Warming Gradient Research Articles

Changes to the tropical circulation in the mid-Pliocene and their implications for future climate

Abstract. The two components of the tropical overturning circulation, the meridional Hadley circulation (HC) and the zonal Walker circulation (WC), are key to the re-distribution of moisture, heat and mass in the atmosphere. The mid-Pliocene Warm Period (mPWP; ∼ 3.3–3 Ma) is considered a very rough analogue of near-term future climate change, yet changes to the tropical overturning circulations in the mPWP are poorly understood. Here, climate model simulations from the Pliocene Model Intercomparison Project (PlioMIP) are analyzed to show that the tropical overturning circulations in the mPWP were weaker than preindustrial circulations, just as they are projected to be in future climate change. The weakening HC response is consistent with future projections, and its strength is strongly related to the meridional gradient of sea surface warming between the tropical and subtropical oceans. The weakening of the WC is less robust in PlioMIP than in future projections, largely due to inter-model variations in simulated warming of the tropical Indian Ocean (TIO). When the TIO warms faster (slower) than the tropical mean, local upper tropospheric divergence increases (decreases) and the WC weakens less (more). These results provide strong evidence that changes to the tropical overturning circulation in the mPWP and future climate are primarily controlled by zonal (WC) and meridional (HC) gradients in tropical–subtropical sea surface temperatures.

Less warming projected during heavy winter precipitation in the Cascades and Sierra Nevada

ABSTRACTLocal rates of warming from increased greenhouse gas concentrations can be different during heavy precipitation than during other times. This variable warming can influence precipitation extremes through the Clausius–Clapeyron relationship and modulate the rate of snowfall decline. Large ensembles of simulations from a regional climate model were used to project, with high signal‐to‐noise ratio, changes in the daily winter temperature versus precipitation intensity relationship from the contemporary period to a mid‐21st century scenario over the Cascades and Sierra Nevada of the United States. Warming rates decreased with increasing precipitation intensity over all montane regions, with the strongest relationship in the northern Cascades (1.2 °C less warming at 100 mm day−1 than at trace amounts). The relationship may be linked to the projected north Pacific meridional warming gradient, as the moisture of the largest precipitation events originates at lower latitudes where warming is less, though other factors may contribute.

Responses of arthropod populations to warming depend on latitude: evidence from urban heat islands.

Biological effects of climate change are expected to vary geographically, with a strong signature of latitude. For ectothermic animals, there is systematic latitudinal variation in the relationship between climate and thermal performance curves, which describe the relationship between temperature and an organism's fitness. Here, we ask whether these documented latitudinal patterns can be generalized to predict arthropod responses to warming across mid- and high temperate latitudes, for taxa whose thermal physiology has not been measured. To address this question, we used a novel natural experiment consisting of a series of urban warming gradients at different latitudes. Specifically, we sampled arthropods from a single common street tree species across temperature gradients in four US cities, located from 35.8 to 42.4° latitude. We captured 6746 arthropods in 34 families from 111 sites that varied in summer average temperature by 1.7-3.4°C within each city. Arthropod responses to warming within each city were characterized as Poisson regression coefficients describing change in abundance per °C for each family. Family responses in the two midlatitude cities were heterogeneous, including significantly negative and positive effects, while those in high-latitude cities varied no more than expected by chance within each city. We expected high-latitude taxa to increase in abundance with warming, and they did so in one of the two high-latitude cities; in the other, Queens (New York City), most taxa declined with warming, perhaps due to habitat loss that was correlated with warming in this city. With the exception of Queens, patterns of family responses to warming were consistent with predictions based on known latitudinal patterns in arthropod physiology relative to regional climate. Heterogeneous responses in midlatitudes may be ecologically disruptive if interacting taxa respond oppositely to warming.

Sensitivity of soil carbon fractions and their specific stabilization mechanisms to extreme soil warming in a subarctic grassland.

