Hemisphere Temperature Research Articles

Apple Sunburn Risk Detection\u2014A\xa0Simple Model for Agricultural Decision Making and Some Fruit Temperature Measurements

As a response to strong radiative heating, the fruit temperature of apples may rise significantly above the air temperature. This may result in damage to the skin tissue and the epidermal and hypodermal cell layers. To avoid economic losses induced by sunburn symptoms on the skin, apple growers need forecasts of the fruit temperature, which will allow them to organize sun-protection measures in time.The temperatures of detached apples, which had been exposed to incident radiation and wind, were measured in order to quantify the extent of fruit heating under the climate conditions of northern Germany. On average, the daily maximum skin temperatures measured on the sunlit south side of the fruit during selected sunny and warm days were about 7 °C above the daily maximum air temperature. However, skin temperatures of more than 40 °C (the predefined warning threshold) were rarely detected, indicating that sunburn is still an uncommon phenomenon in northern Germany. Maximum apple-core temperatures were on average 4 °C higher than the maximum temperatures of ambient air.Based on energy balance principles, a simple model has been developed to predict the diurnal cycle of the sky- and ground-facing hemispherical apple temperatures. Focusing on fruit growers’ needs, daily temperature maxima of the modeled sky-facing hemisphere were compared with skin temperatures measured on the sunlit south side, resulting in a mean absolute error (MAE) of 1.7 °C. Comparison between daily maxima of total sphere temperatures and apple core temperatures provided better correlations (MAE = 0.8 °C).

Little Ice Age climate changes in Southwest China from a stalagmite δ18O record

Climate change during the Little Ice Age (LIA) was characterized by globally widespread but spatiotemporally incoherent cooling with high regional variability. However, the onset, termination, internal structure, and underlying forcing mechanisms of the LIA remain unclear. Here we present a U-Th-dated stalagmite record with an average sampling resolution of 0.8 years and mean age uncertainty less than 4 years from Shijiangjun Cave, Southwest China (SW China). We have characterized the dynamics of the Asian summer monsoon (ASM) on interdecadal to centennial timescales during the LIA at unprecedented accuracy and precision. The onset of the LIA occurred at about 1300 (A.D.) and six weak-ASM events were identified at 1340–1380, 1445–1480, 1520–1540, 1600–1630, 1650–1670, and 1695–1730 (A.D.), respectively. The overall climate variability in Chinese monsoon regions is inconsistent with that in Northwest China (NW China). During the coldest period of the LIA (i.e. after 1500 CE), SW China exhibited a cold and dry pattern, while NW China experienced a cold and wet climate. Moreover, our records from the Asian-Australian monsoon (AAM) region showed coherent changes during the LIA, arguing against the interhemispheric “see-saw” model on interdecadal-centennial timescales. Documented solar minima, lower Northern Hemisphere temperature, and positive phases of PDO and ENSO during the LIA weakened the Asian-Australian summer monsoon, decreasing precipitation throughout the AAM regions.

Uncertainty in aerosol radiative forcing impacts the simulated global monsoon in the 20th century

Abstract. Anthropogenic aerosols are dominant drivers of historical monsoon rainfall change. However, large uncertainties in the radiative forcing associated with anthropogenic aerosol emissions, as well as the dynamical response to this forcing, lead to uncertainty in the simulated monsoon response. We use historical simulations from the “SMURPHS” project, run using HadGEM3-GC3.1, in which the time-varying aerosol emissions are scaled by factors from 0.2 to 1.5 to explore the monsoon sensitivity to historical aerosol forcing uncertainty (present-day versus preindustrial aerosol forcing in the range −0.38 to −1.50 W m−2). The hemispheric asymmetry in emissions generates a strong relationship between scaling factor and both hemispheric temperature contrast and meridional location of tropical rainfall. Averaged over the period 1950–2014, increasing the scaling factor from 0.2 to 1.5 reduces the hemispheric temperature contrast by 0.9 ∘C, reduces the tropical summertime land–sea temperature contrast by 0.3 ∘C and shifts tropical rainfall southwards by 0.28∘ of latitude. The result is a reduction in global monsoon area by 3 % and a reduction in global monsoon intensity by 2 %. Despite the complexity of the monsoon system, the monsoon properties presented above vary monotonically and roughly linearly across scalings. A switch in the dominant influence on the 1950–1980 monsoon rainfall trend between greenhouse gases and aerosol is identified as the scalings increase. Regionally, aerosol scaling has a pronounced effect on Northern Hemisphere monsoon rainfall, with the strongest influence on monsoon area and intensity located in the Asian sector, where local emissions are greatest.

