1.5°C—What will it take?

By Ellie Johnston
November 18, 2025

One of the more promising developments for COP30 so far is a discussion initiated by Brazilian President Lula on the idea of a roadmap to transition away from fossil fuels. This complements the call by the UN Secretary General António Guterres to stick to the 1.5°C limit, although the lack of action to date means that we will now overshoot the 1.5°C limit, even if we begin the much more ambitious action that is needed for a 1.5°C path. The possibility of limiting warming to 1.5°C was reiterated throughout the last two weeks by scientists worldwide through new reports like the IEA’s World Energy Outlook and UNEP Emissions Gap Report.

To bring some clarity to the level of ambition that we are talking about, I created a scenario that results in 1.5°C by 2100 in our En-ROADS Climate Solutions Simulator that we have developed at Climate Interactive with MIT Sloan. Below I go through the key elements of this very high ambition global scenario.

In summary, the level of action required far exceeds what world leaders are proposing right now. At the heart of the scenario is the simple truth that we must take swift action to reduce our dependence on fossil fuels. To do this requires policy mechanisms, like carbon prices, taxes, or mandates, alongside adequate finance and frameworks for a just transition. It is not sufficient just to deploy cheap wind and solar energy.

Why is 1.5°C so important?

A world that limits climate change to 1.5°C by the end of the century would be a vastly safer and healthier world than the one we are heading toward today. If we can get on a 1.5°C path, we can prevent millions of deaths, protect ecosystems, and reduce the most dangerous climate extremes. These indicators also point to larger global systemic risks that have dire consequences for our economy and society.

This 1.5°C scenario saves:

• Months of unbearable heat: In Belém, this is a difference of 4 months of extreme heat and humidity each year! (162 days per year at or above 26°C wet bulb temperature at 1.5°C, vs. 288 days at 3°C).
• Lives: Globally, it would save at least 1.7 million people from dying of extreme heat in the year 2100.
• Food security: Wheat yield losses as a result of climate change are reduced by 67% (5% reduction in wheat yield, vs. 15% in the Baseline Scenario).
• Biodiversity: For insects alone, this scenario would reduce their projected habitat loss by 86%.
• Work and income: When it is too hot, people can’t work outside. This is expected to get worse with rising temperatures, but this scenario can avoid 2 weeks of labor lost each year on average for people in outdoor sectors like construction, fishing, and agriculture.

Explore other impacts of this 1.5°C scenario by looking at the graphs and maps of impacts within En-ROADS.

From the Paris Agreement to the International Court of Justice more recently, countries and international bodies have affirmed that this is a limit we should stick with.

A note on overshoot:

When we talk about overshooting 1.5°C, it means that we will see global temperatures continue to climb for some time, but, with lots more action, we will eventually be able to bend the global temperature downward so that we finish this century with only 1.5°C of warming. To do this, however, requires immediate action. The blue line below is what it could look like, compared to the black line of the Baseline Scenario if we don’t take action.

To achieve this outcome, greenhouse gas emissions need to look something like this:

Some key things to note:

• Fossil fuel CO₂ emissions are the biggest source of emissions today and need to fall the most. In this 1.5°C scenario, they fall 23% from 2025 levels by 2030 and 76% by 2050. Yet just last week, new data showed that fossil fuel emissions rose by 1% last year—moving in the opposite direction of where we need to go.
• Land use needs to shift from being a source of CO₂ emissions to a source of removals. Put simply, instead of cutting down trees and releasing carbon, we need to be growing more trees that capture carbon. (Note how the green area is above zero until 2050 and then is below zero afterwards).
• F-gases, CH₄ (methane), and N₂O (nitrous oxide) all need to decline from current levels. More on these below.
• The grey area that starts in 2040 under the horizontal zero line is carbon dioxide removal (CDR) from approaches that don’t rely on photosynthesis—this includes things like direct air capture and enhanced mineralization.
• Finally, note that even with greenhouse gas emissions falling rapidly in the next decade, global temperatures keep climbing. These things can’t change direction overnight.

But really, what does it take to stick to 1.5°C?

First off, Belém will need to be the turning point, not another COP where leaders talk about cutting emissions while global emissions keep rising. Seriously.

To get on the 1.5°C path, next year we will need to begin rolling out the following actions globally:

