In the final episode of Today I Learned: Climate, Laur Hesse Fisher and Maria Ivanova discuss the proposed temperature thresholds of 1.5 and 2 degrees Celsius. These targets are central to global climate goals, but where did they come from, and why are they so important? The 2-degree Celsius limit was first proposed by economist William Nordhaus in 1975.He suggested the threshold as a guideline of what must be done to prevent harsh climate conditions that humanity had never experienced prior. The simplicity of this number made it memorable and influential in subsequent climate policy discussions.

The 1.5-degree target emerged from the 2009 Copenhagen Climate Summit, driven by the Association of Small Island States (AOSIS). Countries like Fiji and the Maldives pushed for this stricter limit, largely because they themselves faced severe risks from rising sea levels. The IPCC later produced a special report which showed just how different the 1.5- and 2-degree rises were. Nowadays, these temperature goals function as benchmarks in international agreements like the Paris Climate Agreement. While not legally enforceable, they galvanize global action, and have led to profound investment in renewable energy and driving policy changes.

These temperature thresholds are more than numbers: they represent our collective commitment to mitigating climate change and securing our planet's future. Understanding their origins and significance helps us understand the urgency of our climate efforts.