scholarly journals Comment on “No consistent ENSO response to volcanic forcing over the last millennium”

Science ◽  
2020 ◽  
Vol 369 (6509) ◽  
pp. eabc0502 ◽  
Author(s):  
Alan Robock
Keyword(s):  
El Niño ◽  
El Nino ◽  
Volcanic Eruptions ◽  
Last Millennium ◽  
Climate Response ◽  
Volcanic Forcing ◽  
Large Volcanic Eruptions

Dee et al. (Reports, 27 March 2020, p. 1477) claimed that large volcanic eruptions do not produce a detectable El Niño response. However, they come to the wrong conclusion because they have ignored the fundamental climate response to large volcanic eruptions: Volcanic eruptions cool the surface, thus masking the relative El Niño warming.

scholarly journals Response to Comment on “No consistent ENSO response to volcanic forcing over the last millennium”

Science ◽  
2020 ◽  
Vol 369 (6509) ◽  
pp. eabc1733
Author(s):  
Sylvia G. Dee ◽  
Kim M. Cobb ◽  
Julien Emile-Geay ◽  
Toby R. Ault ◽  
R. Lawrence Edwards ◽  
...  
Keyword(s):  
El Niño ◽  
El Nino ◽  
Volcanic Eruptions ◽  
Dynamical Response ◽  
Last Millennium ◽  
Surface Cooling ◽  
Central Pacific ◽  
Volcanic Forcing ◽  
Large Volcanic Eruptions

Robock claims that our analysis fails to acknowledge that pan-tropical surface cooling caused by large volcanic eruptions may mask El Niño warming at our central Pacific site, potentially obscuring a volcano–El Niño connection suggested in previous studies. Although observational support for a dynamical response linking volcanic cooling to El Niño remains ambiguous, Robock raises some important questions about our study that we address here.

No consistent ENSO response to volcanic forcing over the last millennium

Science ◽  
2020 ◽  
Vol 367 (6485) ◽  
pp. 1477-1481 ◽  
Author(s):  
Sylvia G. Dee ◽  
Kim M. Cobb ◽  
Julien Emile-Geay ◽  
Toby R. Ault ◽  
R. Lawrence Edwards ◽  
...  
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Global Climate ◽  
Volcanic Eruptions ◽  
Explosive Volcanism ◽  
Forced Response ◽  
Last Millennium ◽  
Superposed Epoch Analysis ◽  
Volcanic Forcing

The El Niño–Southern Oscillation (ENSO) shapes global climate patterns yet its sensitivity to external climate forcing remains uncertain. Modeling studies suggest that ENSO is sensitive to sulfate aerosol forcing associated with explosive volcanism but observational support for this effect remains ambiguous. Here, we used absolutely dated fossil corals from the central tropical Pacific to gauge ENSO’s response to large volcanic eruptions of the last millennium. Superposed epoch analysis reveals a weak tendency for an El Niño–like response in the year after an eruption, but this response is not statistically significant, nor does it appear after the outsized 1257 Samalas eruption. Our results suggest that those models showing a strong ENSO response to volcanic forcing may overestimate the size of the forced response relative to natural ENSO variability.

Summer Cooling Driven by Large Volcanic Eruptions over the Tibetan Plateau

2018 ◽  
Vol 31 (24) ◽  
pp. 9869-9879 ◽  
Author(s):  
Jianping Duan ◽  
Lun Li ◽  
Zhuguo Ma ◽  
Jan Esper ◽  
Ulf Büntgen ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
El Niño ◽  
El Nino ◽  
Volcanic Eruptions ◽  
The Tibetan Plateau ◽  
Temperature Deviation ◽  
El Niño Event ◽  
El Niño Events ◽  
Large Volcanic Eruptions ◽  
El Nino Events

