Every Year of Climate Delay Makes the Coming 1.5°C Overshoot More Dangerous

Climate commitments have lowered projected global warming from more than 4°C to 2.3°C, provided countries deliver them fully, but the world is still expected to exceed the 1.5°C threshold temporarily. Ahead of the UN Climate Summit on 23 September, attention is shifting from announcing targets to cutting emissions faster, financing developing economies and protecting communities from impacts already unfolding.

The prospect of global warming temporarily exceeding 1.5°C is changing the climate debate. Preventing every breach may no longer be possible, but governments still have considerable influence over how far temperatures rise, how long the overshoot lasts and how much permanent damage occurs before warming begins to decline.

According to the United Nations, climate commitments made since the Paris Agreement have lowered the projected warming trajectory from more than 4°C to about 2.3°C, assuming national pledges are delivered in full. However, present plans remain far removed from the emissions reductions required to preserve a credible route back towards 1.5°C.

A temporary overshoot could leave permanent scars

The 1.5°C limit describes the average increase in global temperature above pre-industrial levels over several decades. It is not crossed simply because one calendar year records unusually high temperatures. An overshoot begins when the longer-term average moves above the limit, reaches a peak and later falls, provided emissions have been reduced deeply enough.

Temporary exceedance should not be confused with temporary consequences. Higher temperatures increase exposure to extreme heat, drought, floods, storms and wildfires, while placing additional pressure on food systems, water supplies, public health and natural ecosystems. Some losses could persist even if temperatures subsequently decline.

UN Secretary-General António Guterres has warned that every fraction of additional warming will cost lives, destroy livelihoods, deepen inequality and push ecosystems closer to irreversible damage. The danger depends not only on whether 1.5°C is exceeded, but also on the height and duration of the overshoot.

A UN Environment Programme assessment indicates that warming could still peak at around 1.8°C even if existing national climate plans and additional net-zero pledges are fully implemented. Returning from such a peak would require sustained emissions reductions over many years, making the credibility and execution of present commitments as important as their stated ambition.

Climate diplomacy has produced promises, but not cuts at the required scale

Countries responsible for nearly 90 per cent of global emissions have submitted updated national climate plans, known as nationally determined contributions or NDCs. The breadth of participation suggests that climate policy has become embedded in national planning, but the collective result remains insufficient.

Full implementation of those plans is expected to reduce emissions by only around 10 per cent by 2035, according to the UN. Keeping the 1.5°C objective within reach would require a reduction of roughly 60 per cent over the same period. The 50-percentage-point difference reveals an implementation and ambition deficit that incremental policy adjustments are unlikely to close.

Faster action would require sharp reductions in carbon dioxide, methane and other short-lived climate pollutants, combined with stronger protection for forests. Electricity systems would also need to absorb far more renewable energy through modern grids, expanded storage and greater electrification of transport, heating and industry.

The transition could reduce exposure to geopolitical and market shocks as well as emissions. Three out of four people live in countries that import more fossil fuels than they export, according to the UN, leaving their economies vulnerable to disruptions in supply and sudden price increases. Renewable energy offers a route towards greater domestic energy security, but only where grids, investment and regulatory capacity develop alongside generation.

The technology is only one part of the equation. Governments must shorten project delays, provide stable policy signals and manage the social effects of industries expanding or contracting. Without those foundations, renewable capacity may grow while transmission bottlenecks, financing constraints and unequal access continue to slow economy-wide decarbonisation.

Finance could determine whether the transition narrows or deepens inequality

Developing countries frequently pay substantially more to borrow for renewable power, electricity networks, storage and climate-resilient infrastructure. High financing costs can make viable projects unaffordable and leave countries dependent on fossil-fuel systems, even where renewable resources are abundant.

The UN has called for cheaper capital, reform of multilateral development banks and greater private investment in developing economies. Progress will depend on the terms attached to that money. Loans that intensify debt pressures may expand clean-energy capacity while reducing the fiscal space available for health, education and climate adaptation.

Questions of ownership and value are equally significant. Many developing countries supply minerals required for batteries and other clean technologies but capture only a limited share of the income generated through processing, manufacturing and finished products. Greater participation in these higher-value activities could turn the energy transition into a source of industrial development rather than another cycle of raw-material dependence.

Workers and communities will also experience the transition unevenly. Fossil-fuel-dependent regions may face lost employment and declining public revenues, while emerging clean industries may create jobs in different locations or require different skills. A credible just-transition strategy therefore needs worker retraining, social protection, regional investment and decent employment standards.

Private investors, governments and vulnerable communities do not always approach climate finance with the same priorities. Investors seek manageable risks and reliable returns, governments must balance affordability and energy security, and highly exposed countries need finance that does not create another layer of debt. Resolving these tensions will require more than announcing larger headline totals.

The next climate test is protection, delivery and accountability

Emissions reductions will shape future warming, but they cannot eliminate hazards already confronting communities. Recent floods and landslides in Nepal and China have illustrated the vulnerability of settlements and infrastructure, while climate-related shocks continue to threaten agriculture, water systems and essential public services across regions.

Adaptation must consequently advance alongside mitigation. Stronger roads and homes, resilient farming, better water management, healthier ecosystems and effective early-warning systems can reduce exposure and give communities more time to prepare for floods, droughts, storms and heatwaves.

Funding remains a defining constraint. Countries facing severe climate risks often have limited fiscal capacity and high borrowing costs, despite contributing relatively little to accumulated global emissions. Without greater adaptation finance, communities with the fewest resources will continue to absorb a disproportionate share of climate losses.

The UN Climate Summit on 23 September will bring together governments, development banks, businesses, financial institutions and civil society under three priorities: accelerate the transition, unlock finance and protect people. Solutions Dialogues will also examine energy, oceans, adaptation, methane, finance, information integrity and green industrialisation.

Greater scrutiny should fall on whether governments identify deliverable policies, whether financial institutions lower the cost of capital, whether adaptation receives sufficient funding and whether responsibilities are matched by deadlines and transparent reporting.