Terrestrial carbon cycle feedbacks to global warming are major uncertainties in climate models. For in-depth understanding of changes in soil organic carbon (SOC) after soil warming, long-term responses of SOC stabilization mechanisms such as aggregation, organo-mineral interactions and chemical recalcitrance need to be addressed. This study investigated the effect of 6years of geothermal soil warming on different SOC fractions in an unmanaged grassland in Iceland. Along an extreme warming gradient of +0 to ~+40°C, we isolated five fractions of SOC that varied conceptually in turnover rate from active to passive in the following order: particulate organic matter (POM), dissolved organic carbon (DOC), SOC in sand and stable aggregates (SA), SOC in silt and clay (SC-rSOC) and resistant SOC (rSOC). Soil warming of 0.6°C increased bulk SOC by 22±43% (0-10cm soil layer) and 27±54% (20-30cm), while further warming led to exponential SOC depletion of up to 79±14% (0-10cm) and 74±8% (20-30) in the most warmed plots (~+40°C). Only the SA fraction was more sensitive than the bulk soil, with 93±6% (0-10cm) and 86±13% (20-30cm) SOC losses and the highest relative enrichment in 13 C as an indicator for the degree of decomposition (+1.6±1.5‰ in 0-10cm and +1.3±0.8‰ in 20-30cm). The SA fraction mass also declined along the warming gradient, while the SC fraction mass increased. This was explained by deactivation of aggregate-binding mechanisms. There was no difference between the responses of SC-rSOC (slow-cycling) and rSOC (passive) to warming, and 13 C enrichment in rSOC was equal to that in bulk soil. We concluded that the sensitivity of SOC to warming was not a function of age or chemical recalcitrance, but triggered by changes in biophysical stabilization mechanisms, such as aggregation.

Aggregations and reproductive events of the narrownose smooth-hound shark (Mustelus schmitti) in relation to temperature and depth in coastal waters of the south-western Atlantic Ocean (38–42°S)

Knowledge of environmental influence on reproductive dynamics in chondrichthyans is critical for effective management. The present study assessed the potential influences of temperature and depth on aggregations and reproductive events of the narrownose smooth-hound shark (Mustelus schmitti), using an analysis criterion based on the co-occurrence of different reproductive stages. Data were collected from 363 sample sites during six research surveys, covering an area of ~47744km2 along the coast (38–42°S, depth of <50m). Aggregations of M. schmitti adults were mostly associated with the warmer spring surveys, with the aggregation sites being significantly warmer than those of non-aggregation. Evidence of pupping and ovulation was observed, almost simultaneously, during all spring surveys. However, the occurrence of these reproductive events showed a clear interannual variability pattern that was significantly explained by water temperature. Particularly, the occurrence of ovulation was associated with temperatures above 16–17°C. These results suggest that M. schmitti adults may follow the warming gradient along the environment and, thus, they aggregate in shallow and productive waters during the course of spring. Their reproductive events could be induced by temperature increase. This scenario suggests that changes in the patterns of bottom temperature may be important drivers of the reproductive dynamics of M. schmitti.

Effects of excessive equatorial cold tongue bias on the projections of tropical Pacific climate change. Part I: the warming pattern in CMIP5 multi-model ensemble

The excessive cold tongue error in the equatorial Pacific has persisted in several generations of climate models. Based on the historical simulations and Representative Concentration Pathway (RCP) 8.5 experiments in the Coupled Model Intercomparison Project phase 5 (CMIP5) multi-model ensemble (MME), this study finds that models with an excessive westward extension of cold tongue and insufficient equatorial western Pacific precipitation tend to project a weaker east-minus-west gradient of sea surface temperature (SST) warming along the equatorial Pacific under increased greenhouse gas (GHG) forcing. This La Nina-like error of tropical Pacific SST warming is consistent with our understanding of negative SST-convective feedback over the western Pacific warm pool. Based on this relationship between the present simulations and future projections, the present study applies an “observational constraint” of equatorial western Pacific precipitation to calibrate the projections of tropical Pacific climate change. After the corrections, CMIP5 models robustly project an El Nino-like warming pattern, with a MME mean increase by a factor of 2.3 in east-minus-west gradient of equatorial Pacific SST warming and reduced inter-model uncertainty. Corrections in projected changes in tropical precipitation and atmospheric circulation are physically consistent. This study suggests that a realistic cold tongue simulation would lead to a more reliable tropical Pacific climate projection.

