Large-scale Temperature Changes Research Articles

Future Physical and Biogeochemical Ocean Conditions under Climate Change along the British Columbia Continental Margin

ABSTRACT Climate change impacts coastal ecosystems through large scale changes in temperature, stratification, circulation and ocean acidification. Here, the potential response of the British Columbia continental margin to climate change is investigated using a regional ocean circulation-biogeochemical model to downscale climate change projections from the Canadian regional and global climate models (CanRCM4/CanESM2) under two Intergovernmental Panel on Climate Change emission scenarios (RCP 4.5 and RCP 8.5). Projections of future physical and biogeochemical conditions for the 2041–2070 period are compared to the recent past (1981–2010). We found an overall annual average warming of >1.6°C in sea surface temperature, increase in stratification in the upper layer, and decrease in surface pH of as much as 0.21. Increasing stratification and changing winds have a limited impact on nitrate availability, phytoplankton biomass and primary production, whilst ocean warming increases primary production by up to 30% in most of the model domain. Increased atmospheric CO2 contributes to acidification over the model domain with a decrease in pH and aragonite saturation (Ωarag) at all depths resulting in an increase of 20 to 32% of the volume of Ωarag ≤1 in the upper 100 m of the continental shelf depending on the climate scenario. Our projected results, therefore, show that future climate change may alter the amount of food available for higher trophic levels and the habitat of benthic species, since bottom waters on the shelf will be undersaturated with respect to aragonite for 2–3 months in mid-summer. Both climate change scenarios results in a similar pattern of changes but projected changes were stronger and more extensive under RCP 8.5 showing the benefit of mitigation efforts in reducing the effect of climate change on marine ecosystem stressors.

Summer temperature variability inferred from tree-ring records in the central Hengduan Mountains, southeastern Tibetan Plateau

Current understanding of the paleoclimatic variability across the Tibetan Plateau (TP) is still limited because of the lack of long-term climatic records. We developed a regional tree–ring width chronology of Picea likiangensis var. balfouriana from the central Hengduan Mountains region, in the southeastern TP. Climate-growth correlation analysis revealed that the current year’s July (cJuly) and the current year’s August (cAugust) mean minimum temperature was the main climatic factor controlling tree-ring growth. Using a linear regression function, we reconstructed this indicator for the past 214 years (1795–2008) to produce the first mean minimum temperature reconstruction for the central Hengduan Mountains. The reconstruction satisfied all statistical calibration and validation tests, and represented 35.9% of the temperature variance recorded over the 1958–2008 instrumental period (34.6% after adjusting for the loss of the degrees of freedom). During the past 214 years, two major cold periods were identified from 1839 to 1853 and 1857–1942, and four major warm periods from 1802 to 1813, 1819–1838, 1972–1981, and 1988–2008. The degree of warming from 1988 to 2008 was unprecedented over the past two centuries. Spatial field correlation with the gridded temperature dataset revealed that our reconstruction captures large-scale regional temperature variations for the southeastern TP and its vicinity. The reconstructed variations were consistent when compared to other regional temperature datasets, historical documents, and records of glacier fluctuations in the surrounding high mountains. This consistency with multiple records suggests that our reconstructed sequence is reliable and it could represent historical large-scale temperature changes on the southeastern TP.

A 564-year annual minimum temperature reconstruction for the east central Tibetan Plateau from tree rings

Minimum temperatures have increased rapidly on the Tibetan Plateau (TP) in recent decades, but there is still a lack of long-term background information to evaluate the nature of the anomaly. Here we present a 709-year tree-ring width chronology from Sabina tibetica Kom. on the east central TP, with reliable coverage from 1451 to 2014. Based on the significant relationship between tree growth and annual minimum temperature (Tmin), from previous April to current March, we reconstruct the pApril-cMarch Tmin for the past 564years. The reconstruction shows six major warm (1490–1623, 1713–1729, 1784–1812, 1868–1877, 1918–1954, 1989–2014) and six major cold (1451–1489, 1624–1712, 1730–1783, 1813–1853, 1878–1917, 1955–1988) periods during the past five hundred years. The level of warming from 1989 to 2014 is unprecedented over the past five centuries. Comparison with other minimum temperature records indicates that our Tmin reconstruction represents large-scale temperature changes on the eastern TP. The positive correlation between the Tmin reconstruction and the Atlantic Multidecadal Oscillation (AMO) suggests that the latter may have played a crucial role on multidecadal temperature variations over the east central TP, with high temperatures coincident with the warm phases of the AMO, and low temperatures related to the cold phases of the AMO, respectively.

