Pattern Of Temperature Response Research Articles

Lignocellulose degradation and temperature adaptation mechanisms during composting of mushroom residue and wood chips at low temperature with inoculation of psychrotolerant microbial agent

Low ambient temperature become the limiting factor of composting in cold regions, thus hindering the recycle of agricultural and forestry wastes. In this study, the composting of mushroom residue and wood chips (MRWC) under low temperature was successfully implemented with inoculation of psychrotolerant cellulolytic microbial agent. Composting entered thermophilic stage on third day and the peak temperature reached to 66.25°C. After 84 days of composting, the degradation rate of cellulose and hemicellulose was 40.85% and 100%, respectively and the compost product was completely mature and met the requirements of organic fertilizer. Metagenomic and transcriptome sequencing were applied to reveal the microbial composition and their substrates conversion functions and adaptation mechanisms through low to high temperatures. Streptomyces, Mesorhizobium, Devosia, Aspergillus and Mucor were dominant genera in the microbial community that were rich in genes of lignocellulose degradation. Various genes related to low temperature adaptation (fatty acid, trehalose, mannitol, betaine metabolism and cold shock mechanism) and high temperature tolerance (heat shock and antioxidant) were detected during MRWC composting. These results indicated that microbes during composting constituted a high-efficiency lignocellulosic ultilization system in cold conditions. Besides, the microbes of microbial agent, especially Streptomyces and Aspergillus, possessed numerous genes involving in lignocellulose degradation and temperature adaptation and quite different temperature response patterns were found to perform in bacteria and fungi. The transcription levels of most these genes in Aspergillus exhibited significant differences under different substrates and temperature conditions, suggesting that the inoculum was crucial to the composting process and beneficial to maintain the temperature of piles. This study demonstrated that the application of psychrotolerant microbes was a promising strategy to increase the efficiency of composting in cold regions and these results could also provided the guidance for optimizing microbial agent.

Neural Networks to Find the Optimal Forcing for Offsetting the Anthropogenic Climate Change Effects

Abstract Of great relevance to climate engineering is the systematic relationship between the radiative forcing to the climate system and the response of the system, a relationship often represented by the linear response function (LRF) of the system. However, estimating the LRF often becomes an ill-posed inverse problem due to high-dimensionality and nonunique relationships between the forcing and response. Recent advances in machine learning make it possible to address the ill-posed inverse problem through regularization and sparse system fitting. Here, we develop a convolutional neural network (CNN) for regularized inversion. The CNN is trained using the surface temperature responses from a set of Green’s function perturbation experiments as imagery input data together with data sample densification. The resulting CNN model can infer the forcing pattern responsible for the temperature response from out-of-sample forcing scenarios. This promising proof of concept suggests a possible strategy for estimating the optimal forcing to negate certain undesirable effects of climate change. The limited success of this effort underscores the challenges of solving an inverse problem for a climate system with inherent nonlinearity. Significance Statement Predicting the climate response for a given climate forcing is a direct problem, while inferring the forcing for a given desired climate response is often an inverse, ill-posed, problem, posing a new challenge to the climate community. This study makes the first attempt to infer the radiative forcing for a given target pattern of global surface temperature response using a deep learning approach. The resulting deeply trained convolutional neural network inversion model shows promise in capturing the forcing pattern corresponding to a given surface temperature response, with a significant implication on the design of an optimal solar radiation management strategy for curbing global warming. This study also highlights the technical challenges that future research should prioritize in seeking feasible solutions to the inverse climate problem.

The heat is on: Predicting urban stream temperature responses to summer storms

AbstractShort‐term increases in stream temperature in response to storm events have frequently been observed in urban areas, highlighting the need for improved understanding of the factors influencing urban stream temperature. Urban land cover complexity and infrastructure designed for rapid water routing to the sewer system create a direct link between storm events and water release processes, influencing urban stream temperature responses. This study aims to identify predictors of diverse stream temperature response patterns to summer storms. We analysed 403 storm events from six urban and semi‐urban catchments along the US East Coast using dynamic time warping to identify archetype patterns of stream temperature responses. We further disentangled observed stream temperature increase patterns to reveal the drivers associated with ‘heat pulses’, which are characterized by a rapid but high‐magnitude temperature increase followed by a sharp temperature drop at the start of the hydrograph increase. Our results show that stream temperature patterns were event‐specific and linked to pre‐event conditions and rainfall–runoff characteristics, with the shape of the hydrograph and rainfall–runoff response identified as the most important determinators of the observed temperature response patterns. Ponded surface waters and storm drains, as well as cooler water from the shallow subsurface, were identified as potential sources contributing to temperature patterns. These findings have important implications for understanding urban hydrology and the contributions of different source zones in urban catchments. Specifically, our results suggest that stream temperature may serve as a cost‐effective tracer providing information about urban water sources and pathways, thus aiding in the understanding of complex urban hydrology.

