The multinational goal to limit global temperature increase to 1.5°C, identified as the threshold to avoid the most significant impacts of climate change, is now out of reach, according to a new report released by the UN Environment Programme (UNEP), which puts a best-case scenario now at 1.8°C.

Despite expectations to surpass the 1.5°C threshold, however, the report, “Limiting Overshoot,” maintains limiting long-term average warming to 1.5°C as the global goal, identifying an “overshoot, peak and decline” pathway, returning to the target level through achieving net negative GHG emissions, as the “best remaining option.”

The new report comes a decade after the adoption of the Paris Agreement by 195 countries in 2015, which included a main goal is to limit the global temperature increase in this century to below 2°C above pre-industrial levels, and to work toward limiting the increase to 1.5°C. There are currently 194 parties to the agreement, after the Trump administration formally removed the U.S. earlier this year.

According to the new UN report, while the international community has made progress on climate change since the adoption of the Paris Agreement, with full implementation of current Nationally Determined Contributions (NDCs), if achieved, projected to enable a slight decline from record GHG emissions in 2030, global action to cut emissions has not been enough to avoid crossing the 1.5°C threshold. The report cites estimates that predict that median projected global warming reaches around 2.6°C by 2100 under current policies, and notes that “even under one of UNEP’s most optimistic scenarios, which assumes implementation of all NDCs and long-term net zero targets, central global warming estimates peak at around 1.8°C.”

According to the UNEP, risks and impacts intensify with every fraction of a degree above 1.5°C, with anticipated impacts including intensified extreme weather, ecosystem loss, and submersion of Small Island Developing States and low-lying coastal cities, with expectations of damage to human health, food security, water supplies, nature, cities, infrastructure, and economies. The report also notes that the risk of hitting irreversible tipping points increases with prolonged and greater temperature increases.

Inger Andersen, Executive Director of UNEP, said:

“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.”

The report presents an “overshoot, peak and decline pathway” to hold temperatures at the lowest possible level and then bring it down by the end of the century, as the best remaining option, while also noting a need to take adaptation actions to reduce vulnerability to the anticipated impacts of climate change. The report spells out three key stages for the pathway, including the “immediate response phase,” of deep emissions cuts – including to methane and other short-lived emissions – and adoption of measures to protect the most vulnerable to climate change impacts, the “coping and containment phase” as temperatures peak, including advancing deep decarbonization and achieving at least net zero emissions while managing severe impacts and risks, and the “long-term resilience phase,” to deliver sustained net negative CO2 emissions.

The report also highlights a need for Carbon Dioxide Removal (CDR) solutions to support the achievement of net negative emissions, but notes a series of limitations and potential tradeoffs to scaling CDR sufficiently, such as uncertainty in areas of scalability, and durability, limitations in geological storage, and risks to biodiversity and food security.

Andersen added:

“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.”

Click here to access the report.