Why do countries need to get more aggressive? The COP six years ago led to the Paris Agreement, in which countries were allowed to set their own, nonbinding targets. Policymakers knew that these targets wouldn’t be sufficient but it was the only way to get broad agreement, and the hope was that countries would then be shamed into further action. Another important outcome of the Paris Agreement was to raise the ambition to limiting warming from 2 degrees Celsius to 1.5 degrees. Limiting warming to 1.5 degrees by 2100 is crucial to avoiding irreversible and potentially catastrophic changes in the planet’s climate. Unfortunately, scientists calculated the Paris Agreement standards would only limit warming to 2.6-3.1 degrees by 2100.

At Paris, countries did pledge to update their “Nationally Determined Contributions” every five years, in a “ratcheting” mechanism that would become increasingly ambitious. As the COP last year was postponed due to the pandemic, Glasgow is the first opportunity since Paris for countries to formally declare their new emissions limits.

OK, so will the COP save the world this time? Absolutely not. Glasgow declarations will certainly miss the ambition of limiting warming to 1.5 degrees. If Glasgow ends well, we should hope for solid commitments that would result in 2 degrees of warming. Although the International Energy Agency announced last week that updated pledges could result in limiting warming to 1.8 degrees, these pledges contain no policy guarantees. When Climate Action Tracker assessed the short-term targets linked to these pledges, it found a resulting warming of at least 2.4 degrees — a small improvement on Paris, but nowhere near good enough. To keep the pressure on and to keep the more ambitious target of only 1.5 degrees of warming alive, an important outcome of COP26 must be an increase in the frequency of these declarations, to an annual cycle rather than every 5 years. Negotiations on this are still ongoing, but we should know the outcome soon.

What’s the most contentious issue in Glasgow? The speed of decarbonization across countries is one of the most fraught COP discussions. While civilization’s long-term survival demands that every country must eventually go to zero emissions, some countries have contributed far more to the carbon currently in the atmosphere. Those countries also happen to be some of the most well-resourced, resilient and safest from climate extremes, such as the U.S. or countries in Europe.

Recognizing the role of global solidarity, the 2009 Copenhagen COP agreement set up a climate finance fund. Wealthier countries pay into the fund to help less wealthy countries both decarbonize and, more recently, adapt to increasingly hostile climates.

How is that fund doing? The aim was to reach $100 billion per year by 2020. Yet the fund is far behind schedule and its accounting is problematic: lumping loans and grants together. In particular, the U.S. has an appalling record on climate finance, despite a recent announcement from the Biden administration that it will increase contributions. Between 2017 and 2018, the U.S. contributed less than France, Germany, Japan or the U.K., while having a larger GDP than all those countries combined.

So, after COP26, are we going to be OK? The pledges at the COP, so far, leave a massive gulf between rhetoric and action. Despite lofty words, there are precious few policy announcements of how ambitious climate goals will actually be met. Although there has been some progress — for the first time, fossil fuel subsidies and phaseouts are being openly discussed — the overall action simply does not match with the science. I can’t say whether we will see the action needed in the future, or where exactly social tipping points lie.

The only fact about the future I can declare with certainty is that the world as we know it is coming to an end. Either we (the global “we”) will remake society in unrecognizable — much healthier and equitable — ways to avoid overwhelming environmental damages or we will see irreversible changes in the climate, large-scale food crises, water scarcity and increasingly unliveable areas across the planet. Most likely, humanity will end up on a scale somewhere between those two worlds, remaking society to limit the extent of future damage while adapting to an increasingly hostile environment. Still, at any point on this scale, it’s the end of the world, as we know it.

What if COP26 fails? The worst-case scenario.

The most likely worst-case scenario is an ever-widening gap between net-zero rhetoric and actual policy. The world is barely on track to meet soft Paris Agreement targets, let alone more ambitious pledges made since Paris before and during this COP. Leaders may leave Glasgow with a warm buzz from inspiring words and promises — but without any intention or power to implement the policies needed to make those words a reality. The more than 2.4-degree rise in temperature we could be looking at is a number that hides the tremendous scale of mass suffering, food system collapse, intolerable heat, multiple and simultaneous extreme weather events, and large-scale, irreversible changes to the climate and ecosystem to come.

On the darkest of days, I imagine how this worst-case scenario might play out in the coming years.

With such slow action, the spreading of fear will make a psychological weapon of the weather. Countries will more and more have to turn to managing unfolding crises, with little time for international cooperation on reducing future emissions. Increasingly, we will begin to dread the onset of summer, anticipating what the season will bring: how many wildfires, heatwaves, hurricanes, and how large they will be. We may adapt by bolstering infrastructure, including sea walls and typhoon-proof buildings, but the changes will outpace what we build. Higher temperatures will render people incapable of working; warming is already increasing suicide rates.