Temperature sensitive contact modes allosterically gate TRPV3.

TRPV Ion channels are sophisticated molecular sensors designed to respond to distinct temperature thresholds. The recent surge in cryo-EM structures has provided numerous insights into the structural rearrangements accompanying their opening and closing; however, the molecular mechanisms by which TRPV channels establish precise and robust temperature sensing remain elusive. In this work we employ molecular simulations, multi-ensemble contact analysis, graph theory, and machine learning techniques to reveal the temperature-sensitive residue-residue interactions driving allostery in TRPV3. We find that groups of residues exhibiting similar temperature-dependent contact frequency profiles cluster at specific regions of the channel. The dominant mode clusters on the ankyrin repeat domain and displays a linear melting trend while others display non-linear trends. These modes describe the residue-level temperature response patterns that underlie the channel's functional dynamics. With network analysis, we find that the community structure of the channel changes with temperature. And that a network of high centrality contacts connects distant regions of the protomer to the gate, serving as a means for the temperature-sensitive contact modes to allosterically regulate channel gating. Using a random forest model, we show that the contact states of specific temperature-sensitive modes are indeed predictive of the channel gate's state. Supporting the physical validity of these modes and networks are several residues identified with our analyses that are reported in literature to be functionally critical. Our results offer high resolution insight into thermo-TRP channel function and demonstrate the utility of temperature-sensitive contact analysis.

Roles of thermal advection in setting the Southern Ocean warming pattern

AbstractThe Southern Ocean is the major region of global ocean heat gain. Most of the heat gain is concentrated in the region of the Antarctic Circumpolar Current (ACC), but SST within the ACC only exhibits a slight increase. Ocean circulation plays a fundamental role in setting the pattern of temperature response to global warming. In this study, a 1/4° Southern Ocean eddy‐permitting model configured based on the Regional Ocean Modeling System is used to study the role of ocean in setting the warming pattern, by examining the response of ocean temperature and heat budget terms to a uniform air–sea heat flux (Qnet) increase. As Qnet increases by a constant value, the SST increases, but with a smaller value within the ACC region. Consequently, more heat flux in the ACC region is induced from the atmosphere to the ocean through thermal adjustment. Heat budget analyses suggest that the surface warming induced by vertical diffusion is largely offset by the cooling effect of heat advection, especially within the ACC region; however, in the subsurface, the effect of vertical diffusion becomes slight, and heat advection dominates the temperature change and induces warming in the ACC region. These results highlight the importance of heat advection in setting the temperature response pattern to air–sea heat flux increase: by transporting more heat from the surface to the deep ocean, the SST increase within the ACC region becomes smaller, and this induces more heat flux from the atmosphere to the ocean and thus makes the ACC region become a major region of heat gain.

Seasonal Succession and Temperature Response Pattern of a Microbial Community in the Yellow Sea Cold Water Mass.