Indian summer monsoon variability in northeastern India during the last two millennia

High-resolution proxy records help to understand natural forcing of climate variability and improving our capability to predict climate variability on decadal to centennial time scales. Present study from the Mawmluh cave, northeastern India shows sudden shifts in speleothem oxygen isotope values, indicating several abrupt changes in the Indian summer monsoon (ISM) during ~212 BCE to 1986 CE. Moderate ISM conditions prevailed during ~212 BCE to 400 CE punctuated with weak intervals, strong ISM during 400 and 500 CE and from 640 to 1060 CE, whereas weak ISM conditions prevailed during 520–540 CE, 820–850 CE and 940–980 CE and after 1060 CE. The interval from 1060 to 1986 CE witnessed decreased precipitation than the previous millennium. The latter phase of the Medieval Climate Anomaly (MCA; 1060 to 1200 CE) was quite drier in contrast to the earlier intervals. The ISM was generally weak during the Little Ice Age (LIA; 1350 to 1850 CE) with short-term pulses of high precipitation when sun-spot activity was high. The data shows the weakest ISM condition during 1640–1740 CE (Maunder Minimum) of the last two millennia. Variations in extra-tropical northern hemisphere temperatures due to volcanic activity and solar insolation, and accompanying northward/southward shifting of the Inter-Tropical Convergence Zone played a pivotal role in modulating the strength of the ISM during the past two millennia.

WMO evaluation of northern hemispheric coldest temperature: −69.6 °C at Klinck, Greenland, 22 December 1991

AbstractA World Meteorological Organization (WMO) Extremes Evaluation Committee investigated an observation of −69.6 °C by Klinck Automatic Weather Station (AWS) in Greenland on 22 December 1991 as the lowest temperature observed in Greenland, thereby making it the lowest recorded near‐surface air temperature for the Northern and Western Hemispheres and for WMO Region VI. The committee examined the metadata and observations of the station as well as the regional synoptic circulation. The committee concluded that the observation is credible in terms of instrument calibration, monitoring of the station and the synoptic situation. Consequently, the WMO Rapporteur accepted the observation as the officially lowest observed near‐surface air temperature for Greenland, the Northern and Western Hemisphere and for WMO Region VI. As a supplement to this investigation, the committee also recommends that opportunities be investigated such that AWS data from Greenland can be efficiently incorporated into real‐time weather forecasts and hence into reanalysis datasets.

Sun-induced synchronizations of the interannual to interdecadal hemispheric mean (land and sea) temperature variations

Some hemispheric variation features of the near surface air and sea-surface temperatures are considered. A specially designed technique of the wavelet-based cross-correlations is used for this purpose. In-phase synchronizations of the hemispheric temperatures as whole as well as such synchronizations between land and sea temperatures are found within the timescales of one, two, and six-seven decades. In contrast, no synchronization is found within the timescales between the above indicated ones. Consideration of the afore-mentioned temperatures in a long integration of the climatic model of the Marchuk Institute of Numerical Mathematics of RAS (the “Pi-Control” experiment when external forces were accepted equal to their mean values during the preindustrial period) shows lack of any synchronization. However, results of the “Historical” experiment when effects of external forces, and, in particular, small variations of the total solar irradiation (TSI), were taken into consideration, reveal similar in-phase synchronizations in the same timescales in which the in-phase synchronizations exist in reality, but during the second half of the XXth century only. Perhaps, it is so because the TSI effects were taken into consideration incorrectly for the first half of the XXth century. All (in reality and in the model runs as well) synchronized temperature variations lag respective TSI variations. From this one can suppose that the namely TSI-variations, despite their amplitudes are very small, synchronize the hemispheric temperature variations.

