Clear anti-phase tendency of volcanic eruptions and consistent U.S. Dollar Index response to volcanic forcing

Numerous studies have presented statistical relations between large volcanic eruptions and ensuing El Niño events or between El Niño events and local economies. However, the relation between volcanic eruptions and economies has not been completely clarified. This study compares volcanic eruptions and the U.S. Dollar Index for the past 54 years (1967–2020) to identify significant economic responses to volcanic activity. There is a clear anti-phase tendency between the volcanic eruptions of the western Pacific and those of the eastern Pacific. And volcanic eruptions and U.S. Dollar Index exhibit a strong correlation and U.S. Dollar Index follows the fluctuation trend of volcanic eruptions with a 1-year delay. Thus, results indicate that changes in forces within the earth due to volcanic eruptions continuously impact the global economy. This study identifies a teleconnection between heterogeneous factors that had not been previously reported and provides a new scientific clue regarding the mechanism how has geodynamics affected the human life.

The influence of decision-making in tree ring-based climate reconstructions

Tree-ring chronologies underpin the majority of annually-resolved reconstructions of Common Era climate. However, they are derived using different datasets and techniques, the ramifications of which have hitherto been little explored. Here, we report the results of a double-blind experiment that yielded 15 Northern Hemisphere summer temperature reconstructions from a common network of regional tree-ring width datasets. Taken together as an ensemble, the Common Era reconstruction mean correlates with instrumental temperatures from 1794–2016 CE at 0.79 (p < 0.001), reveals summer cooling in the years following large volcanic eruptions, and exhibits strong warming since the 1980s. Differing in their mean, variance, amplitude, sensitivity, and persistence, the ensemble members demonstrate the influence of subjectivity in the reconstruction process. We therefore recommend the routine use of ensemble reconstruction approaches to provide a more consensual picture of past climate variability.

Large volcanic eruptions as a natural hazard: The impact of the 536/540 CE double event on the atmospheric circulation, surface climate, vegetation and society in Scandinavia

&lt;p&gt;Large volcanic eruptions that reach the stratosphere cool the surface climate and impact the atmospheric circulation, feeding back on the local climate. The mid-6&lt;sup&gt;th&lt;/sup&gt; century is an outstanding period in climate history that featured an extreme cold period, including one of the coldest decades in the past 2000 years. It was triggered by the 536/540 CE volcanic double event, creating the strongest decadal volcanic forcing in the last two millennia. During this period societal changes are recorded around the world, like the Great Migration period and the outbreak of the Justinian Plague. However, not a lot is known about the causal relationships between global cooling and societal change. Less is known also, about the impact of the large-scale atmospheric circulation on the regional climate, vegetation and society in Scandinavia after this volcanic double event. Here we aim to improve this understanding by combining global climate and regional growing-degree-day (GGD) modeling with climate proxies and archaeological records from Southeastern Norway.&lt;/p&gt;&lt;p&gt;We use PMIP4 past2k runs and the MPI-ESM ensemble simulation of the 6&lt;sup&gt;th/7th &lt;/sup&gt; century (520-680 CE), to analyze the atmospheric circulation, surface climate and vegetation changes as a response to the volcanic double event of 536/540 CE, over Scandinavia, specifically Southeastern Norway. Thereby we focus on the response of the major circulation patterns that influence the climate over Northern Europe: the positive and negative North Atlantic Oscillation, the Scandinavian blocking and the Atlantic ridge. The results of the GDD model, driven with the MPI-ESM model input, are compared to local pollen and climate records and archaeological data (e.g. grave density and settlement records) to shed more light on the local climate, vegetation and society impact. This comparison allows us to better understand how a natural hazard influenced local areas and climate records in Southeastern Norway. This study is part of the VIKINGS project, which focuses on the impact of volcanic eruptions on climate, environment and society in Norway/ Scandinavia.&lt;/p&gt;

Sahel droughts induced by large volcanic eruptions over the last millennium in IPSL-CM6A-LR model

&lt;p&gt;&lt;span&gt;The Sahel region is extremely sensible to alterations in its characteristic precipitation regime, associated with the West African Monsoon (WAM). In fact, the WAM presents strong variability at several timescales which has focused the attention of many works that mainly attribute such changes to variations in the sea surface temperature, the emerging increase of greenhouse gases concentration and to alterations in land use. However, the impact of large volcanic eruptions has been just tentatively addressed. This work aims at shedding more light on the influence of large volcanic eruptions on Sahel rainfall relying on past1000 simulations, covering the last millennium, of the IPSL-CM6A-LR model. The results show the mechanisms involved and the differences between tropical and high-latitude eruptions.&lt;/span&gt;&lt;/p&gt;

Dwindling impact of large volcanic eruptions on global glacier changes in the Anthropocene

&lt;p&gt;Large volcanic eruptions impact climate through the injection of ash and sulfur gas into the atmosphere. While the ash particles fall out rapidly, the gas is converted to sulfate aerosols, which reflect solar radiation in the stratosphere and cause a cooling of the global mean surface temperature. Earlier studies suggested that major volcanic eruptions resulted in positive mass balances and advances of glaciers. Here we perform a multivariate analysis to decompose global glacier mass changes from 1961 to 2005 into components associated with anthropogenic influences, volcanic and solar activity, and El Ni&amp;#241;o Southern Oscillation (ENSO). We find that the global glacier mass loss was mainly driven by the anthropogenic forcing, interrupted by a few years of intermittent mass gains following large volcanic eruptions. The relative impact of volcanic eruptions is dwindling due to strongly increasing greenhouse gas concentrations since the mid of the 20&lt;sup&gt;th&lt;/sup&gt; century. Furthermore, our study indicates that solar activity and ENSO have limited impacts on climate conditions at glacier locations and that volcanic eruptions alone can hardly explain decadal periods of glacier advances documented since the 16&lt;sup&gt;th&lt;/sup&gt; century.&lt;/p&gt;

On the Role of Volcanism in Dansgaard-Oeschger Cycles

A significant influence of major volcanic eruptions on regime shifts and long-term climate variability has been suggested previously. But a statistical assessment of this has been hampered by inaccurate synchronization of large volcanic eruptions to changes in past climate. Here, this is achieved by combining a new record of bipolar volcanism from Greenland and Antarctic ice cores with records of abrupt climate change derived from the same ice cores. We show that at > 99 % confidence bipolar volcanic eruptions occurred more frequently than expected by chance just before the onset of Dansgaard-Oeschger events, the most prominent large-scale abrupt climate changes of the last glacial period. Out of 20 climate change events in the 12–60 ka period, 5 (7) occur within 20 (50) years after a bipolar eruption. Thus, such large eruptions may act as short-term triggers for large-scale abrupt climate change, and may explain part of the variability of Dansgaard-Oeschger cycles.