scholarly journals Atmospheric annular modes in simulations over the past millennium: No long-term response to external forcing

2013 ◽  
Vol 40 (12) ◽  
pp. 3232-3236 ◽  
Author(s):  
J. J. Gómez-Navarro ◽  
E. Zorita
Keyword(s):  
External Forcing ◽  
Annular Modes ◽  
The Past ◽  
Term Response ◽  
Past Millennium

Understanding Changes in the Asian Summer Monsoon over the Past Millennium: Insights from a Long-Term Coupled Model Simulation*

2009 ◽  
Vol 22 (7) ◽  
pp. 1736-1748 ◽  
Author(s):  
Fangxing Fan ◽  
Michael E. Mann ◽  
Caspar M. Ammann
Keyword(s):  
Summer Monsoon ◽  
Radiative Forcing ◽  
Asian Summer Monsoon ◽  
Coupled Model ◽  
Climate System Model ◽  
The Past ◽  
Asian Summer ◽  
Simulation Results ◽  
Past Millennium

Abstract The Asian summer monsoon (ASM) and its variability were investigated over the past millennium through the analysis of a long-term simulation of the NCAR Climate System Model, version 1.4 (CSM 1.4) coupled model driven with estimated natural and anthropogenic radiative forcing during the period 850–1999. Analysis of the simulation results indicates that certain previously proposed mechanisms, such as warmer large-scale temperatures favoring a stronger monsoon through their effect on Eurasian snow cover, appear inconsistent with the mechanisms active in the simulation. Forced changes in tropical Pacific sea surface temperatures play an apparent role in the long-term changes in the ASM. Analyses of the simulation results suggest that the direct radiative effect of solar forcing variations on the ASM is quite weak and that dynamical responses may be far more important. Volcanic radiative forcing leads to a clearly detectable short-term reduction in the strength of the ASM. Comparisons with long-term proxy reconstructions of the ASM are attempted but are limited by the divergent behavior among different reconstructions as well as the limitations in the model’s coupled dynamics.

Extreme summer precipitation in Central Europe over the past millennium: role of external forcing in enseble of simulations with Earth System models

2020 ◽  
Author(s):  
Eduardo Zorita
Keyword(s):  
Extreme Precipitation ◽  
Summer Precipitation ◽  
Climate Extreme ◽  
External Forcing ◽  
Earth System ◽  
The Past ◽  
Summer Time ◽  
The Impact ◽  
Past Millennium

<p>Extreme precipitation in Europe over summer time is one type of climate extreme with strongest impact on societies, at present and over the past centuries. In contrast to mean and extreme temperatures, it is still unclear to what extant the external forcing may modulate the intensity and frequency of this type of hydrological extremes. This contribution focuses on the identification of the impact of external forcing on European extreme precipitation over the past millennium in one small ensembles of simulations with the Earth System model MPI-ESM-P and in the Large Millennium Ensemble with the model CESM.</p><p>Both models realistically simulate the meteorological conditions that give rise to sustained (over several days) strong precipitation, compared to present conditions. The analysis of both ensembles indicates that the role of the external forcing over the past millennium has been weak at most, with individual members of the ensemble providing different timings for period with high and low probability of extreme summer precipitation in this region. This conclusion is also valid for mean summer precipitation.</p><p>This result confirms the evidence obtained from analysis of proxy records, mostly palaeoclimatological records but also historical evidence. This analysis indicates that the frequency and intensity of extreme summer precipitation has been so far independent of the mean climate state.</p>

scholarly journals The response of diatom assemblages in a Jamaican coastal lagoon to hurricane and drought activity over the past millennium

The Holocene ◽  
2021 ◽  
pp. 095968362110190
Author(s):  
Charlotte A Heller ◽  
Neal Michelutti ◽  
Michael J Burn ◽  
Suzanne E Palmer ◽  
John P Smol
Keyword(s):  
Coastal Lagoon ◽  
Lake Level ◽  
Rainfall Variability ◽  
Diatom Assemblages ◽  
Chl A ◽  
Lake Level Changes ◽  
The Past ◽  
Hurricane Activity ◽  
Past Millennium