Explaining the temporal dynamics of marine microorganisms is critical for predicting their changing pattern under environmental disturbances. Although the effect of temperature on microbial seasonality has been widely studied, the phylogenetic structure of the temperature response pattern and the extent to which temperature shift leads to disruptive community changes are still unclear. Here, we explored the microbial seasonal dynamics in the Yellow Sea Cold Water Mass (YSCWM) that occurs in summer and disappears in winter and tested the temperature thresholds and phylogenetic coherence in response to temperature change. The existence of YSCWM generates strong temperature gradients in summer and confers little temperature change during seasonal transition, thus representing a unique intermediate state. The microbial community of YSCWM is more similar to that in the previous YSCWM in winter than that outside YSCWM. Temperature alone explains >50% of the community variation, suggesting that a temperature shift can induce a nearly seasonality-level community variance in summer. Persistence of most previous winter YSCWM inhabitants in YSCWM leads to conservation in predicted functional potentials and cooccurrence patterns, indicating a decisive role of temperature in maintaining functionality. Evaluation of the temperature threshold reveals that a small temperature change can lead to significant community turnover, with most taxa negatively responding to an elevation in temperature. The temperature response pattern is phylogenetically structured, and closely related taxa show an incohesive response. Our study provides novel insights into microbial seasonality and into how marine microorganisms respond to temperature fluctuations. IMPORTANCE Microbial seasonality is driven by a set of covarying factors including temperature. There is still a lack of understanding of the details of the phylogenetic structure and susceptibility of microbial communities in response to temperature variation. Through examination of the microbial community in a seasonally occurring summer cold water mass, which experiences little temperature change during seasonal transition, we show here that the cold water mass leads to nearly seasonality-level variations in community composition and predicted functional profile in summer. Moreover, massive community turnover occurs within a small temperature shift, with most taxa decreasing in abundance in response to increased temperature, and contrasting response patterns are observed between phylogenetically closely related taxa. These results suggest temperature as the fundamental factor over other covarying factors in structuring microbial seasonality, providing important insights into the variation mode of the microbial community under temperature disturbances.

Does Disabling Cloud Radiative Feedbacks Change Spatial Patterns of Surface Greenhouse Warming and Cooling?

AbstractThe processes controlling idealized warming and cooling patterns are examined in 150-yr-long fully coupled Community Earth System Model, version 1 (CESM1), experiments under abrupt CO2forcing. By simulation end, 2 × CO2global warming was 20% larger than 0.5 × CO2global cooling. Not only was the absolute global effective radiative forcing ∼10% larger for 2 × CO2than for 0.5 × CO2, global feedbacks were also less negative for 2 × CO2than for 0.5 × CO2. Specifically, more positive shortwave cloud feedbacks led to more 2 × CO2global warming than 0.5 × CO2global cooling. Over high-latitude oceans, differences between 2 × CO2warming and 0.5 × CO2cooling were amplified by familiar linked positive surface albedo and lapse rate feedbacks associated with sea ice change. At low latitudes, 2 × CO2warming exceeded 0.5 × CO2cooling almost everywhere. Tropical Pacific cloud feedbacks amplified the following: 1) more fast warming than fast cooling in the west, and 2) slow pattern differences between 2 × CO2warming and 0.5 × CO2cooling in the east. Motivated to quantify cloud influence, a companion suite of experiments was run without cloud radiative feedbacks. Disabling cloud radiative feedbacks reduced the effective radiative forcing and surface temperature responses for both 2 × CO2and 0.5 × CO2. Notably, 20% more global warming than global cooling occurred regardless of whether cloud feedbacks were enabled or disabled. This surprising consistency resulted from the cloud influence on non-cloud feedbacks and circulation. With the exception of the tropical Pacific, disabling cloud feedbacks did little to change surface temperature response patterns including the large high-latitude responses driven by non-cloud feedbacks. The findings provide new insights into the regional processes controlling the response to greenhouse gas forcing, especially for clouds.Significance StatementWe analyze the processing controlling idealized warming and cooling under abrupt CO2forcing using a modern and highly vetted fully coupled climate model. We were especially interested to compare simulations with and without cloud radiative feedbacks. Notably, 20% more global warming than global cooling occurred regardless of whether cloud feedbacks were enabled or disabled. This surprising consistency resulted from the cloud influence on forcing, non-cloud feedbacks, and circulation. With the exception of the tropical Pacific, disabling cloud feedbacks did little to change surface temperature response patterns including the large high-latitude responses driven by non-cloud feedbacks. The findings provide new insights into the regional processes controlling the response to greenhouse gas forcing, especially for clouds. When combined with estimates of cooling at the Last Glacial Maximum, the findings also help rule out large (4+ K) values of equilibrium climate sensitivity.

