Historical Temperature Changes Research Articles

Holocene Paleoclimate Changes around Qinghai Lake in the Northeastern Qinghai-Tibet Plateau: Insights from Isotope Geochemistry of Aeolian Sediment

The stable carbon isotope composition of total organic matter (δ13Corg) has been utilized in aeolian sediments, serving as an indicator for reconstructing terrestrial paleoenvironments. The Qinghai Lake (QHL) Basin is a climate-sensitive region of significant importance in paleoclimatic reconstruction. However, the reconstructed climatic variations based on δ13Corg in aeolian sediments in the QHL Basin in the northeastern Qinghai-Tibet Plateau (QTP) are lacking, and their paleoclimatic significance remains poorly understood. By conducting δ13Corg measurements on the Niaodao (ND) aeolian profile near QHL, we reconstructed the paleoclimate changes of 11 ka–present. The variation range of the δ13Corg values in the ND profile indicated the terrestrial ecosystems were not the sole contributor to lacustrine organic matter. The δ13Corg values are an indicator of historical temperature changes in the study area, exhibiting similar trends with the reconstruction of Chinese summer temperatures, East Asian air temperature, global temperature, and Northern Hemisphere summer insolation at 37° N. The temperature increased with high frequency and amplitude oscillations, with strong aeolian activity and low total organic carbon accumulation during the Early Holocene. The temperature was maintained at a high and stable level, with the weakest aeolian activity and intensified pedogenesis during the Middle Holocene. The temperature decreased at a high rate, with renewed aeolian activity and weak pedogenesis during the Late Holocene.

Water-Mass Coordinates Isolate the Historical Ocean Warming Signal

Abstract Persistent warming and water cycle change due to anthropogenic climate change modifies the temperature and salinity distribution of the ocean over time. This “forced” signal of temperature and salinity change is often masked by the background internal variability of the climate system. Analyzing temperature and salinity change in water-mass-based coordinate systems has been proposed as an alternative to traditional Eulerian (e.g., fixed-depth, zonally averaged) coordinate systems. The impact of internal variability is thought to be reduced in water-mass coordinates, enabling a cleaner separation of the forced signal from background variability—or a higher “signal-to-noise” ratio. Building on previous analyses comparing Eulerian and water-mass-based one-dimensional coordinates, here we recast two-dimensional coordinate systems—temperature–salinity (T–S), latitude–longitude, and latitude–depth—onto a directly comparable equal-volume framework. We compare the internal variability, or “noise” in temperature and salinity between these remapped two-dimensional coordinate systems in a 500-yr preindustrial control run from a CMIP6 climate model. We find that the median internal variability is lowest (and roughly equivalent) in T–S and latitude–depth space, compared with latitude–longitude coordinates. A large proportion of variability in T–S and latitude–depth space can be attributed to processes that operate over a time scale greater than 10 years. Overall, the signal-to-noise ratio in T–S coordinates is roughly comparable to latitude–depth coordinates, but is greater in regions of high historical temperature change. Conversely, latitude–depth coordinates have greater signal-to-noise ratio in regions of historical salinity change. Thus, we conclude that the climatic temperature change signal can be more robustly identified in water-mass coordinates. Significance Statement Changes in ocean temperature and salinity are driven both by human-induced climate change and by modes of natural variability in the climate system, such as El Niño–Southern Oscillation. It can be difficult to isolate the human-induced “signal” of climate change from the natural fluctuations or “noise” in the climate system. Water-mass-based methods, which “follow” a parcel of water around the ocean, have been thought to improve on “Eulerian” (i.e., analyses performed at fixed latitude, longitude, and depth) frames of reference as they are less impacted by the noise. However, it is difficult to cleanly compare between water-mass-based methods and Eulerian methods. Here, we aim to quantify the extent to which water-mass-based frameworks improve on Eulerian frameworks in isolating the climate signal from the noise. We recast water-mass and Eulerian methods onto an equivalent grid, enabling a clean comparison between them, and find that doing so increases the signal-to-noise ratio in water-mass-based coordinates in regions of ocean warming. These results emphasize the utility of water-mass-based methods in analyzing long-term climatic temperature change in the ocean.

