A new United Nations assessment confirms that the global community has fallen short of its objective to cap warming at 1.5 degrees Celsius above preindustrial levels. The report outlines a challenging new framework for addressing climate change that will chart an uncertain course for the future.
Ten years ago, the majority of the world’s nations convened in Paris to commit to limiting global temperature increases to “well below” two degrees Celsius, with a more ambitious aspiration of reaching 1.5 degrees Celsius, equivalent to 2.7 degrees Fahrenheit.
However, the 141-page UN report released on Wednesday warns that this threshold will certainly be exceeded. It urges the international community to concentrate on mitigating the degree of “overshoot” and eventually restoring global temperatures to safer levels.
Although renewable energy technologies like wind and solar have advanced significantly, nations continue to combust oil, gas, and coal, emitting carbon dioxide into the atmosphere and trapping the sun’s heat. Consequently, average global temperatures have risen by approximately 1.4 degrees Celsius. The impacts of this warming are now universally felt, manifesting as intensifying heatwaves, droughts, floods, wildfires, and other severe threats to humans, wildlife, and ecosystems.
The strategy proposed in the UN report presents monumental challenges, as it necessitates removing carbon dioxide from the atmosphere on a massive scale. Achieving this could require covering vast land areas with forests or depending on unproven technologies designed to extract carbon from the air, which have yet to demonstrate efficacy at a significant scale.
Under this scenario, the planet would continue to warm for the foreseeable future, and it would take decades or even centuries for temperatures to revert to current levels. Furthermore, certain alterations—such as glacial melt and sea-level rise—would be virtually irreversible.
“This is by no means an acceptable or preferred pathway,” the UN stated in its Wednesday report. “It is simply the best remaining option.”
However, even this contingency plan demands a level of climate ambition and substantial greenhouse gas reductions that have long remained elusive. Compounding these challenges, the Trump administration has withdrawn the United States—the largest historical emitter of greenhouse gases—from the global climate effort and weakened domestic environmental policies.
Based on current national climate policies and prevailing trends, the planet is projected to warm by 2.6 degrees Celsius, or 4.7 degrees Fahrenheit, by the end of the century.
“As long as we lack the necessary political will, we will continue to surpass every target we establish. That is the danger,” remarked Michael Mann, a professor of earth and environmental science at the University of Pennsylvania who was not involved in the report.
Dr. Mann observed that even at present warming levels, “dangerous and catastrophic climate change is already here,” citing last week’s fatal glacial collapse and flooding in Nepal.
UN Secretary-General António Guterres had previously acknowledged that the 1.5-degree Celsius threshold—the most ambitious element of the Paris Agreement—would inevitably be exceeded. The new report makes clear just how narrow the margin is for the overshoot plan to be viable.
Specifically, to bring temperatures back to the 1.5-degree mark this century, peak global warming would have to be constrained to 1.8 degrees Celsius (3.2 degrees Fahrenheit) above preindustrial times. Most scientists consider this highly unlikely.
Subsequently, nations would need to escalate an enormous initiative to remove carbon dioxide from the atmosphere. Even under the most optimistic projections, a single decade of warming could require approximately 50 years to reverse.
Glen Peters, a senior researcher at the CICERO Center for International Climate Research in Norway, noted that the concept of lowering temperatures might sound as simple as “planting a billion trees” to absorb carbon dioxide. However, landmasses larger than entire American states would need to be reforested. This could spark conflicts with agriculture. Higher temperatures could impede forest growth. And naturally, wildfires could thwart progress.
“At any scale, you are bound to encounter some sort of problem,” said Dr. Peters, who was not involved in the report.
The report acknowledges that while technology-based solutions will be necessary, it notes that current industrial capacity to extract carbon dioxide from the atmosphere is extremely limited. This technology has long been controversial, largely because the fossil fuel industry has promoted it as a means to continue utilizing their products. Throughout the industrial age, the combustion of fossil fuels has released immense quantities of heat-trapping carbon dioxide into the atmosphere.
Climate Analytics, a Berlin-based climate science and policy institute, stated that the UN report risked “being a call to apathy,” criticizing it for not more explicitly addressing the necessity to phase out fossil fuels. Although countries committed to transitioning away from oil, gas, and coal at a 2023 international climate summit, carbon emissions continue to rise.
The UN report predicts that average global temperatures will surpass 1.5 degrees Celsius within “the next few years.” At that level of warming, “there are no good outcomes,” stated Inger Andersen, executive director of the UN Environment Program.
The report warns that already frequent extreme weather events, such as heatwaves and floods, will intensify, alongside the melting of glaciers, rising sea levels, and the bleaching of coral reefs. Furthermore, there is a risk of alterations to crucial global systems, such as the weakening or collapse of ocean currents that transport heat northward from the tropics, which hold the potential to “reshape the world forever.”