Structure Design and Manufacturing of the Composite Blade for the Icing Wind Tunnel

The structure design and manufacturing of the fan blade ware researched based on large-scale temperature change, high-revolution, multi-constraint conditions, high-fidelity profile and so on. The numerical modeling was performed in MSC, including strength, stiffness as well as eigenfrequency analysis, optimized to layer thickness and mass of blade. The resin transfer molding (RTM) process was used to ensure the blade geometrical tolerance. Multiform tests were provided to verify that the design and manufacturing is reasonable and the blade satisfies with application requirement.

Elevation gradients of European climate change in the regional climate model COSMO-CLM

A transient climate scenario experiment of the regional climate model COSMO-CLM is analyzed to assess the elevation dependency of 21st century European climate change. A focus is put on near-surface conditions. Model evaluation reveals that COSMO-CLM is able to approximately reproduce the observed altitudinal variation of 2 m temperature and precipitation in most regions and most seasons. The analysis of climate change signals suggests that 21st century climate change might considerably depend on elevation. Over most parts of Europe and in most seasons, near-surface warming significantly increases with elevation. This is consistent with the simulated changes of the free-tropospheric air temperature, but can only be fully explained by taking into account regional-scale processes involving the land surface. In winter and spring, the anomalous high-elevation warming is typically connected to a decrease in the number of snow days and the snow-albedo feedback. Further factors are changes in cloud cover and soil moisture and the proximity of low-elevation regions to the sea. The amplified warming at high elevations becomes apparent during the first half of the 21st century and results in a general decrease of near-surface lapse rates. It does not imply an early detection potential of large-scale temperature changes. For precipitation, only few consistent signals arise. In many regions precipitation changes show a pronounced elevation dependency but the details strongly depend on the season and the region under consideration. There is a tendency towards a larger relative decrease of summer precipitation at low elevations, but there are exceptions to this as well.

The construction of a Central Netherlands temperature

Abstract. The Central Netherlands Temperature (CNT) is a monthly daily mean temperature series constructed from homogenized time series from the centre of the Netherlands. The purpose of this series is to offer a homogeneous time series representative of a larger area in order to study large-scale temperature changes. It will also facilitate a comparison with climate models, which resolve similar scales. From 1906 onwards, temperature measurements in the Netherlands have been sufficiently standardized to construct a high-quality series. Long time series have been constructed by merging nearby stations and using the overlap to calibrate the differences. These long time series and a few time series of only a few decades in length have been subjected to a homogeneity analysis in which significant breaks and artificial trends have been corrected. Many of the detected breaks correspond to changes in the observations that are documented in the station metadata. This version of the CNT, to which we attach the version number 1.1, is constructed as the unweighted average of four stations (De Bilt, Winterswijk/Hupsel, Oudenbosch/Gilze-Rijen and Gemert/Volkel) with the stations Eindhoven and Deelen added from 1951 and 1958 onwards, respectively. The global gridded datasets used for detecting and attributing climate change are based on raw observational data. Although some homogeneity adjustments are made, these are not based on knowledge of local circumstances but only on statistical evidence. Despite this handicap, and the fact that these datasets use grid boxes that are far larger then the area associated with that of the Central Netherlands Temperature, the temperature interpolated to the CNT region shows a warming trend that is broadly consistent with the CNT trend in all of these datasets. The actual trends differ from the CNT trend up to 30 %, which highlights the need to base future global gridded temperature datasets on homogenized time series.

Biogeophysical effects of land use on climate: Model simulations of radiative forcing and large-scale temperature change

Changes in land cover affect climate through the surface energy and moisture budgets. Here we assess the importance of these biogeophysical effects for present-day climate, and quantify the radiative forcing of historical climate change by land use change for comparison with radiative forcings due to anthropogenic changes in greenhouse gases and aerosols. We also discuss the implications of biogeophysical effects for the use of forestry as a tool for mitigating climate change through carbon sequestration. Our model results suggest that since most historical deforestation has taken place in temperate regions where the main climatic effect is an increase in surface albedo, the dominant biogeophysical effect of past land cover change has been a cooling. The northern mid-latitude agricultural regions are simulated to be approximately 1–2 K cooler in winter and spring in comparison with their previously forested state. This conflicts with the suggestion that land use change is responsible for the warming observed over the 20th century. The increase in albedo by 1750 is simulated to exert a negative radiative forcing of approximately −2 W m −2 locally over Europe, China and India, suggesting a potential anthropogenic influence on climate before fossil fuel burning began. The present-day global mean radiative forcing by anthropogenic surface albedo change relative to the natural state is simulated to be −0.2 W m −2, which is comparable with the estimated forcings relative to pre-industrial times by stratospheric and tropospheric ozone, N 2O, the halocarbons, and the direct effect of anthropogenic aerosols. In cold regions, afforestation or reforestation would decrease the surface albedo and induce a positive radiative forcing (warming) which could partly or completely offset the negative forcing (cooling) due to carbon sequestration. This suggests that carbon sink plantations could be less effective than expected at reducing warming, and could even cause further warming. However, we note that reforestation (or avoided deforestation) in tropical regions could exert a double cooling effect through carbon sequestration and increased evaporation and cloud cover.

