scholarly journals Global Warming Attenuates the Tropical Atlantic-Pacific Teleconnection

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Fan Jia ◽  
Lixin Wu ◽  
Bolan Gan ◽  
Wenju Cai
Keyword(s):  
Global Warming ◽  
Tropical Atlantic

scholarly journals Climate Changes of Atlantic Tropical Cyclone Formation Derived from Twentieth-Century Reanalysis

2013 ◽  
Vol 26 (22) ◽  
pp. 8995-9005 ◽  
Author(s):  
Ruifang Wang ◽  
Liguang Wu
Keyword(s):  
Global Warming ◽  
North Atlantic ◽  
Wind Shear ◽  
Vertical Wind Shear ◽  
The United States ◽  
Tropical Atlantic ◽  
The North ◽  
The Caribbean ◽  
The North Atlantic ◽  
Twentieth Century Reanalysis

Abstract Whereas some studies linked the enhanced tropical cyclone (TC) formation in the North Atlantic basin to the ongoing global warming, other studies attributed it to the warm phase of the Atlantic multidecadal oscillation (AMO). Using the National Oceanic and Atmospheric Administration (NOAA) Earth System Research Laboratory (ESRL) Twentieth Century Reanalysis (20CR) dataset, the present study reveals the distinctive spatial patterns associated with the influences of the AMO and global warming on TC formation in the North Atlantic basin. Two leading empirical orthogonal function (EOF) patterns are identified in the climate change of TC formation on time scales longer than interannual. The first pattern is associated with the AMO and its spatial pattern shows the basin-scale enhancement of TC formation during the AMO positive phase. The second pattern is associated with global warming, showing enhanced TC formation in the east tropical Atlantic (5°–20°N, 15°–40°W) and reduced TC formation from the southeast coast of the United States extending southward to the Caribbean Sea. In the warm AMO phase, the basinwide decrease in vertical wind shear and increases in midlevel relative humidity and maximum potential intensity (MPI) favor the basinwide enhancement of TC formation. Global warming suppresses TC formation from the southeast coast of the United States extending southward to the Caribbean Sea through enhancing vertical wind shear and reducing midlevel relative humidity and MPI. The enhanced TC formation in the east tropical Atlantic is due mainly to a local increase in MPI or sea surface temperature (SST), leading to a close relationship between the Atlantic SST and TC activity over the past decades.

scholarly journals Impact of an AMOC weakening on the stability of the southern Amazon rainforest

2021 ◽  
Author(s):  
Catrin Ciemer ◽  
Ricarda Winkelmann ◽  
Jürgen Kurths ◽  
Niklas Boers
Keyword(s):  
Global Warming ◽  
Greenland Ice Sheet ◽  
Meridional Overturning Circulation ◽  
Amazon Rainforest ◽  
State Transitions ◽  
Freshwater Flux ◽  
Gradual Change ◽  
Tropical Atlantic ◽  
The Stability ◽  
Amazon Rainfall

AbstractThe Atlantic Meridional Overturning Circulation (AMOC) and the Amazon rainforest are potential tipping elements of the Earth system, i.e., they may respond with abrupt and potentially irreversible state transitions to a gradual change in forcing once a critical forcing threshold is crossed. With progressing global warming, it becomes more likely that the Amazon will reach such a critical threshold, due to projected reductions of precipitation in tropical South America, which would in turn trigger vegetation transitions from tropical forest to savanna. At the same time, global warming has likely already contributed to a weakening of the AMOC, which induces changes in tropical Atlantic sea-surface temperature (SST) patterns that in turn affect rainfall patterns in the Amazon. A large-scale decline or even dieback of the Amazon rainforest would imply the loss of the largest terrestrial carbon sink, and thereby have drastic consequences for the global climate. Here, we assess the direct impact of greenhouse gas-driven warming of the tropical Atlantic ocean on Amazon rainfall. In addition, we estimate the effect of an AMOC slowdown or collapse, e. g. induced by freshwater flux into the North Atlantic due to melting of the Greenland Ice Sheet, on Amazon rainfall. In order to provide a clear explanation of the underlying dynamics, we use a simple, but robust mathematical approach (based on the classical Stommel two-box model), ensuring consistency with a comprehensive general circulation model (HadGEM3). We find that these two processes, both caused by global warming, are likely to have competing impacts on the rainfall sum in the Amazon, and hence on the stability of the Amazon rainforest. A future AMOC decline may thus counteract direct global-warming-induced rainfall reductions. Tipping of the AMOC from the strong to the weak mode may therefore have a stabilizing effect on the Amazon rainforest.

