Volcano impacts on climate and biogeochemistry in a coupled carbon–climate model

Abstract

Abstract. Volcanic eruptions induce a dynamical response in the climate system characterized by short-term global reductions in both surface temperature and precipitation, as well as a response in biogeochemistry. The available observations of these responses to volcanic eruptions, such as to Pinatubo, provide a valuable method to compare against model simulations. Here, the Community Climate System Model Version 3 (CCSM3) reproduces the physical climate response to volcanic eruptions in a realistic way, as compared to direct observations from the 1991 eruption of Mount Pinatubo. The model's biogeochemical response to eruptions is smaller in magnitude than observed, but because of the lack of observations, it is not clear why or where the modeled carbon response is not strong enough. Comparison to other models suggests that this model response is much weaker over tropical land; however, the precipitation response in other models is not accurate, suggesting that other models could be getting the right response for the wrong reason. The underestimated carbon response in the model compared to observations could also be due to the ash and lava input of biogeochemically important species to the ocean, which are not included in the simulation. A statistically significant reduction in the simulated carbon dioxide growth rate is seen at the 90 % level in the average of 12 large eruptions over the period 1870-2000, and the net uptake of carbon is primarily concentrated in the tropics, with large spatial variability. In addition, a method for computing the volcanic response in model output without using a control ensemble is tested against a traditional methodology using two separate ensembles of runs; the method is found to produce similar results in the global average. These results suggest that not only is simulating volcanoes a good test of coupled carbon-climate models, but also that this test can be performed without a control simulation in cases where it is not practical to run separate ensembles with and without volcanic eruptions.

Impact of Solar Radiation Modification on Allowable CO2 Emissions: What Can We Learn From Multimodel Simulations?

“…This statement is also supported by former studies (Eliseev, 2012;Govindasamy et al, 2002;Keller et al, 2014;Lauvset et al, 2017;Matthews & Caldeira, 2007;Muri et al, 2015;Sonntag et al, 2018) which suggest that SRM is likely to strengthen carbon uptake by both ocean and terrestrial ecosystems. This finding is also supported by the modeled response of the carbon cycle to major volcanic eruptions (Brovkin et al, 2010;MacMartin et al, 2016;Rothenberg et al, 2012;Tjiputra & Otterå, 2011). In both cases, the same mechanism is at play.…”

Climate and carbon cycle dynamics in a CESM simulation from 850 to 2100 CE

“…In the top10 case, values return to normal after about 16 years, while in the top3 case, they tend to return already after about 6 years and overshoot. This overshoot is not straightforward to understand and did not seem to occur in earlier versions of the model (Frölicher et al, 2011;Rothenberg et al, 2012). In MPI-ESM the response is a priori more straightforward and slower: in the top10 case the atmosphere looses about 2.5 Pg C, reaches a minimum after 2-4 years, and returns to pre-eruption values after 10-16 years.…”

Impact of an extremely large magnitude volcanic eruption on the global climate and carbon cycle estimated from ensemble Earth System Model simulations

“…In a recent discussion paper Rothenberg et al (2012) describe the response of the Community Climate Model Version 3 (CCSM3) to tropical volcanic eruptions as represented by the time-varying volcanic forcing from Ammann et al (2003) in the period 1870 to 2000 and the 1992 Pinatubo eruption in particular. They find that while their precipitation anomalies are comparable to observations, the biogeochemical response is smaller than observed and also smaller than modelled by Jones and Cox (2001).…”