Large volcanic eruptions may cause abrupt summer cooling over large parts of the globe. However, no comparable imprint has been found on the Tibetan Plateau (TP). Here, we introduce a 400-yr-long temperature-sensitive network of 17 tree-ring maximum latewood density sites from the TP that demonstrates that the effects of tropical eruptions on the TP are generally greater than those of extratropical eruptions. Moreover, we found that large tropical eruptions accompanied by subsequent El Niño events caused less summer cooling than those that occurred without El Niño association. Superposed epoch analysis (SEA) based on 27 events, including 14 tropical eruptions and 13 extratropical eruptions, shows that the summer cooling driven by extratropical eruptions is insignificant on the TP, while significant summer temperature decreases occur subsequent to tropical eruptions. Further analysis of the TP August–September temperature responses reveals a significant postvolcanic cooling only when no El Niño event occurred. However, there is no such cooling for all other situations, that is, tropical eruptions together with a subsequent El Niño event, as well as extratropical eruptions regardless of the occurrence of an El Niño event. The averaged August–September temperature deviation ( Tdev) following 10 large tropical eruptions without a subsequent El Niño event is up to −0.48° ± 0.19°C (with respect to the preceding 5-yr mean), whereas the temperature deviation following 4 large tropical eruptions with an El Niño association is approximately 0.23° ± 0.16°C. These results indicate a mitigation effect of El Niño events on the TP temperature response to large tropical eruptions. The possible mechanism is that El Niño events can weaken the Indian summer monsoon with a subsequent decrease in rainfall and cooling effect, which may lead to a relatively high temperature on the TP, one of the regions affected by the Indian summer monsoon.

Volcanoes and ENSO over the Past Millennium

2008 ◽  
Vol 21 (13) ◽  
pp. 3134-3148 ◽  
Author(s):  
Julien Emile-Geay ◽  
Richard Seager ◽  
Mark A. Cane ◽  
Edward R. Cook ◽  
Gerald H. Haug
Keyword(s):  
El Niño ◽  
El Nino ◽  
Volcanic Eruptions ◽  
Explosive Volcanism ◽  
The Past ◽  
El Niño Event ◽  
Volcanic Forcing ◽  
El Niño Events ◽  
Past Millennium ◽  
El Nino Events

Abstract The controversial claim that El Niño events might be partially caused by radiative forcing due to volcanic aerosols is reassessed. Building on the work of Mann et al., estimates of volcanic forcing over the past millennium and a climate model of intermediate complexity are used to draw a diagram of El Niño likelihood as a function of the intensity of volcanic forcing. It is shown that in the context of this model, only eruptions larger than that of Mt. Pinatubo (1991, peak dimming of about 3.7 W m−2) can shift the likelihood and amplitude of an El Niño event above the level of the model’s internal variability. Explosive volcanism cannot be said to trigger El Niño events per se, but it is found to raise their likelihood by 50% on average, also favoring higher amplitudes. This reconciles, on one hand, the demonstration by Adams et al. of a statistical relationship between explosive volcanism and El Niño and, on the other hand, the ability to predict El Niño events of the last 148 yr without knowledge of volcanic forcing. The authors then focus on the strongest eruption of the millennium (A.D. 1258), and show that it is likely to have favored the occurrence of a moderate-to-strong El Niño event in the midst of prevailing La Niña–like conditions induced by increased solar activity during the well-documented Medieval Climate Anomaly. Compiling paleoclimate data from a wide array of sources, a number of important hydroclimatic consequences for neighboring areas is documented. The authors propose, in particular, that the event briefly interrupted a solar-induced megadrought in the southwestern United States. Most of the time, however, volcanic eruptions are found to be too small to significantly affect ENSO statistics.

Threshold of the volcanic forcing that leads the El Niño-like warming in the last millennium: results from the ERIK simulation

2015 ◽  
Vol 46 (11-12) ◽  
pp. 3725-3736 ◽  
Author(s):  
Hyung-Gyu Lim ◽  
Sang-Wook Yeh ◽  
Jong-Seong Kug ◽  
Young-Gyu Park ◽  
Jae-Hun Park ◽  
...  
Keyword(s):  
El Niño ◽  
El Nino ◽  
Last Millennium ◽  
Volcanic Forcing

scholarly journals “El Niño Like” Hydroclimate Responses to Last Millennium Volcanic Eruptions

2016 ◽  
Vol 29 (8) ◽  
pp. 2907-2921 ◽  
Author(s):  
Samantha Stevenson ◽  
Bette Otto-Bliesner ◽  
John Fasullo ◽  
Esther Brady
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Temporal Structure ◽  
Volcanic Eruptions ◽  
Teleconnection Pattern ◽  
Last Millennium ◽  
Surface Cooling ◽  
Proxy Reconstructions ◽  
Neutral Conditions