Sub-alpine trees testify late 20th century rapid retreat of Gangotri glacier, Central Himalaya

Our understanding on glacier-climate link in the Himalayan region is constrained due to lack of long-term observational and high-resolution proxy records. Hostile weather conditions and difficult approaches to access glaciers due to rough terrains largely limit observational studies on glaciers in the Himalaya. Sub-alpine trees and shrubs close to glaciers, growth of which is very sensitive to fluctuations in temperature, provide precise continuous record on climate and glacier behaviour to supplement the observational records back to several centuries. To unfold the Gangotri glacier dynamics in the past, we developed tree-ring chronologies and studied the colonization pattern of the trees in the region. Tree-ring chronologies of Himalayan birch and Himalayan pine developed from their respective upper tree line ecotone in the Gangotri glacier forefields showed impact of temperature on the growth variations. A comparison of Himalayan pine chronology with temperature proxies revealed regional and hemispheric scale temperature signal. Using tree-ring chronologies we show expansion (retreat) of the Gangotri glacier during cool (warm) phases that are also in agreement with the glacier fluctuation records from Central Asia and Southern Tibet. Moreover, using tree colonization pattern in the glacier forefields we established for the first time that the Gangotri glacier terminus receded ~1.853 km since the late 16th century (1571 C.E.), major part of which (1.79 km) receded since 1935 C.E. The glacier retreat, associated with the onset of 20th century warming got accelerated since 1957 C.E. (1.567 km). In view of our findings, the Gangotri glacier might further face accelerated recession in the 21st century under the projected warming.

Response of heterogeneous rainfall variability in East Asia to Hadley circulation reorganization during the late Quaternary

The Quaternary East Asian summer rainfall evolution reconstructed with the Chinese speleothem δ18O records shows the consistency throughout the region of East Asia, and has long been considered equivalent to the monsoon intensity. Its variation and teleconnection with global climate were usually interpreted by the meridional shift of the intertropical convergence zone (ITCZ). However, many other proxy records, climate simulations and meteorological observations suggest the inconsistent rainfall patterns in the different regions of East Asia on multi-timescales. Such spatial heterogeneity in Quaternary East Asian summer rainfall indicates that the hydroclimate in this region is not fully paced by the migration of the ITCZ. Here, we report a sediment record of rainfall evolution during the last 400 ka in the northern East China Sea, and this record, in combination with a transient climate model simulation, indicates an out-of-phase relationship between rainfall over middle-southeastern East Asia and northern and southwestern East Asia on the precession band, with high boreal summer insolation corresponding to the increased rainfall intensity in the northern and southwestern East Asia, however, decreased rainfall intensity in the middle East Asia. We attribute this regional heterogeneity in East Asian rainfall to the reorganization of the Hadley circulation, including shifts in the ascending branch (ITCZ) and descending branch (subtropical westerly jet), in response to changes in the hemispheric meridional temperature gradient. Our results highlight the crucial role of the Hadley circulation in the East Asian hydroclimate and have important implications for future climate projections.

Breaks in Linear Trends or Parts of Cycles?

