Earth Observation Data Group

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:

This set of netcdf files provides ice particle retrievals produced by applying the Optimal Retrieval of Aerosol and Cloud (ORAC) algorithm to the Advanced Himawari Imager aboard the Himawari-8 satellite. These retrievals accompany the paper "Transient ice ring observed during the 15 January 2022 eruption of Hunga volcano" by Prata et al. accepted for publication in the journal Communications Earth & Environment.

Abstract:

Aerosol-cloud interactions (ACI) are considered to be the most uncertain driver of present-day radiative forcing due to human activities. The non-linearity of cloud-state changes to aerosol perturbations make it challenging to attribute causality in observed relationships of aerosol radiative forcing. Using correlations to infer causality can also be challenging when meteorological variability also drives both aerosol and cloud changes independently. Natural and anthropogenic aerosol perturbations from well defined sources provide “opportunistic experiments” (also known as natural experiments) to investigate ACI in cases where causality may be more confidently inferred. These perturbations cover a wide range of locations and spatio-temporal scales, including point sources such as volcanic eruptions or industrial sources, plumes from biomass burning or forest fires, and tracks from individual ships or shipping corridors. We review the different experimental conditions and conduct a synthesis of the available satellite data sets and field campaigns to place these opportunistic experiments on a common footing, facilitating new insights and a clearer understanding of key uncertainties in aerosol radiative forcing. Strong liquid water path increases due to aerosol perturbations are largely ruled out by averaging across experiments. Cloud albedo perturbations are strongly sensitive to background meteorological conditions. Opportunistic experiments have significantly improved process level understanding of ACI, but it remains unclear how reliably the relationships found can be scaled to the global level, thus, demonstrating a need for deeper investigation in order to improve assessments of aerosol radiative forcing and climate change.