Abstract The hydroclimate response to volcanic eruptions depends both on volcanically induced changes to the hydrologic cycle and on teleconnections with the El Niño–Southern Oscillation (ENSO), complicating the interpretation of offsets between proxy reconstructions and model output. Here, these effects are separated, using the Community Earth System Model Last Millennium Ensemble (CESM-LME), by examination of ensemble realizations with distinct posteruption ENSO responses. Hydroclimate anomalies in monsoon Asia and the western United States resemble the El Niño teleconnection pattern after “Tropical” and “Northern” eruptions, even when ENSO-neutral conditions are present. This pattern results from Northern Hemisphere (NH) surface cooling, which shifts the intertropical convergence zone equatorward, intensifies the NH subtropical jet, and suppresses the Southeast Asian monsoon. El Niño events following an eruption can then intensify the ENSO-neutral hydroclimate signature, and El Niño probability is enhanced two boreal winters following all eruption types. Additionally, the eruption-year ENSO response to eruptions is hemispherically dependent: the winter following a Northern eruption tends toward El Niño, while Southern volcanoes enhance the probability of La Niña events and Tropical eruptions have a very slight cooling effect. Overall, eruption-year hydroclimate anomalies in CESM disagree with the proxy record in both Southeast Asia and North America, suggesting that model monsoon representation cannot be solely responsible. Possible explanations include issues with the model ENSO response, the spatial or temporal structure of volcanic aerosol distribution, or data uncertainties.

scholarly journals Assessing the impact of large volcanic eruptions of the Last Millennium on Australian rainfall regimes

2017 ◽  
Author(s):  
Stephanie Blake ◽  
Sophie C. Lewis ◽  
Allegra N. LeGrande
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Regional Climate ◽  
Volcanic Eruptions ◽  
Explosive Volcanism ◽  
Climate Forcing ◽  
Last Millennium ◽  
Precipitation Anomalies ◽  
The Impact

Abstract. Explosive volcanism is an important natural climate forcing, impacting global surface temperatures and regional precipitation. Although previous studies have investigated aspects of the impact of tropical volcanism on various ocean-atmosphere systems and regional climate regimes, volcanic eruptions remain a poorly understood climate forcing and climatic responses are not well constrained. In this study, volcanic eruptions are explored in particular reference to Australian precipitation, and both the Indian Ocean Dipole (IOD) and El Nino-Southern Oscillation (ENSO). Using nine realisations of the Last Millennium (LM) with different time-evolving forcing combinations, from the NASA GISS ModelE2-R, the impact of the 6 largest tropical volcanic eruptions of this period are investigated. Overall, we find that volcanic aerosol forcing increased the likelihood of El Nino and positive IOD conditions for up to four years following an eruption, and resulted in positive precipitation anomalies over northwest (NW) and southeast (SE) Australia. Larger atmospheric sulfate loading coincides with more persistent positive IOD and El Nino conditions, enhanced positive precipitation anomalies over NW Australia, and dampened precipitation anomalies over SE Australia.

Different Impacts of Northern, Tropical, and Southern Volcanic Eruptions on the Tropical Pacific SST in the Last Millennium

2018 ◽  
Vol 31 (17) ◽  
pp. 6729-6744 ◽  
Author(s):  
Meng Zuo ◽  
Wenmin Man ◽  
Tianjun Zhou ◽  
Zhun Guo
Keyword(s):  
El Niño ◽  
El Nino ◽  
Volcanic Eruptions ◽  
Enso Cycle ◽  
Last Millennium ◽  
Westerly Wind ◽  
Central Pacific ◽  
The Pacific ◽  
Sst Anomaly ◽  
The Impact

The impact of northern, tropical, and southern volcanic eruptions on the Pacific sea surface temperature (SST) and the different response mechanisms arising due to differences in the volcanic forcing structure are investigated using the Community Earth System Model Last Millennium Ensemble (CESM-LME). Analysis of the simulations indicates that the Pacific features a significant El Niño–like SST anomaly 5–10 months after northern and tropical eruptions, and with a weaker such tendency after southern eruptions, possibly reflective of the weaker magnitude of these eruptions. The Niño-3 index peaks with a lag of one and a half years after northern and tropical eruptions. Two years after all three types of volcanic eruptions, a La Niña–like SST anomaly pattern over the equatorial Pacific is observed, which seems to form an El Niño–Southern Oscillation (ENSO) cycle. The westerly wind anomaly over the western to central Pacific plays an essential role in favoring the development of an El Niño following all three types of eruptions. Thus, the key point of the question is to find the causes of the westerly wind enhancement. The shift of the intertropical convergence zone (ITCZ) can explain the El Niño–like response to northern eruptions, which is not applicable for tropical or southern eruptions. The ocean dynamical thermostat mechanism is the fundamental cause of the anomalous westerly wind for all three types of eruptions.

