Overshoot Explained: What the Latest Climate Science Means

What should investors make of the latest developments in climate science?

On the one hand, the latest climate scenarios suggest that the most extreme warming pathways are becoming less plausible. At the same time, the recent UNEP report on temperature overshoot highlights an uncomfortable reality: exceeding 1.5°C is now inevitable. Taken together, these developments point to a nuanced climate outlook: climate action is working, but not yet fast enough to avoid dangerous levels of warming.

To understand what this means in practice, it helps to look at both findings side by side.

The good news: Climate action is changing the outlook

For decades, climate scientists have worked with a shared set of emissions scenarios that represent different futures. These are not predictions. Instead, scenarios are used to ask "what if” questions: What if coal generation continues? What if climate policies become stricter? These scenarios help explore how different socioeconomic trends, technologies and policy choices could affect future climate outcomes.

The newest generation of emissions scenarios has now been developed under CMIP7, the latest phase of the Coupled Model Intercomparison Project. These scenarios will be used in new climate-model projections and will help inform the next IPCC assessment.

One notable modification in the new scenarios is how they are presented. Earlier IPCC scenarios were identified by technical labels such as RCP 4.5 or RCP 8.5, referring to how much extra heat was trapped in the atmosphere by the end of the century. The CMIP7 scenarios instead use more intuitive and descriptive labels based on emission trajectories, ranging from “Low-to-negative” to “High".

The more consequential change, however, lies in what these scenarios say about the future of global warming. The most striking change concerns the upper end of the emissions spectrum. The new high-emissions pathway has been revised downward, with projected warming reaching around 3.3°C above pre-industrial levels by 2100, compared with an estimated 4.7°C for the highest-emissions pathway in the previous generation of scenarios.

Figure: CMIP7 climate scenarios showing potential global emissions trajectories (left) and associated changes in global temperature (right)(Source: World Climate Research Programme, reproduced from Van Vuuren et al, 2026, under CC BY 4.0 )

There has been significant debate over the driving force of the upper-end shift. One reason for this change is good news: climate action is already influencing the range of futures we consider plausible. A coal-dominated 21st century now looks unrealistic. The rapid growth of renewables and clean-energy investment has changed the global energy outlook. India offers one example of this shift: Carbon Brief reports that clean energy met all of the increase in the country’s electricity demand over the past two years, helping to keep power-sector emissions flat despite rising demand. India’s total emissions continue to increase, but developments like these show that the energy transition is making a tangible difference.

This progress extends beyond renewables: falling battery and energy-storage costs, alongside the electrification of transport and heating, and stronger clean industrial policies, are also reshaping the emissions pathways now considered genuinely plausible.

But that is not the whole story. Another factor behind the shift at the upper end is the limited plausibility of RCP 8.5 as a high-end baseline. Developed in 2011, the scenario assumed no climate policy, a tripling of global emissions by 2100 and a fivefold increase in coal use. Many climate researchers have argued that we were never headed towards such an extreme future to begin with.

Whatever the drivers of the shift, the downward revision of the highest warming estimate does not mean the climate challenge has eased. While the upper end has shifted downward, the lower-emissions pathways have become harder to achieve.

There is another aspect of the new IPCC scenarios that merits attention: all low-emissions pathways that eventually bring global temperatures back down rely on large-scale carbon dioxide removal (CDR). This reliance stands in contrast to the very limited current scale and development of CDR. The State of Carbon Dioxide Removal report published earlier this year finds that novel CDR is still extremely small, at around 0.002 GtCO₂ per year. That is less than 0.03% of the total annual carbon removal projected for 2050 in pathways consistent with the Paris Agreement.

The reality check: Overshoot is now unavoidable

If the changing climate scenarios demonstrate what climate action has achieved, the latest findings on temperature overshoot reveal how much remains to be done.

Overshoot occurs when global warming temporarily exceeds the 1.5°C threshold before potentially falling back down later this century. The latest UNEP report makes clear that avoiding such an exceedance of 1.5°C is no longer realistic. The challenge is therefore not only to limit how high temperatures rise, but also how long they remain elevated.

This distinction matters. Exceeding 1.5°C is not simply a temporary departure from a target that can be corrected later without consequences. The higher temperatures rise, and the longer they remain elevated, the greater the risks of irreversible damage to ecosystems, livelihoods and infrastructure.

Does that mean giving up on the 1.5°C target of the Paris Agreement? Quite the opposite. Every fraction of a degree matters. Recent events offer a stark reminder of the risks: from devastating flash floods in Nepal and Tibet to extreme heat, drought and wildfires in Europe, and the emerging effects of this year's powerful El Niño. The consequences of the climate crisis are being felt around the world. These events underscore the importance of limiting future warming: lower peak temperatures mean less severe climate impacts, reduced adaptation needs and less dependence on uncertain future carbon removal.

Some headlines framed the UNEP report as a "strategic retreat", but this misses the point. The message is a reality check: current trends still point to very dangerous levels of warming, but faster emissions cuts and carbon removal can still reduce peak temperatures and future climate risk.

What this means for climate action and investment

Taken together, these developments point to an important conclusion: the future is neither predetermined nor entirely within our control.

Mitigation remains a priority, because every year of delay raises peak warming. At the same time, adaptation must accelerate as water stress, flooding and other climate impacts intensify. For impact investors like responsAbility, this means directing capital towards solutions that can reduce emissions and strengthen resilience, from renewable energy and energy efficiency to climate-smart agriculture, resilient infrastructure and adaptation-focused investments.

As the world gears up for COP31 in Türkiye, the latest climate science offers neither a reason for complacency nor cause for despair. Overshoot changes the framing, but not the need for action. The challenge is to avoid fatalism, stay honest about where we are, and recognise the agency we still have: the lower and shorter the overshoot, the more climate risk we can still avoid.

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