Reconstructing pre-industrial hurricane activity and aridity from natural archives places modern trends within the context of long-term natural variability. The first reconstruction of Atlantic hurricane activity in Jamaica was based on a sediment record previously obtained from a coastal lagoon. Specifically, an Extended Hurricane Activity (EHA) index was developed from high-resolution geochemical data that linked fluctuations in lake-level changes to rainfall variability associated with hurricane activity. Here, we analyse the same sediment core from which the EHA index was developed to assess the response of biological indicators, namely fossil diatom assemblages and sediment chlorophyll a (chl- a) concentrations, to hydrometeorological events (tropical cyclone-induced precipitation and droughts) over the past ~1500 years. The diatom assemblages responded sensitively to changes in salinity associated with lake-level changes driven by the balance of precipitation and evaporation. Aquatic production (inferred from sediment chl- a, which includes its main diagenetic products) and salinity (inferred from ITRAXTM µXRF chlorine counts) vary inversely following ca. 1300 CE, likely due to enhanced nutrient delivery from freshwater runoff during periods of elevated precipitation. Although the temporal resolution of our biological data is less-well resolved than that of the geochemical record, it generally tracks long-term trends in rainfall variability inferred by the EHA index over the past millennium. This further demonstrates the potential of using biological proxies from coastal lagoons to track past hurricane activity and aridity.

Statistical Characteristics of Global Daily Extreme Precipitation during the last 3350 years (1501BC – 1849 AD) 

2021 ◽  
Author(s):  
Woon Mi Kim ◽  
Richard Blender ◽  
Michael Sigl ◽  
Christoph Raible ◽  
Martina Messmer
Keyword(s):  
Extreme Precipitation ◽  
Extreme Values ◽  
Volcanic Eruptions ◽  
Statistical Characteristics ◽  
External Forcing ◽  
Return Periods ◽  
Shape Parameters ◽  
Orbital Parameters ◽  
The Past

<div> <p>Torrential rainfall and floods have had devastating impacts on civilizations throughout history. Thus, understanding long-term characteristics of extreme precipitation is necessary to identify physical mechanisms involved in such events and to be able to assess, not only the past, but also the present and future risk of extreme precipitation for society. However, the scarce spatial and temporal distribution of existing datasets on extreme precipitation complicates a detailed study of such events in the paleo climate context.  </p> </div><div> <p>In this study, we employ the newly produced seamless simulations from the Community Earth System Model v1.2.2 that covers the period from 1501 BC to 1849 AD to analyze the daily extreme precipitation before the preindustrial period. We explore the statistical characteristics of extreme precipitation and their association with natural external forcing, such as changes in the orbital parameters, solar cycle, insolation, and volcanic eruptions. For this, we applied to the simulations an extreme value analysis  by adopting a peak-over-threshold method (Coles et al., 2001). The 99th percentile of daily precipitation anomalies with respect to 1501BC - 1849AD are taken as the extreme values and these extremes are fitted to the Generalized Pareto Distribution to create time-stationary and covariate models (GPD models) at each grid point.  </p> </div><div> <p>The stationary GPD model shows that over the mid-latitudes, high scale and negative shape parameters predominate in the Pacific while the opposite condition occurs in the Atlantic sector. Over the Southern Ocean, low scale and negative shape parameters are more common. The covariate GPD models indicate some connection between the external forcing and extreme precipitation. The changes in the orbital parameters are slightly connected to the extreme precipitation over the tropical Atlantic and southern Indian oceans. Among all the forcing, the volcanic eruptions are the most influential in the extreme precipitation during the past 3350 years. The return periods of extreme precipitation decrease over the tropical Pacific, and the mid-latitude oceans and lands after volcanic eruptions, indicating that such eruptions likely increase the occurrence of extreme precipitation in these regions. Over the regions where a decrease in extreme precipitation is followed after the eruptions, such as India, Australia, and eastern Asia, the return periods decrease after volcanic eruptions.  </p> </div><div> <p>Overall, our study provides a long-term continuous view on the global extreme precipitation, which elucidates some complementary information to the currently available proxy and instrumental observations on extreme precipitation events. </p> <p> </p> </div><div> <p>Coles, S., Bawa, J., Trenner, L., & Dorazio, P. (2001). An introduction to statistical modeling of extreme values (Vol. 208, p. 208). London: Springer. </p> </div>

Two Hundred Years of Land Use and Vegetation Change in a Remnant Coastal Woodland in Southern Australia

