Mechanisms for Global Warming Impacts on Madden–Julian Oscillation Precipitation Amplitude

2019 ◽  
Vol 32 (20) ◽  
pp. 6961-6975 ◽  
Author(s):  
Hien X. Bui ◽  
Eric D. Maloney
Keyword(s):  
Global Warming ◽  
Coupled Model ◽  
Static Stability ◽  
Moisture Gradient ◽  
Madden Julian Oscillation ◽  
Surface Warming ◽  
Moisture Advection ◽  
Diabatic Processes ◽  
Intercomparison Project ◽  
Moisture Profiles

Abstract Mechanisms that cause changes in Madden–Julian oscillation (MJO) precipitation amplitude under global warming are examined in models from phase 5 of the Coupled Model Intercomparison Project. Under global warming in representative concentration pathway 8.5, MJO precipitation intensifies in most models relative to current climate while MJO wind circulations increase at a slower rate or weaken. Changes in MJO precipitation intensity are partially controlled by changes in moisture profiles and static stability. The vertical moisture gradient increases in the lower half of the troposphere in response to the surface warming, while the vertical static stability gradient increases due to preferential warming in the upper troposphere. A nondimensional quantity called α has been defined that gives the efficiency of vertical advective moistening associated with diabatic processes in the free troposphere, and has been hypothesized by previous studies to regulate MJO amplitude. The term α is proportional to the vertical moisture gradient and inversely proportional to static stability. Under global warming, the increased vertical moisture gradient makes α larger in models, despite increased static stability. Although α increases in all models, MJO precipitation amplitude decreases in some models, contrary to expectations. It is demonstrated that in these models more top-heavy MJO diabatic heating with warming overwhelms the effect of increased α to make vertical moisture advection less efficient.

scholarly journals Expansion of the Hadley Cell under Global Warming: Winter versus Summer

2012 ◽  
Vol 25 (24) ◽  
pp. 8387-8393 ◽  
Author(s):  
Sarah M. Kang ◽  
Jian Lu
Keyword(s):  
Global Warming ◽  
Outer Boundary ◽  
Coupled Model ◽  
Static Stability ◽  
Hadley Cell ◽  
Scaling Analysis ◽  
Zonal Winds ◽  
Scaling Relationship ◽  
Intercomparison Project ◽  
Upper Level

Abstract A scaling relationship is introduced to explain the seasonality in the outer boundary of the Hadley cell in both climatology and trend in the simulations of phase 3 of the Coupled Model Intercomparison Project (CMIP3). In the climatological state, the summer cell reaches higher latitudes than the winter cell since the Hadley cell in summer deviates more from the angular momentum conserving state, resulting in weaker upper-level zonal winds, which enables the Hadley cell to extend farther poleward before becoming baroclinically unstable. The Hadley cell can also reach farther poleward as the ITCZ gets farther away from the equator; hence, the Hadley cell extends farther poleward in solstices than in equinoxes. In terms of trend, a robust poleward expansion of the Hadley cell is diagnosed in all seasons with global warming. The scaling analysis indicates this is mostly due to an increase in the subtropical static stability, which pushes poleward the baroclinically unstable zone and hence the poleward edge of the Hadley cell. The relation between the trends in the Hadley cell edge and the ITCZ is also discussed.

Tropical expansion driven by poleward advancing subtropical front

2020 ◽  
Author(s):  
Hu Yang ◽  
Gerrit Lohmann ◽  
Xiaoxu Shi ◽  
Evan J. Gowan
Keyword(s):  
Global Warming ◽  
Coupled Model ◽  
Dynamical Mechanism ◽  
Model Simulations ◽  
Subtropical Front ◽  
Surface Warming ◽  
Meridional Displacement ◽  
Intercomparison Project ◽  
The Tropics ◽  
Natural Climate