Understanding the trends and periodicities in geophysical processes is imperative for assessing and forecasting their future change. However, it is possible to mistreat parts of cycles as linear trends with sudden breaks when analysing short-term data. We demonstrate this through the analysis of solar irradiance data as well as Northern Hemisphere (NH) and Southern Hemisphere (SH) sea surface temperature (SST) data sets, with emphasis on the (a) analyses of trends in total solar irradiance (TSI) and (b) association of trends in SST with solar activity during the period from 1900 to 2017. The trends estimated using singular spectrum analysis together with linear regression revealed statistically significant long periodic non-linear trends in both TSI and SST data. Our results suggest that the appraisal of linear trends to identify their breaks/sudden changes is a biased approach when analysing data sets of shorter periods, when the data are governed by long periodic dynamical processes. The non-linear trends identified in SST data may be physically associated with the TSI trend change and anthropogenic CO2. A plausible physical mechanism is also discussed with respect to the influence of solar activity on the trend in atmospheric CO2. Finally, our study concludes that (1) breaks in linear trends are pseudo-attribution of parts of cycles, and (2) the statistically significant trends in NH and SH SST are mainly associated with loadings from trend changes in solar irradiance.

Neural network prediction of parameters of biomass ashes, reused within the circular economy frame

Artificial neural networks were used for the prediction of three biomass ash fusion temperatures: initial deformation temperature IDT, hemispherical temperature HT and flow temperature FT based on chemical composition of the ash. Applicability of 400 neural network configurations (of linear, MLP, RBF and GRNN types) was verified statistically. Multilayer perceptron with 12 inputs representing fractions of the ash compounds, 11 hidden neurons and three outputs (IDT, HT, FT) proved to be the optimal neural model configuration. Statistical analysis suggested also, that considering intrinsic dispersion within the raw experimental data (literature data supplemented with the authors’ own results describing the halloysite addition effect), quality of the resulting 3-output IDT-HT-FT model (IDT prediction with R 2 0.615, HT with R 2 0.756 and FT with R 2 0.729) could be regarded satisfactory for the identification and generalization of the discussed relationships. Analysis of the neural model sensitivity in respect to the input variables demonstrated, that the most important factors affecting all ash transition temperatures in the 3-output IDT-HT-FT model were: K 2 O, SiO 2 , CaO and Al 2 O 3 fractions. Moreover, individual sensitivity in respect to IDT, HT and FT temperatures slightly varied (characteristics provided by independently established 1-output networks – IDT model, HT model and FT model, respectively). Statistically verified neural network working as the 3-output IDT-HT-FT model can be applied in various computational tasks in biofuels energy sector required by Industry 4.0 principles, as well as in the selected Circular Economy problems. • Chemical compositions of the ashes were correlated with their melting temperatures. • Ash melting temperatures can be effectively predicted by neural network model. • Predictions of neural models are more accurate compared to statistical models. • Sensitivity of each melting temperature in respect to ash components is different. • The results can improve the technologies of biomass energy conversion.

Mid‐Holocene Sahara‐Sahel Precipitation From the Vantage of Present‐Day Climate

AbstractTo account for the wet mid‐Holocene (ca. 6 ka) Sahara‐Sahel region, we exploit teleconnections from four large‐scale ocean‐atmosphere‐land forcings: El Niño–Southern Oscillation (ENSO), Atlantic Multidecadal Oscillation (AMO), hemispherical temperature difference, and net energy input at the equator; they offer theoretical bases for estimating effects of large‐scale forcing on mid‐Holocene Sahara‐Sahel rainfall. Together, these forcings explain 16–64% of historical rainfall variability, with the highest percentages in the Sahel region. With estimates for mid‐Holocene time, latitudes where rainfall today averages 1,000, 500, or 200 mm/year are reconstructed to have lain ~2.5° farther north. Calculated mid‐Holocene rainfall at 15°N, 17.5°N, and 20°N exceeds that today by ~250, 100, and 20 mm/year. These shifts account for more than half of paleoclimatic estimates of mid‐Holocene rainfall and are comparable with the General Circulation Model (GCM) runs that match paleorainfall estimates most closely. Mid‐Holocene radiation may have affected Sahel precipitation indirectly via teleconnections from oceanic regions.