Geothermal ecosystems as natural climate change experiments: The ForHot research site in Iceland as a case study

This article describes how natural geothermal soil temperature gradients in Iceland have been used to study terrestrial ecosystem responses to soil warming. The experimental approach was evaluated at three study sites in southern Iceland; one grassland site that has been warm for at least 50 years (GO), and another comparable grassland site (GN) and a Sitka spruce plantation (FN) site that have both been warmed since an earthquake took place in 2008. Within each site type, five ca. 50 m long transects, with six permanent study plots each, were established across the soil warming gradients, spanning from unwarmed control conditions to gradually warmer soils. It was attempted to select the plots so the annual warming levels would be ca. +1, +3, +5, +10 and +20 °C within each transect. Results of continuous measurements of soil temperature (Ts) from 2013-2015 revealed that the soil warming was relatively constant and followed the seasonal Ts cycle of the unwarmed control plots. Volumetric water content in the top 5 cm of soil was repeatedly surveyed during 2013-2016. The grassland soils were wetter than the FN soils, but they had sometimes some significant warming-induced drying in the surface layer of the warmest plots, in contrast to FN. Soil chemistry did not show any indications that geothermal water had reached the root zone, but soil pH did increase somewhat with warming, which was probably linked to vegetation changes. As expected, the potential decomposition rate of organic matter increased significantly with warming. It was concluded that the natural geothermal gradients at the ForHot sites in Iceland offered realistic conditions for studying terrestrial ecosystem responses to warming with minimal artefacts.

Ocean acidification and warming gradients modulate interaction strength between different mesograzers and macroalgae

Event Abstract Back to Event Ocean acidification and warming gradients modulate interaction strength between different mesograzers and macroalgae Eduardo Sampaio1, 2*, Ivan F. Rodil1, Fatima Vaz-Pinto1, Angela Fernandez1 and Francisco Arenas1 1 Interdisciplinary Centre of Marine and Environmental Research (CIIMAR/CIMAR), Portugal 2 Marine and Environmental Sciences Centre (MARE), Portugal In the future, continuous rise in the levels of atmospheric CO2, along with concomitant increases in temperatures, will lead to alterations in global climate with consequent effects on marine ecosystems. By regulating top-down in a critical trophic level, macroalgae-herbivore interactions play a key role in shaping marine community structures. Taking into account previous studies, gradients of ocean warming and acidification may have cumulative effects on organism metabolism, which can induce great variations on the strength of such interactions. Within this context, we aimed to assess the effects of warming and acidification on macroalgae-herbivore interaction strength, using different mesograzers. For this purpose, three cosmopolitan and closely associated rocky intertidal species were chosen: the herbivores Melita palmata and Gibbula umbilicalis, and the green macroalga Ulva rigida. Two consecutive mesocosm experiments consisting of a two-day consumption trial and a seven-day macroalgae-herbivore interaction trial were performed under crossed treatments of pH (two levels: ambient and acidification) and temperature (four levels: 13.5 ºC, 16.1 ºC, 19.9 ºC and 22.1ºC). Grazer identity differences were obvious, as warming and acidification produced notorious differences in each grazer’s survival and consumption rates. M. palmata was shown to be the most affected by climate stressors, while also being the most voracious grazer. Macroalgae-herbivore interaction strength was strongly altered over gradients of temperature depending on pH levels. In short, acidification appears to accelerate the interaction strength profile effects stemmed from increasing gradients of temperature. In the near future, slight warming and acidification increases may lead to stronger top-down control. However if extreme conditions are reached, herbivorous pressure may lessen, allowing seaweeds to thrive. Keywords: warming, acidification, macroalgae, herbivore, interaction strength. Conference: XIX Iberian Symposium on Marine Biology Studies, Porto, Portugal, 5 Sep - 9 Sep, 2016. Presentation Type: Poster Presentation Topic: 2. GLOBAL CHANGES, INVASIVE SPECIES AND CONSERVATION Citation: Sampaio E, Rodil IF, Vaz-Pinto F, Fernandez A and Arenas F (2016). Ocean acidification and warming gradients modulate interaction strength between different mesograzers and macroalgae. Front. Mar. Sci. Conference Abstract: XIX Iberian Symposium on Marine Biology Studies. doi: 10.3389/conf.FMARS.2016.05.00180 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 04 May 2016; Published Online: 03 Sep 2016. * Correspondence: Mr. Eduardo Sampaio, Interdisciplinary Centre of Marine and Environmental Research (CIIMAR/CIMAR), Porto, Porto, 4050-123, Portugal, edusilvasampaio@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Eduardo Sampaio Ivan F Rodil Fatima Vaz-Pinto Angela Fernandez Francisco Arenas Google Eduardo Sampaio Ivan F Rodil Fatima Vaz-Pinto Angela Fernandez Francisco Arenas Google Scholar Eduardo Sampaio Ivan F Rodil Fatima Vaz-Pinto Angela Fernandez Francisco Arenas PubMed Eduardo Sampaio Ivan F Rodil Fatima Vaz-Pinto Angela Fernandez Francisco Arenas Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Assemblages of micronektonic fishes and invertebrates in a gradient of regional warming along the Western Antarctic Peninsula

