The world is expected to exceed a critical climate threshold. How far temperatures rise—and what happens to people, animals and the planet along the way—still depends on the choices we make now.
For years, 1.5 degrees Celsius has been one of the defining numbers of the climate crisis. The goal, established under the Paris Agreement, has been to pursue efforts to limit global warming to 1.5°C above preindustrial levels, reducing the likelihood and severity of some of the most dangerous consequences of a rapidly warming planet.
Now, the United Nations is acknowledging something considerably harder to hear. A new report released September 2 by the United Nations Environment Programme says that under current policies and alternative near-term trajectories, exceeding 1.5°C is now widely assessed as unavoidable. UNEP says global temperatures are likely to cross that threshold within the next few years.
The report, Limiting Overshoot: Navigating Exceedance of 1.5°C and Pathways Towards Return, does not declare the climate fight over. Instead, it confronts a different question: what happens when preventing the crossing of 1.5°C is no longer the only task, and humanity must also determine how far beyond that line temperatures rise, how long they remain there and whether they can eventually be brought back down?
Entering an Era of Overshoot
The term we are likely to hear much more often is overshoot. In simple terms, climate overshoot describes a period in which global temperatures rise beyond 1.5°C, eventually peak and then—if greenhouse-gas emissions are cut deeply enough and carbon dioxide is ultimately removed from the atmosphere faster than it is added—begin declining again. UNEP calls an “overshoot, peak and decline” pathway the best remaining option for minimizing the magnitude and duration of the exceedance and attempting to return temperatures below 1.5°C.
That makes both the height and duration of the overshoot extraordinarily important. The UNEP report finds that higher peak warming and longer periods above 1.5°C are associated with greater risks for people and nature. The longer temperatures remain elevated, the greater the danger of reaching adaptation limits and crossing thresholds that may produce irreversible changes.
There is an understandable temptation to hear “1.5°C is unavoidable” and conclude that the target has been lost, so the rest no longer matters. But climate change does not work like a pass-or-fail exam. Crossing 1.5°C does not make 1.6°C inevitable, and reaching 1.8°C does not make 2°C acceptable. UNEP’s most optimistic scenario now sees warming peaking around 1.8°C, while most of the other scenarios it examined peak higher. Every fraction of a degree avoided still reduces risks and damage.
The decimal points matter far more than they appear to.
Half a Degree Is Not a Small Difference
On an ordinary thermometer, the difference between 1.5°C and 2°C looks almost trivial. Across an entire planet, that half-degree can radically alter the outlook for species and ecosystems.
The Intergovernmental Panel on Climate Change examined approximately 105,000 species and projected that at 1.5°C of warming, 6% of insects, 8% of plants and 4% of vertebrates could lose more than half of their climatically determined geographic range. At 2°C, those estimates rise to 18% of insects, 16% of plants and 8% of vertebrates. In the case of insects, the projected percentage triples over that seemingly small half-degree.
Warm-water coral reefs provide an even more dramatic example. The IPCC projects declines of 70–90% at 1.5°C of warming. At 2°C, projected losses rise to more than 99%. The consequences extend to human communities as well: climate-related risks to health, livelihoods, food security, water supplies, human security and economic growth all increase with warming and are projected to be greater at 2°C than at 1.5°C.
Those numbers are one reason crossing the threshold cannot become permission to surrender. There are human lives, animal lives and entire ecosystems inside those decimal points. The question is no longer simply whether the world crosses 1.5°C, but how much additional harm can still be prevented once it does.
Coming Back Down Does Not Undo Everything
The idea of overshoot can sound reassuring if it is reduced to a graph: temperatures go above the line, humanity gets its emissions under control and eventually the line comes back down. The physical world is considerably messier. Returning global temperatures below 1.5°C someday would not necessarily restore the world that existed before the threshold was crossed.