Transient Climate Simulations with the HadGEM1 Climate Model: Causes of Past Warming and Future Climate Change

Abstract The ability of climate models to simulate large-scale temperature changes during the twentieth century when they include both anthropogenic and natural forcings and their inability to account for warming over the last 50 yr when they exclude increasing greenhouse gas concentrations has been used as evidence for an anthropogenic influence on global warming. One criticism of the models used in many of these studies is that they exclude some forcings of potential importance, notably from fossil fuel black carbon, biomass smoke, and land use changes. Herein transient simulations with a new model, the Hadley Centre Global Environmental Model version 1 (HadGEM1), are described, which include these forcings in addition to other anthropogenic and natural forcings, and a fully interactive treatment of atmospheric sulfur and its effects on clouds. These new simulations support previous work by showing that there was a significant anthropogenic influence on near-surface temperature change over the last century. They demonstrate that black carbon and land use changes are relatively unimportant for explaining global mean near-surface temperature changes. The pattern of warming in the troposphere and cooling in the stratosphere that has been observed in radiosonde data since 1958 can only be reproduced when the model includes anthropogenic forcings. However, there are some discrepancies between the model simulations and radiosonde data, which are largest where observational uncertainty is greatest in the Tropics and high latitudes. Predictions of future warming have also been made using the new model. Twenty-first-century warming rates, following policy-relevant emissions scenarios, are slightly greater in HadGEM1 than in the Third Hadley Centre Coupled Ocean–Atmosphere General Circulation Model (HadCM3) as a result of the extra forcing in HadGEM1. An experiment in which greenhouse gases and other anthropogenic forcings are stabilized at 2100 levels and held constant until 2200 predicts a committed twenty-second-century warming of less than 1 K, whose spatial distribution resembles that of warming during the twenty-first century, implying that the local feedbacks that determine the pattern of warming do not change significantly.

Using paleoclimate proxy-data to select optimal realisations in an ensemble of simulations of the climate of the past millennium

We present and describe in detail the advantages and limitations of a technique that combines in an optimal way model results and proxy-data time series in order to obtain states of the climate system consistent with model physics, reconstruction of past radiative forcing and proxy records. To achieve this goal, we select among an ensemble of simulations covering the last millennium performed with a low-resolution 3-D climate model the ones that minimise a cost function. This cost function measures the misfit between model results and proxy records. In the framework of the tests performed here, an ensemble of 30 to 40 simulations appears sufficient to reach reasonable correlations between model results and reconstructions, in configurations for which a small amount of data is available as well as in data-rich areas. Preliminary applications of the technique show that it can be used to provide reconstructions of past large-scale temperature changes, complementary to the ones obtained by statistical methods. Furthermore, as model results include a representation of atmospheric and oceanic circulations, it can be used to provide insights into some amplification mechanisms responsible for past temperature changes. On the other hand, if the number of proxy records is too low, it could not be used to provide reconstructions of past changes at a regional scale.

Detecting and Attributing External Influences on the Climate System: A Review of Recent Advances

AbstractThis paper reviews recent research that assesses evidence for the detection of anthropogenic and natural external influences on the climate. Externally driven climate change has been detected by a number of investigators in independent data covering many parts of the climate system, including surface temperature on global and large regional scales, ocean heat content, atmospheric circulation, and variables of the free atmosphere, such as atmospheric temperature and tropopause height. The influence of external forcing is also clearly discernible in reconstructions of hemispheric-scale temperature of the last millennium. These observed climate changes are very unlikely to be due only to natural internal climate variability, and they are consistent with the responses to anthropogenic and natural external forcing of the climate system that are simulated with climate models. The evidence indicates that natural drivers such as solar variability and volcanic activity are at most partially responsible for the large-scale temperature changes observed over the past century, and that a large fraction of the warming over the last 50 yr can be attributed to greenhouse gas increases. Thus, the recent research supports and strengthens the IPCC Third Assessment Report conclusion that “most of the global warming over the past 50 years is likely due to the increase in greenhouse gases.”

Interdecadal Changes of Temperature in the Beijing Region and its Heat Island Effect

Large scale temperature changes and heat island effect in the Beijing region are investigated in this paper using the annual mean temperature data from 1960 to 2000 at 20 meteorological stations. Main conclusions are the following two points. First, the interannual changes of the temperature in the region show a feature of large-scale temperature change. 1981 is a remarkable jump point, the temperature increases by 0.55°C after the jump and the warming rate in the recent 40 years is 0.25°C/10-year. Second, the urban heat island effect in the Beijing region is typical. The averaged urban heat island intensity over 1960~2000 is about 1°C. Along with the acceleration of urban construction and urbanization, the urban heat island intensity is also increasing, and its growth rate in the recent 40 years is 0.31°C/10-year.