Micronektonic fishes and invertebrates were sampled with 32 midwater trawls at nine sites along the Western Antarctic Peninsula (WAP) in the austral fall (March–April) of 2010. Study sites were located within four hypothesized hydrographic regions: near Joinville Island in Region I, at Croker Passage, near Anvers Island, and near Renaud Island in Region II, within Marguerite Bay and the Marguerite Trough in Region III, and near Charcot Island in Region IV. A total of 62 taxa representing 12 taxonomic groups of pelagic invertebrates and 9 families of fish were captured, but assemblages were dominated by only a few species. The most numerically abundant taxa were the euphausiids, Thysanoessa macrura, Euphausia superba, and E. crystallorophias, combining to contribute nearly 79% of the total catch. Biomass dominants included E. superba, which contributed more than 44% of the total catch, the notothenioid Pleuragramma antarctica, and the salp, Salpa thompsoni. A comparison of total catches among sites revealed that the largest volumetric abundances and biomasses were captured at the Marguerite Bay site.Cluster analysis of abundance data identified distinct multispecies assemblages at Joinville Island in Region I, Croker Passage in Region II, Marguerite Bay in Region III, and Charcot Island in Region IV. A fifth distinct assemblage included samples from sites near Anvers and Renaud Island in Region II, and from the Marguerite Trough in Region III. Assemblages at Joinville Island and Croker Passage were both dominated by E. superba and S. thompsoni, but hydrographic conditions at Joinville Island favored a neritic assemblage, underscored by substantial numbers of P. antarctica. The assemblage at Croker Passage was more oceanic in nature with major inputs from the myctophid, Electrona antarctica and the hyperiid amphipod, Themisto gaudichaudii. Marguerite Bay and Charcot Island were well-mixed assemblages with strong representation by both neritic and oceanic fauna. The mid-peninsula assemblage was oceanic in character, being overwhelmingly dominated by Thysanoessa macrura and T. gaudichaudii.Pleuragramma antarctica were captured at five sites: Joinville Island, Croker Passage, Marguerite Bay, and the two sites near Charcot Island. They were completely absent at the two sites near Anvers Island, at Renaud Island, and in the Marguerite Trough. One fish was captured in Croker Passage. The majority of fish captured in Marguerite Bay were larger than 150 mm standard length (SL), with very few fish of smaller size present. If resident populations of Pleuragramma reproduce and recruit locally rather than being sustained by larval advection, those populations will be highly susceptible to local disappearance. This may be the causative factor behind the absence of Pleuragramma from the mid-peninsula region. Continued warming and subsequent sea ice reductions may not only cause Pleuragramma population collapses in the Marguerite Bay and Charcot Island regions, but may also change the character of the faunal assemblages along the WAP to those of an oceanic system.