<p>Abundance of evidence shows that the tropics are expanding in the past four decades. Despite many attempts to decipher its cause, the underlying dynamical mechanism driving tropical expansion is still not clear. Here, based on observations and multi-model simulations from the Coupled Model Intercomparison Project phase 5 (CMIP5), the variations and trends of tropical width are explored from a regional perspective. We find that the width of the tropics closely follows the meridional displacement of oceanic subtropical front. Under global warming, the subtropical ocean experiences more surface warming due to convergence of surface water. Such enhanced warming, superimposing onto the variation of Pacific Decadal Oscillation, leads to poleward advancing of subtropical front and drives the tropical expansion. Our results, supported by both observations and model simulations, imply that the observed expanding tropics may largely attributed to the anthropogenic global warming rather than the natural climate variability.</p>

scholarly journals Scant evidence for a volcanically forced winter warming over Eurasia following the Krakatau eruption of August 1883

2020 ◽  
Vol 20 (22) ◽  
pp. 13687-13700
Author(s):  
Lorenzo M. Polvani ◽  
Suzana J. Camargo
Keyword(s):  
Coupled Model ◽  
Large Magnitude ◽  
Low Latitude ◽  
Surface Warming ◽  
Winter Warming ◽  
Pinatubo Eruption ◽  
Intercomparison Project ◽  
Volcanic Aerosols ◽  
Instrumental Period ◽  
New Evidence

Abstract. A recent study has presented compelling new evidence suggesting that the observed Eurasian warming in the winter following the 1992 Pinatubo eruption was, in all likelihood, unrelated to the presence of volcanic aerosols in the stratosphere. Building on that study, we turn our attention to the only other low-latitude eruption in the instrumental period with a comparably large magnitude: the Krakatau eruption of August 1883. We study the temperature anomalies in the first winter following that eruption in detail, analyzing (1) observations, (2) reanalyses, and (3) models. Three findings emerge from our analysis. First, the observed post-Krakatau winter warming over Eurasia was unremarkable (only between 1σ and 2σ of the distribution from 1850 to present). Second, reanalyses based on assimilating surface pressure alone indicate the existence of very large uncertainties, so much so that a Eurasian cooling is not incompatible with those reanalyses. Third, models robustly show the complete absence of a volcanically forced Eurasian winter warming: here, we analyze both a 100-member initial-condition ensemble and 140 simulations from Phase 5 of the Coupled Model Intercomparison Project. This wealth of evidence strongly suggests that, as in the case of Pinatubo, the observed warming over Eurasia in the winter of 1883–84 was, in all likelihood, unrelated to the Krakatau eruption. This, taken together with a similar result for Pinatubo, leads us to conclude that if volcanically forced Eurasian winter warming exists at all, an eruption with a magnitude far exceeding these two events would be needed to produce a detectable surface warming.

Challenges in Constraining Future Change of Global Land Precipitation in CMIP6 Models

2020 ◽  
Author(s):  
June-Yi Lee ◽  
Kyung-Sook Yun ◽  
Arjun Babu ◽  
Young-Min Yang ◽  
Eui-Seok Chung ◽  
...  
Keyword(s):  
Global Warming ◽  
Emission Scenario ◽  
Coupled Model ◽  
Precipitation Change ◽  
Cmip5 Models ◽  
Model Intercomparison ◽  
Projected Change ◽  
Global Land ◽  
Intercomparison Project ◽  
Global Mean

<p><span>The Coupled Model Intercomparison Project Phase 5 (CMIP5) models have showed substantial inter-model spread in estimating annual global-mean precipitation change per one-degree greenhouse-gas-induced warming (precipitation sensitivity), ranging from -4.5</span><span>–4.2</span><span>%</span><sup><span>o</span></sup><span>C<sup>-1</sup>in the Representative Concentration Pathway (RCP) 2.6, the lowest emission scenario, to 0.2–4.0</span><span>%</span><sup><span>o</span></sup><span>C<sup>-1</sup>in the RCP 8.5, the highest emission scenario. The observed-based estimations in the global-mean land precipitation sensitivity during last few decades even show much larger spread due to the considerable natural interdecadal variability, role of anthropogenic aerosol forcing, and uncertainties in observation. This study tackles to better quantify and constrain global land precipitation change in response to global warming by analyzing the new range of Shared Socio-economic Pathway (SSP) scenarios in the </span><span>Coupled Model Intercomparison Project Phase 6 (CMIP6) compared with RCP scenarios in the CMIP5. We show that the range of projected change in annual global-mean land (ocean) precipitation by the end of the 21<sup>st</sup>century relative to the recent past (1995-2014) in the 23 CMIP6 models is over 50% (20%) larger than that in corresponding scenarios of the 40 CMIP5 models. The estimated ranges of precipitation sensitivity in four Tier-1 SSPs are also larger than those in corresponding CMIP5 RCPs. The large increase in projected precipitation change in the highest quartile over ocean is mainly due to the increased number of high equilibrium climate sensitivity (ECS) models in CMIP6 compared to CMIP5, but not over land due to different response of thermodynamic moisture convergence and dynamic processes to global warming. We further discuss key challenges in constraining future precipitation change and source of uncertainties in land precipitation change.</span></p>

