scholarly journals More Frequent, Longer, and Hotter Heat Waves for Australia in the Twenty-First Century

2014 ◽  
Vol 27 (15) ◽  
pp. 5851-5871 ◽  
Author(s):  
Tim Cowan ◽  
Ariaan Purich ◽  
Sarah Perkins ◽  
Alexandre Pezza ◽  
Ghyslaine Boschat ◽  
...  
Keyword(s):  
Twentieth Century ◽  
Climate Models ◽  
Heat Waves ◽  
First Century ◽  
Maximum Temperature ◽  
Historical Period ◽  
Tropical Regions ◽  
Summer Heat ◽  
Ensemble Mean ◽  
Twenty First Century

Abstract Extremes such as summer heat waves and winter warm spells have a significant impact on the climate of Australia, with many regions experiencing an increase in the frequency and duration of these events since the mid-twentieth century. With the availability of Coupled Model Intercomparison Project phase 5 (CMIP5) climate models, projected changes in heat waves and warm spells are investigated across Australia for two future emission scenarios. For the historical period encompassing the late twentieth century (1950–2005) an ensemble mean of 15 models is able to broadly capture the observed spatial distribution in the frequency and duration of summer heat waves, despite overestimating these metrics along coastal regions. The models achieve a better comparison to observations in their simulation of the temperature anomaly of the hottest heat waves. By the end of the twenty-first century, the model ensemble mean projects the largest increase in summer heat wave frequency and duration to occur across northern tropical regions, while projecting an increase of ~3°C in the maximum temperature of the hottest southern Australian heat waves. Model consensus suggests that future winter warm spells will increase in frequency and duration at a greater rate than summer heat waves, and that the hottest events will become increasingly hotter for both seasons by century’s end. Even when referenced to a warming mean state, increases in the temperature of the hottest events are projected for southern Australia. Results also suggest that following a strong mitigation pathway in the future is more effective in reducing the frequency and duration of heat waves and warm spells in the southern regions compared to the northern tropical regions.

scholarly journals What Caused the Observed Twentieth-Century Weakening of the Walker Circulation?

2011 ◽  
Vol 24 (24) ◽  
pp. 6501-6514 ◽  
Author(s):  
Scott B. Power ◽  
Greg Kociuba
Keyword(s):  
Twentieth Century ◽  
Climate Models ◽  
Southern Oscillation ◽  
Walker Circulation ◽  
Natural Variability ◽  
First Century ◽  
External Forcing ◽  
Wide Range ◽  
Twenty First Century ◽  
The Walker Circulation

Abstract The Walker circulation (WC) is one of the world’s most prominent and important atmospheric systems. The WC weakened during the twentieth century, reaching record low levels in recent decades. This weakening is thought to be partly due to global warming and partly due to internally generated natural variability. There is, however, no consensus in the literature on the relative contribution of external forcing and natural variability to the observed weakening of the WC. This paper examines changes in the strength of the WC using an index called BoxΔP, which is equal to the difference in mean sea level pressure across the equatorial Pacific. Change in both the observations and in World Climate Research Programme (WCRP) Coupled Model Intercomparison Project phase 3 (CMIP3) climate models are examined. The annual average BoxΔP declines in the observations and in 15 out of 23 models during the twentieth century (results that are significant at or above the 95% level), consistent with earlier work. However, the magnitude of the multimodel ensemble mean (MMEM) 1901–99 trend (−0.10 Pa yr−1) is much smaller than the magnitude of the observed trend (−0.52 Pa yr−1). While a wide range of trends is evident in the models with approximately 90% of the model trends in the range (−0.25 to +0.1 Pa yr−1), even this range is too narrow to encompass the magnitude of the observed trend. Twenty-first-century changes in BoxΔP under the Special Report on Emissions Scenarios (SRES) A1B and A2 are also examined. Negative trends (i.e., weaker WCs) are evident in all seasons. However, the MMEM trends for the A1B and A2 scenarios are smaller in magnitude than the magnitude of the observed trend. Given that external forcing linked to greenhouse gases is much larger in the twenty-first-century scenarios than twentieth-century forcing, this, together with the twentieth-century results mentioned above, would seem to suggest that external forcing has not been the primary driver of the observed weakening of the WC. However, 9 of the 23 models are unable to account for the observed change unless the internally generated component of the trend is very large. But indicators of observed variability linked to El Niño–Southern Oscillation (ENSO) and the Interdecadal Pacific Oscillation have modest trends, suggesting that internally variability has been modest. Furthermore, many of the nine “inconsistent” models tend to have poorer simulations of climatic features linked to ENSO. In addition, the externally forced component of the trend tends to be larger in magnitude and more closely matches the observed trend in the models that are better able to reproduce ENSO-related variability. The “best” four models, for example, have a MMEM of −0.2 Pa yr−1 (i.e., approximately 40% of the observed change), suggesting a greater role for external forcing in driving the observed trend. These and other considerations outlined below lead the authors to conclude that (i) both external forcing and internally generated variability contributed to the observed weakening of the WC over the twentieth century and (ii) external forcing accounts for approximately 30%–70% of the observed weakening with internally generated climate variability making up the rest.

