NAIROBI, Sept 2 — Global temperatures are likely to exceed 1.5°C within the next few years, bringing increasingly dangerous climate risks and impacts. However, it remains possible to reverse the rise and achieve the goals of the Paris Agreement, according to a new UN Environment Programme (UNEP) report.
The Limiting Overshoot report identifies an “overshoot, peak and decline” pathway as the best remaining option to limit the magnitude and duration of warming beyond 1.5°C and return below the threshold as quickly as possible.
“This summer’s scorching heat, raging wildfires and deadly floods are a warning of what lies ahead. We must make the overshoot above 1.5 degrees as small and short as possible. That demands an overshoot of ambition” said UN Secretary-General Antőnio Guterres.
This pathway would minimize peak temperature rise through immediate and sustained cuts to greenhouse gas emissions, including methane, on the road to net-zero, and bring down temperatures through long-term net-negative emissions, with carefully governed Carbon Dioxide Removal (CDR) – the process of removing carbon from the air and storing it through afforestation or other means – an essential part of the mix.
At the same time, following this pathway would involve adaptation actions that reduce vulnerability to the current, expected and unexpected impacts of climate change on societies, communities and economies – although there will likely be limits to adaptation and irreversible impacts, especially if peak temperatures are not minimized. The report stresses such a pathway would reduce risks and impacts, make adaptation less difficult and expensive, and increase the chances of lowering temperatures.
“There are no good outcomes if we remain above 1.5°C. Across the globe, extreme heatwaves are already proving that climate impacts will strike faster, hit harder, and last longer – costing more lives and causing deeper disruption,” said Inger Andersen, Executive Director of UNEP. “Now is the time we must double down on climate action. We can – and must – get on the right path. By cutting greenhouse gas emissions, strengthening resilience and adaptation, and ensuring exceedance of 1.5°C is as small and short as possible.”
Devastating impacts
The most optimistic scenario will see temperature rise peak at 1.8°C above pre-industrial levels, above the goal of limiting warming to 1.5°C set by the Paris Agreement. Most other scenarios predict higher peaks.
Above 1.5°C, risks and impacts will intensify with every extra fraction of a degree and every year. Anticipated impacts include intensified extreme weather, ecosystem loss, and submersion of Small Island Developing States and low-lying coastal cities. Severe damage to human health, food security, water supplies, nature, cities, infrastructure, and economies is expected.
The report warns that the likelihood of crossing irreversible tipping points increases with the magnitude and duration of higher temperatures. These include the destabilization of major ice sheets, degradation of the Amazon rainforest and disruption of the Atlantic Meridional Overturning Circulation (the system of currents that moves warm surface water north and cold deep water south, playing a key role in regulating the climate). Some impacts may emerge abruptly, while others will accumulate over time.
Considering the scale of the risks and the co-benefits of climate interventions such as a rapid transition away from fossil fuels to renewable energy – improving air quality and public health, lowering energy costs and increasing access to electricity – the report urges accelerated, collective and global action to get on an overshoot, peak and decline pathway. How quickly and strongly this action happens will define the shape and trajectory of the pathway.
Conditions for success
Strong political commitment, effective policies, inclusive governance and adequate financing are key to tackling climate change, while equity and justice must guide all responses. Countries with greater responsibility for climate change should lead with faster and more ambitious action.
The report also stresses that mitigation and adaptation must progress together and respond to emerging risks. Measures that address both, such as nature-based cooling solutions, should be prioritised. Adaptation efforts already underway provide a foundation, but they must become more transformative and flexible to address rapidly emerging and increasingly unpredictable risks.
Responding to a changed future
Years of inaction mean that even if a return to below 1.5°C is secured, irreversible losses and permanently changed conditions are certain. Many communities may be forced to relocate or change livelihoods, while societies will face the challenge of re-adjustment. This raises issues of justice, power, and political legitimacy, which will require new, inclusive governance arrangements to resolve difficult issues.
This report is a reminder that an overshoot, peak and decline pathway is a next generation climate frontier, but one which cannot be left unattended to for the next generation to tackle. Immediate action is required for such a pathway to remain possible.