Our ‘best remaining’ climate strategy – Expert Reaction

Andy Reisinger, Honorary Associate Professor, Australian National University, and lead author of the report’s chapter on mitigation, comments:

“This is the first report by a United Nations agency that says unambiguously that we will cross 1.5°C in the next few years, given insufficient actions to reduce greenhouse gas emissions.

“It’s a wake-up call to governments and industry to confront this reality, but not a reason to give up on 1.5°C as a long-term goal. The failure to reduce emissions has increasingly dangerous and disruptive consequences around the world, in the form of significant heat-related deaths, flooding, disruption to food production and economies, ice loss in mountain and polar regions, and repeated mass bleaching of coral reefs. These losses and damages will escalate further and often land hardest on the shoulders of those least responsible for those mounting risks.

“Adapting to climate change clearly must become a greater focus, but there are limits to how much adaptation can prevent. At the same time as dealing with increasing climate-related disasters, the world therefore needs to accelerate efforts to reduce emissions of all greenhouse gases and reach at least net-zero CO₂ emissions globally by mid-century.

“We know how to and can still do this. This would halt global warming as close to 1.5°C as is still possible and keep at least some of the risks manageable. More importantly, the report emphasizes that the long-term goal remains to return to 1.5°C, as indeed governments reaffirmed only last year. Bringing global warming back down will be challenging and complex but is possible, provided that governments and industry begin to think and act beyond current net-zero targets.

“As the report says, this is by no means an acceptable or preferred path to take, but is by now simply the best remaining option.”

Conflict of interest statement: “I’m an author of several parts of the report but have received no funding for this work. I’m a member of He Pou A Rangi, New Zealand’s Climate Change Commission, but my input to the report and my comments reflect my personal views and insights only.”

Dr Suli Vunibola, Senior Lecturer at the Department of Environmental Management, Lincoln University, comments: 

“All along, Earth as a natural life-supporting system has been on our side, absorbing all our human-related transactions. The need not to overshoot 1.5°C is not only about irreversible catastrophes but also about allowing natural systems to help us down the emissions curve, rather than becoming our worst enemy when we cross the tipping point.

“More research and more scientific panels and reports are being conducted to support stronger evidence-based calls for climate mitigation and adaptation to build climate resilience, but we are not addressing the root cause: overproduction and consumption.

“A good case scenario would be: let’s collectively support necessary production, which will genuinely heal our natural systems and all humans’ well-being over the long term and avoid overshoot, and strictly omit unnecessary production globally. It will be difficult, as much of our global economic and geopolitical systems depend on the persistence of fossil-fuel and carbon-intensive industrial production, which remains a fundamental driver of global carbon emissions.

“Pacific Small Island Developing States contribute only approximately 0.03% of global greenhouse-gas emissions, yet we remain among the most vulnerable to the consequences of the climate crisis. Business as usual is not the answer; a total system reconfiguration will be.”

Conflict of interest statement: “I do not have any conflict of interest.”

Dr Nicholas Cradock-Henry, Principal Social Scientist, Earth Sciences New Zealand, comments:</4>

“The evidence is clear; it is now almost certain the world will warm past 1.5°C, requiring transformational changes to dramatically reduce global greenhouse emissions, and adapt to the inevitable adverse consequences. While sobering, UNEP’s report on limiting overshoot (which will complement forthcoming outputs from the IPCC’s 7^th Assessment, with a Special Report on Cities due early 2027, followed by reports from Working Groups 1-3, through to 2029), represents climate science at its best; weighing the breadth and depth of scientific literature; providing clear-eyed assessment; and delivering policy-relevant information for decision-makers. The scientists have done their work.

“This departure from historical climate baselines will manifest through changes in temperature, rainfall, frequency and severity of extremes that will exceed the capability and capacity of many social and economic systems to cope. Agriculture and food security, water availability, human health and livelihoods, will be impacted. Furthermore, these effects will not be evenly distributed, falling disproportionately on marginalised, Indigenous, and vulnerable populations worldwide who possess the least capacity to cope.

“For Aotearoa New Zealand, the report provides another reminder of our own exposure, and need for greater resilience.

“First, as a globally connected trading nation, international supply chain shocks, shifting marine ecosystems, and geopolitical tensions will be exacerbated. This will have material effects on our economy.

“Second, we must incorporate overshoot into adaptation planning, now. Prudent risk management dictates that we cannot afford to dismiss tail-risk extremes. Rather, we must account for the compounding and cascading impacts of changing hazards to safeguard our long-term agricultural productivity and interconnected infrastructure.

“Finally, we must act. We will not be unaffected. This will require a coordinated, all-of-society approach to respond immediately, acknowledge the true scale of the challenge, and mobilise a comprehensive response. We must simultaneously reduce emissions and accelerate adaptation, cope with and contain unavoidable losses, and embed resilience as a national priority.

“Resilience is not a luxury; it is a necessity we can no longer afford to ignore. It is essential for safeguarding wellbeing and securing a sustainable, prosperous, and equitable future for all.”