Temperature sensitivity of soil bacterial community along contrasting warming gradient

Soil microbial communities potentially mediate the feedbacks to climate change, and thus, the understanding of microbial ecology is central to predict future global warming. However, the direct warming effects on microbial communities are uncertain due to the confounding effects of plant traits and soil heterogeneities. Here, we exposed alpine meadow soil microcosms to temperature between 10 and 40°C for 28 days, to evaluate the temperature relationship of the bacterial community structure and microbial functions. Our results showed that sustained exposure to contrasting temperature produced compositionally and functionally distinct microbial communities. The degree of these changes was dependent on the magnitude of warming, as shown by a consistent increase in the dissimilarities and a shift of the carbon (C) use pattern along the temperature gradient. We found that the bacterial community temporal dynamics followed a gradual process of succession, and the turnover rate was substantially accelerated (P=0.012) by warmer temperatures; every 1°C elevation in soil temperature was estimated to increase the turnover by 0.001. Consistently, contrasting temperature was found to be the dominant factor explained 6.1% of the total variation of the microbial community structures; however, the incubation duration and the interaction between incubation temperature and duration explained 5.4% and 4.1% of the variation, respectively. As anticipated, the shift in bacterial community rapidly translated to a similar change in enzymes activities and C utilization. In addition, potential indicator species were screened; these species characterized the temperature gradient. Collectively, our findings indicate that direct warming effects on soil bacterial community could substantially alter certain function and that contrasting temperatures would accelerate the bacterial community turnover–temperature relationship in this alpine meadow soil.

Environmental Forcing Shapes Regional House Mosquito Synchrony in a Warming Temperate Island

Seasonal changes in the abundance of exothermic organisms can be expected with climate change if warmer temperatures can induce changes in their phenology. Given the increased time for ectothermic organism development at lower temperatures, we asked whether population dynamics of the house mosquito, Culex pipiens s.l. (L.) (Diptera: Culicidae), in Jeju-do (South Korea), an island with a gradient of warming temperatures from north to south, showed differences in sensitivity to changes in temperature along the warming gradient. In addition, we asked whether synchrony, that is, the degree of concerted fluctuations in mosquito abundance across locations, was affected by the temperature gradient. We found the association of mosquito abundance with temperature to be delayed by 2 wk in the north when compared with the south. The abundance across all our sampling locations had a flat synchrony profile that could reflect impacts of rainfall and average temperature on the average of all our samples. Finally, our results showed that population synchrony across space can emerge even when abundance is differentially impacted by an exogenous factor across an environmental gradient.

Climate change simulated by full and mixed-layer ocean versions of CSIRO Mk3.5 and Mk3.0: Large-scale sensitivity

The CSIRO Mk3.5 coupled atmosphere-ocean model includes upgrades to atmospheric and oceanic processes that remove a cold bias of the earlier Mk3.0. The global mean warming over the 21st century from Mk3.5 is 3.1 K under the CMIP3 A1B scenario, some 25% larger than that from Mk3.0. Two mixed-layer ocean versions of Mk3.5 were constructed, and these are also more sensitive than Mk3.0. To elucidate these differences, a simple feedback analysis is extended to Mk3.5, using changes for doubled CO2 in each model version. The net feedback for the low-mid latitude region is the main driver of the sensitivity contrast. The clear-sky component is consistently larger in Mk3.5, as is the increase in specific humidity, even after standardizing by the global warming. Cloud forcing provides a small positive feedback, which is stronger in cases that had larger declines in low-layer cloud. The net positive feedback for the higher-latitude region is larger in the coupled Mk3.5 than Mk3.0, which had more stable Arctic sea ice. However, some contrasts differed among the versions. As for Mk3.0, the surface warming in the coupled Mk3.5 is suppressed over that from the MLO case. Over the ocean, the pattern of suppression is similar to the change in energy flux into the surface in the coupled model. There is also a gradient of equatorial warming in the Asia-Pacific region that relates to the change in net convergence of heat transport by ocean currents. The effect of this pattern on regional rainfall is a focus of Part 2 of the study.

