Abstract
Volcanic eruptions are an important influence on decadal to centennial climate variability. Large eruptions lead to the formation of a stratospheric sulphate aerosol layer which can cause short-term global cooling. This response is modulated by feedback processes in the earth system, but the influence from future warming has not been assessed before. Using earth system model simulations we find that the eruption-induced cooling is significantly weaker in the future state. This is predominantly due to an increase in planetary albedo caused by increased tropospheric aerosol loading with a contribution from associated changes in cloud properties. The increased albedo of the troposphere reduces the effective volcanic aerosol radiative forcing. Reduced sea-ice coverage and hence feedbacks also contribute over high-latitudes, and an enhanced winter warming signal emerges in the future eruption ensemble. These findings show that the eruption response is a complex function of the environmental conditions, which has implications for the role of eruptions in climate variability in the future and potentially in the past.
Highlights
Volcanic eruptions are a major driver of climate variability on a variety of timescales
Large tropical eruptions are capable of injecting sulphur dioxide into the stratosphere where it forms sulphate aerosol that may persist with an e-folding time of around 1 year, spreading globally with a resultant negative radiative forcing (Rampino and Self 1982; Robock 2000)
The RCP6 scenario leads to a global mean top of the atmosphere anthropogenic radiative forcing at 6 W m−2 by the year 2100, and is intermediate in terms of greenhouse gas forcing between the more extreme RCP8.5 and the RCP2.6 mitigation scenarios
Summary
Volcanic eruptions are a major driver of climate variability on a variety of timescales. After the eruption of Mount Pinatubo in 1991, an estimated 20 Mt of SO2 was introduced into the stratosphere (Robock 2000) leading to a global cooling of around 0.3 °C (Lehner et al 2016) and a reduction in global precipitation (Trenberth and Dai 2007). Understanding the influence of volcanic eruptions contributes to understanding climate variability (Timmreck 2012; Zanchettin 2017). RCP6 control and eruption simulations (this study) RCP6 RCP6 Background. 286 pre-ind no eruption SST, eruption ice. 463 RCP6 no eruption SST, eruption ice. The constant background stratospheric volcanic AOD is equal to 0.0097, several orders of magnitude lower than the peak Tambora AOD
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