New data shows that the Earth reached a potentially ominous temperature milestone last month.

Why it matters: January 2024 marked the first time that the global average surface temperature anomaly exceeded 1.5°C during a 12-month period, according to the Copernicus Climate Change Service.

• The breach of 1.5-degrees is symbolic, and may be temporary, but it shows how close the world is to bumping up against the 1.5-degree Paris target even if during short time periods.

Details: The 12 months lasted from February 2023 through January 2024.

• Tracking 12-month running mean temperatures clearly shows the large spike that began last year extending into 2024.

Zoom in: January was also the warmest such month on record, Copernicus found, backing initial data from Japan.

• Copernicus found the global average temperature for the month was 1.66°C (2.98°F) above preindustrial levels.
• Keeping the 1.5°C Paris target viable is a central goal of UN Climate Summits. Many vulnerable countries see it as necessary for their survival.
• Yet scientific assessments consistently show that target is slipping out of reach.

Reality check: While exceeding 1.5°C in the 12-month running mean has some significance, the target contained in the Paris Climate Agreement refers to a long-term, 20- to 30-year average.

• So the Paris target has not actually been exceeded based on that meaning.

Between the lines: Last year was the warmest year on record.

• It saw record high sea surface temperatures, deadly heat waves and other extreme weather events that prompted new research into whether climate change has in fact sped up.

What they're saying: Stephanie Roe, an IPCC author who works as the head of WWF's global climate and energy program, called the new data a "seismic moment for the climate," in a statement to Axios.

• She emphasized the need to slash greenhouse gas emissions in order prevent "every additional increment of warming."