Some climate effects may diminish as temperatures decline, but others can persist for decades, centuries or longer. UNEP warns that higher and longer overshoot increases the likelihood of irreversible losses and tipping points, including destabilization of major ice sheets, degradation of the Amazon rainforest and disruption of major ocean circulation systems. Even a successful eventual return below 1.5°C would therefore take place in a world permanently changed by some of what occurred during the overshoot.
An extinct species does not return when the temperature graph falls. A destroyed ecosystem may not simply reconstruct itself, and a community forced from its home by rising seas or repeated disasters cannot necessarily return to the life it had before. That is why limiting the peak matters just as much as eventually bringing temperatures down. The objective cannot be to tolerate whatever warming occurs now because we hope to reverse it later.
Adaptation Is No Longer About a Distant Future
Climate policy has often been discussed primarily in terms of mitigation: reduce emissions now to prevent future damage. Mitigation remains indispensable, but UNEP’s new assessment makes clear that mitigation and adaptation must now advance together. Climate impacts are already occurring, and additional warming is coming even under the most optimistic scenarios.
That means governments have to think simultaneously about reducing the causes of climate change and protecting people from its consequences. Communities need infrastructure capable of handling heavier rainfall and flooding, protections against increasingly dangerous heat, resilient food and water systems, wildfire preparedness, disaster planning and healthy ecosystems that provide natural buffers against climate impacts.
Who receives those protections matters too. Climate change does not distribute its consequences according to who caused the most emissions. Communities with fewer financial resources, countries with less historical responsibility for warming and people already facing environmental or economic vulnerability can be among those least equipped to absorb repeated disasters. Adaptation cannot simply become another way of telling vulnerable people to survive conditions they had little role in creating while high-emission systems continue largely unchanged.
We Cannot Talk About Climate Without Talking About Food
Any serious discussion of those systems eventually reaches a politically uncomfortable subject: what we produce and what we eat. Food is sometimes treated as a side issue in climate conversations dominated by power plants, cars and fossil fuels, but the numbers do not support leaving it there.
According to the latest available data from the United Nations Food and Agriculture Organization, global agrifood systems produced approximately 16.5 billion tonnes of carbon-dioxide-equivalent emissions in 2023, representing about 32% of total human-caused greenhouse-gas emissions. Those emissions occur throughout the food system, including agricultural production, land-use change, manufacturing, transportation, packaging, retail, household consumption and waste.
The contributions within that system are not equal. FAO identifies livestock as the largest single component of global agrifood-system emissions in 2023, responsible for approximately 4.3 billion tonnes of carbon-dioxide equivalent. Deforestation accounted for another roughly 2.8 billion tonnes. Animal agriculture also presents a particular climate challenge because carbon dioxide is only one part of its footprint: livestock systems generate methane, including through the digestion of ruminant animals, as well as methane and nitrous oxide associated with manure, feed and production.
Land use adds another layer. Raising animals and growing crops for animal feed require enormous areas of agricultural land, while forests and other intact ecosystems can store carbon and provide habitat for wildlife. The IPCC has found that shifting consumption from animal proteins toward plant proteins can reduce pressure on land, creating opportunities for reforestation or the restoration of natural ecosystems while reducing greenhouse-gas emissions.
A credible climate conversation cannot acknowledge those realities and then stop at the edge of our plates.
Food-System Change Is Bigger Than Personal Choice
That does not mean responsibility for transforming a global food system should simply be dropped into the lap of the person standing in a grocery-store aisle. Individual choices matter, but those choices are made within systems shaped by agricultural subsidies, food prices, availability, public procurement, corporate practices, land-use policy and government investment.
Meaningful food-system climate policy therefore has to operate on several levels at once. Governments can reduce food loss and waste, protect forests from agricultural expansion, invest in sustainable production, make plant-based foods more accessible and affordable, reconsider incentives that lock agriculture into high-emission practices and help farmers transition toward systems capable of feeding people with a smaller environmental footprint. Consumers, institutions and communities can also influence demand through the foods they purchase, serve and normalize.