Historical Simulations With HadGEM3‐GC3.1 for CMIP6

AbstractWe describe and evaluate historical simulations which use the third Hadley Centre Global Environment Model in the Global Coupled configuration 3.1 (HadGEM3‐GC3.1) and which form part of the UK's contribution to the sixth Coupled Model Intercomparison Project, CMIP6. These simulations, run at two resolutions, respond to historically evolving forcings such as greenhouse gases, aerosols, solar irradiance, volcanic aerosols, land use, and ozone concentrations. We assess the response of the simulations to these historical forcings and compare against the observational record. This includes the evolution of global mean surface temperature, ocean heat content, sea ice extent, ice sheet mass balance, permafrost extent, snow cover, North Atlantic sea surface temperature and circulation, and decadal precipitation. We find that the simulated time evolution of global mean surface temperature broadly follows the observed record but with important quantitative differences which we find are most likely attributable to strong effective radiative forcing from anthropogenic aerosols and a weak pattern of sea surface temperature response in the low to middle latitudes to volcanic eruptions. We also find evidence that anthropogenic aerosol forcings play a role in driving the Atlantic Multidecadal Variability and the Atlantic Meridional Overturning Circulation, which are key features of the North Atlantic ocean. Overall, the model historical simulations show many features in common with the observed record over the period 1850–2014 and so provide a basis for future in‐depth study of recent climate change.

The Roles of the Atmosphere and Ocean in Driving Arctic Warming Due to European Aerosol Reductions

AbstractClean air policies can have significant impacts on climate in remote regions. Previous modeling studies have shown that the temperature response to European sulfate aerosol reductions is largest in the Arctic. Here we investigate the atmospheric and ocean roles in driving this enhanced Arctic warming using a set of fully coupled and slab‐ocean simulations (specified ocean heat convergence fluxes) with the Norwegian Earth system model (NorESM), under scenarios with high and low European aerosol emissions relative to year 2000. We show that atmospheric processes drive most of the Arctic response. The ocean pathway plays a secondary role inducing small temperature changes mostly in the opposite direction of the atmospheric response. Important modulators of the temperature response patterns are changes in sea ice extent and subsequent turbulent heat flux exchange, suggesting that a proper representation of Arctic sea ice and turbulent changes is key to predicting the Arctic response to midlatitude aerosol forcing.

Processes shaping the spatial pattern and seasonality of the surface air temperature response to anthropogenic forcing

In the period 1960–2010, the land surface air temperature (SAT) warmed more rapidly over some regions relative to the global mean. Using a set of time-slice experiments, we highlight how different physical processes shape the regional pattern of SAT warming. The results indicate an essential role of anthropogenic forcing in regional SAT changes from the 1970s to 2000s, and show that both surface–atmosphere interactions and large-scale atmospheric circulation changes can shape regional responses to forcing. Single forcing experiments show that an increase in greenhouse gases can lead to regional changes in land surface warming in winter (DJF) due to snow-albedo feedbacks, and in summer (JJA) due to soil-moisture and cloud feedbacks. Changes in anthropogenic aerosol and precursor (AA) emissions induce large spatial variations in SAT, characterized by warming over western Europe, Eurasia, and Alaska. In western Europe, SAT warming is stronger in JJA than in DJF due to substantial increases in clear sky shortwave radiation over Europe, associated with decreases in local AA emissions since the 1980s. In Alaska, the amplified SAT warming in DJF is due to increased downward longwave radiation, which is related to increased water vapor and cloud cover. In this case, although the model was able to capture the regional pattern of SAT change, and the associated local processes, it did not simulate all processes and anomalies correctly. For the Alaskan warming, the model is seen to achieve the correct regional response in the context of a wider North Pacific anomaly that is not consistent with observations. This demonstrates the importance of model evaluation that goes beyond the target variable in detection and attribution studies.

