In what they call “a code red for humanity,” the world’s leading climate scientists on Monday delivered their starkest warning yet about the deepening climate emergency, with some of the changes already set in motion forecasted to be “irreversible” for centuries to come.

A highly anticipated report by the UN’s climate panel warns that limiting global warming to close to 1.5 degrees Celsius or even 2 degrees Celsius above pre-industrial levels “will be beyond reach” in the next two decades without immediate, rapid and large-scale reductions in greenhouse gas emissions.

The 1.5 degrees Celsius threshold is a crucial global target because beyond this level, so-called tipping points become more likely. Tipping points refer to an irreversible change in the climate system, locking in further global heating.

At 2 degrees Celsius of global warming, the report says heat extremes would often reach critical thresholds for agriculture and human health.

“The message of the UN climate report cannot be misunderstood: the consequences of climate change are stronger and faster than we thought before,” says Christian Eriksen, Bellona’s head of policy and research. “The changes will be more far-reaching and, in many cases irreversible. Politicians can no longer ignore the warnings; we need brave leaders who can tell us what we need to hear, who will create support for the changes we need, and will take strong and swift action.”

The Intergovernmental Panel on Climate Change’s latest findings – based on more than 14,000 studies and approved by 195 member states on Friday – deals with the physical science basis of climate change and outline how humans are altering the planet. It is the first installment of four reports released under the IPCC’s current assessment cycle, with subsequent reports scheduled to be published next year.

The first part of the IPCC’s Sixth Assessment Report provides world leaders with a gold standard summation of modern climate science ahead of UN climate talks – known as COP 26 – set for November in Glasgow, Scotland. Bellona will participate in the talks.

“The climate panel is crystal clear that the 1.5-degree target requires immediate and comprehensive reductions in greenhouse gas emissions,” says Bellona President Frederic Hauge. “Here, not only zero emissions by 2050 apply, but everything we do, every single year ahead. I still have faith, but in the next two or three years, action must be taken to enable us to reverse the trend. Capturing and storing CO₂ becomes even more important as a tool.”

Humans have already heated the planet by roughly 1.1 degrees Celsius, or 2 degrees Fahrenheit, since the 19th century, largely by burning coal, oil and gas for energy. The consequences of that are palpable across the globe. This summer alone, withering heat waves have killed hundreds of people in the United States and Canada, floods have devastated Germany and China, and wildfires have raged out of control in Siberia, Turkey and Greece.

But that’s just for starters, says the report. Even if nations started sharply cutting emissions today, total global warming is likely to rise around 1.5 degrees Celsius within the next two decades, a hotter future that is now essentially locked in.

At 1.5 degrees of warming, scientists have found, the dangers grow considerably. Nearly 1 billion people worldwide could swelter in more frequent life-threatening heat waves. Hundreds of millions more would struggle for water because of severe droughts. Some animal and plant species alive today will be gone. Coral reefs, which sustain fisheries for large swaths of the globe, will suffer more frequent mass die-offs.

However, says the report, not all is lost. Humanity can still prevent the planet from getting even hotter. Doing so would require a coordinated effort among the world’s nations to stop adding carbn dioxide to the atmosphere by 2050, entailing a rapid shift away from fossil fuels starting immediately, as well as potentially removing vast amounts of carbon dioxide from the atmosphere. If that happened, global warming would likely level off at around 1.5 degrees Celsius, the report concludes.

Hauge spotlighted petroleum-rich Norway’s role in helping to make – or break – this effort.

“This is an ethical and moral question. Who do we want to be?” he says. “Will we be the ones who made money pumping up the last of the oil? Norway cannot, in such a crisis situation for the climate, be the last country to make money on the last of the oil. In such a situation, it would be morally reprehensible to grant more exploration licenses on the Norwegian shelf. The search must stop immediately.”

The IPCC has previously recognized that the transition away from fossil fuels will be a huge undertaking that requires “rapid, far-reaching and unprecedented changes” across all aspects of society.

It has also underscored the point that limiting global warming to 1.5 degrees Celsius “could go hand in hand with ensuring a more sustainable and equitable society,” with clear benefits to both humans and natural ecosystems.

However, a U.N. analysis published earlier this year found that pledges made by countries around the world to curb greenhouse gas emissions were still “very far” from the profound measures required to avoid the most devastating impacts of climate breakdown.