Drivers of urban heat in Hong Kong over the past 116 years

Understanding how the urban heat island (UHI) effect changes over time and its drivers are essential to efforts in mitigating its impacts through future planning efforts. In Hong Kong, urbanization has occurred for >150 years, but historical analyses of UHI have been limited by the absence of suitable “rural” reference weather observations prior to the 1980's. Here, we used historical maps, meteorological observations from the Hong Kong Observatory, and climate model output from the 20th Century Reanalysis to examine the influence of historical drivers of urban heat from 1884 to 2000. Using the three drivers including total urbanized area, cumulative area of reclaimed land, and a proxy for past urban morphology, we developed linear models of the relationship between urbanization and UHI. Our analysis shows that UHI has a well-correlated positive and statistically significant relationship with all drivers of urban heat in Hong Kong. Historical temperature change in urban Hong Kong (1884–2000) was 0.95 °C, whereas regional climate change over the same period was 0.71 °C. Our results corroborate with historical understanding of Hong Kong's rapid, intensive urban development and furthers understanding on urbanization's effects on local microclimates on a century-long timescale.

The Effect of Temperature on Intestinal Flora Imbalance Based on Time Series Prediction Model

A series of effects caused by temperature change are the biggest problems faced by biological systems. These irregular environmental characteristics have brought new challenges to people and even animal groups. The immune function of human intestinal flora has a great protective effect on other organs and the body environment. It can help the human body carry out intestinal digestion, food absorption, nutritional metabolism, and so on. Based on the above situation, this paper uses the time series prediction model to study the factors affecting the imbalance of intestinal flora in the process of temperature change. Firstly, biological experiments are carried out with animals to simulate the human environment. Based on the sequence information of historical temperature change parameters, a temperature prediction device based on time series model is proposed. The effects of air factors and carbon dioxide content on the prediction results are evaluated by statistical analysis. Secondly, in order to ensure the accuracy of the experimental data, the neural network algorithm is used to optimize the model, and the white blood cell count is used to analyze the influence of temperature change on the intestinal flora structure of the two organisms. Finally, the experimental results are applied to the human environment to analyze the research results. The results showed that with the irregular change of temperature, the number of intestinal flora and internal colony structure also changed. The richness index in the normal temperature environment is relatively large, which can effectively explain the high richness of intestinal microflora in the experimental population. Further analyze the subjects and distinguish the animals according to sex. The number of Bacteroides in the intestinal flora of male animals was higher than that of female animals, but this phenomenon disappeared immediately after physical ligation. In addition, the intestinal flora abundance of female animals is higher than that of male animals, and the metabolic level is faster.

Backward simulation of temperature changes of District Heating networks for enabling loading history in predictive maintenance

District Heating (DH) networks, like most of industries, are in transition to the fourth​ industry age and they are retrofitting themselves with different sensing and inspection technologies to enable cyber connectivity for different purposes, such as system optimization, failure detection, maintenance, etc. Since DH pipes show different ageing behaviour under different conditions and initially the pre-insulated bounded pipes had been designed for a minimum of 30 years life span, a long-term loading history is required for predictive maintenance (PdM) purposes and it is necessary to understand the ageing of the DH pipes. These historical temperature changes of the networks are not available for such a long period and they are usually limited to the past few years. To exploit the available implemented technologies for PdM , the missing data must become available to understand the ageing patterns and expand the ageing model to the pipes in use. In this research, various Machine Learning (ML) techniques such as Support Vector Machine (SVM), Random Forest algorithm (RF), Artificial Neural Networks (ANN) have been tested to train a model and backward simulate the temperature changes of the system based on recorded weather data. Various none-temperature variables have been used to enhance the prediction qualities to the real-world data. The historical temperature changes of the system shall be used for different ageing estimation such as fatigue cycles or remaining useful life of the polyurethane (PUR) foam.

Species richness and endemism pattern of Fagaceae in Southwest China and their environmental interpretation.