1. Phase out fossil fuels
   • Accelerate the retirement of coal power plants to 10%/year. For comparison, the global retirement rate in 2024 was only about 1%, so this would be a 10-fold increase. Because twice as much new coal capacity came online last year than was retired, global coal capacity actually grew by roughly 1%.
   • Implement a carbon price of at least $250/ton with additional policies to discourage coal, oil, and gas development. This is nearly twice the current carbon price in Sweden (around $130 per ton). The carbon price that is used in other models is sometimes much higher than this, so consider this estimate conservative. There are lots of ideas out there about how to handle this. Basically, we have to have something that makes it unprofitable for any polluter to put CO₂ emissions into the atmosphere. Right now, many can do it for free.
2. Boost renewables and energy storage
   • Wind and solar: Wind and solar are already among the cheapest sources of new electricity worldwide, but meeting the 1.5°C goal requires pushing their deployment even faster. This means expanding incentives, rethinking permitting processes, and creating hospitable markets for their deployment.
   • Storage: Alongside wind and solar, we need breakthroughs to bring down the costs of energy storage. Affordable batteries and other storage technologies are essential in order to use high levels of renewable energy. This is also a major opportunity for emerging economies to leapfrog fossil-fuel infrastructure. In regions with unstable grids, even a small solar-plus-battery system can be transformative. Today, roughly 1 billion people worldwide are served by healthcare facilities that face intermittent or unreliable power. Local renewable systems—such as microgrids or rooftop solar with batteries—can keep vital equipment running, support patient care, and maintain operations during extreme weather or supply-chain disruptions.
3. Boost electrification and hydrogen
   • Over the next 30 years, we need to switch nearly every machine, vehicle, and building system that currently relies on fossil fuels to clean electricity. That means increasing electric vehicles from just 5% of transport today to more than 60% by 2050, and increasing electric heating and equipment in buildings and industry from 45% to 85%. And for the sectors where electrification isn’t practical, such as long-distance aviation and shipping, we will need major advances in hydrogen and synthetic fuels produced from renewables.
4. Energy efficiency
   • Assume that energy efficiency steadily improves beyond what would otherwise occur. In some regions, this is already happening. Between 2010 and 2022, countries such as the UK, Germany, Japan, and China achieved sustained reductions in energy intensity of more than 2% per year. These changes are driven by, among other things, improved fuel economy standards and adoption of EVs.
5. Waste
   • We need to implement the full range of available actions here. Some emissions in this sector cannot be fully eliminated, however. As a result, we can only achieve a 77% reduction in methane emissions from waste by 2050. To put this in perspective, keep in mind that any kind of organic matter that rots releases emissions. What we can do:
   • Energy systems: If we extract fossil fuels, then we must maintain and monitor the infrastructure to ensure it doesn’t leak—from pumpjacks to pipelines to power plants. But even once we’re done using this infrastructure, we still need to monitor it to ensure it doesn’t leak.
   • Landfills and wastewater treatment: Best practices here include recycling, composting, and capturing methane from landfills and wastewater before it leaks into the atmosphere.
   • Industrial waste emissions: CO₂ emissions from cement and iron production and N₂O emissions from processes like nylon and fertilizer production can be mitigated through capture or reduction practices. Similarly, reducing F-gas emissions involves recovering gases from old equipment and using alternative refrigerants in new equipment.
6. Agriculture
   • First we need to do everything we can to reduce unnecessary methane and nitrous oxide emissions in our agricultural processes.
   • Shift toward more plant-based diets: Today, roughly 23% of average global diets come from animal products, and without additional action, that share could rise to 30% by 2100. Bringing the global average closer to 20% would cut methane emissions from agriculture by one-third by 2100. Doing this would also help prevent deforestation.
   • Less food waste: Today, about 30% of all food produced is lost or wasted. Reducing this to around 20% would ease pressure on land, water, and fertilizer use and cut methane and nitrous oxide emissions from agriculture by 13%. These practices can include investing in food storage infrastructure and programs to rescue and redistribute unused food.
7. Forests
   • Cut deforestation 10% per year alongside cuts to forest degradation. Recent experience in the Brazilian Amazon—where deforestation fell 11% in one year thanks to strengthened policies and monitoring—shows this level of progress is achievable.
8. Carbon removal
   • Finally, we need some carbon removal. In the scenario, I opted for a portfolio of carbon dioxide removal approaches, including both planting trees and experimental approaches like direct air capture. The result is that carbon removal expands to store up to 8 gigatons of carbon a year by the second half of the century.

Choices about this scenario:

I tried to create a scenario that minimized as much as possible relying on technology that doesn’t exist yet at scale. Technologies like carbon capture and storage for fossil fuels and bioenergy, direct air capture, and hydrogen are areas of significant technological innovation, but their economics and other practical constraints make it difficult to imagine depending on them heavily. That said, we will still need to rely far more on these technologies than we do now and will need them to be successful to get on a 1.5°C path.

Thoughts on other energy sources:

1. What about bioenergy? Expanding the use of bioenergy, whether for electricity generation or fuel, generally contributes to carbon emissions. While some level of bioenergy use will occur where people can source it locally (e.g., for cooking and heating), it’s not an energy source we should scale up globally.
2. What about nuclear? In this scenario, nuclear power grows more rapidly than we have seen in recent decades due to a modest subsidy, but it still provides a much smaller fraction of the energy supply by the end of the century compared to wind and solar. Nuclear simply doesn’t have the cost advantages that wind and solar do, among other limitations.

This is a scenario where the global population follows the UN’s expected growth trajectory, with population peaking at 10.3 billion people by around 2080, and economic growth continues to climb but is lower than it would be without climate change. The scenario keeps other assumptions—like climate sensitivity (3.0°C)—at the default levels of En-ROADS. If you want to change any of the inputs I tested or create your own 1.5°C scenario, please dive in. En-ROADS is designed for anyone to use.

The scientific literature has a number of 1.5°C scenarios that were published for the IPCC’s 2018 Special Report on 1.5°C. However, those scenarios are now out of date, because they assumed emissions reductions that have not happened in the last seven years or more. Newer pathways from UNEP, Climate Analytics, and the IEA are complements to this back of the envelope scenario I’ve created here.

Explore the impacts, change the inputs, see if you can make a version that you like better, then let’s point our decisions towards getting on this track. There’s no time to lose.