LONG-TERM spectral components of global, north and south hemisphere temperatures over the last millennium and solar-lunar forcing

Data of temperature anomalies from different sites worldwide for the last millennium are used to extract long-term components in global, northern and southern hemisphere temperatures for their quantitative contribution to climate change to evaluate and to search for possible causes. The Method of Global Minimum which is capable of making a self-consistent selection of trends from a data set and singling out harmonics with varying phase and amplitude is applied. Quantitative description of all components of the spectra including trends extracted for the first time by self-consistent method is given and discussed. Temperature trends have highest amplitude in north, south hemispheres and globally that leads to their largest contribution to climate change. Trend in north hemisphere temperature described by nonstationary sinusoid at period ∼1270 yr shows maximum near 1300 (medieval warming), deep minimum near 1700 (Maunder's minimum) and rise since 1700 to present. Trend in south hemisphere has smoothed maximum for medieval epoch, minimum near 1800 (Dalton's minimum) and rise since 1800. Both trends go up together since ∼1800, but north hemisphere temperature grows faster. Trend in global temperature described by nonstationary sinusoid at period ∼1000 yr demonstrates deep smoothed minimum near 1750 and subsequent rise with rate of increase ∼0.5 °C/100yr since 1800. Amplitude of the nonstationary cycle began rise since 1250 and continue to rise for present and close future. Temporal changes of amplitude and phase of nonstationary spectral components have typical features of nonlinear oscillations that points to a nonlinear mechanism supporting the periodical oscillations. It is shown that the 33-yr nonstationary component in global temperature has the highest rate of change ∼1.2 °C/100yr or 0.12 °C/10yr, which can explain rapid temperature changes (from warming to subsequent cooling and vice versa). It is also shown that periods of the temperature spectra include integers of periods of historically-known eclipse cycles and of periods related with motions of Jupiter, Saturn and Venus. Therefore Sun and Moon, Jupiter, Saturn and Venus influence on climate variability. The result also means existence of high-number commensurabilities between mean motions in the system Sun –Earth–Moon and these planets.

Major Volcanic Eruptions and Their Impacts on Southern Hemisphere Temperatures During the Late 19th and 20th Centuries, as Simulated by CMIP5 Models

AbstractWhile much is known about the impacts of volcanic forcing on Northern Hemisphere (NH) climates, knowledge about Southern Hemisphere (SH) responses is still in its infancy. We examine volcanic impacts on SH temperatures following eight major late 19th and 20th century eruptions (Agung, 1963; Colima, 1913; El Chichón, 1982; Pinatubo, 1991; Krakatau, 1883; Quizapu, 1932; Santa Maria, 1902; Tarawera, 1886). Coupled Model Intercomparison Project, Phase 5 (CMIP5) historical simulations are used to analyze near‐surface land temperatures. We demonstrate that four of the eight major eruptions (Krakatau, Santa Maria, Agung, and Pinatubo) significantly lowered mean SH temperatures; these tropical eruptions emitted at least 20 Tg of SO2 into the stratosphere. SH responses typically lagged NH temperature cooling responses by 1–2 months, excluding Pinatubo. Responses differ spatially and temporally with each eruption, highlighting the importance of investigating events individually. Overall, we observe relatively strong (between −0.19°C and −0.36°C) austral autumn/winter SH cooling.

Late summer temperature variability for the Southern Rocky Mountains (USA) since 1735 CE: applying blue light intensity to low-latitude Picea engelmannii Parry ex Engelm

