On the additivity of climate responses to the volcanic and solar forcing in the early 19th century
<p>The early 19th century was the coldest period over the past 500 years, when strong tropical volcanic events and a solar minimum coincided. The 1809 unidentified eruption and the 1815 Tambora eruption happened consecutively during the Dalton minimum of solar irradiance; however, the relative...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2022-11-01
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| Series: | Earth System Dynamics |
| Online Access: | https://esd.copernicus.org/articles/13/1535/2022/esd-13-1535-2022.pdf |
| Summary: | <p>The early 19th century was the coldest period over the past 500 years, when strong tropical volcanic events and a solar minimum coincided. The 1809 unidentified eruption and the 1815 Tambora eruption happened consecutively during the Dalton minimum of solar irradiance; however, the relative role of the two forcing (volcano and solar) agents is still unclear. In this study, we examine the responses from a set of early
19th century simulations with combined and separated volcanic and solar
forcing agents, as suggested in the protocol for the past1000 experiment of
the Paleoclimate Modelling Intercomparison Project – Phase 4 (PMIP4). From
20-member ensemble simulations with the Max Planck Institute Earth system
model (MPI-ESM1.2-LR), we find that the volcano- and solar-induced surface
cooling is additive in the global mean/large scale, regardless of combining
or separating the forcing agents. The two solar reconstructions (SATIRE (Spectral and Total Irradiance
REconstruction-Millennia model) and
PMOD (Physikalisch-Meteorologisches Observatorium Davos)) contribute to a cooling before and after 1815 of <span class="inline-formula">∼0.05</span> and <span class="inline-formula">∼0.15</span> K monthly average near-surface air cooling, respectively, indicating a limited solar contribution to the early 19th century cold period. The volcanic events provide the main cooling contributions, inducing a surface cooling that peaks at <span class="inline-formula">∼0.82</span> K for the 1809 event and <span class="inline-formula">∼1.35</span> K for Tambora. After the Tambora eruption, the temperature in most regions increases toward climatology largely within 5 years, along with the reduction of volcanic forcing. In the northern extratropical oceans, the temperature increases slowly at a constant rate until 1830, which is related to the reduction of seasonality and the concurrent changes in Arctic sea-ice extent. The albedo feedback of Arctic sea ice is found to be the main contributor to the Arctic amplification of the cooling signal. Several non-additive responses to solar and volcanic forcing happen on regional scales. In the atmosphere, the stratospheric polar vortex tends to strengthen when combining both volcano and solar forcing, even though the two forcing agents separately induce opposite-sign changes in stratospheric temperatures and zonal winds. In the ocean, when combining the two forcings, additional surface cold water propagates to the northern extratropics from the additional solar cooling in the tropics, which results in regional cooling along the propagation. Overall, this study not only quantifies the surface responses from combinations of the volcano and solar forcing, but also highlights the components that cannot be simply added from the responses of the individual forcing agents, indicating that a relatively small forcing agent (such as solar in early 19th century) can impact the response from the large forcing (such as the 1815 Tambora eruption) when considering regional climates.</p> |
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| ISSN: | 2190-4979 2190-4987 |