scholarly journals Probabilistic projections of future warming and climate sensitivity trajectories

2021 ◽  
Author(s):  
Philip Goodwin
Keyword(s):  
Global Warming ◽  
Climate Sensitivity ◽  
Climate Model ◽  
Heat Content ◽  
Surface Warming ◽  
Observational Uncertainty ◽  
Future Global Warming ◽  
Intercomparison Project ◽  
Future Warming ◽  
Probabilistic Projections

Abstract Projections of future global mean surface warming for a given forcing scenario remain uncertain, largely due to uncertainty in the climate sensitivity. The ensemble of Earth system models from the Climate Model Intercomparison Project phase 6 (CMIP6) represent the dominant tools for projecting future global warming. However, the distribution of climate sensitivities within the CMIP6 ensemble is not representative of recent independent probabilistic estimates, and the ensemble contains significant variation in simulated historic surface warming outside agreement with observational datasets. Here, a Bayesian approach is used to infer joint probabilistic projections of future surface warming and climate sensitivity for SSP scenarios. The projections use an efficient climate model ensemble filtered and weighted to encapsulate observational uncertainty in historic warming and ocean heat content anomalies. The probabilistic projection of climate sensitivity produces a best estimate of 2.9 °C, and 5th to 95th percentile range of 1.5 to 4.6 °C, in line with previous estimates using multiple lines of evidence. The joint projection of surface warming over the period 2030 to 2040 has a 50% or greater probability of exceeding 1.5 °C above preindustrial for all SSPs considered: 119, 126, 245, 370 and 585. Average warming by the period 2050 to 2060 has a greater than 50% chance of exceeding 2 °C for SSPs 245, 370 and 585. These results imply that global warming is no longer likely to remain under 1.5 °C, even with drastic and immediate mitigation, and highlight the importance of urgent action to avoid exceeding 2 °C warming.

scholarly journals On the Mechanisms of Pacific Decadal Oscillation Modulation in a Warming Climate

2019 ◽  
Vol 32 (5) ◽  
pp. 1443-1459 ◽  
Author(s):  
Tao Geng ◽  
Yun Yang ◽  
Lixin Wu
Keyword(s):  
Growth Rate ◽  
Global Warming ◽  
Pacific Decadal Oscillation ◽  
Decadal Variability ◽  
Coupled Model ◽  
Growth Time ◽  
Coupled Mode ◽  
Warming Climate ◽  
The Pacific ◽  
Intercomparison Project

Abstract Changes of the Pacific decadal oscillation (PDO) under global warming are investigated by using outputs from phase 5 of the Coupled Model Intercomparison Project (CMIP5) and a theoretical midlatitude air–sea coupled model. In a warming climate, the decadal variability of the PDO is found to be significantly suppressed, with the amplitude reduced and the decadal cycle shifted toward a higher-frequency band. We used the theoretical model put forward by Goodman and Marshall (herein the GM model) to underpin the potential mechanisms. The GM model exhibits a growing coupled mode that resembles the simulated PDO. It is found that the suppression of the PDO appears to be associated with the acceleration of Rossby waves due to the enhanced oceanic stratification under global warming. This shortens the PDO period and reduces PDO amplitude by limiting the growth time of the coupled mode. The GM model also suggests that the increase of growth rate due to strengthening of oceanic stratification tends to magnify the PDO amplitude, counteracting the Rossby wave effect. This growth rate influence, however, plays a secondary role.