Observed Coherent Trends of Surface and Upper-Air Wind Speed over China since 1960

AbstractPrevious studies indicated that surface wind speed over China declined during past decades, and several explanations exist in the literature. This study presents long-term (1960–2009) changes of both surface and upper-air wind speeds over China and addresses observed evidence to interpret these changes. It is found that surface wind over China underwent a three-phase change over the past 50 yr: (i) it step changed to a strong wind level at the end of the 1960s, (ii) it declined until the beginning of the 2000s, and (iii) it seemed to be steady and even recovering during the very recent years. The variability of surface wind speed is greater at higher elevations and less at lower elevations. In particular, surface wind speed over the elevated Tibetan Plateau has changed more significantly. Changes in upper-air wind speed observed from rawinsonde are similar to surface wind changes. The NCEP–NCAR reanalysis indicates that wind speed changes correspond to changes in geopotential height gradient at 500 hPa. The latter are further correlated with the changes of latitudinal surface temperature gradient, with a correlation coefficient of 0.88 for the past 50 yr over China. This strongly suggests that the spatial gradient of surface global warming or cooling may significantly change surface wind speed at a regional scale through atmospheric thermal adaption. The recovery of wind speed since the beginning of the 2000s over the Tibetan Plateau might be a precursor of the reversal of wind speed trends over China, as wind over high elevations can respond more rapidly to the warming gradient and atmospheric circulation adjustment.

Climatic drivers of hourly to yearly tree radius variations along a 6 °C natural warming gradient

Climate affects the timing, rate and dynamics of tree growth, over time scales ranging from seconds to centuries. Monitoring how a tree's stem radius varies over these time scales can provide insight into intra-annual stem dynamics and improve our understanding of climate impacts on tree physiology and growth processes. Here, we quantify the response of radial conifer stem size to environmental fluctuations via a novel assessment of tree circadian cycles. We analyze four years of sub-hourly data collected from 56 larch and spruce trees growing along a natural temperature gradient of ∼6°C in the central Swiss Alps. During the growing season, tree stem diameters were greatest at mid-morning and smallest in the late evening, reflecting the daily cycle of water uptake and loss. Along the gradient, amplitudes calculated from the stem radius cycle were ∼50% smaller at the upper site (∼2200m a.s.l.) relative to the lower site (∼800m a.s.l.). We show changes in precipitation, temperature and cloud cover have a substantial effect on typical growing season diurnal cycles; amplitudes were nine times smaller on rainy days (>10mm), and daily amplitudes are approximately 40% larger when the mean daily temperature is 15–20°C than when it is 5–10°C. We find that over the growing season in the sub-alpine forests, spruce show greater daily stem water movement than larch. However, under projected future warming, larch could experience up to 50% greater stem water use, which may severely affect future growth on already dry sites. Our data further indicate that because of the confounding influences of radial growth and short-term water dynamics on stem size, conventional methodology probably overstates the effect of water-linked meteorological variables (i.e. precipitation and relative humidity) on intra-annual tree growth. We suggest future studies use intra-seasonal measurements of cell development and consider whether climatic factors produce reversible changes in stem diameter. These study design elements may help researchers more accurately quantify and attribute changes in forest productivity in response to future warming.

