The Reliance School

1,900 Words / 8 min. Read

In December 2015, 195 nations signed the landmark Paris Agreement, with the goal of rapidly decreasing emissions and limiting warming to below 1.5 °C (2.7 °F).

The Paris Agreement is a legally binding international treaty on climate change. It was adopted by 196 Parties at the UN Climate Change Conference (COP21) in Paris, France, on 12 December 2015.

Its overarching goal is to hold “the increase in the global average temperature to well below 2 °C above pre-industrial levels” and pursue efforts “to limit the temperature increase to 1.5 °C above pre-industrial levels.” However, world leaders have stressed the need to limit global warming to 1.5 °C by the end of this century.¹

No amount of climate change is “safe,” but 1.5 °C was set as a limit due to greatly increased risk to our ecosystems and society at higher levels of warming.² To achieve this goal, global emissions would need to drop 50% by 2030, and be reduced to net zero by the 2050s.³

It should come as no surprise that we’re nowhere close to achieving these reductions,⁴ but the situation is far worse than most people realize. In 2025, three briefs were published showing that not only are we not on track to stay under 1.5 °C; we may have already crossed over the line. In this post we’ll be taking a closer look at that data, and the consequences of crossing this threshold so much sooner than projected.

Defining Warming

Before we dive into the details, let’s define our terms. When we’re talking about degrees of warming, we’re talking about global surface temperature, or GST.⁵ That’s the average temperature across the entire planet; at the equator, at the poles, on oceans, on land, day and night, summer and winter.

For our baseline, we’re using the GST from 1880; that’s when we first started taking reliable measurements of global temperature,⁶ and it’s also right around the time of the Industrial Revolution, when we began burning fossil fuels at scale.^7,8 In 1880, the GST was around 14 °C, or 57 °F.⁹ So when we say that the earth has warmed by 1.5 °C, we’re saying that the GST has increased to 15.5 °C, or 59.7 °F.

That warming isn’t evenly distributed, which we’ll cover in detail with the next post. But first, let’s touch on another important aspect: timeframe. 2024 was the hottest year on record, with global temperatures 1.55 °C above baseline¹⁰ (2025 looks to be following suit).¹¹ And in November 2023, the global temperature reached a staggering 2 °C (3.9 °F) above the pre-industrial average.¹²

But when scientists and policymakers talk about crossing a climate threshold, they’re talking about a rolling average of a decade or more (the IPCC uses 20 to 30-year averages).¹³ In 2018, the IPCC projected that we would “officially” cross this threshold around 2040;¹⁴ in 2021, their 6th assessment report updated that projection to the mid-2030s.¹⁵ But new research is indicating that the planet has already breached that limit - 10 to 15 years earlier than expected.

The Research

In February 2025, two communications briefs were published in Nature Climate Change with evidence that we’re currently living in the era of 1.5 °C. Both are linked here if you’d like to read them in full, and we’ve highlighted some key passages below.

A year above 1.5 °C signals that Earth is most probably within the 20-year period that will reach the Paris Agreement limit

Twelve months at 1.5 °C signals earlier than expected breach of Paris Agreement threshold

Both briefs demonstrate that a year above 1.5 °C (as we experienced in 2024) is a strong indicator that we’ve entered a long-term period with temperatures above that threshold. According to the first brief:

Observations reveal that the first single year exceeding 0.6 °C, 0.7 °C, 0.8 °C, 0.9 °C and 1.0 °C warming thresholds have consistently fallen within the first 20-year period in which average temperature reached the same thresholds. This pattern motivates the hypothesis that a similar behaviour may apply to the 1.5 °C threshold.

If true, the occurrence of the first single year at 1.5 °C warming would imply that the 20-year period that reaches the Paris Agreement’s lower goal has already started and that the expected impacts at a 1.5 °C warming level will start to emerge.

Our analyses demonstrate that, unless ambitious emissions cuts are implemented, the world’s first year at 1.5 °C warming is virtually certain (99% on average) to fall within the 20-year period that reaches the 1.5 °C warming level.¹⁶

The second brief comes to a similar conclusion:

Projections of the first occurrence of 12 consecutive months above 1.5 °C tend to occur after long-term warming has already reached 1.5 °C. Hence, in CMIP6 simulations, 12 consecutive months above 1.5 °C indicates that the Paris Agreement threshold is likely to have already been crossed (estimated exceedance probability of 0.76).