scholarly journals Impacts of 1.5 °C and 2 °C Global Warming on Net Primary Productivity and Carbon Balance in China’s Terrestrial Ecosystems

2020 ◽  
Vol 12 (7) ◽  
pp. 2849
Author(s):  
Li Yu ◽  
Fengxue Gu ◽  
Mei Huang ◽  
Bo Tao ◽  
Man Hao ◽  
...  
Keyword(s):  
Global Warming ◽  
Primary Productivity ◽  
Net Primary Productivity ◽  
Climate Adaptation ◽  
Coupled Model ◽  
Terrestrial Ecosystems ◽  
Northern China ◽  
Ecosystem Model ◽  
Intercomparison Project ◽  
Potential Risks

Assessing potential impacts of 1.5 °C and 2 °C global warming and identifying the risks of further 0.5 °C warming are crucial for climate adaptation and disaster risk management. Four earth system models in the Coupled Model Intercomparison Project Phase 5 (CMIP5) and a process-based ecosystem model are used in this study to assess the impacts and potential risks of the two warming targets on the carbon cycle of China’s terrestrial ecosystems. Results show that warming generally stimulates the increase of net primary productivity (NPP) and net ecosystem productivity (NEP) under both representative concentration pathway (RCP) 4.5 and RCP8.5 scenarios. The projected increments of NPP are higher at 2 °C warming than that at 1.5 °C warming for both RCP4.5 and RCP8.5 scenarios; approximately 13% and 19% under RCP4.5, and 12.5% and 20% under RCP8.5 at 1.5 °C and 2 °C warming, respectively. However, the increasing rate of NPP was projected to decline at 2 °C warming under the RCP4.5 scenario, and the further 0.5 °C temperature rising induces the decreased NPP linear slopes in more than 81% areas of China’s ecosystems. The total NEP is projected to be increased by 53% at 1.5 °C, and by 81% at 2 °C warming. NEP was projected to increase approximately by 28% with the additional 0.5 °C warming. Furthermore, the increasing rate of NEP weakens at 2 °C warming, especially under the RCP8.5 scenario. In summary, China’s total NPP and NEP were projected to increase under both 1.5 °C and 2 °C warming scenarios, although adverse effects (i.e., the drop of NPP growth and the reduction of carbon sequestration capacity) would occur in some regions such as northern China in the process of global warming.

Indian Ocean Dipole Response to Global Warming in the CMIP5 Multimodel Ensemble*

2013 ◽  
Vol 26 (16) ◽  
pp. 6067-6080 ◽  
Author(s):  
Xiao-Tong Zheng ◽  
Shang-Ping Xie ◽  
Yan Du ◽  
Lin Liu ◽  
Gang Huang ◽  
...  
Keyword(s):  
Global Warming ◽  
Indian Ocean ◽  
Indian Ocean Dipole ◽  
Coupled Model ◽  
Equatorial Indian Ocean ◽  
Easterly Wind ◽  
Thermocline Feedback ◽  
Intercomparison Project ◽  
Eastern Equatorial Indian Ocean ◽  
Dipole Response

Abstract The response of the Indian Ocean dipole (IOD) mode to global warming is investigated based on simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5). In response to increased greenhouse gases, an IOD-like warming pattern appears in the equatorial Indian Ocean, with reduced (enhanced) warming in the east (west), an easterly wind trend, and thermocline shoaling in the east. Despite a shoaling thermocline and strengthened thermocline feedback in the eastern equatorial Indian Ocean, the interannual variance of the IOD mode remains largely unchanged in sea surface temperature (SST) as atmospheric feedback and zonal wind variance weaken under global warming. The negative skewness in eastern Indian Ocean SST is reduced as a result of the shoaling thermocline. The change in interannual IOD variance exhibits some variability among models, and this intermodel variability is correlated with the change in thermocline feedback. The results herein illustrate that mean state changes modulate interannual modes, and suggest that recent changes in the IOD mode are likely due to natural variations.

