UN says that we will overshoot the 1.5°C climate threshold: where to go from here?

At the start of the month a landmark publication from the UN’s Environmental Programme confirmed what climate scientists have been warning about for a number of years. It is now widely assessed that exceeding the threshold of 1.5°C degrees of global warming is unavoidable. This is cause for concern, because the IPCC tells us that past this threshold, the earth systems can become deregulated. This increases the likelihood of  ‘sudden, cascading and irreversible’ climate risks that can reach catastrophic scales. Recent extreme weather events around the world have already demonstrated how climate impacts can cascade onto people’s livelihoods and communities.

But, while this shocking headline may bring climate dread and anxiety, it does not mean by any sense that our fight against climate change is over – quite the opposite, we need to intensify our efforts. We must continue taking meaningful action for people, the planet and our future.

What does ‘overshoot’ mean?

Around 100 countries at the UNFCCC Conference in 2009 called for warming to be limited to below 1.5°C relative to pre-industrial levels. This was agreed formally in the Paris Agreement, a legally binding climate pact which states that warming should be limited to ‘well below’ 2°C with the threshold of 1.5°C used as a major figure. Climate models since then have shown that limiting warming to 1.5°C may include an overshoot window; rather than temperatures stopping at 1.5°C, warming could peak above this level for a brief period of time and by a moderate margin (e.g. 0.1°C) before eventually declining as greenhouse gas emissions are reduced.

Figure 1: Reversing Overshoot. Source

The UN Environment Programme’s new report Limiting Overshoot makes clear that this threshold will be surpassed, so focus is turning to how the future trajectory can be lowered. Although a breach of the Paris Agreement target would require average annual temperatures to be above 1.5°C for at least 20 consecutive years, the fact that we are increasingly seeing individual years surpass this threshold implies that we are getting closer – especially considering that once the threshold is breached, the temperature trend tends to be upwards.

Why this could be dangerous

The UN report, as well as IPCC models, show that any duration of time spent above 1.5°C allows climate risks to multiply. One of the greatest concerns is that higher temperatures increase the likelihood of crossing climate tipping points. These are large-scale, potentially irreversible changes to Earth systems, including the ice sheets, the Atlantic Meridional Overturning Circulation (AMOC) and the Amazon rainforest. Once triggered, these systems may not simply return to their previous state if temperatures later decline, and may accelerate further warming out of human control.

Climate science researchers find that 1.5°C is a danger point for many of these tipping systems. Alpine glaciers, for example, may not be able to reform after summer melting at this high temperature. This will leave long-term impacts on the local ecosystem, as well as wider effects on sea levels and ocean currents.

A more prolonged overshoot could also increase pressure on food and water supplies. Projections indicate significant declines in global food production under severe climate change, while at 2°C many human and natural systems would face substantially greater stress. This is why every fraction of a degree matters.

Furthermore, environmental crises compound with one another, and with most planetary boundaries being breached, and biosphere integrity in particular having world-shaking consequences, global warming reaching into overshoot territory is bad news.

How to act in the face of a possible catastrophe?

Climate communications rooted in fear and alarmism can overwhelm people, reduce their sense of agency and lead to disengagement when not paired with clear pathways for action. However, the reasons for concern stated by the IPCC and the IFoA certainly ring the alarm bells.

We therefore need to focus on clear pathways for action. Climate scientists have laid out a number of pathways to reduce our overshoot. They are simple in principle but require dedicated action and policy. Transitioning away from fossil fuels, and using low-carbon energy instead. Reducing meat and dairy products. Improving energy and resource efficiency and circularity. And then, for the net negative portion of the equation, restoring ecosystems, protect carbon sinks like peatland and rivers to scale carbon dioxide removal technologies. Perhaps this still won’t be enough in the context of an overshoot, and we will need measures complementary to reaching net zero in time.

One thing is certain, as is demonstrated by this report – the more we wait, the harder change becomes. Every fraction of a degree counts, and overshoot only makes action more urgent. Every fraction of a degree makes it harder to go back down to safe levels, and every increment away from those safe levels comes with an increased level of risk.

While the headline is alarming, it simply confirms an outcome that has been speculated for a number of years, tied to insufficient climate action. The key takeaway is that the lower the peak temperature, and the shorter the duration of overshoot, the lower the risks faced by people and ecosystems. Limiting the rise to 1.5°C is a target rather than an end point, 1.5°C is far better than 1.6°C, which is far better than 1.7°C, and so on. Additionally, with the right level of action, it is possible to come back down to under 1.5°C of warming – as long as everyone plays their part.

Mitigation and adaption

This report strengthens the argument that climate governance should move from mitigation-only approaches to include adaptation. While we must continue to transition towards fossil-free energy solutions and net zero practices, for many people, climate impacts are already a stark reality, as exemplified by the recent tragedy in Nepal – meaning that where possible, adaptation is needed urgently. Communities are experiencing extreme heat, flooding, drought and changing ecosystems regardless of whether global warming is measured at 1.4°C, 1.5°C or 2°C. Mitigation is therefore no longer enough in places where the effects are being felt.

Adaptation measures can also have the benefit of connecting climate change to the things people experience and care about: clean air, safe water, healthy ecosystems, secure homes, and reliable energy. Building a ‘resilient’ community provides immediate social benefits as well as building capacity for adaptation.  Studies have shown that communities with stronger infrastructure, resources, social networks and support are better equipped to cope with climate hazards.

 Successful transition planning should include reducing impacts on the environment, and adapting to the environmental crisis. Many of the solutions can be replicated: renewable energy tends to better resist global shocks; plant-based diets may be able to help resist pressures on agriculture; reversible heat pumps can reduce emissions while helping cope with extreme heat waves.

Amplifying solutions

In the face of climate dread, collaboration and learning from successful approaches can provide concrete examples of pathways forward.

There are already some reasons for optimism. Climate projections have changed significantly as governments, businesses and communities have adopted new policies and technologies. Although future scenarios remain bleak if current policy measures are pursued (as we are heading to 2.7°C warming), climate action has led to the highest-emissions scenarios to be regarded as unlikely. This is an important demonstration of how important international policy will be to mitigate overshoot, and that true progress can be achieved.

Spain’s transition away from coal provides one example of how climate action can be combined with wider community needs. As coal mines closed, the Spanish government committed €250 million to affected mining communities following months of research and negotiation. The agreement included early retirement for older miners, retraining for green jobs, investment in local economies and environmental restoration.

The ministry of Ecological Transitions in Spain wished to make this deal an example of good practice. For businesses and membership organisations, this provides an important reminder that climate action is not separate from realities of employment, skills, and community wellbeing. A successful transition needs to consider all of these dimensions together.

As well as mitigating future emissions from coal, this project also adapted the local community for the future, building social infrastructure and upskilling workers through investment. Adaptation can be an investment in the future rather than simply a response to disaster. Preparing before hazards occur can reduce disruption, protect livelihoods and avoid the much greater costs associated with responding after the event.

Join CAFA

Associations and membership organisations have a unique role to play in building climate resilience and preparing for the coming change. They bring together people and organisations facing shared challenges, creating opportunities to exchange knowledge and coordinate transitions across a sector.

This is particularly valuable when climate risks feel complex or uncertain. Associations can help translate emerging science and policy into practical guidance for their members, while creating space to share what is working and where further support is needed. They can also use their collective voice to highlight the needs of their sector and advocate for the conditions that make meaningful action possible at industrial, business or professional level.

CAFA helps associations and member organisations lead their sector towards net zero, offering support, access to our network and bespoke guidance. Join today.