If 1.5°C anomalies continue beyond 18 months, breaching the Paris Agreement threshold is virtually certain.¹⁷

In other words, there’s a 76% to 99% likelihood that we’re currently living in a world that’s 1.5 °C (2.7 °F) warmer than our baseline.

In March 2025, a third brief was published titled Global Warming has Accelerated Significantly, which found that:

Recent record-hot years have caused a discussion whether global warming has accelerated, but previous analysis found that acceleration has not yet reached a 95% confidence level given the natural temperature variability. Here we account for the influence of three main natural variability factors: El Niño, volcanism, and solar variation. The resulting adjusted data show that after 2015, global temperature rose significantly faster than in any previous 10-year period since 1945.¹⁸

When adjusted for that natural variability, their results show that warming has accelerated from 0.15-0.2 °C per decade (1980-2000) to 0.4 °C per decade (2015-2025). When this analysis was applied to five of the best-known global temperature data sets (NASA, NOAA, HadCRU, Berkeley, and ERA5), all showed that we would cross the 1.5 °C threshold between 2024 and 2026, in line with the previous two briefs.

This may come as no surprise to anyone who’s been following this subject (we continue to set new records for fossil fuel consumption with each passing year),¹⁹ but it’s a sobering confirmation that the pace of warming is once again outstripping our projections.²⁰

The Consequences of 1.5 °C

Climate change isn’t distributed evenly, and in How Will 1.5° of Warming Affect America? we’ve created a series of interactive maps showing how temperature and rainfall is projected to change in our country. But first, let’s look at the effects on our planet as a whole. In 2018, the IPCC released a special report on the consequences of 1.5 °C of warming; we’ve linked the report below, along with an interactive summary from Carbon Brief.

Global Warming of 1.5 ºC

The impacts of climate change at 1.5C, 2C and beyond

As expected, there’s very little good news. A world that’s 1.5 °C warmer is facing rising sea levels, coastal inundation, ocean acidification, ice-free Arctic summers, loss of snowpack and glacial aquifers, more frequent heat waves, extended droughts, increased flooding and extreme rainfall, more severe tropical storms, decreased corn and wheat yields, a higher incidence of vector-borne diseases, and trillions in lost capital.²¹ And to heighten the injustice, the worst effects of warming will be felt by the people least responsible for it.²²

More importantly, breaching 1.5 °C in the 2020s puts us firmly on track to exceed 2 °C of warming before 2050,²³ which the Institute and Faculty of Actuaries define as a “catastrophic” risk trajectory. In their 2025 report on planetary solvency, they warn that:

Warming above 1.5 °C is extremely risky. The chance of triggering multiple climate tipping points cannot be ruled out, such as the irreversible collapse of ice sheets, abrupt permafrost thaw, Amazon dieback and halting major ocean current circulation. Impacts could be catastrophic, including significant loss of capacity to grow major staple crops and multi-metre sea level rise.

Tipping points may interact to form tipping cascades, which would further accelerate the rate of warming and severity of climate impacts. If multiple tipping points are triggered, there may be a point of no return, after which it may be impossible to stabilise the climate.²⁴

The risks identified in this trajectory include the breakdown of critical ecosystem services and Earth systems, major extinction events in multiple regions, over $10 trillion in global GDP loss, frequent food and water crises, worsening socio-political fragmentation, failure of vulnerable states, mass migration and mortality events, and over 800 million preventable deaths worldwide.²⁴

Clearly, this is a scenario we want to avoid at all costs. Our dependence on fossil fuels and continued overshoot of planetary boundaries²⁵ is akin to playing a game of Russian roulette with the future of humanity (albeit with worse odds; IPCC projections give a 1 in 5.6 chance of current warming in the pipeline being an apocalyptic 4.5 °C/8.1 °F or higher).²⁶ Yet while few of us would feel comfortable trusting our lives (or the lives of our children) to a revolver with a bullet in the chamber, the world at large has continued to churn out record-breaking emissions.¹⁹

The Path Forward

The first step towards preparing for this future is understanding what it might look like, and that’s exactly what you’re doing by reading this. But while it’s important to understand the severity of the risks that we're facing, we also need to give ourselves the time and space to process this information, both intellectually and emotionally.