Understanding the Atmospheric Temperature Adjustment to CO2 Perturbation at the Process Level

AbstractClimate model comparisons show that there is considerable uncertainty in the atmospheric temperature response to CO2 perturbation. The uncertainty results from both the rapid adjustment that occurs before SST changes and the slow feedbacks that occur after SST changes. The analysis in this paper focuses on the rapid adjustment. We use a novel method to decompose the temperature change in AMIP-type climate simulation in order to understand the adjustment at the process level. We isolate the effects of different processes, including radiation, convection, and large-scale circulation in the temperature adjustment, through a set of numerical experiments using a hierarchy of climate models. We find that radiative adjustment triggers and largely controls the zonal mean atmospheric temperature response pattern. This pattern is characterized by stratospheric cooling, lower-tropospheric warming, and a warming center near the tropical tropopause. In contrast to conventional views, the warming center near the tropopause is found to be critically dependent on the shortwave absorption of CO2. The dynamical processes largely counteract the effect of the radiative process that increases the vertical temperature gradient in the free troposphere. The effect of local convection is to move atmospheric energy vertically, which cools the lower troposphere and warms the upper troposphere. The adjustment due to large-scale circulation further redistributes energy along the isentropic surfaces across the latitudes, which cools the low-latitude lower troposphere and warms the midlatitude upper troposphere and stratosphere. Our results highlight the importance of the radiative adjustment in the overall adjustment and provide a potential method to understand the spread in the models.

Unraveling the relationship between the topographic distribution patterns of skin temperature and perspiration response in dromedary camels

The question of how skin temperature (Tsk), measured at different regions of the skin, can affect sudomotor activity and thus show a pattern in topographic distribution for the perspiration response (PR) rate in dromedary camels was approached and examined in this experiment. Under natural summer conditions, four healthy dromedary bulls, with a mean body mass of 420 kg and age of three years, were measured for Tsk and PR in seven skin regions (i.e. head, neck, shoulder, axillary, hump, flank, and hip) twice daily [between 04:00-05:00 h with a mean ambient temperature (Ta) of 26·78 °C and relative humidity (RH) of 18·25% as well as between 13:00-14:00 h with Ta of 44·78 °C and RH of 5·90%] for two successive days. The experiment has clearly demonstrated some novel findings. In fact, results pointed out that Tsk (P < 0·05) exhibited a distinct topographic pattern that faded almost completely at a higher Ta. Meanwhile, PR unexpectedly manifested a uniform (P ≥ 0·05) distribution throughout the experiment, which appears to serve an eco-teleological purpose in dromedaries. Moreover, the obtained findings indicated that the hump and hip regions in particular can work as thermal windows, yet all seven skin regions can predict whole-skin PR fairly accurately (R2 ≥ 0·90; P < 0·000). Above all, analysis indicated that Tsk in many regions can affect perspiration in camels (R2 < 0·82; P < 0·000), but it failed to demonstrate a topographic pattern in perspiration response at higher or lower Ta; therefore, the data attests that no specific relationship may exist between the topography of a perspiration pattern and the level of regional Tsk. Some shortcomings were noted herein, but research dealing with this subject may very well improve our understanding of the basic functional mechanisms of the thermoregulatory system in this species.

Arctic Amplification Response to Individual Climate Drivers

AbstractThe Arctic is experiencing rapid climate change in response to changes in greenhouse gases, aerosols, and other climate drivers. Emission changes in general, as well as geographical shifts in emissions and transport pathways of short‐lived climate forcers, make it necessary to understand the influence of each climate driver on the Arctic. In the Precipitation Driver Response Model Intercomparison Project, 10 global climate models perturbed five different climate drivers separately (CO2, CH4, the solar constant, black carbon, and SO4). We show that the annual mean Arctic amplification (defined as the ratio between Arctic and the global mean temperature change) at the surface is similar between climate drivers, ranging from 1.9 (± an intermodel standard deviation of 0.4) for the solar to 2.3 (±0.6) for the SO4 perturbations, with minimum amplification in the summer for all drivers. The vertical and seasonal temperature response patterns indicate that the Arctic is warmed through similar mechanisms for all climate drivers except black carbon. For all drivers, the precipitation change per degree global temperature change is positive in the Arctic, with a seasonality following that of the Arctic amplification. We find indications that SO4 perturbations produce a slightly stronger precipitation response than the other drivers, particularly compared to CO2.

Quantitative analysis of urban cold island effects on the evolution of green spaces in a coastal city: a case study of Fuzhou, China.

