Climate Projections Very Likely Underestimate Future Volcanic Forcing and Its Climatic Effects
Geoengineering News
Abstract
Standard climate projections represent future volcanic eruptions by a constant forcing inferred from 1850 to 2014 volcanic forcing. Using the latest ice-core and satellite records to design stochastic eruption scenarios, we show that there is a 95% probability that explosive eruptions could emit more sulfur dioxide (SO2) into the stratosphere over 2015–2100 than current standard climate projections (i.e., ScenarioMIP). Our simulations using the UK Earth System Model with interactive stratospheric aerosols show that for a median future eruption scenario, the 2015–2100 average global-mean stratospheric aerosol optical depth (SAOD) is double that used in ScenarioMIP, with small-magnitude eruptions (<3 Tg of SO2) contributing 50% to SAOD perturbations. We show that volcanic effects on large-scale climate indicators, including global surface temperature, sea level and sea ice extent, are underestimated in ScenarioMIP because current climate projections do not fully account for the recurrent frequency of volcanic eruptions of different magnitudes.
Key Points
There is a 95% chance that the time-averaged 2015–2100 volcanic SO2 flux from explosive eruptions exceeds the time-averaged 1850–2014 flux
Standard climate projections very likely underestimate the 2015–2100 stratospheric aerosol optical depth and volcanic climate effects
Small-magnitude eruptions (<3 Tg SO2) contribute 30%–50% of the volcanic climate effects in a median future eruption scenario
Plain Language Summary
Climate projections are the simulations of Earth's climate in the future using complex climate models. Standard climate projections, as in Intergovernmental Panel on Climate Change Sixth Assessment Report, assume that explosive volcanic activity over 2015–2100 are of the same level as the 1850–2014 period. Using the latest ice-core and satellite records, we find that explosive eruptions could emit more sulfur dioxide into the upper atmosphere for the period of 2015–2100 than standard climate projections. Our climate model simulations show that the impacts of volcanic eruptions on climate, including global surface temperature, sea level and sea ice extent, are underestimated because current climate projections do not fully account for the recurrent frequency of volcanic eruptions. We also find that small-magnitude eruptions occur frequently and can contribute a significant effect on future climate.
Source: AGU
david....@carbon-cycle.co.uk
What this does not say is what happens after 2100. If there is no reversal on the level of greenhouse gases in the atmosphere or there is no geo-engineering to cool the planet, we will be unloading kilometre thick ice loading from Greenland and Antarctica (which has the most volcanos of anywhere on the planet. It also has a super volcano which may be awoken by the melting). On the flip side we will be adding up to 60 metres of water pressure loading across the oceans. There is little question that there will be increased vulcanism and more sulphur emissions. Accurate modelling of the increase in vulcanism after 2100 maybe difficult/impossible as it is somewhat uncharted territory I suspect. It would seem to me that an increase in vulcanism will likely be a lot more in the coming centuries as the melting rate increases.
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