1998 ◽  
Vol 46 (6) ◽  
pp. 629 ◽  
Author(s):  
Ian D. Lunt
Keyword(s):  
Land Use ◽  
Vegetation Change ◽  
Eucalyptus Species ◽  
Ecological Studies ◽  
The Past ◽  
Fire Exclusion ◽  
Settlement Changes ◽  
Term Response ◽  
Aboriginal Burning

Post-settlement changes in vegetation and land use were examined in a reputedly undisturbed woodland remnant at Ocean Grove, southern Victoria, the site of earlier ecological studies. The vegetation has passed through at least three structural phases since European colonisation: an open grassy woodland dominated by Allocasuarina and Eucalyptus species and Banksia marginata Cav. with few shrubs; an open scrub of Acacia pycnantha Benth.; and a closed scrub of Allocasuarina littoralis (Salisb.) L.A.S.Johnson, which now dominates the reserve. Tree and shrub density has progressively increased, from perhaps less than 20 trees ha–1 in the early 1800s, to over 3000 trees ha–1 in 1996. Most large Allocasuarina trees established in the late 1930s or early 1940s, and Allocasuarina littoralis appears to have invaded rapidly thereafter. Surprisingly, A. littoralis was not recorded in an 1894 plant census, and might have been locally rare last century. Vegetation changes over the past 200 years can be attributed to the long-term absence of fire. The abundant recruitment of Acacia species in the mid- to late-1800s may have been a rapid response to the curtailment of Aboriginal burning, and the more recent invasion of A. littoralis a longer-term response to fire exclusion. The importance of active vegetation management for biodiversity conservation in the future is stressed.

scholarly journals Separating Forced from Chaotic Climate Variability over the Past Millennium

2013 ◽  
Vol 26 (18) ◽  
pp. 6954-6973 ◽  
Author(s):  
Andrew P. Schurer ◽  
Gabriele C. Hegerl ◽  
Michael E. Mann ◽  
Simon F. B. Tett ◽  
Steven J. Phipps
Keyword(s):  
Climate Variability ◽  
Volcanic Eruptions ◽  
Forced Response ◽  
Ice Age ◽  
Mean Annual Temperature ◽  
External Forcing ◽  
The Past ◽  
Hemispheric Temperature ◽  
Wide Range ◽  
Past Millennium

Abstract Reconstructions of past climate show notable temperature variability over the past millennium, with relatively warm conditions during the Medieval Climate Anomaly (MCA) and a relatively cold Little Ice Age (LIA). Multimodel simulations of the past millennium are used together with a wide range of reconstructions of Northern Hemispheric mean annual temperature to separate climate variability from 850 to 1950 CE into components attributable to external forcing and internal climate variability. External forcing is found to contribute significantly to long-term temperature variations irrespective of the proxy reconstruction, particularly from 1400 onward. Over the MCA alone, however, the effect of forcing is only detectable in about half of the reconstructions considered, and the response to forcing in the models cannot explain the warm conditions around 1000 CE seen in some reconstructions. The residual from the detection analysis is used to estimate internal variability independent from climate modeling, and it is found that the recent observed 50- and 100-yr hemispheric temperature trends are substantially larger than any of the internally generated trends even using the large residuals over the MCA. Variations in solar output and explosive volcanism are found to be the main drivers of climate change from 1400 to 1900, but for the first time a significant contribution from greenhouse gas variations to the cold conditions during 1600–1800 is also detected. The proxy reconstructions tend to show a smaller forced response than is simulated by the models. This discrepancy is shown, at least partly, to be likely associated with the difference in the response to large volcanic eruptions between reconstructions and model simulations.

Enabling Community Well-being Self-Monitoring in the Context of Mining: The Naskapi Nation of Kawawachikamach

2016 ◽  
Vol 1 (2) ◽  
Author(s):  
Robert Klinck ◽  
Ben Bradshaw ◽  
Ruby Sandy ◽  
Silas Nabinacaboo ◽  
Mannie Mameanskum ◽  
...  
Keyword(s):  
Indigenous Peoples ◽  
Well Being ◽  
Aboriginal Community ◽  
Self Monitoring ◽  
Community Engaged Research ◽  
The Past ◽  
Mineral Development ◽  
Iron Deposits ◽  
Term Monitoring