How to accurately model species macro-richness patterns and endemism centers is a key focus of biodiversity conservation efforts and a hot biogeographical topic. Southwest China is one of regions with high Fagaceae species richness, the species diversity patterns and driving mechanisms are unclear. In this study, the distribution pattern of species richness (SR), weighted endemism (WE), and corrected weighted endemism (CWE) indices were estimated based on 7258 occurrence points of 161 Fagaceae species in Southwest China using both occurrence-to grid method and species distribution model (SDM). We used the spatial autoregressive (SAR) model to analyze the relationship between diversity indices and environmental factors. Overall, the three SDM-simulated diversity indices were more continuous in values than that of the occurrence-to grid method, though the distributions of those indices obtained by the two methods were similar. The areas with high SR value were mainly distributed in the south edge of Yunnan, north Guangxi and southwest Guangxi (62-89 species). The maximum of WE concentrated in south Yunnan and west Guangxi (1.77-5.02). The highest CWE (0.07-0.17) was found in southeast Tibet, Qinling-Daba Mountains, southwest Guangxi, and southeast Yunnan. The SAR models showed significant effect of precipita-tion in the driest month, standard deviations of seasonal temperature, altitude range and soil organic carbon content on SR. The effects of precipitation in the driest month, standard deviations of seaso-nal temperature, potential evaporation and altitude range on the WE were significant. The precipitation in the driest month, standard deviations of seasonal temperature, historical temperature change, coefficient of variation of enhanced vegetation index and altitude variation had significant effects on the CWE. The R2 of SAR model for SR, WE and CWE was 0.857, 0.733, 0.593, respectively, being higher than that of ordinary least squares (OLS) (R2=0.689, 0.425, 0.422). In conclusion, water availability, climate seasonality, habitat heterogeneity, historical climate change and soil condition were the most important factors limiting the distribution of SR and WE of Fagaceae in Southwest China. The SR and WE centers of Fagaceae were located in south and southeast Yunnan, southwest Guangxi, west Guangxi, Qinling-Daba Mountains, and southeast Tibet, where should be adequately protected.

Warm-season temperature reconstruction from high-elevation juniper tree rings over the past millennium in the Pamir region

Despite the great interest in the study of climate change in Central Asia, there are still research gaps; the spatial distribution of the natural proxy data is uneven, and our knowledge of past climate variability is incomplete. Recently many investigations have focused mainly on the region of the Tibetan Plateau and Tian Shan Mountains. Dendroclimatological field research in the western and central parts of the Pamir-Alay Mountains was conducted in the summer of 2015, within glacial cirques at elevations above 3000 m. On the basis of 49 juniper samples with northern exposures, warm season (May–September) Tmin values were reconstructed from 1301 to 2015 a.d. The reconstruction explains 53.6% of the actual temperature variance during the period 1941–1990. On the basis of the newly-developed paleoclimatological record, the time and duration of the MWP, TP, and LIA was established for the Pamir region. Close agreement between other temperature-related proxy records suggest that the reconstruction is highly reliable and captures the regional cold/warm periods of Central Asia. Therefore, the results of this study can contribute to understanding historical temperature changes in the Pamir region and its surroundings.

Climate change in Northeast China between 1849 and 2008

At the treeline, tree growth rate is known to be very sensitive to climate change. Width of tree rings is often used to estimate climatic conditions when direct measures of temperature and precipitation at the site are unavailable. In this study, tree ring data and available site-specific climatic data were analysed and correlated to reconstruct historical temperature changes from 1849 to 2008 at the Changbai Mountain treeline. One hundred and seventy-five Betula ermanii trees were selected from seven plots at the upper treeline area on the north-facing slopes of the Changbai Mountains. Two hundred and ninety-one tree ring cores were extracted from these trees to develop the B. ermanii chronology. The tree ring width index was found to be significantly related (R2 = 0.43, p < 0.01) to the mean annual temperature at the Tianchi weather station nearby during the period of 1953–2008. A transfer function was developed from the relationship to reconstruct the mean annual temperature from 1849 to 1952, for which a climatic record at Tianchi were unavailable. The results suggest a wavelike temperature increase with alternations between rapid warming and gentle cooling periods at the Changbai Mountains treeline for the 160 years. In Northeast China, the temperature has increased 0.07 °C per decade with significant fluctuation (p < 0.05, SD = 0.64) according to the extrapolated data. The extrapolation is based on the relationship between the Tianchi station and the other 164 weather stations throughout the Northeast. Temperature increase would significantly affect the sustainability of the alpine ecosystems in the Changbai Mountains as well as the agro-ecosystem management of the Northeast China Plain, a designated farmland area for crop production by the Chinese government.