So if reading this has brought up feelings of stress and anxiety for you, take a moment to turn off your device and do something that feels grounding for you. That could be anything from taking a shower or a walk, to reaching out to a loved one for conversation and support. Because personal wellbeing is such a foundational aspect of resilience, we’ve written a full article on working with climate anxiety, where we’ve covered six ways to work with the feelings that this subject can bring up.

Our main focus at the Reliance School is on actionable steps that you and your community can take to prepare for a warmer world, and How to Survive the Future is our comprehensive guide to building security and sustainability in all aspects of your life. In [5 Keys to Surviving the Future] and [6 Principles of Resilience], we’ve summarized the core principles of that guide to create a crash-course on personal resilience. And in our series on climate havens, we’ve identified four key factors to consider if you’re searching for a lower-risk area to call home.

If you prefer to consume your information in hard copy, we’ve compiled an essential reading list covering everything from climate science and community to preparation and permaculture. And over the coming months, we’ll be continuing to expand our free content to cover more topics.

Whatever you choose to focus on, the key is making it actionable and achievable. Don’t just consume information; take small steps each week to increase your preparedness and capacity for change. The challenges are immense, but we’re choosing to face them, and we hope you do too.

Footnotes & References

1. The Paris Agreement (United Nations Framework Convention on Climate Change)
2. 1.5°C: what it means and why it matters (United Nations)
3. Paris Agreement (Wikipedia)
4. Countries (Climate Action Tracker)
5. Global Temperature (NASA)
6. Why does the temperature record shown on your “Vital Signs” page begin at 1880? (NASA)
7. Industrial Revolution (Wikipedia)
8. Annual greenhouse gas emissions including land use (Our World in Data)
9. World of Change: Global Temperatures (NASA Earth Observatory)
10. 2024 is the first year to exceed 1.5°C above pre-industrial level (Copernicus Climate Change Service)
11. Earth is heading for a second year above 1.5°C climate goal (Madeleine Cuff, NewScientist)
12. Global temperature exceeds 2°C above pre-industrial average on 17 November (Copernicus Climate Change Service)
13. What's in a number? The meaning of the 1.5-C climate threshold (Tom Di Liberto, Sarah Kapnick, Joe Casola, Brittany Croll, Victoria Moreno, Russell Vose, Climate.gov)
14. In-depth Q&A: The IPCC’s special report on climate change at 1.5C (Carbon Brief)
15. What the new IPCC report says about when world may pass 1.5C and 2C (Zeke Hausfather, Carbon Brief)
16. A year above 1.5 °C signals that Earth is most probably within the 20-year period that will reach the Paris Agreement limit (Emanuele Bevacqua, Carl-Friedrich Schleussner, Jakob Zscheischler, Nature Climate Change)
17. Twelve months at 1.5 °C signals earlier than expected breach of Paris Agreement threshold (Alex Cannon, Nature Climate Change)
18. Global Warming has Accelerated Significantly (Stefan Rahmstorf, Grant Foster)
19. Fossil fuel CO2 emissions increase again in 2024 (Global Carbon Budget)
20. Why the recent ‘acceleration’ in global warming is what scientists expect (Zeke Hausfather, Carbon Brief)
21. Global Warming of 1.5 ºC (IPCC)
22. Exceeding 1.5C of global warming will hit poorest the hardest (Andrew King, Luke Harrington, Carbon Brief)
23. When might the world exceed 1.5C and 2C of global warming? (Zeke Hausfather, Carbon Brief)
24. Planetary Solvency – finding our balance with nature (Institute and Faculty of Actuaries)
25. All planetary boundaries mapped out for the first time, six of nine crossed (Stockholm Resilience Centre)
26. Climate Scorpion – the sting is in the tail (Institute and Faculty of Actuaries)