Change trends of temperature and precipitation in the Loess Plateau Region of China, 1961–2010

The Loess Plateau is the most severe soil and water loss area in the world. The changing trends of annual mean temperature and annual precipitation over the last 50years in the Loess Plateau Region (LPR) are investigated using observed time series from all available stations. The trends are assessed for both the entire LPR and its five integrated management divisions using the gridded data. It is shown that the region-averaged annual mean temperature has significantly increased over the last 50years (1.91°C/50yr), whereas the region-averaged annual precipitation shows a non-significant negative trend (−29.11mm/50yr). Spatially, there is an enhanced warming gradient but an obvious drying to weak wetting gradient from the southeast to the northwest across the region. On divisional scales, a significant warming trend is detected for all the divisions. A significant drying trend and a nearly significant drying trend are found for the first and second divisions, respectively, and a non-significant positive trend for other divisions. Therefore the region can be divided into the southeast warming and drying sub-region (SESR) and the northwest warming and weak wetting sub-region (NWSR). Further analysis shows that the SESR has a significant warming trend (1.71°C/50yr) and a significant drying trend (−47.62mm/50yr), and the NWSR has a significant warming trend (2.25°C/50yr) but a non-significant wetting trend (15.20mm/50yr). These results may have important implication in addressing the challenge of climate change in terms of the integrated management of the LPR.

Mechanisms Contributing to the Warming Hole and the Consequent U.S. East–West Differential of Heat Extremes

Abstract A linear trend calculated for observed annual mean surface air temperatures over the United States for the second-half of the twentieth century shows a slight cooling over the southeastern part of the country, the so-called warming hole, while temperatures over the rest of the country rose significantly. This east–west gradient of average temperature change has contributed to the observed pattern of changes of record temperatures as given by the ratio of daily record high temperatures to record low temperatures with a comparable east–west gradient. Ensemble averages of twentieth-century climate simulations in the Community Climate System Model, version 3 (CCSM3), show a slight west–east warming gradient but no warming hole. A warming hole appears in only several ensemble members in the Coupled Model Intercomparison Project phase 3 (CMIP3) multimodel dataset and in one ensemble member of simulated twentieth-century climate in CCSM3. In this model the warming hole is produced mostly from internal decadal time-scale variability originating mainly from the equatorial central Pacific associated with the Interdecadal Pacific Oscillation (IPO). Analyses of a long control run of the coupled model, and specified convective heating anomaly experiments in the atmosphere-only version of the model, trace the forcing of the warming hole to positive convective heating anomalies in the central equatorial Pacific Ocean near the date line. Cold-air advection into the southeastern United States in winter, and low-level moisture convergence in that region in summer, contribute most to the warming hole in those seasons. Projections show a disappearance of the warming hole, but ongoing greater surface temperature increases in the western United States compared to the eastern United States.

Attribution of climate change: a methodology to estimate the potential contribution to increases in potato yield in Scotland since 1960

AbstractMaincrop potato yields in Scotland have increased by 30–35 t ha−1 since 1960 as a result of many changes, but has changing climate contributed anything to this? The purpose of this work was to answer this question. Daily weather data for the period 1960–2006 were analysed for five locations covering the zones of potato growing on the east coast of Scotland (between 55.213 and 57.646 N) to determine trends in temperature, rainfall and solar radiation. A physiologically based potato yield model was validated using data obtained from a long‐term field trial in eastern Scotland and then employed to simulate crop development and potential yield at each of the five sites. Over the 47 years, there were significant increases in annual air and 30 cm soil temperatures (0.27 and 0.30 K decade−1, respectively), but no significant changes in annual precipitation or in the timing of the last frost in spring and the first frost of autumn. There was no evidence of any north to south gradient of warming. Simulated emergence and canopy closure became earlier at all five sites over the period with the advance being greater in the north (3.7 and 3.6 days decade−1, respectively) than the south (0.5 and 0.8 days decade−1, respectively). Potential yield increased with time, generally reflecting the increased duration of the green canopy, at average rates of 2.8 t ha−1 decade−1 for chitted seed (sprouted prior to planting) and 2.5 t ha−1 decade−1 for unchitted seed. The measured warming could contribute potential yield increases of up to 13.2 t ha−1 for chitted potato (range 7.1–19.3 t ha−1) and 11.5 t ha−1 for unchitted potato (range 7.1–15.5 t ha−1) equivalent to 34–39% of the increased potential yield over the period or 23–26% of the increase in actual measured yields.