Mean-state dependence of future tropical-Atlantic sector climate projections

2020 ◽  
Author(s):  
Wonsun Park ◽  
Mojib Latif ◽  
Arielle Stela Imbol Nkwinkwa Njouodo
Keyword(s):  
Global Warming ◽  
Climate Model ◽  
Horizontal Resolution ◽  
Tropical Pacific ◽  
Climate Projections ◽  
Tropical Atlantic ◽  
Atlantic Sector ◽  
Sst Bias ◽  
The Mean ◽  
Mean State

<p>Mean state and internal variability in the tropics are crucially linked to air-sea interactions. State-of-the-art climate models exhibit long-standing problems not only in simulating tropical mean climate, such as too cold sea surface temperature (SST) over the central tropical Pacific and too warm SST over the eastern tropical Pacific and Atlantic, but also with respect to seasonal and longer variability. These biases question the credibility of future climate projections with the models, and it has not been shown to date whether or how such SST biases affect the projections. Here we focus on the tropical Atlantic (TA) and investigate how the mean state influences climate projections over the region.</p><p>We use two versions of the Kiel Climate Model (KCM) in global warming simulations, in which only atmosphere model resolution differs: one version carries ECHAM5 with a horizontal resolution of T42 (~2.8°) and 31 vertical levels, and the other ECHAM5 with a horizontal resolution of T255 (~0.47°) and 62 levels. Although only the atmospheric resolutions differ, the two KCM versions exhibit very different mean states over the tropical TA, with the higher-resolution version, among others, featuring much reduced warm SST bias over the eastern basin.</p><p>The response to increasing atmospheric carbon dioxide levels is found to be sensitive to the mean state. The model employing high atmospheric resolution and featuring a small SST bias projects an eastward-amplified SST warming over the TA, consistent with the pattern of interannual SST variability simulated under present-day conditions and in line with the observed SST trends since the mid-20<sup>th</sup> century. The model employing low-resolution and exhibiting a large SST bias projects more uniform SST change. Atmospheric changes also vastly differ among the two model versions.</p><p>Analysis of models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5) support the KCM’s results: models with small SST bias project stronger warming over the eastern TA, while models with large SST bias either project uniform warming across the equator or largest warming in the west. This study suggests that reducing model bias may enhance global warming projections over the TA sector.</p>

Modelling ecosystem adaptation and dangerous rates of global warming

2019 ◽  
Vol 3 (2) ◽  
pp. 221-231 ◽  
Author(s):  
Rebecca Millington ◽  
Peter M. Cox ◽  
Jonathan R. Moore ◽  
Gabriel Yvon-Durocher
Keyword(s):  
Climate Change ◽  
Global Warming ◽  
Diffusion Rate ◽  
Individual Species ◽  
Genetic Evolution ◽  
Rates Of Change ◽  
Rapid Climate Change ◽  
Warming Climate ◽  
Intraspecies Competition ◽  
High Trait

Abstract We are in a period of relatively rapid climate change. This poses challenges for individual species and threatens the ecosystem services that humanity relies upon. Temperature is a key stressor. In a warming climate, individual organisms may be able to shift their thermal optima through phenotypic plasticity. However, such plasticity is unlikely to be sufficient over the coming centuries. Resilience to warming will also depend on how fast the distribution of traits that define a species can adapt through other methods, in particular through redistribution of the abundance of variants within the population and through genetic evolution. In this paper, we use a simple theoretical ‘trait diffusion’ model to explore how the resilience of a given species to climate change depends on the initial trait diversity (biodiversity), the trait diffusion rate (mutation rate), and the lifetime of the organism. We estimate theoretical dangerous rates of continuous global warming that would exceed the ability of a species to adapt through trait diffusion, and therefore lead to a collapse in the overall productivity of the species. As the rate of adaptation through intraspecies competition and genetic evolution decreases with species lifetime, we find critical rates of change that also depend fundamentally on lifetime. Dangerous rates of warming vary from 1°C per lifetime (at low trait diffusion rate) to 8°C per lifetime (at high trait diffusion rate). We conclude that rapid climate change is liable to favour short-lived organisms (e.g. microbes) rather than longer-lived organisms (e.g. trees).

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