Distributions of Tropical Precipitation Cluster Power and Their Changes under Global Warming. Part II: Long-Term Time Dependence in Coupled Model Intercomparison Project Phase 5 Models

2017 ◽  
Vol 30 (20) ◽  
pp. 8045-8059 ◽  
Author(s):  
Kevin M. Quinn ◽  
J. David Neelin
Keyword(s):  
Global Warming ◽  
High Resolution ◽  
Rain Rate ◽  
Climate Model ◽  
Coupled Model ◽  
Atmospheric Model ◽  
Department Of Energy ◽  
Model Intercomparison ◽  
Intense Storm ◽  
Intercomparison Project

Abstract Distributions of precipitation cluster power (latent heat release rate integrated over contiguous precipitating pixels) are examined in 1°–2°-resolution members of phase 5 of the Coupled Model Intercomparison Project (CMIP5) climate model ensemble. These approximately reproduce the power-law range and large event cutoff seen in observations and the High Resolution Atmospheric Model (HiRAM) at 0.25°–0.5° in Part I. Under the representative concentration pathway 8.5 (RCP8.5) global warming scenario, the change in the probability of the most intense storm clusters appears in all models and is consistent with HiRAM output, increasing by up to an order of magnitude relative to historical climate. For the three models in the ensemble with continuous time series of high-resolution output, there is substantial variability on when these probability increases for the most powerful storm clusters become detectable, ranging from detectable within the observational period to statistically significant trends emerging only after 2050. A similar analysis of National Centers for Environmental Prediction (NCEP)–U.S. Department of Energy (DOE) AMIP-II reanalysis and Special Sensor Microwave Imager and Imager/Sounder (SSM/I and SSMIS) rain-rate retrievals in the recent observational record does not yield reliable evidence of trends in high power cluster probabilities at this time. However, the results suggest that maintaining a consistent set of overlapping satellite instrumentation with improvements to SSM/I–SSMIS rain-rate retrieval intercalibrations would be useful for detecting trends in this important tail behavior within the next couple of decades.

scholarly journals Accelerated hydrological cycle over the Sanjiangyuan region induces more streamflow extremes at different global warming levels

2020 ◽  
Author(s):  
Peng Ji ◽  
Xing Yuan ◽  
Feng Ma ◽  
Ming Pan
Keyword(s):  
Global Warming ◽  
Land Surface ◽  
Yangtze River ◽  
Climate Models ◽  
Hydrological Cycle ◽  
Yellow River ◽  
Coupled Model ◽  
Ecological Processes ◽  
Intercomparison Project ◽  
Streamflow Extremes

Abstract. Serving source water for the Yellow, Yangtze and Lancang-Mekong rivers, the Sanjiangyuan region concerns ~ 700 million people over its downstream areas. Recent research suggests that the Sanjiangyuan region will become wetter in a warming future, but future changes in streamflow extremes remain unclear due to the complex hydrological processes over high-land areas and limited knowledge of the influences of land cover change and CO2 physiological forcing. Based on high resolution land surface modeling during 1979~2100 driven by the climate and ecological projections from 11 newly released Coupled Model Intercomparison Project Phase 6 (CMIP6) climate models, we show that different accelerating rates of precipitation and evapotranspiration at 1.5 °C global warming level induce 55 % more dry extremes over Yellow river and 138 % more wet extremes over Yangtze river headwaters compared with the reference period (1985~2014). An additional 0.5 °C warming leads to a further nonlinear and more significant increase for both dry extremes over Yellow river (22 %) and wet extremes over Yangtze river (64 %). The combined role of CO2 physiological forcing and vegetation greening, which used to be neglected in hydrological projections, is found to alleviate dry extremes at 1.5 and 2.0 °C warming levels but to intensify dry extremes at 3.0 °C warming level. Moreover, vegetation greening contributes half of the differences between 1.5 and 3.0 °C warming levels. This study emphasizes the importance of ecological processes in determining future changes in streamflow extremes, and suggests a dry gets drier, wet gets wetter condition over headwaters.

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