The IPCC identifies dietary shifts toward a greater share of plant-based protein sources as a climate-mitigation opportunity capable of reducing greenhouse-gas footprints and land demands. Importantly for a publication concerned not only with human interests but with the lives of other animals, the IPCC also recognizes animal-welfare benefits associated with plant-based alternatives to animal products.
That does not make plant-based food a magic climate solution. There is no single one. Renewable energy alone will not solve the climate crisis, nor will electric vehicles, tree planting, dietary change or recycling. Energy, transportation, buildings, industry, land use, agriculture, consumption and waste all contribute to the larger system. Addressing one does not excuse inaction on the others.
But food belongs in that conversation, and animal agriculture should not be treated as uniquely exempt from scrutiny simply because changing it can be culturally or politically uncomfortable.
“Unavoidable” Does Not Mean Inevitable
There is another danger in the language surrounding overshoot: it can make the present situation sound like something that simply happened to humanity. It did not.
The Paris Agreement was adopted in 2015, and scientists had been warning governments about climate change for decades before that. Governments made commitments, technologies improved and renewable energy expanded, but global action still failed to reduce emissions quickly enough to preserve a pathway that reliably avoids crossing 1.5°C. UNEP now says years of insufficient action have made some level of overshoot unavoidable.
That distinction matters for accountability. “Unavoidable now” does not mean “always inevitable.” Political choices, corporate decisions, infrastructure investments and patterns of production and consumption helped determine the path that brought us here. Past choices narrowed the options available today; today’s choices will determine how much narrower those options become for the people who come after us.
The purpose of acknowledging that history is not to assign blame simply for the satisfaction of doing so. It is to recognize that climate outcomes are influenced by decisions—and decisions can change.
Climate Change Is Also a Political Choice
The atmosphere does not care which political party someone belongs to. Heatwaves do not check voter registration, floods do not distinguish between ideological identities and wildfires do not stop at the border between a red county and a blue one. The physical consequences of climate change are indifferent to politics.
The tools societies use to confront those consequences, however, are deeply political. Governments make decisions about energy, transportation, agriculture, land use, pollution, infrastructure, disaster preparedness, research, public investment and climate adaptation. They determine which industries receive public support, which environmental protections are enforced and how quickly communities transition away from systems that increase emissions.
That makes climate science relevant when evaluating anyone asking for the authority to govern. The question should not simply be whether a candidate “believes” in climate change. Climate change is not a matter of personal belief. Voters can ask whether candidates accept the scientific evidence and, just as importantly, what they are prepared to do with it.
Will they support meaningful reductions in greenhouse-gas emissions while helping communities transition fairly? Will they confront methane emissions, protect forests and ecosystems, prepare communities for extreme heat and flooding, and address the role of agriculture and the food system? Will they follow evidence when the necessary policy is difficult, expensive or politically inconvenient?
Those answers should matter when we vote.
The Threshold Is Falling. Our Responsibility Isn’t.
The expected crossing of 1.5°C deserves to be understood for what it is: a serious failure after decades of scientific warnings and insufficient action. But treating that failure as the end of the climate fight would compound it.
Every fraction of a degree still matters because every fraction changes the risks faced by people, animals and ecosystems. Every year spent in overshoot matters because longer exposure increases damage and the possibility of irreversible losses. And every policy capable of reducing the eventual peak, shortening the overshoot or helping communities survive what can no longer be avoided still matters.
That means climate action cannot end with acknowledging the science. It requires political participation. Learn where elected officials stand. Ask candidates what they intend to do. Contact lawmakers, attend public meetings, organize locally, support credible climate policies and align with candidates and elected officials willing to treat climate science as evidence rather than ideology.
And if you are looking for a political home where environmental protection, human wellbeing and the interests of other animals are understood as interconnected rather than competing concerns, get involved with the Humane Party.
The climate crisis will not be solved by one election, one candidate or one political party. But it will be shaped by the people we entrust with political power and the policies we are willing to demand from them.
Some consequences can no longer be avoided. That makes the choices still available to us more important, not less.
What we refuse to accept now will help determine how much worse this becomes.
The Humane Herald 