Rui Song

Abstract:

The polar regions are warming rapidly, exceeding the global average due to greenhouse gas emissionsfrom human activities. Using CMIP6 simulations, HadCRUT5 data, and MERRA-2 aerosol records, thisstudy shows that major 20th-century volcanic eruptions, Agung (1963), El Chicho´n (1982), and Pinatubo(1991) temporarily offset polar warming through sulfate-induced cooling. The Agung eruption suppressedArctic surface air temperature anomalies for approximately 4-5 years (1964–1968), El Chicho´n for asimilar duration (1983–1987), and Pinatubo for about 4-5 years (1992–1996), demonstrating a consistentmulti-year cooling response following each event.Without these eruptions, Arctic surface air temperatureanomalies would have increased by up to 0.5 °C, whereas volcanic activity caused short-term coolingranging from –0.07 °C to –0.4 °C. Arctic minimum temperatures (Tmin) are rising faster than maximumtemperatures (Tmax), indicating asymmetric warming. In contrast, Antarctic responses were weaker,moderated by oceanic and atmospheric dynamics. Collectively, these eruptions produced episodic multi-year cooling that temporarily interrupted the ongoing Arctic warming trajectory, with warming resumingas volcanic aerosol forcing diminished. Spatial patterns reveal pronounced warming in the central Arctic,Greenland, and Siberia in the absence of volcanic forcing, highlighting the role of eruptions in modulating polar warming and providing insights relevant to future geoengineering considerations.

Abstract:

Europe is warming much faster than the global average, yet the relative contributions of individual anthropogenic drivers to its urban warming remain uncertain. Using CMIP5 single-forcing simulations and observations from HadCRUT5 dataset, we determine the influence of greenhouse gases (GHGs), aerosols from anthropogenic sources (Aaer), together with change in land-use (LU) forcing on urban Europe’s rising surface air temperature (SAT) since 1850. The local Europe Amplification Factor (EAF), the ratio of regional to global SAT trends, reveals that LU forcing has intensified nearly threefold relative to the global mean since the industrial era, driving urban European warming almost twice the global rate. LU forcing exhibits the strongest amplification (EAF ≈ 3.0) compared with GHG forcing (EAF ≈ 2.0), highlighting the critical role of surface modifications in accelerating regional urban warming. Future projections under RCP6.0 and RCP8.5 indicate persistent EAF values exceeding 2.0 over densely populated regions, underscoring the need for integrated emission- and land-management strategies to mitigate urban Europe’s amplified warming.