Urbanization is accompanied by drastic changes in the distribution of urban green space (UGS). This study aimed to analyze the relationship between the land surface temperature difference (∆LST) and the evolution of UGSs in the main area of Fuzhou City from 1993 to 2013 using a set of remote sensing images. The results manifest that with the maximum area of UGS loss, the less UGS extension, and the less UGS exchange, the UGS area declined sharply, which results in the rise of urban thermal problem and demonstrates the negative relationship between the UGS area and its internal land surface temperature (LST). Different UGS evolution types produced a diversified temperature response pattern. According to the profile assessment, a ∆LST above 10°C, caused by the UGS loss converted to construction land, occurred in the peak position of the online profiles. Among the UGS loss, the conversion of water had the most apparent ∆LST, followed by wetlands and forest/grass areas. The threshold value of the UGS loss area (TVoA) was quantified by analyzing the temperature change effects based on the UGS evolution temperature effect index (GETX). We concluded that the urban heat island (UHI) can be effectively alleviated by keeping the magnitude of the UGS extensions equal to the UGS loss and the UGS utilization area below 0.04km2 in Fuzhou City. Further analysis clarified that vegetation cover changes and the evolution of UGSs were the main factors controlling the distribution of the cold/heat island.

Contrasting Tropical Climate Response Pattern to Localized Thermal Forcing Over Different Ocean Basins

AbstractWe contrast the spatial patterns of tropical climate response to localized thermal forcing over different ocean basins in an atmospheric model coupled to a slab ocean. A localized forcing poleward of the climatological storm tracks produces a tropical climate response pattern that is nearly independent of the forcing location. Regardless of the location of extratropical forcing, a common zonally asymmetric La Niña‐like pattern of sea surface temperature response accompanies a northward shift of the Intertropical Convergence Zone. In contrast, a localized tropical forcing produces essentially opposite tropical climate response patterns depending on the forced ocean basin. The northern tropical Pacific (Atlantic) heating induces a warming (cooling) throughout the tropical Pacific, a weakening (strengthening) of the equatorial Pacific trade winds, and a northward (southward) shift of the Southern Pacific Convergence Zone. Our study provides a pathway forward for improving future projections of tropical climate under different anthropogenic forcing scenarios.

Comparative Analysis of Responses of Land Surface Temperature to Long-Term Land Use/Cover Changes between a Coastal and Inland City: A Case of Freetown and Bo Town in Sierra Leone

Urban growth and its associated expansion of built-up areas are expected to continue through to the twenty second century and at a faster pace in developing countries. This has the potential to increase thermal discomfort and heat-related distress. There is thus a need to monitor growth patterns, especially in resource constrained countries such as Africa, where few studies have so far been conducted. In view of this, this study compares urban growth and temperature response patterns in Freetown and Bo town in Sierra Leone. Multispectral Landsat images obtained in 1998, 2000, 2007, and 2015 are used to quantify growth and land surface temperature responses. The contribution index (CI) is used to explain how changes per land use and land cover class (LULC) contributed to average city surface temperatures. The population size of Freetown was about eight times greater than in Bo town. Landsat data mapped urban growth patterns with a high accuracy (Overall Accuracy &gt; 80%) for both cities. Significant changes in LULC were noted in Freetown, characterized by a 114 km2 decrease in agriculture area, 23 km2 increase in dense vegetation, and 77 km2 increase in built-up area. Between 1998 and 2015, built-up area increased by 16 km2, while dense vegetation area decreased by 14 km2 in Bo town. Average surface temperature increased from 23.7 to 25.5 °C in Freetown and from 24.9 to 28.2 °C in Bo town during the same period. Despite the larger population size and greater built-up extent, as well as expansion rate, Freetown was 2 °C cooler than Bo town in all periods. The low temperatures are attributed to proximity to sea and the very large proportion of vegetation surrounding the city. Even close to the sea and abundant vegetation, the built-up area had an elevated temperature compared to the surroundings. The findings are important for formulating heat mitigation strategies for both inland and coastal cities in developing countries.

Subtropical sea-surface warming and increased salinity during Eocene Thermal Maximum 2

Eocene Thermal Maximum 2 (ETM-2; ca. 54.2 Ma) represents the second largest of the major Eocene hyperthermals, yet comparatively little is known about the scale and rate of climatic change for key regions. Here we provide the first detailed records of subtropical sea-surface warming and salinization for ETM-2 at two subtropical locations, Ocean Drilling Program Sites 1209 (North Pacific) and 1265 (South Atlantic). Coupled planktic foraminiferal Mg/Ca and δ18O indicate 2-4 °C of rapid warming and local salinization of ~1-2 ppt at both sites. The increase in sea-surface temperature is equivalent to anomalies reported from higher latitude sites, and is consistent with theory on the expected pattern of spatial temperature response to greenhouse gas forcing in an ice-free world (i.e., no ice-albedo feedback). Similarly, the observed salinization is consistent with the hypothesis of enhanced meridional vapor transport and increased subtropical aridity in a warmer world.

