scholarly journals Strengthening of the hydrological cycle in future scenarios: atmospheric energy and water balance perspective

2012 ◽  
Vol 3 (2) ◽  
pp. 523-560 ◽  
Author(s):  
A. Alessandri ◽  
P. G. Fogli ◽  
M. Vichi ◽  
N. Zeng
Keyword(s):  
Global Warming ◽  
20Th Century ◽  
21St Century ◽  
Hydrological Cycle ◽  
Surface Fluxes ◽  
Mitigation Scenario ◽  
Budget Analysis ◽  
Large Perturbation ◽  
Decadal Scale ◽  
Global Precipitation

Abstract. Future climate scenarios experiencing global warming are expected to strengthen hydrological cycle during 21st century by comparison with the last decades of 20th century. We analyze strengthening of the global-scale increase in precipitation from the perspective of changes in whole atmospheric water and energy balances. Furthermore, by combining energy and water equations for the whole atmosphere we profitably obtain constraints for the changes in surface fluxes and for the partitioning at the surface between sensible and latent components. Above approach is applied to investigate difference in strengthening of hydrological cycle in two scenario centennial simulations performed with an Earth System model forced with specified atmospheric concentration pathways. Alongside the medium-high non-mitigation scenario SRES A1B, we considered a new aggressive-mitigation scenario (E1) with reduced fossil fuel use for energy production aimed at stabilizing global warming below 2 K. Quite unexpectedly, mitigation scenario is shown to strengthen hydrological cycle more than SRES A1B till around 2070. Our analysis shows that this is mostly a consequence of the larger increase in the negative radiative imbalance of atmosphere in E1 compared to A1B. This appears to be primarily related to the abated aerosol concentration in E1, which considerably reduces atmospheric absorption of solar radiation compared to A1B. In contrast, last decades of 21st century (21C) show marked increase of global precipitation in A1B compared to E1, despite the fact that the two scenarios display almost same overall increase of radiative imbalance with respect to 20th century. Our results show that radiative cooling is weakly effective in A1B throughout all 21C, so that two distinct mechanisms characterize the diverse strengthening of hydrological cycle in mid and end 21C. It is only through a very large perturbation of surface fluxes that A1B achieves larger increase of global precipitation in the last decades of 21C. Our energy/water budget analysis shows that this behavior is ultimately due to a bifurcation in the Bowen ratios change between the two scenarios. This work warns that mitigation policies, by abating aerosols, may lead to unexpected stronger intensification of hydrological cycle and associated changes that may last for decades after that global warming is effectively mitigated. On the other hand, it is here suggested that predictable components of the radiative forcing by aerosols may have the potential to effectively contribute to the decadal-scale predictability of changes in the hydrological strength.

scholarly journals Strengthening of the hydrological cycle in future scenarios: atmospheric energy and water balance perspective

2012 ◽  
Vol 3 (2) ◽  
pp. 199-212 ◽  
Author(s):  
A. Alessandri ◽  
P. G. Fogli ◽  
M. Vichi ◽  
N. Zeng
Keyword(s):  
Global Warming ◽  
Hydrological Cycle ◽  
Surface Fluxes ◽  
The Other ◽  
Mitigation Scenario ◽  
Budget Analysis ◽  
Other Hand ◽  
Large Perturbation ◽  
Decadal Scale ◽  
Global Precipitation

Abstract. Future climate scenarios experiencing global warming are expected to strengthen the hydrological cycle during the 21st century (21C). We analyze the strengthening of the global-scale increase in precipitation from the perspective of changes in whole atmospheric water and energy balances. By combining energy and water equations for the whole atmosphere, we obtain constraints for the changes in surface fluxes and partitioning at the surface between sensible and latent components. We investigate the differences in the strengthening of the hydrological cycle in two centennial simulations performed with an Earth system model forced with specified atmospheric concentration pathways. Alongside the Special Report on Emissions Scenario (SRES) A1B, which is a medium-high non-mitigation scenario, we consider a new aggressive-mitigation scenario (E1) with reduced fossil fuel use for energy production aimed at stabilizing global warming below 2 K. Our results show that the mitigation scenario effectively constrains the global warming with a stabilization below 2 K with respect to the 1950–2000 historical period. On the other hand, the E1 precipitation does not follow the temperature field toward a stabilization path but continues to increase over the mitigation period. Quite unexpectedly, the mitigation scenario is shown to strengthen the hydrological cycle even more than SRES A1B till around 2070. We show that this is mostly a consequence of the larger increase in the negative radiative imbalance of atmosphere in E1 compared to A1B. This appears to be primarily related to decreased sulfate aerosol concentration in E1, which considerably reduces atmospheric absorption of solar radiation compared to A1B. The last decades of the 21C show a marked increase in global precipitation in A1B compared to E1, despite the fact that the two scenarios display almost the same overall increase of radiative imbalance with respect to the 20th century. Our results show that radiative cooling is weakly effective in A1B throughout the 21C. Two distinct mechanisms characterize the diverse strengthening of the hydrological cycle in the middle and end- 21C. It is only through a very large perturbation of surface fluxes that A1B achieves a larger increase in global precipitation in the last decades of the 21C. Our energy/water budget analysis shows that this behavior is ultimately due to a bifurcation in the Bowen ratio change between the two scenarios. This work warns that mitigation policies that promote aerosol abatement, may lead to an unexpected stronger intensification of the hydrological cycle and associated changes that may last for decades after global warming is effectively mitigated. On the other hand, it is also suggested that predictable components of the radiative forcing by aerosols may have the potential to effectively contribute to the decadal-scale predictability of changes in the hydrological strength.

