Role of volcanic forcing on future global carbon cycle

Abstract

Abstract. Using a fully coupled global climate-carbon cycle model, we assess the potential role of volcanic eruptions on future projection of climate change and its associated carbon cycle feedback. The volcanic-like forcings are applied together with a business-as-usual IPCC-A2 carbon emissions scenario. We show that very large volcanic eruptions similar to Tambora lead to short-term substantial global cooling. However, over a long period, smaller eruptions similar to Pinatubo in amplitude, but set to occur frequently, would have a stronger impact on future climate change. In a scenario where the volcanic external forcings are prescribed with a five-year frequency, the induced cooling immediately lower the global temperature by more than one degree before it returns to the warming trend. Therefore, the climate change is approximately delayed by several decades, and by the end of the 21st century, the warming is still below two degrees when compared to the present day period. Our climate-carbon feedback analysis shows that future volcanic eruptions induce positive feedbacks (i.e., more carbon sink) on both the terrestrial and oceanic carbon cycle. The feedback signal on the ocean is consistently smaller than the terrestrial counterpart and the feedback strength is proportionally related to the frequency of the volcanic eruption events. The cooler climate reduces the terrestrial heterotrophic respiration in the northern high latitude and increases net primary production in the tropics, which contributes to more than 45 % increase in accumulated carbon uptake over land. The increased solubility of CO 2 gas in seawater associated with cooler SST is offset by a reduced CO 2 partial pressure gradient between the ocean and the atmosphere, which results in small changes in net ocean carbon uptake. Similarly, there is nearly no change in the seawater buffer capacity simulated between the different volcanic scenarios. Our study Correspondence to: J. F. Tjiputra (jtj061@uib.no) shows that even in the relatively extreme scenario where large volcanic eruptions occur every five-years period, the induced cooling leads to a reduction of 46 ppmv atmospheric CO 2 concentration as compared to the reference projection of 878 ppmv, at the end of the 21st century.

The Response of Permafrost and High‐Latitude Ecosystems Under Large‐Scale Stratospheric Aerosol Injection and Its Termination

“…• Stratospheric aerosol injection may help slow down the current rate of permafrost degradation • Regional differences in temperature and precipitation led to differences in the timing of permafrost degradation up to 40 years • It is important to investigate the regional effects of climate engineering, particularly in high-latitude ecosystems cooling of surface temperature, which have also been demonstrated to have extended impacts on the land carbon cycle (Robock, 2013;Tjiputra & Otterå, 2011).…”

“…Among them, one of the most discussed method is stratospheric aerosol injection (SAI), which mimics the effect of large volcanic eruptions in nature. The excess sulfur aerosol introduced by SAI or volcanic eruptions induces negative radiative forcing by scattering more incoming solar radiation back to the space, leading to net cooling of surface temperature, which have also been demonstrated to have extended impacts on the land carbon cycle (Robock, ; Tjiputra & Otterå, ).…”

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

“…The sensitivity of the carbon cycle to such eruptions has been investigated by Jones and Cox (2001), Frölicher et al (2011), Brovkin et al (2010), and Tjiputra and Otterå (2011) using different Earth system models. For this shortlived forcing, the land response appears to be the driver of most post-eruption carbon cycle changes, with a range of magnitudes and time horizons associated with the different models.…”

Underestimation of the Tambora effects in North American taiga ecosystems

“…The atmospheric CO 2 concentration was slightly reduced for 15 years after the Tambora erupted (Mac-Farling Meure et al 2006), likely because the carbon uptake over land increased. This was driven by the lower temperatures, which could have reduced ecosystem respiration in northern latitudes and increased net primary production in the tropics (Tjiputra andOtterå 2011, Kandlbauer et al 2013). However, there is no consensus on the terrestrial biosphere responses and associated mechanisms at regional level (Raible et al 2016).…”