at scale.