Revisiting the existence of the global warming slowdown during the early 21st century

2021 ◽  
pp. 1-40
Keyword(s):  
Global Warming ◽  
Greenhouse Gas ◽  
Selection Bias ◽  
21St Century ◽  
Linear Trend ◽  
Warming Trend ◽  
Short Term ◽  
Early 21St Century ◽  
Decadal Scale ◽  
Global Temperature Change

Abstract There are heated debates on the existence of the global warming slowdown during the early 21st century. Although efforts have been made to clarify or reconcile the controversy over the issue, it is not explicitly addressed, restricting the understanding of global temperature change particularly under the background of increasing greenhouse-gas concentrations. Here, using extensive temperature datasets, we comprehensively reexamine the existence of the slowdown under all existing definitions during all decadal-scale periods spanning 1990-2017. Results show that the short-term linear-trend dependent definitions of slowdown make its identification severely suffer from the period selection bias, which largely explains the controversy over its existence. Also, the controversy is further aggravated by the significant impacts of the differences between various datasets on the recent temperature trend and the different baselines for measuring slowdown prescribed by various definitions. However, when the focus is shifted from specific periods to the probability of slowdown events, we find the probability is significantly higher in the 2000s than in the 1990s, regardless of which definition and dataset are adopted. This supports a slowdown during the early 21st century relative to the warming surge in the late 20th century, despite higher greenhouse-gas concentrations. Furthermore, we demonstrate that this decadal-scale slowdown is not incompatible with the centennial-scale anthropogenic warming trend, which has been accelerating since 1850 and never pauses or slows. This work partly reconciles the controversy over the existence of the warming slowdown and the discrepancy between the slowdown and anthropogenic warming.

“Band Wagon and Gravy Train”: uses and abuses along the Silk Road

Afghanistan ◽  
2019 ◽  
Vol 2 (2) ◽  
pp. 171-194
Author(s):  
Warwick Ball
Keyword(s):  
20Th Century ◽  
21St Century ◽  
Silk Road ◽  
Late 20Th Century ◽  
Ancient Trade ◽  
International Image ◽  
Academic Discussion ◽  
The Silk Road

The Silk Road as an image is a relatively new one for Afghanistan. It appeals to both the pre-Islamic and the perceived Islamic past, thus offering an Islamic balance to previous identities linked to Bamiyan or to the Kushans. It also appeals to a broader and more international image, one that has been taken up by many other countries. This paper traces the rise of the image of the Silk Road and its use as a metaphor for ancient trade to encompass all contacts throughout Eurasia, prehistoric, ancient and modern, but also how the image has been adopted and expanded into many other areas: politics, tourism and academia. It is argued here that the origin and popularity of the term lies in late 20th century (and increasingly 21st century) politics rather than any reality of ancient trade. Its consequent validity as a metaphor in academic discussion is questioned

The role of science in the study of and response to space threats

2019 ◽  
Vol 89 (8) ◽  
pp. 777-799
Author(s):  
B. M. Shustov
Keyword(s):  
Comparative Analysis ◽  
20Th Century ◽  
21St Century ◽  
Space Debris ◽  
The Sun ◽  
National Program ◽  
Biological Hazard ◽  
Academy Of Sciences ◽  
Space Activities

During the second half of the 20th century and the beginning of the 21st century, space hazards multiplied, the most urgent of which is space debris. Professionals working in space are exposed to this hazard daily and are aware of it as a problem. Furthermore, increasing attention is being paid to the unpredictable behavior of the Sun, which produces the so-called space weather. The asteroid-comet hazard is considered as potentially having the most catastrophic consequences. No manifestations of biological hazard have yet been observed, although as space activities develop, it is becoming increasingly important. The appropriate time scale for astrophysical hazards is many millions of years, so from a practical perspective, they have no importance. This article briefly describes the main types of space hazards. The author analyzes the results of research and practical work in the field, both worldwide and specifically in Russia. Comparative analysis leads to the clear conclusion that a national program must be developed for the study of space hazards and to respond to space threats. This article is based on a report made by the author at the meeting of the Presidium of the Russian Academy of Sciences (RAS) on January 15, 2019.

About the Nature of Global Warming Decrease at the Beginning of 21st Century

2018 ◽  
Vol 482 (3) ◽  
pp. 315-318
Author(s):  
E. Volodin ◽  
◽  
A. Gritsun ◽  
Keyword(s):  
Global Warming ◽  
21St Century

Global warming influences dynamics of plague’s epidemic manifestations in XX-XXI centuries

2017 ◽  
pp. 38-40
Author(s):  
E.S. Zenkevich ◽  
N.V. Popov
Keyword(s):  
Global Warming ◽  
20Th Century ◽  
Modern Trend ◽  
Climate Fluctuations ◽  
The World ◽  
Low Incidence ◽  
High Level

During the second half of 20th century, a high level of plague incidence in the world was in 1960–1979 and 1990–2009. The significant decrease of infection cases was in 1950–1959, 1980–1989, 2010–2015. It is noticed, that the observed cyclical nature of the alternation of high and low incidence plague’s periods, in many respects related to modern trend of climate fluctuations.

scholarly journals Upper Colorado River Basin 20th century droughts under 21st century warming: Plausible scenarios for the future

2021 ◽  
Vol 21 ◽  
pp. 100206
Author(s):  
Connie A. Woodhouse ◽  
Rebecca M. Smith ◽  
Stephanie A. McAfee ◽  
Gregory T. Pederson ◽  
Gregory J. McCabe ◽  
...  
Keyword(s):  
20Th Century ◽  
River Basin ◽  
21St Century ◽  
Colorado River ◽  
Colorado River Basin ◽  
Upper Colorado River Basin ◽  
The Future
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