Though hard to detect, rising temperatures will also increase the prevalence and spread of diseases. There is already evidence this is happening with Lyme disease and malaria, along with probable links for tick-borne encephalitis, yellow fever, plague, dengue, African trypanosomiasis, influenza, cholera, hemorrhagic fevers and schistosomiasis, to mention just a few. Moreover, the impact of climatic changes on the availability and nutritional content of food could hasten vicious cycles whereby malnutrition leads to compromised immune systems driving further disease spread. There will be increasing numbers of global health crises, including pandemics.

As the overdrawing of groundwater continues, exacerbated by soaring temperatures, water shortages will become the norm. Even under lower warming scenarios of around 2 degrees, water shortages and extreme events like floods and heatwaves will likely hit several food-producing regions at once. Global food prices will then rocket. Studies are showing again and again that yields may drop dramatically even by 2030 and certainly by 2050. With our trajectory — without making the changes activists are demanding — it is conceivable that supermarket shelves will start to get patchy by the middle of this century, and perhaps even earlier in countries with lower purchasing power.

Researchers have already found 467 different pathways for how health, water, food, infrastructure and security have been recently impacted by climate change, from heatwaves to floods, drought to sea-level rise. All these impacts are set to worsen. The fear of the future will continue to rise.

In this scenario, we could expect a turn to strong-men leaders, with fearful citizens panicking as shortages start to be felt. At current rates of warming, hundreds of millions will be looking for climatic refuge by 2050. Migration would likely be used as a dog whistle by opportunistic politicians to push an agenda of increasingly fascist policies. Border fences would go up, and detention centers for migrants in the U.S. and EU would expand, becoming increasingly permanent fixtures. Climate change has already been identified as a driving force for Central American migration. As institutions decay and tensions mount, violence and war could break out.

This would be happening in a global society that is already failing to protect the vulnerable, feed the hungry and alleviate the suffering of the poor. As the world warms, the mega-wealthy would attempt survival by putting up walls or moving to higher ground, or underground — already a booming business, with disused, fortified missile silos being snapped up for millions of dollars. The exodus has already begun, with some of the richest humans in history already defecting from society, buying both visas and mansions in places like New Zealand, where the climate won’t be as bad, for a while at least. Meanwhile, an underclass would eke out ever more brutal lives, while food and water scarcity increases.

This might sound like a depiction from a sci-fi novel or the comments section on some conspiracy YouTube channel. But it isn’t. This worst-case warming scenario is based on the accepted, scientific studies outlining the impacts on food, water and social systems resulting from our past and current actions. That we are already on the road to the death of current global civilization is no longer up for debate. At present, the actions to prevent this reality are shockingly deficient, and if we don’t see significant progress at COP26, the possibilities for future action will become even narrower.

But there are alternative roads.

What if COP succeeds? The best-case scenario.

The best outcome for this COP would be an announced phase out of oil and gas (rather than just coal), an acknowledgment of developed countries failure to provide $100 billion in climate finance and a guarantee to help lower-income countries deal with the loss and damage of climate change going forward, and an agreement by all the parties to the convention to more frequently ratchet up their climate action commitments in line with what is necessary to limit warming as much as possible.

But that would only be the beginning. For large-scale change to be effective and rapid, institutions must move together: The legal system, the civil service, national and international banking institutions, and local and national governments must all move in the same direction. The mandate for such large-scale change will most likely be won when community and civic groups take action, when we reach a social tipping point whereby governments can no longer delay or ignore problems or public will.

The best-case scenario is not an outcome so much as a path that must be taken to avoid the worst-case outcome. In this scenario, activist climate movements will likely be a driving force, and leaders will come out of this COP with an overwhelming pressure to act on their targets and to announce and legislate truly ambitious policies for change. Ideally, global leaders, for the first time, would realize that it is far too late for gradual change.

What then might it look like for the pillars of civilization — governments, legal systems, communities and businesses, globally — to align to reduce emissions as rapidly as possible?

Governments around the world would take advantage of the astonishingly low costs of renewable energy to electrify infrastructure, which is flexible, clean and efficient. We already have the solutions to decarbonize 65-75 percent of energy use via technologies like cheap renewable electricity and energy efficiency. Leaders across the rich world would accept that the reduction of remaining emissions will be more expensive and will require further investment to bring costs down, including in electricity storage and hydrogen infrastructure. They would build policies around this. Policymakers would understand that the cost of these technologies will reduce rapidly as they are deployed — each new battery and hydrogen electrolyzer is a chance to improve performance and decrease costs. The future of energy is small, fast and modular. Think: the rapid adoption of smartphones and the internet rather than the slow, heavy, immovable infrastructure of fossil fuels.

