GloSAT, a new extended temperature dataset, pushes the observational record back to 1781 and finds the late 1700s–mid‑1800s were cooler than the conventional 1850–1900 baseline, partly due to major early‑1800s volcanic eruptions. The compilation attributes about 0.09 °C of warming to humans between 1750 and 1850; a separate study adds 0.1–0.2 °C from early CO₂ increases. While the findings revise how much early human activity warmed the planet, experts say they do not change current climate targets or immediately accelerate expected impacts.
New GloSAT Record Extends Global Temperatures to 1781 — Suggests Early Emissions Caused More Warming Than Thought
Researchers have published GloSAT, a new, extended global temperature dataset that reaches back to 1781 and offers a fuller picture of Earth’s climate before the commonly used 1850 baseline. By adding nearly seven decades of historical observations, the compilation changes how scientists assess the magnitude of early human influence on global temperature.
What GloSAT Shows
The dataset indicates that heat‑trapping gases rose by roughly 2.5% between 1750 and 1850. GloSAT attributes about 0.09 °C of warming to human activity across that 100‑year span. A separate analysis published in Environmental Research Letters estimated an additional 0.1–0.2 °C of early warming from increased CO₂, bringing total early anthropogenic warming estimates to a slightly higher range than previously recognized.
Why the Earlier Record Matters
Most climate assessments and model simulations use 1850 (or the 1850–1900 period) as the conventional “preindustrial” baseline. By extending records back to 1781, GloSAT captures climate variations — including large volcanic eruptions in the early 1800s that temporarily cooled the planet — that make the late 1700s through 1849 appear cooler than the standard 1850–1900 baseline.
“It changes our perception of how far we have already pushed the climate system in important ways,” said Peter Thorne, professor at Maynooth University and director of the ICARUS Climate Research Centre. He also noted that uncertainties grow the further back observations extend, but that the earlier period was “undeniably cooler.”
Implications — What Changes and What Doesn’t
Although GloSAT suggests the historical baseline may have been cooler and that humans contributed measurable warming earlier than often assumed, scientists emphasize this does not alter current climate targets or make projected impacts suddenly occur sooner. As Thorne explained, assessments of impacts have typically been calculated relative to more recent reference periods. The new findings mainly refine our understanding of cumulative historical warming and the timing of early human influence.
Context From Observational Agencies
The U.S. National Oceanic and Atmospheric Administration (NOAA) continues to use the 1850 start date in its global climate record. NOAA reported that the average temperature for the first 11 months of this year was about 1.18 °C above the long‑term average and estimated a 99.9% chance that 2025 will rank among the five warmest years on record.
Takeaway
GloSAT enriches the historical climate record and suggests early industrial‑era emissions contributed modest but measurable warming. The results underscore the importance of long-term observations and careful baseline choices when quantifying the total human impact on climate, while reinforcing that near‑term policy targets and projected impacts remain based on established reference periods.
