Climate Leaders are Talking About ‘Overshoot’ Into the Warming Danger Zone. Here’s What It Means.

For years, the rallying cry of global climate action has been a single, stark number: 1.5°C. This was the guardrail, the “safe” limit for planetary warming established by the 2015 Paris Agreement. But now, a subtle yet significant shift is occurring in the halls of power and science. With global temperatures continuing to climb, leaders are increasingly conceding that the world is likely to temporarily breach this critical threshold.

This admission, however, is not a white flag. Instead, it’s a strategic pivot to a new, more perilous phase of the climate fight—one focused on the concept of “overshoot.”

What Exactly is ‘Overshoot’?

In climate science, “overshoot” doesn’t mean blowing past the 1.5°C limit and giving up. Think of it not as a point of no return, but as a dangerous neighborhood we may be forced to drive through. The goal is to get through it as quickly and carefully as possible, minimizing the damage, and then find a route back to safer ground.

The 1.5°C figure isn’t a single-year spike; it’s a average measured over a decade or two. While 2023 was the first year where the global annual average temperature temporarily hit 1.5°C, the multi-year average currently sits around 1.3°C. The official breach will only be declared once this decadal average consistently exceeds 1.5°C.

Why is 1.5°C a Critical ‘Limit,’ Not Just a ‘Goal’?

Scientists insist that 1.5°C is not an arbitrary target, but a physical boundary.

“We have a real risk of triggering irreversible changes in Earth systems when we breach 1.5°C,” said Johan Rockstrom, director of Germany’s Potsdam Institute for Climate Research. “In Belem, we have more scientific evidence than we had 10 years ago that 1.5°C is a real limit. It’s not a target, it’s not a goal, it’s a limit, it’s a boundary. Go beyond it, we increase suffering of people, and we increase risk of crossing tipping points.”

The dangers that begin to escalate at and beyond this threshold are severe and interconnected:

• Ecosystem Collapse: The vast majority of the world’s coral reefs would face mass bleaching and die, devastating marine biodiversity and the communities that depend on them.

• Extreme Weather: The frequency and intensity of killer heatwaves, devastating floods, and prolonged droughts would increase exponentially.

• Tipping Points: This is the greatest fear. Breaching 1.5°C dramatically raises the risk of activating irreversible feedback loops, such as the complete melting of the Greenland and West Antarctic ice sheets (locking in multi-meter sea level rise), the drying out and die-back of the Amazon rainforest (releasing vast stores of carbon), or the collapse of the Atlantic Meridional Overturning Circulation (which regulates weather patterns in Europe and the Americas).

The Inevitable Breach: A New Reality Check

For years, UN officials have publicly maintained that the 1.5°C goal was still within reach. But the data has painted a grimmer picture. The planet is currently on a trajectory for about 2.6°C of warming based on current policies.

This reality is now being acknowledged at the highest levels. In a blunt assessment last month, UN Secretary-General António Guterres stated, “Overshooting is now inevitable, which means that we are going to have a period, bigger or smaller, with higher or lower intensity, above 1.5°C in the years to come.” He quickly added, “Now, that doesn’t mean that we are condemned to live with 1.5°C lost. No.”

This sentiment was echoed by UN climate chief Simon Stiell, who framed the new mission: “The science is clear: We can and must bring temperatures back down to 1.5°C after any temporary overshoot.”

The Mechanics of the U-Turn: How Do We Cool the Planet Back Down?

The theory behind overshoot hinges on a two-pronged approach:

1. Aggressive Emission Cuts: The primary and most urgent task remains the same: stop adding carbon dioxide and other greenhouse gases to the atmosphere by rapidly phasing out fossil fuels.

2. Carbon Dioxide Removal (CDR): Once emissions hit “net zero,” the planet will stop warming. To actually cool it, we must actively remove the legacy carbon pollution already in the air. This relies on both enhancing natural “sinks” (like reforestation and ocean health) and developing Carbon Dioxide Removal technologies that can scrub CO2 directly from the atmosphere.

This is where the immense challenge lies. As Ottmar Edenhofer, chief economist at the Potsdam Institute, starkly put it, “Without carbon dioxide removal, it is simply impossible to manage the overshoot scenario.” The necessary CDR technologies are still in their infancy, unproven at the planetary scale required.

The High Stakes of the Danger Zone

Scientists are now grappling with critical, unresolved questions about the overshoot period. Is the greater danger the peak temperature we hit (e.g., 1.7°C vs. 2.0°C), or the total duration of time we spend above 1.5°C? The answer is likely both, and the impacts will be felt in real time through more extreme weather and rising seas.

The latest analysis from Climate Action Tracker illustrates the best-case scenario: if the world undertakes the most ambitious emissions reductions possible, temperatures are likely to breach 1.5°C around 2030, peak at about 1.7°C, and not fall back below the 1.5°C limit until the 2060s. This implies at least three decades in the danger zone.

However, the world’s current course is not for a small, manageable overshoot, but a complete and catastrophic miss, with temperatures still rising by the end of the century.

Reflecting on the lost decade, Rockstrom offered a sobering summary: “Ten years ago, we had a more orderly pathway for staying away from 1.5°C entirely, basically with low or no overshoot. Now we are 10 years later, we have failed.”

The conversation has now fundamentally shifted. The goal is no longer just to avoid the danger zone, but to survive our passage through it and engineer a way back. The margin for error has vanished, and the cost of the U-turn will be astronomical.

  Donate Here