CLIMATE CHANGE SCENARIOS FOR THE U.S. NATIONAL ASSESSMENT

2003 ◽  
Vol 84 (12) ◽  
pp. 1711-1724 ◽  
Author(s):  
Michael C. MacCracken ◽  
Eric J. Barron ◽  
David R. Easterling ◽  
Benjamin S. Felzer ◽  
Thomas R. Karl
Keyword(s):  
Climate Change ◽  
Twentieth Century ◽  
Climate Models ◽  
Climatic Conditions ◽  
First Century ◽  
Climate Change Scenarios ◽  
Climate Scenarios ◽  
National Assessment ◽  
Twenty First Century ◽  
The U.S

In support of the U.S. National Assessment of the Potential Consequences of Climate Variability and Change, climate scenarios were prepared to serve as the basis for evaluating the vulnerability of environmental and societal systems to changes projected for the twenty-first century. Since publication of the results of the assessment at the end of 2000, the National Research Council's report Climate Change Science: An Analysis of Some Key Questions, and the U.S. government's U.S. Climate Action Report—2002 have both relied on the assessment's findings. Because of the importance of these findings, it is important to directly address questions regarding the representativeness and usefulness of the model-based projections on which the findings were based. In particular, criticisms have focused on whether the climate models that were relied upon adequately represented twentieth-century conditions and whether their projections of conditions for the twenty-first century were outliers. Reexamination of the approach used in developing and evaluating the climate scenarios indicates that the results from the two primary climate modeling groups that were relied upon allowed the generation of climate scenarios that span much of the range of possible future climatic conditions projected by the larger set of model simulations, which was compiled for the IPCCs Third Assessment Report. With the set of models showing increasing agreement in their simulations of twentieth-century trends in climate and of projected changes in climate on subcontinental to continental scales, the climate scenarios that were generated seem likely to provide a plausible representation of the types of climatic conditions that could be experienced during the twenty-first century. Warming, reduced snow cover, and more intense heavy precipitation events were projected by all models, suggesting such changes are quite likely. However, significant differences remain in the projection of changes in precipitation and of the regional departures in climate from the larger-scale patterns. For this reason, evaluating potential impacts using climate scenarios based on models exhibiting different regional responses is a necessary step to ensuring a representative analysis. Utilizing an even more encompassing set of scenarios in the future could help move from mainly qualitative toward more certain and quantitative conclusions.

scholarly journals Explaining the Spread in Global Mean Thermosteric Sea Level Rise in CMIP5 Climate Models*

2015 ◽  
Vol 28 (24) ◽  
pp. 9918-9940 ◽  
Author(s):  
Angélique Melet ◽  
Benoit Meyssignac
Keyword(s):  
Twentieth Century ◽  
Sea Level ◽  
Radiative Forcing ◽  
Climate Models ◽  
First Century ◽  
Model Ensemble ◽  
Ocean Heat Uptake ◽  
Feedback Parameter ◽  
Twenty First Century ◽  
Global Mean

Abstract The ocean stores more than 90% of the energy excess associated with anthropogenic climate change. The resulting ocean warming and thermal expansion are leading contributors to global mean sea level (GMSL) rise. Confidence in projections of GMSL rise therefore depends on the ability of climate models to reproduce global mean thermosteric sea level (GMTSL) rise over the twentieth century. This study first compares the GMTSL of the climate models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) to observations over 1961–2005. Although the model ensemble mean is within the uncertainty of observations, the model ensemble exhibits a large spread. The authors then aim to explain the spread in CMIP5 climate model GMTSL over the twentieth and twenty-first centuries. It is shown that the climate models’ GMTSL rise depends linearly on the time-integrated radiative forcing F (under continuously increasing radiative forcing). The constant of proportionality μ expresses the transient thermosteric sea level response of the climate system, and it depends on the fraction of excess heat stored in the ocean, the expansion efficiency of heat, the climate feedback parameter, and the ocean heat uptake efficiency. The across-model spread in μ explains most (>70%) of the across-model spread in GMTSL rise over the twentieth and twenty-first centuries, while the across-model spread in time-integrated F explains the rest. The time-integrated F explains less variance in the across-model GMTSL rise in twenty-first-century than in twentieth-century simulations, as the spread in F is reduced over the twenty-first century because the anthropogenic aerosol forcing, which is a large source of uncertainty in F, becomes relatively smaller.