Conceptual understanding of climate change with a globally resolved energy balance model

The future climate change projections are essentially based on coupled general circulation model (CGCM) simulations, which give a distinct global warming pattern with arctic winter amplification, an equilibrium land-sea warming contrast and an inter-hemispheric warming gradient. While these simulations are the most important tool of the Intergovernmental Panel on Climate Change (IPCC) predictions, the conceptual understanding of these predicted structures of climate change and the causes of their uncertainties is very difficult to reach if only based on these highly complex CGCM simulations. In the study presented here we will introduce a very simple, globally resolved energy balance (GREB) model, which is capable of simulating the main characteristics of global warming. The model shall give a bridge between the strongly simplified energy balance models and the fully coupled 4-dimensional complex CGCMs. It provides a fast tool for the conceptual understanding and development of hypotheses for climate change studies, which shall build a basis or starting point for more detailed studies of observations and CGCM simulations. It is based on the surface energy balance by very simple representations of solar and thermal radiation, the atmospheric hydrological cycle, sensible turbulent heat flux, transport by the mean atmospheric circulation and heat exchange with the deeper ocean. Despite some limitations in the representations of the basic processes, the models climate sensitivity and the spatial structure of the warming pattern are within the uncertainties of the IPCC models simulations. It is capable of simulating aspects of the arctic winter amplification, the equilibrium land-sea warming contrast and the inter-hemispheric warming gradient with good agreement to the IPCC models in amplitude and structure. The results give some insight into the understanding of the land-sea contrast and the polar amplification. The GREB model suggests that the regional inhomogeneous distribution of atmospheric water vapor and the non-linear sensitivity of the downward thermal radiation to changes in the atmospheric water vapor concentration partly cause the land-sea contrast and may also contribute to the polar amplification. The combination of these characteristics causes, in general, dry and cold regions to warm more than other regions.

Spatiotemporal dynamics of the Urals’ climate in the second half of the 20th century

Dynamics of the surface air temperature and amount of precipitation in the Polar, Northern, and Southern Urals in the 20th century is analyzed. Charts of the temperature distribution in the Urals for the period from 1961 to 2000, taking into account the relief, are plotted in the geographical informational system on the basis of data of instrumental measurements at meteorological stations with the use of the multiple regression analysis and raster modeling. The northeastern direction of the warming gradient and increase of falling precipitations in the period under review is established. Time series of anomalies of the average annual air temperature and amount of precipitation in the 20th century at three meteorological stations, situated in the Polar, Northern, and Southern Urals, are analyzed. The tendency of the growth of anomalies of the average annual temperature and total amount of precipitation is revealed.

The use of open‐top chambers in forests for evaluating warming effects on herbaceous understorey plants

AbstractOpen‐top chambers (OTCs) are widely used experimental warming devices in open‐field ecosystems such as tundra and alpine heath. However, knowledge of their performance in temperate deciduous forest ecosystems is largely lacking. The application of OTCs in forests might become important in the future since the effects of climate warming on growth, reproduction, and future distribution of understorey forest herbs have rarely been investigated. Therefore, polycarbonate OTCs covered with (OTCs+GF) and without permeable polypropylene GardenFleece (OTCs−GF) were installed in a temperate deciduous forest to create an experimental warming gradient. Short‐term responses in phenology, growth, and reproduction of a model understorey forest herb (Anemone nemorosa L.) to OTC installation were determined. In a second growing season, an in‐depth study of multiple abiotic conditions inside OTCs−GF was performed. Both OTCs+GF and OTCs−GF raised air and soil temperature in a realistic manner (ca. +0.4°C to +1.15°C), but OTCs−GF only in the leafless period (up to +1.5°C monthly average soil temperature). The early flowering forest herb A. nemorosa also showed a clear phenotypic response to OTC installation. Based on these facts and the large ecological drawbacks associated with OTCs+GF (mostly in connection with a higher relative air humidity and a lower light quantity) and very modest abiotic changes in OTCs−GF, we encourage the use of OTCs−GF in deciduous forest ecosystems for evaluating climate‐warming effects on early flowering understorey forest herbs. There is also a potential to use this warming method on later flowering species, but this needs further research.