scholarly journals Assessing the impact of large volcanic eruptions of the last millennium (850–1850 CE) on Australian rainfall regimes

2018 ◽  
Vol 14 (6) ◽  
pp. 811-824 ◽  
Author(s):  
Stephanie A. P. Blake ◽  
Sophie C. Lewis ◽  
Allegra N. LeGrande ◽  
Ron L. Miller
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Volcanic Eruptions ◽  
Explosive Volcanism ◽  
Climate Forcing ◽  
Last Millennium ◽  
North West ◽  
Precipitation Anomalies ◽  
The Impact

Abstract. Explosive volcanism is an important natural climate forcing, impacting global surface temperatures and regional precipitation. Although previous studies have investigated aspects of the impact of tropical volcanism on various ocean–atmosphere systems and regional climate regimes, volcanic eruptions remain a poorly understood climate forcing and climatic responses are not well constrained. In this study, volcanic eruptions are explored in particular reference to Australian precipitation, and both the Indian Ocean Dipole (IOD) and El Niño–Southern Oscillation (ENSO). Using nine realisations of the last millennium (LM) (850–1850 CE) with different time-evolving forcing combinations, from the NASA GISS ModelE2-R, the impact of the six largest tropical volcanic eruptions of this period are investigated. Overall, we find that volcanic aerosol forcing increased the likelihood of El Niño and positive IOD conditions for up to four years following an eruption, and resulted in positive precipitation anomalies over north-west (NW) and south-east (SE) Australia. Larger atmospheric sulfate loading during larger volcanic eruptions coincided with more persistent positive IOD and El Niño conditions, enhanced positive precipitation anomalies over NW Australia, and dampened precipitation anomalies over SE Australia.

scholarly journals Decadal variation of extreme drought and flood in North China revealed by documentary-based seasonal precipitation reconstruction for the past 300 years

2018 ◽  
Author(s):  
Jingyun Zheng ◽  
Yingzhuo Yu ◽  
Xuezhen Zhang ◽  
Zhixin Hao
Keyword(s):  
El Niño ◽  
North China ◽  
El Nino ◽  
Volcanic Eruptions ◽  
Extreme Drought ◽  
Seasonal Precipitation ◽  
Extreme Floods ◽  
Spatial Coverage ◽  
Droughts And Floods ◽  
Large Volcanic Eruptions

Abstract. Using the 17-sites seasonal precipitation reconstructions from an unique historical archive, Yu-Xue-Fen-Cun, the decadal variations of extreme droughts and floods (i.e., the event with occurrence probability of less than 10 % from 1951 to 2000) in North China were investigated, by considering both the probabilities of droughts/floods occurrence in each site and spatial coverage (i.e., percentage of sites). Then, the possible linkages of extreme droughts and floods with ENSO (i.e., El Niño and La Niña) episodes and large volcanic eruptions were discussed. The results show that there were 29 extreme droughts and 28 extreme floods in North China from 1736 to 2000. Extreme droughts occurred more frequently (2 or more events) during the 1770s–1780s, 1870s, 1900s–1920s, 1940s and 1980s–1990s, among which the most frequent (3 events) occurred in the 1900s and the 1920s. While more frequent extreme floods occurred in the 1770s, 1790s, 1820s, 1880s, 1910s and 1950s–1960s, among which the most frequent (4 events) occurred in the 1790s and 1880s. For the total of extreme droughts and floods, they are more frequent in the 1770s, 1790s, 1870s–1880s, 1900s–1920s and 1960s, and the highest frequency (5 events) occurred in the 1790s. A higher probability of the extreme drought was found when El Niño occurred in the current year or the previous year. However, no significant connections were found not only between the occurrences of extreme floods and ENSO episodes, but also between the occurrences of extreme droughts/floods and large volcanic eruptions.

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