scholarly journals A Model Study of Heat Waves over North America: Meteorological Aspects and Projections for the Twenty-First Century

2012 ◽  
Vol 25 (14) ◽  
pp. 4761-4784 ◽  
Author(s):  
Ngar-Cheung Lau ◽  
Mary Jo Nath
Keyword(s):  
Twentieth Century ◽  
North America ◽  
Heat Wave ◽  
General Circulation ◽  
Heat Waves ◽  
General Circulation Models ◽  
Reanalysis Data ◽  
First Century ◽  
Twenty First Century ◽  
The Impact

Abstract The characteristics of summertime heat waves in North America are examined using reanalysis data and simulations by two general circulation models with horizontal resolution of 50 and 200 km. Several “key regions” with spatially coherent and high amplitude fluctuations in daily surface air temperature are identified. The typical synoptic features accompanying warm episodes in these regions are described. The averaged intensity, duration, and frequency of occurrence of the heat waves in various key regions, as simulated in the two models for twentieth-century climate, are in general agreement with the results based on reanalysis data. The impact of climate change on the heat wave characteristics in various key regions is assessed by contrasting model runs based on a scenario for the twenty-first century with those for the twentieth century. Both models indicate considerable increases in the duration and frequency of heat wave episodes, and in number of heat wave days per year, during the twenty-first century. The duration and frequency statistics of the heat waves in the mid-twenty-first century, as generated by the model with 50-km resolution, can be reproduced by adding the projected warming trend to the daily temperature data for the late twentieth century, and then recomputing these statistics. The detailed evolution of the averaged intensity, duration, and frequency of the heat waves through individual decades of the twentieth and twenty-first centuries, as simulated and projected by the model with 200-km resolution, indicates that the upward trend in these heat wave measures should become apparent in the early decades of the twenty-first century.

scholarly journals Comparing Twentieth- and Twenty-First-Century Patterns of Interannual Precipitation Variability over the Western United States and Northern Mexico*

2012 ◽  
Vol 13 (1) ◽  
pp. 366-378 ◽  
Author(s):  
Tyler W. Ruff ◽  
Yochanan Kushnir ◽  
Richard Seager
Keyword(s):  
United States ◽  
Twentieth Century ◽  
Interannual Variability ◽  
Climate Models ◽  
Precipitation Variability ◽  
First Century ◽  
Western United States ◽  
Spatial Structures ◽  
Northern Mexico ◽  
Twenty First Century

Abstract The ability of coupled climate models to simulate the patterns of interannual precipitation variability over the western half of the United States and northern Mexico is investigated by applying principal component analysis to observations and model output. Global Precipitation Climatology Centre (GPCC) observations are compared to the pooled twentieth-century warm- and cold-season precipitation averages simulated by five coupled global climate models included in the Intergovernmental Panel on Climate Change Fourth Assessment Report. The pooled model spatial structures (EOFs) closely match those of the GPCC observations for both halves of the year. Additionally, the twenty-first-century model pooled EOFs are almost identical in spatial extent and amplitude to their twentieth-century counterparts. Thus, the spatial characteristics of large-scale precipitation variability in the western United States are not projected to change in the twenty-first century. When global observed and modeled seasonally averaged sea surface temperature anomalies are correlated with the time series corresponding to the three leading EOFs to discern sources of each mode of precipitation variability, a pattern reminiscent of El Niño is found to be the only significant association. The spatial structures of variability also appear independent of the model-predicted precipitation trend over the twenty-first century, indicating that the mechanisms responsible for the trend are different from those associated with interannual variability. The results of this study lend confidence in the pooled model predictions of seasonal precipitation patterns, and they suggest that future changes will primarily result from the contribution of the mean trend over which statistically stationary interannual variability is superimposed.