Spatial patterns of radiative forcing and surface temperature response

AbstractExamination of effective radiative forcing (ERF), a measure of changes in Earth's energy balance, facilitates understanding the role of various drivers of climate change. For short‐lived compounds, ERF can be highly inhomogeneous geographically. The relationship between the spatial patterns of ERF and surface temperature response is poorly characterized, however. We examine that relationship in the latest generation of global climate models. We find that the uneven distribution of historical aerosol, ozone, and land use forcing leads to substantial differences compared to the well‐mixed greenhouse gases (WMGHG). There is a stronger response per unit global mean forcing to historical inhomogeneous forcing than to WMGHG both globally and in much of the Northern Hemisphere (NH) extratropics, in fairly good agreement with results inferred from observations. Our results indicate that the enhanced global mean response is attributable to the concentration of inhomogeneous forcing in the NH extratropics, where there is strongest sensitivity to forcing, rather than to processes specific to the inhomogeneous forcers. In many regions, inclusion of inhomogeneous forcing greatly increases the spread in historical temperature changes simulated by the models, suggesting that better forcing characterization could play an important role in improving modeling of decadal‐scale regional climate change. Finally, incorporating observed temperatures, the results provide estimates of global historical aerosol forcing (−1.0 ± 0.4 W m−2) consistent with other studies (though with narrower uncertainties) and also provide constraints on NH and NH extratropical historical aerosol forcing (−1.4 ± 0.6 and −1.2 ± 0.6 W m−2, respectively) and aerosol + ozone forcing.

Limnological and ecological sensitivity of Rwenzori mountain lakes to climate warming

An increasing number of studies forecast that anthropogenic climate change poses serious consequences for the biodiversity and ecosystem functioning of high-elevation mountain lakes, through a series of both direct and indirect effects. The impacts of future climate warming on alpine ecosystems are of particular concern, given that warming is expected to be most pronounced at high elevations around the globe. Here, we evaluate the limnological and ecological sensitivity of high-ele- vation lakes in the Rwenzori Mountains (Uganda-D. R. Congo) to climate change. This is done by comparing the species assemblages of larval chiron- omid remains deposited recently in lake sediments with those deposited at the base of short cores (dated to within or shortly after the Little Ice Age) in 16 lakes. Chironomid-based reconstructions of mean annual air temperature (MATemp) are made using a variety of inference models (with transfer functions based on weighted averaging, weighted-averaging partial least squares, and a weighted modern analogue technique), and two different calibration data sets, one covering the full regional temperature gradient and one comprising only high-elevation Rwenzori lakes and ponds. The reconstructed historical temperature change ranges between a cooling of -2.03C and a warming of ?3.22C (with n = 16 lakes 9 3 models 9 2 calibration data sets). How- ever, excluding the atypical mid-elevation lake Mahoma (2,990 m altitude), we find a three-to-one ratio of cases of inferred warming against inferred cooling, and of the 24 D MATemp values exceeding 0.60C, 23 are positive and only one is negative. Chironomid-inferred temperature changes mostly fall within the error range of the regional temperature inference models. A generalized linear mixed model analysis of the combined result from all lakes (except Mahoma) nevertheless indicates significantly warmer MATemp (on average ?0.38 ± 0.11C) at present

Air temperature changes in the Canadian Arctic from the early instrumental period to modern times

