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How has global temperature risen since the Industrial Revolution?
Executive Summary
Global average surface temperatures have risen by about 1.0–1.2°C since the mid-19th century baseline commonly used to represent pre‑industrial conditions, with most authoritative datasets clustering around ~1.1°C of warming and recent years setting consecutive records. The pace of warming has accelerated since the mid‑20th century and especially since 1975, driven primarily by human emissions of greenhouse gases, with recent months and years showing temporary exceedances of the 1.5°C threshold used in policy debates [1] [2] [3].
1. The core claim: How much warmer is Earth since the Industrial Revolution?
Multiple independent reconstructions converge on a clear range: approximately 1.0 to 1.2°C warmer now than the late‑19th century or the 1850–1900 baseline that scientists use as a proxy for pre‑industrial climate. Several analyses cite about 1.1°C of global mean surface warming since 1880–1900, while datasets that start in 1850 or use different baselines report similar values near 1.07–1.1°C, reflecting consistent estimates across methods and institutions [1] [2] [4]. This convergence matters because it shows independent temperature records—land stations, sea surface measurements, and reanalyses—produce a robust central estimate, even as precise decimals vary with baseline choice and data coverage.
2. The acceleration story: Why the rate of warming matters right now
The warming trend is not steady: instrumental records and recent analyses document a faster rate of warming since the mid‑20th century and a marked acceleration after 1975. Long‑term averages show decadal increases on the order of 0.06–0.08°C per decade since the late 19th century, with the post‑1975 rate rising to roughly 0.15–0.20°C per decade in many datasets. That acceleration explains why global warming moved from gradual to clearly detectable impacts within living memory and why records in the 21st century, including the warmest years and months on record, cluster at the top of the temperature distribution [1] [5] [2].
3. Recent highs and the 1.5°C policy threshold: Temporary exceedances versus sustained warming
Recent monitoring has documented streaks in which rolling 12‑month averages reached or exceeded 1.5°C above the 1850–1900 baseline, producing headlines about the world briefly crossing the 1.5°C threshold. Scientific bodies emphasize the difference between temporary exceedances—driven by the long‑term trend combined with short‑term variability such as El Niño—and a permanently sustained global mean at or above 1.5°C. Observations show the world is already about 1.0–1.1°C warmer on a long‑term basis and trending toward 1.5°C within decades if current emissions continue, but temporary exceedances highlight how close the system is to that policy benchmark [6] [3].
4. Why different sources give slightly different numbers: baselines, coverage, and methods
Apparent discrepancies—some statements saying ~1.0°C, others ~1.1°C or 1.07°C—stem from technical choices: the exact pre‑industrial baseline (mid‑19th century windows vs. earlier periods), whether datasets include high‑latitude sparse observations, how marine temperatures are sampled, and statistical smoothing of short‑term variability. Agencies using 1850–1900 as the baseline report one number, while reconstructions that start in 1880 or use different averaging procedures can differ by a few hundredths to a tenth of a degree. These methodological differences do not undermine the central fact: the planet has warmed by about one degree Celsius, with multiple lines of evidence pointing to human greenhouse gas emissions as the dominant cause [7] [8] [4].
5. The big picture: implications and what the numbers really signal
The roughly 1°C of long‑term warming already observed corresponds to measurable changes in extreme heat, sea level, cryosphere loss, and ecosystem stress, and the accelerated rate since 1975 explains why impacts have intensified over recent decades. Recent record years and the approach to 1.5°C are signals that the climate system is responding to cumulative emissions: persistent warming will further increase the frequency and intensity of extremes. The datasets and reports referenced here make it clear that the central scientific conclusion is robust—human activity has raised global temperature by about a degree, accelerating in recent decades and bringing the world closer to internationally negotiated thresholds [1] [5] [3].