The Naskapi Nation of Kawawachikamach is an Aboriginal community located in northern Quebec near the Labrador Border. Given the region’s rich iron deposits, the Naskapi Nation has considerable experience with major mineral development, first in the 1950s to the 1980s, and again in the past decade as companies implement plans for further extraction. This has raised concerns regarding a range of environmental and socio-economic impacts that may be caused by renewed development. These concerns have led to an interest among the Naskapi to develop a means to track community well-being over time using indicators of their own design. Exemplifying community-engaged research, this paper describes the beginning development of such a tool in fall 2012—the creation of a baseline of community well-being against which mining-induced change can be identified. Its development owes much to the remarkable and sustained contribution of many key members of the Naskapi Nation. If on-going surveying is completed based on the chosen indicators, the Nation will be better positioned to recognize shifts in its well-being and to communicate these shifts to its partners. In addition, long-term monitoring will allow the Naskapi Nation to contribute to more universal understanding of the impacts of mining for Indigenous peoples.

Courting the Youth Vote in 2008: The Obama Effect

2009 ◽  
Vol 5 ◽  
Author(s):  
Lindsey C Bohl
Keyword(s):  
Presidential Elections ◽  
Voter Registration ◽  
The Internet ◽  
The Past ◽  
Several Variables ◽  
High Turnout ◽  
Short And Long Term ◽  
Use Of The Internet ◽  
Youth Vote

This paper examines a few of the numerous factors that may have led to increased youth turnout in 2008 Election. First, theories of voter behavior and turnout are related to courting the youth vote. Several variables that are perceived to affect youth turnout such as party polarization, perceived candidate difference, voter registration, effective campaigning and mobilization, and use of the Internet, are examined. Over the past 40 years, presidential elections have failed to engage the majority of young citizens (ages 18-29) to the point that they became inclined to participate. This trend began to reverse starting in 2000 Election and the youth turnout reached its peak in 2008. While both short and long-term factors played a significant role in recent elections, high turnout among youth voters in 2008 can be largely attributed to the Obama candidacy and campaign, which mobilized young citizens in unprecedented ways.

Impact of FII’s and FDI’s on Indian Stock Market

2016 ◽  
Vol 1 (1) ◽  
Author(s):  
Dr. Kamlesh Kumar Shukla
Keyword(s):  
Stock Market ◽  
Financial Markets ◽  
Global Economy ◽  
Short Term ◽  
Earnings Growth ◽  
The Past ◽  
Bull Market ◽  
Indian Stock Market

FIIs are companies registered outside India. In the past four years there has been more than $41 trillion worth of FII funds invested in India. This has been one of the major reasons on the bull market witnessing unprecedented growth with the BSE Sensex rising 221% in absolute terms in this span. The present downfall of the market too is influenced as these FIIs are taking out some of their invested money. Though there is a lot of value in this market and fundamentally there is a lot of upside in it. For long-term value investors, there’s little because for worry but short term traders are adversely getting affected by the role of FIIs are playing at the present. Investors should not panic and should remain invested in sectors where underlying earnings growth has little to do with financial markets or global economy.

Chinese Medicine Protein and Peptide in Gene and Cell Therapy

2019 ◽  
Vol 20 (3) ◽  
pp. 251-264 ◽  
Author(s):  
Yinlu Feng ◽  
Zifei Yin ◽  
Daniel Zhang ◽  
Arun Srivastava ◽  
Chen Ling
Keyword(s):  
Chinese Medicine ◽  
Cell Therapy ◽  
Future Research ◽  
The Past ◽  
Promising Strategy ◽  
Wide Range ◽  
New Directions ◽  
Gene And Cell Therapy ◽  
Proteins And Peptides

The success of gene and cell therapy in clinic during the past two decades as well as our expanding ability to manipulate these biomaterials are leading to new therapeutic options for a wide range of inherited and acquired diseases. Combining conventional therapies with this emerging field is a promising strategy to treat those previously-thought untreatable diseases. Traditional Chinese medicine (TCM) has evolved for thousands of years in China and still plays an important role in human health. As part of the active ingredients of TCM, proteins and peptides have attracted long-term enthusiasm of researchers. More recently, they have been utilized in gene and cell therapy, resulting in promising novel strategies to treat both cancer and non-cancer diseases. This manuscript presents a critical review on this field, accompanied with perspectives on the challenges and new directions for future research in this emerging frontier.

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