An Erratum has been published for this article in International Journal of Climatology 25(14) 2005, 1955–1956. This article presents a detailed account of air temperature (using four thermal parameters: mean daily air temperature (MDAT), maximum daily temperature (TMAX), minimum daily temperature (TMIN), and diurnal temperature range (DTR)) in the Canadian Arctic from 1819 to 1859. As source data, the authors have used hourly, two-hourly, four-hourly, or six-hourly temperature measurements carried out during exploratory (land or marine) expeditions sent mainly by the Royal Navy to find the Northwest Passage and later also during a lost expedition under the command of Sir John Franklin. Standard climate analyses (using monthly means) and more detailed and precise analyses based on daily data showing a wide spectrum of temperature regimes were conducted. The latter analysis examined the frequency of occurrence of MDAT in particular intervals, day-to-day variability of MDAT, annual courses of MDAT and DTR, and the frequency of occurrence of different kinds of characteristic days (e.g. very warm, warm, severe cold, very cold). All studied aspects of historical temperature changes in the Canadian Arctic from 1819 to 1859 were compared with present-day (1961–1990) values. All the results obtained suggest that in the nineteenth century a moderate cooling occurred in the Canadian Arctic. The average annual temperature during the study period was only about 0.3 °C lower in comparison with the present-day value. The most typical features in the annual courses of air temperature in the study period were very cold winter months (December to February, 1.0–2.5 °C below today's norm) and warm springs (March to May, 0.2–2.6 °C above today's norm). The majority of mean monthly and daily temperatures lie within one SD from the modern mean. Copyright © 2005 Royal Meteorological Society.

Importance of Sulfate Aerosol in Evaluating the Relative Contributions of Regional Emissions to the Historical Global Temperature Change

During the negotiations of the KyotoProtocol the delegation of Brazil presentedan approach for distributing the burden ofemissions reductions among the Partiesbased on the effect of their cumulativehistorical emissions on the global-averagenear-surface temperature. The Letter tothe Parties does not limit the emissions tobe considered to be only greenhouse gas(GHG) emissions. Thus, in this paper weexplore the importance of anthropogenicSOx emissions that are converted tosulfate aerosol in the atmosphere, togetherwith the cumulative greenhouse gasemissions, in attributing historicaltemperature change. We use historicalemissions and our simple climate model toestimate the relative contributions toglobal warming of the regional emissions byfour Parties: OECD90, Africa and LatinAmerica, Asia, and Eastern Europe and theFormer Soviet Union. Our results show thatfor most Parties the large warmingcontributed by their GHG emissions islargely offset by the correspondingly largecooling by their SOx emissions. Thus,OECD90 has become the dominant contributorto recent global warming following itslarge reduction in SOx emissions after1980.

Key points on temperature change of the past 2000 years in China *

Abstract Temperature change of the past 2000 years in China is discussed based on the winter half-year temperature series of the past 2000 years in eastern China reconstructed recently, and other related studies. The main conclusions are as follows: (1) The Little Ice Age (LIA) in China began in the early of the 14th century (1320s) and ended in the beginning of the 20th century (1910s), which was composed of four evident cold stages and three short warming stages. The cold period in the Wei, Jin and South-North dynasties (210s–560s) was the only one comparable with LIA for the past 2000 years. (2) The Medieval Warm Period (MWP) in China began in the 930s and ended in the 1310s, which was composed of two warm stages over 100 years and a cold stage less than 100 years. (3) The climate in the Sui and Tang dynasties should be divided into two stages: the climate in the 570s–770s was as warm as that in the 20th century; while the temperature in the 780s–920s was lower than that in the 1950s–1970s. (4) In eastern China as a whole, winter half-year temperature variation with over 1 °C occurred between the cold and warm stages on centennial scale, while the changing rate exceeded 1.0 °C per century. (5) There exists an about 1350-year periodicity in the historical temperature change. Inferred from the periodicity, the most likely historical analogue for the warming in the 20th century is the warm stage of the Sui and Tang dynasties (570s–770s), instead of the Medieval Warm Period. (6) Although it was critically warm, the temperature of the 20th century in eastern China is still within the threshold of the variability of the last 2000 years.