Future Changes in Northern Hemisphere Snowfall

2013 ◽  
Vol 26 (20) ◽  
pp. 7813-7828 ◽  
Author(s):  
John P. Krasting ◽  
Anthony J. Broccoli ◽  
Keith W. Dixon ◽  
John R. Lanzante
Keyword(s):  
Twentieth Century ◽  
Northern Hemisphere ◽  
Climate Models ◽  
Global Climate ◽  
Noise Analysis ◽  
Coupled Model ◽  
Surface Air Temperature ◽  
Global Climate Models ◽  
First Century ◽  
Twenty First Century

Abstract Using simulations performed with 18 coupled atmosphere–ocean global climate models from phase 5 of the Coupled Model Intercomparison Project (CMIP5), projections of the Northern Hemisphere snowfall under the representative concentration pathway (RCP4.5) scenario are analyzed for the period 2006–2100. These models perform well in simulating twentieth-century snowfall, although there is a positive bias in many regions. Annual snowfall is projected to decrease across much of the Northern Hemisphere during the twenty-first century, with increases projected at higher latitudes. On a seasonal basis, the transition zone between negative and positive snowfall trends corresponds approximately to the −10°C isotherm of the late twentieth-century mean surface air temperature, such that positive trends prevail in winter over large regions of Eurasia and North America. Redistributions of snowfall throughout the entire snow season are projected to occur—even in locations where there is little change in annual snowfall. Changes in the fraction of precipitation falling as snow contribute to decreases in snowfall across most Northern Hemisphere regions, while changes in total precipitation typically contribute to increases in snowfall. A signal-to-noise analysis reveals that the projected changes in snowfall, based on the RCP4.5 scenario, are likely to become apparent during the twenty-first century for most locations in the Northern Hemisphere. The snowfall signal emerges more slowly than the temperature signal, suggesting that changes in snowfall are not likely to be early indicators of regional climate change.

scholarly journals Corporate headquarters in the twenty-first century: an organization design perspective

2020 ◽  
Vol 9 (1) ◽  
Author(s):  
Sven Kunisch ◽  
Markus Menz ◽  
David Collis
Keyword(s):  
Twentieth Century ◽  
Organization Design ◽  
Business Environment ◽  
First Century ◽  
Future Research ◽  
Corporate Headquarters ◽  
Special Collection ◽  
Design Perspective ◽  
Twenty First Century

Abstract The corporate headquarters (CHQ) of the multi-business enterprise, which emerged as the dominant organizational form for the conduct of business in the twentieth century, has attracted considerable scholarly attention. As the business environment undergoes a fundamental transition in the twenty-first century, we believe that understanding the evolving role of the CHQ from an organization design perspective will offer unique insights into the nature of business activity in the future. The purpose of this article, in keeping with the theme of the Journal of Organization Design Special Collection, is thus to invigorate research into the CHQ. We begin by explicating four canonical questions related to the design of the CHQ. We then survey fundamental changes in the business environment occurring in the twenty-first century, and discuss their potential implications for CHQ design. When suitable here we also refer to the contributions published in our Special Collection. Finally, we put forward recommendations for advancements and new directions for future research to foster a deeper and broader understanding of the topic. We believe that we are on the cusp of a change in the CHQ as radical as that which saw its initial emergence in the late nineteenth/early twentieth century. Exactly what form that change will take remains for practitioners and researchers to inform.

scholarly journals Projected Changes in Climate Extremes Using CMIP6 Simulations Over SREX Regions

2021 ◽  
Vol 5 (3) ◽  
pp. 481-497
Author(s):  
Mansour Almazroui ◽  
Fahad Saeed ◽  
Sajjad Saeed ◽  
Muhammad Ismail ◽  
Muhammad Azhar Ehsan ◽  
...  
Keyword(s):  
Spatial Variability ◽  
Extreme Events ◽  
First Century ◽  
Maximum Temperature ◽  
Annual Maximum ◽  
Temperature And Precipitation ◽  
Projected Change ◽  
Twenty First Century ◽  
Projected Changes ◽  
The Tropics