Conflict of interest statement: “Dr Cradock-Henry is the Programme Lead of the Endeavour Fund for the ‘Accelerating Adaptation to Climate Change’ programme (2025–2030). He is a Lead Author for Working Group II of the Intergovernmental Panel on Climate Change (IPCC) Seventh Assessment Report.”

Dr Sam Dean, Chief Scientist – Future Climate, Earth Sciences New Zealand, comments:

“As this report emphasises, in the next few years the Earth will exceed the warming threshold within the Paris agreement of 1.5°C above preindustrial. It is also looking unlikely that we will be able to stay below 2°C given our global progress to date on reducing emissions in the face of growing economic production. This report considers what an overshoot looks like, one where we manage to return back to our current warming level by 2100.  The likely impacts on ecosystems, hazards and societal health are outlined; with these being both complex and confronting. Practically, climate change will infiltrate and impact our lives on an ever more regular basis, almost certainly throwing in a few surprises along the way.

“The report also highlights the levels of co-ordinated international mitigation effort that would be required to limit the overshoot to 70 years (with a peak of 1.7°C), including the significant negative emissions that will be needed beyond carbon-zero. In this context, it is important to recognise that net zero carbon is unlikely to represent the end point of our mitigation journey, but rather an early milestone on the path to restoring global temperatures. While we can remain hopeful about the future, we must consider what the unique consequences of climate change will be and how we best prepare for them.”

Conflict of interest statement: “Dr Dean is the Chief Scientist for Future Climate at Earth Sciences New Zealand. He has worked extensively on the projections of climate change impacts on Aotearoa New Zealand and was a contributing author for Working Group II of the Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report.”

Alex Macmillan, Public Health Physician & Professor of Environmental Health, University of Otago, Co-Director Climate Health Aotearoa national research centre, comments:

“We all deserve a future where responsible action on climate change protects people from the escalating human costs of climate change.

“The new UN report on climate overshoot confirms we won’t meet our global commitment to a safe climate and have to work back to it, with irreversible damage to people and nature. Returning from overshoot will be painful and uncertain but must remain the goal. Every public dollar will need to do double duty for healthy fair adaptation and eliminating climate pollution.

“Overshoot is grievous. It means facing major losses of life and health, for people and nature we depend on. Locally, superheated storms and flooding are already affecting many, and worsening inequities. Rapid responses need to be designed for equity, including a precautionary approach to new technologies, and community support for mental, emotional and health impacts.

“Opportunities remain for wellbeing through well-designed action across transport, energy, housing, and food production. In all these areas, we have effective responses already being implemented successfully elsewhere.

“Instead, our government has weakened requirements to reduce emissions, and responded inadequately on adaptation. Companies most responsible for climate change are successfully undermining life-saving action, while being protected from accountability by new legislation.

“As doctors, we’ve seen this before with smoking. Change required exposing unethical and unlawful company tactics, restricting harmful advertising, and ending dangerous influence on policy. It’s time we did this for major climate polluters.

“Individual actions add up, but hope comes from collective citizenship demanding cross-party commitment to a safe climate that recognises the devastating effects of climate disruption, and the opportunities for health and happiness in wise action.”

Conflict of interest statement: “No conflicts of interest to declare.”

Professor of Political Science Bronwyn Hayward, University of Canterbury, comments:

“Last month during the heat wave in Western Europe, the UK parliament noted that the world is approaching 1.5°C of global warming ‘faster than previously anticipated’. The World Meteorology Organisation also concluded that average temperatures ‘are likely to continue at or near record levels in the next five years’.

“The Limiting Overshoot report has been written to consider this harsh reality. What should governments do now as temperatures surge above 1.5 degrees Celsius?

“In ‘overshoot’, adaptation shifts from a second tier response (something we do after we tackle mitigation) to an immediate integrated policy priority. It’s no longer enough to reduce emissions to prevent even worse disasters, we also need to urgently adapt to protect people, biodiversity, food production, and our economies from unprecedented heat waves, droughts, fires, record global ocean temperatures, severe storms, floods and landslides, sea level rise, glacial melt, and coastal inundation.

“Many of the leading international authors of this report also attended an Adaptation Futures event held in October 2025 in Christchurch, jointly hosted by the World Adaptation Science Programme and the University of Canterbury, supported by a consortia of NZ universities, businesses, and international funders.

“Concern about the very real limits to adaptation in a world over 1.5°C of warming was an important focus at that meeting. It was therefore a huge loss for NZ that the Minister of Climate Change was not released by his cabinet to attend this meeting, despite a longstanding engagement in his diary.

“Why do I dwell on this? Because New Zealand needs to urgently face up to the implications of our rapidly warming world and learn from others to protect our futures in extreme weather.

“The report highlights key challenges for the Pacific and anticipates a significant push to greater use of engineering techniques including carbon capture and storage, but there is no guarantee, for example, that favoured net zero policies (particularly tree planting) will work in a world over 1.5°C of warming, where fires are a regular event. We will also need global agreements to manage the unintended consequences of geoengineering to avoid some of the worst excesses of magical thinking, which could have wide ranging problems for food production and human health.