Our study examines the application of using blue intensity (BI) methods to develop a late summer maximum temperature (Tmax) reconstruction for the Southern Rocky Mountains—a mid-latitude (i.e., 36° N), arid region in North America. We reconstruct August–September (AS) Tmax for the period 1735–2015 CE using a composite latewood BI (LWB) Engelmann spruce (Picea engelmannii Parry ex Engelm.) chronology from multiple sites across the Sangre de Cristo Mountains in Northern New Mexico, USA. This study presents the first BI-derived temperature reconstruction for the lower mid-latitudes (30–45° N) of North America. We compare the climate response of multiple tree-ring parameters: LWB, earlywood BI (EWB), ∆BI (earlywood BI minus latewood BI), ring width (RW), and maximum latewood density (MXD). Of all parameters, the site-composite LWB and ∆BI chronologies show the strongest correlations with AS Tmax. Reconstructed AS Tmax demonstrates fluctuating warm and cool periods during the latter portion of the Little Ice Age (ca. 1730–1850) and pronounced warming through the early to mid-twentieth century (ca. 1920–1950s). The reconstruction also documents substantial warming over the last decade, the trend of which appears to be anomalous within the context of the past ca. 280 years. We highlight the potential for BI methods to be successfully used at high-elevation, mid-latitude locations where temperature proxy datasets are scarce or non-existent. As many places across the mid-latitudes lack contiguous, temporally resolved, decadal-scale paleotemperature proxies, we suggest here that BI methods can be effective at improving the spatial gaps in the Northern Hemisphere temperature proxy network.

Persistent warm Mediterranean surface waters during the Roman period

Reconstruction of last millennia Sea Surface Temperature (SST) evolution is challenging due to the difficulty retrieving good resolution marine records and to the several uncertainties in the available proxy tools. In this regard, the Roman Period (1 CE to 500 CE) was particularly relevant in the socio-cultural development of the Mediterranean region while its climatic characteristics remain uncertain. Here we present a new SST reconstruction from the Sicily Channel based in Mg/Ca ratios measured on the planktonic foraminifer Globigerinoides ruber. This new record is framed in the context of other previously published Mediterranean SST records from the Alboran Sea, Minorca Basin and Aegean Sea and also compared to a north Hemisphere temperature reconstruction. The most solid image that emerges of this trans-Mediterranean comparison is the persistent regional occurrence of a distinct warm phase during the Roman Period. This record comparison consistently shows the Roman as the warmest period of the last 2 kyr, about 2 °C warmer than average values for the late centuries for the Sicily and Western Mediterranean regions. After the Roman Period a general cooling trend developed in the region with several minor oscillations. We hypothesis the potential link between this Roman Climatic Optimum and the expansion and subsequent decline of the Roman Empire.

Model uncertainties in climate change impacts on Sahel precipitation in ensembles of CMIP5 and CMIP6 simulations

The impact of climate change on Sahel precipitation suffers from large uncertainties and is strongly model-dependent. In this study, we analyse sources of inter-model spread in Sahel precipitation change by decomposing precipitation into its dynamic and thermodynamic terms, using a large set of climate model simulations. Results highlight that model uncertainty is mostly related to the response of the atmospheric circulation to climate change (dynamic changes), while thermodynamic changes are less uncertain among climate models. Uncertainties arise mainly because the models simulate different shifts in atmospheric circulation over West Africa in a warmer climate. We linked the changes in atmospheric circulation to the changes in Sea Surface Temperature, emphasising that the Northern hemispheric temperature gradient is primary to explain uncertainties in Sahel precipitation change. Sources of Sahel precipitation uncertainties are shown to be the same in the new generation of climate models (CMIP6) as in the previous generation of models (CMIP5).

Observed extreme precipitation trends and scaling in Central Europe

In this publication we aim to relate observed changes in Central European extreme precipitation to the respective large-scale thermodynamic state of the atmosphere. Maxima of long-term (1901–2013) daily precipitation records from a densely sampled Central European station network, spanning Austria, Switzerland, Germany and the Netherlands, are scaled with Northern Hemispheric and regional temperature anomalies. Scaling coefficients are estimated at station level and aggregated to infer a robust regional extreme precipitation – temperature relationship. Across Central Europe, an overall intensification and a positive scaling signal with Northern Hemispheric temperature is detected in annual, summer, and winter single-day to monthly maximum precipitation. Generally, the estimates are consistent also when only considering data after 1950, and the scaling of annual maxima is also significant for all individual countries but Austria. However, scaling magnitudes are found to vary considerably between seasons and subregions. Also, scaling with regional temperature is non-significant, except for winter extreme precipitation.

