Long-Term Trends in Global Surface Temperature Anomalies and Their Regional Drivers
DOI:
https://doi.org/10.5281/zenodo.22819496Keywords:
global surface temperature, instrumental temperature record, HadCRUT5, GISTEMP, Berkeley Earth, Arctic amplification, land-ocean warming contrast, aerosol forcing, climate change attribution, radiative forcingAbstract
We present an updated assessment of long-term trends in global-mean and regional surface temperature
anomalies using three independent instrumental datasets (HadCRUT5, GISTEMP, Berkeley Earth) spanning
1901-2025, combined with ERA5 reanalysis for spatial attribution. Global-mean surface temperature has risen 1.28
degrees Celsius (1901-2025 linear trend) relative to the 1850-1900 baseline, with the most recent decade
(2016-2025) averaging 1.19 degrees Celsius above baseline, consistent across all three datasets to within 0.06
degrees Celsius. Warming is strongly spatially heterogeneous: the Arctic (60-90N) warmed at 0.75 degrees Celsius
per decade since 1979, nearly four times the global rate, while land areas overall warmed 0.32 degrees Celsius per
decade against 0.19 degrees Celsius per decade over oceans, a land-ocean contrast attributable primarily to
differing effective heat capacity and moisture availability rather than radiative forcing differences. Regional
decomposition using a multiple linear regression attribution framework indicates that greenhouse gas forcing
explains 1.28 to 1.51 degrees Celsius of observed warming globally, partially offset by anthropogenic aerosol
cooling estimated at -0.2 to -0.4 degrees Celsius, with the largest aerosol masking concentrated over South and
East Asia. Internal variability, dominated by Pacific Decadal Oscillation phase, explains most of the residual
decadal-scale deviation from the forced trend, including the early-2000s warming slowdown. Trend uncertainty
attributable to historical sea surface temperature bias correction and Arctic data sparsity remains the largest source
of inter-dataset spread. These results confirm that observed warming is predominantly forcing-driven, regionally
amplified by sea-ice albedo feedback and land-sea thermal contrast, and that aerosol-forced regional cooling is a
first-order modulator of the spatial warming pattern requiring continued monitoring as aerosol emissions decline.
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