“This report, like the AF2025 meeting, stresses the power of social trust and inclusive decision making. Indigenous leadership, local community knowledge, and building social cohesion, by investing in health, housing and education are all vital to support a nation capable of taking concerted action to protect itself.

“One disappointment I have is the report doesn’t highlight injustices to children as global temperatures rise. In another study released this week (which includes a NZ co-author Dr Luke Harrington), 11% of the world’s children aged 0 to 9 years are already experiencing 100 or more days of ‘attributable heat stress’ each year (compared to only 6% of their grandparents aged 60 to 69 years). As we cross 1.5° C of warming, 13% of the world’s children are exposed to 100 or more days of high heat stress or humidity.

“While both older populations and children are sensitive to a heating world, it is children and young people globally, particularly in low income and Indigenous communities, in New Zealand and the Pacific, Asia and Sub-Saharan Africa who are already struggling with an insecure future, who will now face more and more injustice unless we take urgent action.”

Conflict of interest statement: “I co-convened Adaptation Futures 2025 and have held a variety of roles in the IPCC.”

Dr Scott Nodder, Principal Scientist at Earth Sciences NZ, comments:

“The Limiting Overshoot report is a timely reinforcement of the importance of responding appropriately to the climate crisis by reducing greenhouse gas emissions.

“The report also considers Carbon Dioxide Removal (CDR) techniques, such as afforestation and bioenergy with carbon capture and storage, as mitigation approaches to limit the exceedance of the 1.5°C planetary threshold. The IPCC states that CDR is necessary to mop up legacy carbon and offset the hard-to-abate emissions of transport and cement production. CDR technologies, however, should not be viewed as an ‘easy’ option to negate our obligations to drastically reduce, if not eliminate, greenhouse gas emissions, especially if we are to meet net-zero by 2050. This is reflected in the UNEP report, which is explicit in outlining the socio-economic and environmental consequences if this aim is not achieved.

“The oceans are a large reservoir of carbon (~60 times greater than the atmosphere) with potential for increased removal by marine CDR (mCDR). These techniques involve enhancing natural chemical (e.g., ocean alkalinity enhancement) and biological (e.g., ocean nutrient fertilization, macroalgae growth and burial) processes.

“However, research and development of mCDR lags terrestrial CDR, reflecting the difficulty of evaluating effectiveness, risks and permanence in a highly dynamic ocean. Ecosystem response to mCDR deployment at scale is currently uncertain. In addition, robust baselines and monitoring and verification techniques are needed to confirm additional carbon removal, and there is a lack of governance and societal understanding for mCDR. Even if the benefits outweigh the risks, it is unlikely that mCDR could be deployed at scale for at least a decade, and consequently it is not an immediate solution to the 1.5°C overshoot.”

Conflict of interest statement: “Scott Nodder co-leads an MBIE Endeavour Fund Research Programme using natural analogues to assess mCDR.”

Erin Da Silva, Fellow of the Institute of Sustainability and Environmental Professionals and Member of Engineering New Zealand, comments:

“The overshoot timeline fits uncomfortably well with infrastructure design life.”There is no single endpoint for infrastructure design, because the conditions it must operate in will continue to change. Over its lifetime, infrastructure is likely to face conditions that exceed the assumptions it was originally designed for, particularly during periods of peak warming. As a result, the engineering design paradigm needs to shift.

“Traditional assumptions that historical performance can be used to predict future conditions are no longer reliable. Engineers will need to become comfortable working with uncertainty and lower-confidence projections when making design decisions.

“The goal is not to design for the worst-case scenario or eliminate risk through ever-increasing safety margins and over-specification. Instead, engineers will need to make informed decisions today, supported by clear trigger points for future intervention as conditions evolve.

“This means designing adaptive systems that can be monitored, evaluated and modified over time. We need to move beyond a model of “build, operate and maintain” to one of “build, monitor, evaluate, learn and adapt”. In a world of changing climate conditions, resilience cannot be achieved through a single investment decision. It requires ongoing monitoring, learning and adaptation throughout the life of the system.”

Conflict of interest statement: “Erin is currently employed by KPMG; however, she is commenting in a personal capacity and as a member of Engineering NZ.”

Drew Bingham, Principal Science Advisor, Threats Science, Department of Conservation, comments:

“This report highlights the urgent need to prepare for climate change impacts on our species and ecosystems, which will continue to intensify even with strong action to limit the overshoot of 1.5 degrees of warming. DOC has work underway to prepare for climate change impacts through our climate change adaptation action plan before options narrow and costs rise. However, the scale of climate change impacts is enormous and beyond DOC’s ability to address all of it at once. Because of this, we’ll must be targeted in approach, focusing on actions that make the most impact.”

Conflict of interest statement: “I have no conflicts of interest for this report.”

Our colleagues at the AusSMC, SMC UK, Spain, Taiwan, and Korea have also gathered comments.