The 1.5°C threshold represents the global temperature rise above pre-industrial levels that scientists consider a critical limit to avoid the most severe impacts of climate change. This number comes from decades of research and was cemented as a goal in the Paris Agreement of 2015. The agreement aimed to keep warming well below 2°C, with efforts to limit it to 1.5°C.

Since the Industrial Revolution, burning fossil fuels, deforestation, and industrial activities have caused greenhouse gas concentrations to soar, leading to temperatures now surpassing the 1.5°C mark. This level of warming has already caused significant changes and brings the planet closer to dangerous tipping points.

The 1.5°C threshold is not just about preventing further warming - it’s about protecting ecosystems, vulnerable communities, and the planet’s long-term stability.

A small difference of 0.5°C might not sound significant, but in terms of climate impacts, it’s the difference between manageable challenges and catastrophic consequences. Here’s how the impacts compare at these levels:
‍

1. Extreme Weather Events: At 1.5°C, heatwaves, droughts, and hurricanes are already more intense than in pre-industrial times. At 2°C, these events become far more frequent and severe. For example:
   ‍
   • At 1.5°C, about 14% of the global population will experience extreme heatwaves.
     ‍
   • At 2°C, this number rises to 37%, exposing hundreds of millions more to life-threatening heat.
     ‍
2. Sea-Level Rise: Limiting warming to 1.5°C could reduce sea-level rise by 10 centimeters compared to 2°C. While 10 centimeters might sound small, it’s enough to protect millions of people living in coastal areas.
   ‍
3. Ecosystem Impacts: Coral reefs are particularly vulnerable to warming. At 1.5°C, scientists predict that 70–90% of coral reefs could be lost. At 2°C, nearly all coral reefs would disappear, devastating marine biodiversity and the communities that rely on them.
   ‍
4. Food Security: Warming above 1.5°C increases the likelihood of crop failures and reduced yields, particularly in regions already vulnerable to food insecurity.
   ‍

Every fraction of a degree matters. The closer we stay to 1.5°C, the fewer lives are lost, the less damage occurs, and the more ecosystems can adapt.

As of 2024, the planet has already warmed by over 1.5°C, surpassing the critical threshold set in the Paris Agreement. For perspective, CO₂ concentrations in the atmosphere are now over 420 parts per million (ppm), compared to 280 ppm before industrialization. Without drastic reductions in emissions, the warming trajectory could push the planet closer to even more dangerous tipping points.
‍

Why does this matter? Surpassing 1.5°C increases the likelihood of crossing tipping points - thresholds where natural systems undergo irreversible changes. For example:
‍

• Melting Ice Sheets: Greenland and Antarctic ice sheets could begin irreversible melting, leading to sea-level rise over centuries.
  ‍
• Amazon Rainforest Dieback: Rising temperatures and deforestation could push the Amazon past a tipping point, turning it from a carbon sink to a carbon source.
  ‍
• Permafrost Thawing: Melting permafrost could release large amounts of methane, accelerating warming.
  ‍

Surpassing 1.5°C isn’t just about the environment; it’s about protecting human lives and livelihoods. Vulnerable populations, particularly in developing countries, are already feeling the worst impacts of climate change. Floods, droughts, and heatwaves hit hardest in places where people have fewer resources to cope, making existing challenges like poverty even worse.

To prevent warming from going even higher, global emissions must fall as quickly as possible and reach net zero by 2050. This requires urgent action at every level, from international agreements to local community initiatives, as well as a focus on clean energy, reforestation, and sustainable practices.