In 2022, analysis by the World Meteorological Organisation indicated a 50% likelihood that global average temperatures would rise 1.5°C above pre-industrial levels within the next 5 years. Four years later, the latest report by the United Nations Environment Programme demonstrates that the 1.5°C threshold is now very likely to be exceeded, which is known as “overshoot”.
1.5°C is a legally binding threshold that came out of the landmark climate policy known as the Paris Agreement, launched at the 2015 Conference of the Parties (COP) in Paris. It was spearheaded by many, and it will become the focus of litigation in the coming years. Litigation is an important phase in many social movements and can cause meaningful change.
The threshold of 1.5°C represented the most optimistic limit countries hoped they could achieve. In recent years, we have moved into a phase of the Paris Agreement known as the global stocktake, where countries outline how much carbon and other greenhouse gas emissions they produce.
At present, countries globally have reduced emissions enough to currently limit warming to 2.6°C to 2.9°C, which is clearly not enough. For every 0.1°C above 1.5°C, we push the natural world closer to irreversible tipping points, such as the the Atlantic Meridional Overturning Circulation (AMOC), where large-scale melting of the Greenland ice sheet causes cold, fresh water to flow rapidly into the North Atlantic. This could cause the AMOC to shut down, resulting in significant cooling in Europe and North America and potentially altering large-scale global weather patterns. Worryingly, we do not know enough about these tipping points.
Scientists use climate models —which we use to project future and past climates — to consider a range of scenarios. Some of the most optimistic scenarios include technologies that we do not have. Current climate policy is already becoming more “technology” focused. We have investment in a range of carbon capture methods. We have carbon markets to trade carbon, but in some cases, trees planted for carbon capture have regularly been cut down for the timber industry, meaning they do not capture the carbon needed.
We have a focus on AI in several areas, including early warning systems, which have been shown to be one of the most cost-effective ways to reduce the impact of extreme weather. But there is a limit to the capability of all models, and there is a rising cost associated with the water and energy use of data centres, which remains largely ungoverned.
Another area that is growing is geoengineering. This is a topic that is used in combination with an overshoot scenario to artificially cool the planet. The most frequently considered type is solar modification; where aerosols are sprayed into the sky to reflect sunlight, thereby having a cooling effect.
A report by the Royal Society showed that, for solar modification to be effective, 1,500 planes would need to take off in the first year, and the process would need to be harmonised across the globe. If this does not occur, monsoon cycles could be altered, pushing whole regions into potential famine. It is also unclear what the climate would default to if solar modification stopped.
1.5°C has always drawn criticism because it can depoliticise the climate crisis, and this focus on technology as a silver bullet, unless used in an ethical way, can do the same. It can be used to draw our attention away from the fundamental issue that the current way of living was never sustainable and has created large inequalities in how different people live, both within and between countries, especially those in the Global South.
This is a thread that also runs through climate justice, where climate becomes a story about how we can improve the world to become more just and use resources equitably and sustainably. This theme will be important as we head into a potential overshoot world.
Another emerging argument is degrowth. This builds on the work of the planetary boundaries, which are nine boundaries beyond which irreversible damage can be done to parts of the Earth’s system. Degrowth suggests that we currently use more energy than can be sustained and need to reduce the amount of energy we use. However, this does not give enough focus to climate inequities.
1.5°C was important – it and the COP process reduced emissions to a degree and started important conversations. It also fuelled a protest stage of the climate movement. We could suggest that this was all it was designed to achieve: starting a conversation that led to a reduction in emissions. But it wasn’t enough.
The steps that happen next are important, and there is promise. The Santa Marta Conference started a process in which countries felt renewed energy around climate and there has been progress on climate and health topics. Climate education and communication can be used as effective tools against the misinformation that will emerge as we head into an overshoot world. It is important that we continue to have a just transition and head towards climate transformation.
