1. An exceeded limit does not become meaningless
What happens to a limit once it has been exceeded?
In everyday politics, a dangerous answer suggests itself: sooner or later, the limit is treated as history. First, 1.5°C was the goal. Then the threshold is crossed. And eventually the argument may become: we now live in a world above 1.5°C, so we simply have to adapt to the new normal.
That shortcut is wrong.
On 2 September 2026, the United Nations Environment Programme (UNEP) published a notable report: Limiting Overshoot: Navigating exceedance of 1.5°C and pathways towards return. It no longer examines only how an exceedance of 1.5°C might be prevented. It addresses the more uncomfortable question of what happens if the world exceeds that limit — and whether a later return below 1.5°C is still possible.
Its central message is clear: exceeding the limit does not make it meaningless. It changes the conditions under which politics, law and planning have to operate.
UNEP explicitly notes that the existing international legal framework does not disappear if warming exceeds 1.5°C. The Paris Agreement, the UN Framework Convention on Climate Change and other international obligations continue to apply. The UNEP report is not itself a source of law; it synthesises existing obligations and international jurisprudence. The benchmark does not vanish. The factual conditions under which it must be met become more difficult.
So the supposed “new normal” is precisely not a licence for weaker standards.
2. Overshoot does not mean one unusually hot year
The debate about 1.5°C is often mixed up with individual annual temperature records. One calendar year above 1.5°C does not yet mean what UNEP calls overshoot.
The report refers to the multi-decadal global warming level. UNEP assumes that the world is likely to exceed this long-term 1.5°C level in the coming years. Overshoot therefore describes a phase in which long-term warming rises above 1.5°C and later — in the most favourable case — is brought back below it.
This definition already contains a decisive insight: a return of global mean temperature is not the same as a return of the world to its former state. Ecological, social and infrastructural systems have memory.
3. As harm grows, so do the demands on action
This is why the legal section of the UNEP report is especially important. UNEP refers to developments in international jurisprudence and describes state due diligence as dynamic. Its standard evolves with scientific knowledge and with the probability and gravity of foreseeable harm.
In other words: the better a risk is understood and the more serious its potential consequences become, the less state action can proceed as if the underlying conditions had not changed.
UNEP draws a notable consequence for a higher or longer-lasting overshoot: increasing climate risks can justify higher requirements for appropriate state action. Above 1.5°C, the need for deep, rapid and sustained emissions reductions does not diminish; it becomes more urgent.
Adaptation changes as well. Planning should not respond only to current conditions. The legal and risk framework described in the report supports taking plausible peak warming and harms into account in state adaptation planning where those harms may persist even if temperatures later decline. What concrete assessment follows from this depends on the applicable body of law.
4. What declines is not automatically restored
Political and planning models still often assume, at least implicitly, that a system develops along relatively stable conditions. If a pressure is later reduced, a return to an earlier state can appear conceptually possible.
The reality of complex systems is often different.
Ecosystems can cross tipping points. Species can disappear. Glaciers can be lost. Coastlines can change permanently. Infrastructure can lock spatial and economic development into particular patterns for decades. Investments can entrench emissions or resource dependencies. Institutions can become tied to a path once taken.
UNEP therefore works with concepts such as path dependency, lock-in and irreversibility. The decisive question is not only whether a pressure later falls again. It is what happened to the system during the period of exceedance.
A temperature curve can return. A lost system state may not.
That is why long-lived decisions cannot be assessed solely by looking at the state of affairs on the day a permit, plan or investment decision is made.
So the question is not only: what does the situation look like today? It is also: which future developments are scientifically plausible and relevant to the decision — and what does our decision lock in for the future?
5. Species move — protected areas do not
As the climate warms, the ranges of many species shift poleward or to higher elevations. Ecological communities change. A protected area, however, cannot simply move a few hundred kilometres north.
An obvious but dangerous response would be this: if the species for which an area was originally protected disappear or its composition changes, the basis for protection also disappears. UNEP expressly rejects that logic.
Climate-driven changes in species composition do not, by themselves, justify withdrawing area-based protection. Where resilience is already declining, more targeted or stronger protection of ecological functions may instead be required.
Protected areas do more than preserve an inventory of particular species. They can buffer microclimates, provide refugia, enable movement, store carbon and maintain ecological connectivity. In this context, UNEP explicitly describes protected areas as “critical climate infrastructure”.
Under changing conditions, nature conservation can mean neither freezing a historical state at any cost nor using change as an argument for abandoning protection.
Systemic Legal Development
Functional continuity of protection
When a protected system changes, the assessment must ask which ecological functions, relationships and protection services persist, emerge or become more important. The concept does not replace legally protected species, habitat types or concrete conservation objectives. A shift in conditions alone must not automatically lead to a lower level of protection. The specific legal consequence depends on the applicable protection regime.
6. The real problem: static law in dynamic systems
Legal and planning systems often work with reference conditions: baseline surveys, maps, thresholds, forecasts, protected features, design assumptions and models of how a system works. These references are necessary. But they can age.
The more-than-human world changes. Climate, water balance, species distribution and resource availability change. At the same time, many legal and planning decisions have effects that last for decades. This is where an updating problem emerges: a decision can be formally based on a correct baseline and still become systemically wrong if its long-term viability depends on conditions that are foreseeably changing.
Dynamic reference-setting does not mean: when reality gets worse, we lower the standard.
It means that the reference space, assumptions, measures and decision basis must remain reviewable and capable of being updated in light of new evidence, while the normative protection objective remains in place unless a change to that objective is separately justified.
The Future Check addresses the same issue at a different level. It is not meant to replace climate projections or specialist assessments. But it must be capable of showing when the viability of a long-term decision depends on changing future system conditions. Future states, lock-in, reversibility and adaptability then become decision dependencies that require clarification.
7. A simple test rule
A simple systemic test rule can be derived from the report:
The longer a decision lasts, the more strongly it locks in future options, and the more serious or irreversible its possible consequences, the less a static snapshot is enough.
At least four questions then have to be asked:
Which plausible future system states are relevant to the decision?
Which consequences could persist even if the pressure that caused them later declines?
Which lock-ins or losses of future options does the decision create?
And what monitoring, review or adaptation mechanisms exist if underlying assumptions prove wrong?
This is not a demand for omniscient planning. No one can predict the exact state of complex systems decades in advance. It is a method for dealing with uncertainty more responsibly.
Perhaps the most dangerous political effect of overshoot would not be the additional warming alone. It would be normalisation. Once a limit has been exceeded, there is an incentive to turn the new state into the new benchmark.
1.5°C remains a reference point. Harm above that level does not disappear because we become accustomed to its existence. And later cooling does not reverse irreversible losses.
The limit can be exceeded. That does not make it meaningless.
Source
United Nations Environment Programme (UNEP): Limiting Overshoot: Navigating exceedance of 1.5°C and pathways towards return. Nairobi 2026. DOI: 10.59117/20.500.11822/49857.
Note on interpretation
The terms “functional continuity of protection” and the systemic test questions derived from the report are interpretations developed within Systemic Legal Development. They are not terms or independent legal doctrines used by UNEP. In particular, the report does not establish a general legal decision lock.