Influences of West Pacific Sea Surface Temperature on Covarying Eurasian Droughts Since the Little Ice Age

The Western Pacific Warm Pool (WP), with the highest sea surface temperature (SST) in the world, has strong impacts on the drought variations in Eurasia. However, since the little ice age (1250–1850, LIA), the co-climatic drought pattern due to WP warming in Eurasia remains unclear. This is a long-term warming background for the current warming period (CWP). In this paper, we use both instrumental data and 1625 tree-ring width records from Eurasia to investigate the drought patterns in both modern and historical periods. This study revealed two seesaw precipitation patterns, namely the Central Asia–Mongolia (CAMO) and Northern Europe–Southern Europe (NESE) patterns. When the Western Pacific Warm Pool sea surface temperature (WPSST) is high, precipitation increases in Central Asia and Northern Europe, and decreases in Mongolia and southern Europe. When the positive (negative) phase event of the El Niño–Southern Oscillation (ENSO) occurs, the WPSST is reduced (increased), and the decreases (increases) of precipitation in Central Asia and Northern Europe and the increases (decreases) in precipitation in Mongolia and southern Europe are more obvious. The CAMO dipole has been strengthened since the LIA. The CAMO dipole is positively correlated with solar radiation and Northern Hemisphere temperature, and negatively correlated with Pacific decadal oscillations (PDO).

An Interpretable Extreme Gradient Boosting Model to Predict Ash Fusion Temperatures

The hemispherical temperature (HT) is the most important indicator representing ash fusion temperatures (AFTs) in the Polish industry to assess the suitability of coal for combustion as well as gasification purposes. It is important, for safe operation and energy saving, to know or to be able to predict value of this parameter. In this study a non-linear model predicting the HT value, based on ash oxides content for 360 coal samples from the Upper Silesian Coal Basin, was developed. The proposed model was established using the machine learning method—extreme gradient boosting (XGBoost) regressor. An important feature of models based on the XGBoost algorithm is the ability to determine the impact of individual input parameters on the predicted value using the feature importance (FI) technique. This method allowed the determination of ash oxides having the greatest impact on the projected HT. Then, the partial dependence plots (PDP) technique was used to visualize the effect of individual oxides on the predicted value. The results indicate that proposed model could estimate value of HT with high accuracy. The coefficient of determination (R2) of the prediction has reached satisfactory value of 0.88.

A lake sediment stable isotope record of late-middle to late Holocene hydroclimate variability in the western Guatemala highlands

Long-term perspectives on past hydroclimate variability provide context for evaluating the potential future impacts of changes in Northern Hemisphere temperatures and oceanic-atmospheric circulation on the timing and distribution of precipitation in Central America. Here we use the isotopic composition of fine-grained (< 63 μm), endogenic CaCO3 (δ18Ocalcite and δ13Ccalcite) from Lake Kail, located in the western highlands of Guatemala, to infer multi-decadal to multi-centennial-scale variability in the balance between precipitation and evaporation (P/E) over the last ∼6000 years. The sediment age model is based on 210Pb and 41 14C ages, with chronological uncertainty estimated using Bayesian methods. A model that couples lake hydrology and isotope mass balance is applied to characterize the isotopic responses of lake water and calcite to changes in drought-controlling climate variables such as precipitation, temperature and relative humidity. The δ18Ocalcite variations indicate intermediate-to-dry P/E conditions during the late-middle Holocene from ∼6000 to ∼4100 calyrBP. There was then a shift to drier conditions at the start of the late Holocene until ∼3050 calyrBP, followed by a trend to wetter conditions until ∼1500 calyrBP. The most recent ∼1500 years is characterized by high and relatively stable P/E, with particularly wet intervals from ∼1500 to 1170 calyrBP and from 470 to 260 calyrBP. Comparisons of the Lake Kail δ18Ocalcite record with Central American/circum-Caribbean proxy datasets spanning the late-middle and late Holocene indicate northern tropical hydroclimate changes were highly variable across space and time and were likely driven by regional oceanic-atmospheric responses with a secondary influence by insolation forcing.