That’s not all there is to the best-case scenario. Decision-makers could introduce policies such as the rapid expansion of national bike infrastructure and pedestrianization. Safer cycling and e-bikes bring longer distances into reach and reduce cars on the road. Strict building standards could also be enforced, and a universal building insulation program could be rolled out. These changes would save money, save millions of lives from air and noise pollution, build tighter communities, provide better housing, deliver healthier lifestyles and safer neighborhoods.

As our urban environments change for the better, countries would have to ban the new development of fossil fuel resources, roads and airport expansions. Frequent flyer levies could be introduced, penalizing each additional flight at an increasing rate. Eventually, with the waning lobbying power of high-carbon sectors, governments would completely phase out subsidies from fossil fuels, accelerating the transition. Their influence is already declining, and the world’s largest fossil fuel companies are already exposed to serious legal risk for knowingly polluting the atmosphere and misinforming the public about climate change.

There is more. Even if the energy system is decarbonized fast, the food system as it stands could alone push us into climate catastrophe. Understanding that animal agriculture is the biggest single driver of biodiversity loss and a massive contributor to climate change, policy makers would shift agricultural subsidies to incentivize plant-based diets, help farmers improve cultivation practices and encourage biodiversity protection. In a best-case scenario, the public would enhance this dynamic with a continued shift to plant-based diets. Individual actions can then spur systems-change, a shift that would accelerate rapidly when 20-30 percent of the public become vegetarian. Such a shift would open up huge opportunities, both in plant-based diets and for the 27 percent of global, habitable land on which animals once grazed. Farmers could be paid to transition to plant-based cultivation or to leave land for nature and local communities. This would protect biodiversity and provide access to the outdoors for people to enjoy the health benefits of spending time in nature.

Even if all these changes are implemented, it would still not be enough in the longer term. The flow of emissions would have been staunched but, simultaneously, the atmospheric concentration of greenhouse gases must be actively reduced through carbon sequestration. Governments would need to commit to a global agreement for redirecting agricultural and fossil fuel subsidies to natural climate solutions and independent landholders, revolutionizing land management and increasing the carbon stored in soils and vegetation. But only natural approaches won’t cut it. In a best-case scenario, further in the future after emissions have been slashed as far as possible, governments might force the aviation sector to pay for the mechanical extraction of carbon from the atmosphere, as, say, part of an agreement to permit it to continue operations. Technological innovation will be needed, one way or another, to remove carbon from the atmosphere.

None of these interventions are expensive if the long-term benefits are weighed against the costs. Already new renewables are cheaper than existing fossil fuels in many places around the world. Indeed, researchers have evaluated the now-removed Clean Electricity Performance Program component of Biden’s Build Back Better bill and found it would be more affordable than doing nothing (not even taking into account the health and environmental damage of fossil fuel infrastructure). But we are still talking about dollars and cents in crude cost-benefit-analyses. In a truly best-case scenario, we’d move away from narrow metrics of success like GDP growth and focus on broader sets of societal outcomes, from life expectancy to water quality to biodiversity protection.

In a best-case scenario, all of this would be done while ensuring society’s poorest and most marginalized benefit from these changes. One way to do this would be to raise a carbon fee — charging for the emission of carbon into the atmosphere while the funds are directly returned to the poorest in society. Another would be by ensuring the people have more input into decision-making in the form of citizens’ assemblies. In 2020, the U.K. ran a climate citizens’ assembly: One hundred and eight people from across the country, from all backgrounds, were first informed about climate change by scientists and then asked what they’d like to do about it. They came up with a frequent flyer tax, proposed phasing out SUVs and argued for a 20-40 percent voluntary cut in red meat. None of that would be enough on its own, but it’s far better than the policies the U.K. government is considering today. Better yet, it’s what people want, when they know the facts. More citizens’ assemblies around the world could offer the political cover for government officials to enact bold climate action.

Even in this best-case scenario, in which the world is remade in staggering, beneficial ways to address climate change, we need to remember that the climate will get worse before getting better. Some slowly unfolding problems, such as sea level rise, will continue for hundreds of years. In a best-case world, funding for adaptation will have to rapidly increase. Governments could sign international agreements for the well-managed migration of the millions of climate migrants we are already beginning to see today. In a best-case world, migration might be seen as an opportunity, including for stemming the population declines across many nations.

The next few years will decide the degree of warming at the end of this century. It will decide whether the millions suffering today will become billions. It will decide how many will get sick from the spreading of existing and new diseases. It will decide how extensive the crop losses and food shortages will be. It will decide the degree of conflict and violence and suffering.

This is the weight on leaders’ shoulders as they wrap up COP26. In truth, there is no world in which any efforts would be enough to completely avoid more tragedy. In any future situation, every bit of warming matters and therefore every action matters. Some slow progress is being made, but we are yet to see the kind of significant action that would push us closer towards the best-case future, and we are still far too close to realizing the worst-case one.