Relationship of tropospheric stability to climate sensitivity and Earth’s observed radiation budget

Climate feedbacks generally become smaller in magnitude over time under CO2 forcing in coupled climate models, leading to an increase in the effective climate sensitivity, the estimated global-mean surface warming in steady state for doubled CO2 Here, we show that the evolution of climate feedbacks in models is consistent with the effect of a change in tropospheric stability, as has recently been hypothesized, and the latter is itself driven by the evolution of the pattern of sea-surface temperature response. The change in climate feedback is mainly associated with a decrease in marine tropical low cloud (a more positive shortwave cloud feedback) and with a less negative lapse-rate feedback, as expected from a decrease in stability. Smaller changes in surface albedo and humidity feedbacks also contribute to the overall change in feedback, but are unexplained by stability. The spatial pattern of feedback changes closely matches the pattern of stability changes, with the largest increase in feedback occurring in the tropical East Pacific. Relationships qualitatively similar to those in the models among sea-surface temperature pattern, stability, and radiative budget are also found in observations on interannual time scales. Our results suggest that constraining the future evolution of sea-surface temperature patterns and tropospheric stability will be necessary for constraining climate sensitivity.

Common Warming Pattern Emerges Irrespective of Forcing Location

AbstractThe Earth's climate is changing due to the existence of multiple radiative forcing agents. It is under question whether different forcing agents perturb the global climate in a distinct way. Previous studies have demonstrated the existence of similar climate response patterns in response to aerosol and greenhouse gas (GHG) forcings. In this study, the sensitivity of tropospheric temperature response patterns to surface heating distributions is assessed by forcing an atmospheric general circulation model coupled to an aquaplanet slab ocean with a wide range of possible forcing patterns. We show that a common climate pattern emerges in response to localized forcing at different locations. This pattern, characterized by enhanced warming in the tropical upper troposphere and the polar lower troposphere, resembles the historical trends from observations and models as well as the future projections. Atmospheric dynamics in combination with thermodynamic air‐sea coupling are primarily responsible for shaping this pattern. Identifying this common pattern strengthens our confidence in the projected response to GHG and aerosols in complex climate models.

Emission metrics for quantifying regional climate impacts of aviation

Abstract. This study examines the impacts of emissions from aviation in six source regions on global and regional temperatures. We consider the NOx-induced impacts on ozone and methane, aerosols and contrail-cirrus formation and calculate the global and regional emission metrics global warming potential (GWP), global temperature change potential (GTP) and absolute regional temperature change potential (ARTP). The GWPs and GTPs vary by a factor of 2–4 between source regions. We find the highest aviation aerosol metric values for South Asian emissions, while contrail-cirrus metrics are higher for Europe and North America, where contrail formation is prevalent, and South America plus Africa, where the optical depth is large once contrails form. The ARTP illustrate important differences in the latitudinal patterns of radiative forcing (RF) and temperature response: the temperature response in a given latitude band can be considerably stronger than suggested by the RF in that band, also emphasizing the importance of large-scale circulation impacts. To place our metrics in context, we quantify temperature change in four broad latitude bands following 1 year of emissions from present-day aviation, including CO2. Aviation over North America and Europe causes the largest net warming impact in all latitude bands, reflecting the higher air traffic activity in these regions. Contrail cirrus gives the largest warming contribution in the short term, but remain important at about 15 % of the CO2 impact in several regions even after 100 years. Our results also illustrate both the short- and long-term impacts of CO2: while CO2 becomes dominant on longer timescales, it also gives a notable warming contribution already 20 years after the emission. Our emission metrics can be further used to estimate regional temperature change under alternative aviation emission scenarios. A first evaluation of the ARTP in the context of aviation suggests that further work to account for vertical sensitivities in the relationship between RF and temperature response would be valuable for further use of the concept.