AbstractThis paper presents projected changes in extreme temperature and precipitation events by using Coupled Model Intercomparison Project phase 6 (CMIP6) data for mid-century (2036–2065) and end-century (2070–2099) periods with respect to the reference period (1985–2014). Four indices namely, Annual maximum of maximum temperature (TXx), Extreme heat wave days frequency (HWFI), Annual maximum consecutive 5-day precipitation (RX5day), and Consecutive Dry Days (CDD) were investigated under four socioeconomic scenarios (SSP1-2.6; SSP2-4.5; SSP3-7.0; SSP5-8.5) over the entire globe and its 26 Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX) regions. The projections show an increase in intensity and frequency of hot temperature and precipitation extremes over land. The intensity of the hottest days (as measured by TXx) is projected to increase more in extratropical regions than in the tropics, while the frequency of extremely hot days (as measured by HWFI) is projected to increase more in the tropics. Drought frequency (as measured by CDD) is projected to increase more over Brazil, the Mediterranean, South Africa, and Australia. Meanwhile, the Asian monsoon regions (i.e., South Asia, East Asia, and Southeast Asia) become more prone to extreme flash flooding events later in the twenty-first century as shown by the higher RX5day index projections. The projected changes in extremes reveal large spatial variability within each SREX region. The spatial variability of the studied extreme events increases with increasing greenhouse gas concentration (GHG) and is higher at the end of the twenty-first century. The projected change in the extremes and the pattern of their spatial variability is minimum under the low-emission scenario SSP1-2.6. Our results indicate that an increased concentration of GHG leads to substantial increases in the extremes and their intensities. Hence, limiting CO2 emissions could substantially limit the risks associated with increases in extreme events in the twenty-first century.

‘A Heap of Broken Images’? Reviving Austro-German Debates over Musical Meaning, 1900–36

2013 ◽  
Vol 138 (1) ◽  
pp. 129-174 ◽  
Author(s):  
Matthew Pritchard
Keyword(s):  
Twentieth Century ◽  
Educational Theory ◽  
First Century ◽  
Critical Hermeneutics ◽  
Musical Meaning ◽  
Force And Motion ◽  
The Status ◽  
Musical Interpretation ◽  
Twenty First Century

AbstractThis article examines a range of writings on the status of musical interpretation in Austria and Germany during the early decades of the twentieth century, and argues their relevance to current debates. While the division outlined by recent research between popular-critical hermeneutics and analytical ‘energetics’ at this time remains important, hitherto neglected contemporary reflections by Paul Bekker and Kurt Westphal demonstrate that the success of energetics was not due to any straightforward intellectual victory. Rather, the images of force and motion promoted by 1920s analysis were carried by historical currents in the philosophy, educational theory and arts of the time, revealing a culturally situated source for twenty-first-century analysis's preoccupations with motion and embodiment. The cultural relativization of such images may serve as a retrospective counteraction to the analytical rationalizing processes that culminated specifically in Heinrich Schenker's later work, and more generally in the privileging of graphic and notational imagery over poetic paraphrase.

scholarly journals Evaluation of flood damage reduction throughout Japan from adaptation measures taken under a range of emissions mitigation scenarios

2021 ◽  
Vol 165 (3-4) ◽  
Author(s):  
Tao Yamamoto ◽  
So Kazama ◽  
Yoshiya Touge ◽  
Hayata Yanagihara ◽  
Tsuyoshi Tada ◽  
...  
Keyword(s):  
Twentieth Century ◽  
Flood Damage ◽  
First Century ◽  
Mitigation Measures ◽  
Damage Cost ◽  
Adaptation Measures ◽  
Inundation Depth ◽  
Late Twentieth ◽  
Twenty First Century ◽  
Late Twentieth Century

AbstractThis study aimed to evaluate the impact of climate change on flood damage and the effects of mitigation measures and combinations of multiple adaptation measures in reducing flood damage. The inundation depth was calculated using a two-dimensional unsteady flow model. The flood damage cost was estimated from the unit evaluation value set for each land use and prefectures and the calculated inundation depth distribution. To estimate the flood damage in the near future and the late twenty-first century, five global climate models were used. These models provided daily precipitation, and the change of the extreme precipitation was calculated. In addition to the assessment of the impacts of climate change, certain adaptation measures (land-use control, piloti building, and improvement of flood control level) were discussed, and their effects on flood damage cost reduction were evaluated. In the case of the representative concentration pathway (RCP) 8.5 scenario, the damage cost in the late twenty-first century will increase to 57% of that in the late twentieth century. However, if mitigation measures were to be undertaken according to RCP2.6 standards, the increase of the flood damage cost will stop, and the increase of the flood damage cost will be 28% of that in the late twentieth century. By implementing adaptation measures in combination rather than individually, it is possible to keep the damage cost in the future period even below that in the late twentieth century. By implementing both mitigation and adaptation measures, it is possible to reduce the flood damage cost in the late twenty-first century to 69% of that in the late twentieth century.

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