Large-scale temperature inferences from tree rings: a review

This paper is concerned with dendroclimatic research aimed at representing the history of very large-scale temperature changes. It describes recent analyses of the data from a widespread network of tree-ring chronologies, made up of ring width and densitometric measurement data spanning three to six centuries. The network was built over many years from trees selected to maximise their sensitivity to changing temperature. This strategy was adopted so that temperature reconstructions might be achieved at both regional and very large spatial scales. The focus here is on the use of one growth parameter: maximum latewood density (MXD). The detailed nature of the temperature sensitivity of MXD across the whole network has been explored and the dominant common influence of mean April–September temperature on MXD variability is demonstrated. Different approaches to reconstructing past temperature for this season include the production of detailed year-by-year gridded maps and wider regional integrations in the form of subcontinental and quasi-hemispheric-scale histories of temperature variability spanning some six centuries. These ‘hemispheric’ summer series can be compared with other reconstructions of temperature changes for the Northern Hemisphere over the last millennium. The tree-ring-based temperature reconstructions show the clear cooling effect of large explosive volcanic eruptions. They also exhibit greater century-timescale variability than is apparent in the other hemispheric series and suggest that the late 15th and the 16th centuries were cooler than indicated by some other data. However, in many tree-ring chronologies, we do not observe the expected rate of ring density increases that would be compatible with observed late 20th century warming. This changing climate sensitivity may be the result of other environmental factors that have, since the 1950s, increasingly acted to reduce tree-ring density below the level expected on the basis of summer temperature changes. This prevents us from claiming unprecedented hemispheric warming during recent decades on the basis of these tree-ring density data alone. Here we show very preliminary results of an investigation of the links between recent changes in MXD and ozone (the latter assumed to be associated with the incidence of UV radiation at the ground).

A time-slice experiment with the ECHAM4 AGCM at high resolution: the impact of horizontal resolution on annual mean climate change

The climate response to increasing levels of atmospheric greenhouse gases, prescribed according to the International Panel of Climate Change (IPCC) scenario IS92a, is studied in two model simulations. The reference simulation is a transient response experiment performed with a medium-resolution (T42) coupled general circulation model of the atmosphere and ocean (ECHAM4/OPYC) developed at the Max-Planck-Institute for Meteorology. For two 30-year “time slices”, representing the present-day climate and the future climate at the time of effective CO2 doubling, the annual mean climate states are compared with those obtained from the high-resolution (T106) ECHAM4 model forced with monthly sea surface temperatures and sea-ice from the coupled model. The large-scale changes in temperature, zonal wind, sea-level pressure and precipitation are broadly similar. This applies, in particular, to the respective zonal means. In general, except for precipitation, the responses in the time-slice experiments are slightly weaker than those simulated in the coupled model due to a smaller effect of the horizontal resolution on the simulations of the future (warmer) period than on the simulations of the present period. On a regional scale, the impact of horizontal resolution is smaller in the Southern than in the Northern Hemisphere, where the response differences are caused mainly by changes in the positions of the stationary waves. Although the precipitation responses are broadly similar, there are few notable exceptions such as a more pronounced maximum over the equatorial oceans in the T106 experiment but a weaker response over low-latitude land areas. Differences in precipitation response are found especially in areas with strong topographical control such as South America, for example.

Late-glacial fossil midge stratigraphies (Insecta: Diptera: Chironomidae) from the Swiss Alps

Chironomid midges (Insecta: Diptera: Chironomidae) are sensitive indicators of environmental change, but relatively few studies have been made of the response of European midge faunas to the high amplitude climatic oscillations of the late-glacial. In this study, late-glacial assemblages of chironomid midges from four Swiss lakes, or former lakes, [Gerzensee (603 m), Leysin (1230 m), Regenmoos (1260 m) and Hérémence (2300 m)] were compared and contrasted. The study focused on the response of chironomid assemblages to the beginning and end of the Younger Dryas cold interval (c. 12 690–11 485 cal. yr BP) and to minor cold climatic fluctuations (Gerzensee Oscillation, c.13200–12800 cal. yr BP, and Preboreal Oscillation, c. 113 65–11 100 cal. yr BP). The durations of these climatic fluctuations were defined climato-stratigraphically based on oxygen isotope boundaries and the chronology was derived by correlation with GRIP oxygen isotope records. Major differences in the composition of the four lakes' chironomid assemblages reflected differences in altitude and local environmental conditions. Nevertheless, each lake fauna showed a marked response to the major and minor climatic oscillations, demonstrating that large-scale temperature change had an overriding influence on the distribution of chironomid midges.

Causes of twentieth-century temperature change near the Earth's surface

Observations of the Earth's near-surface temperature show a global-mean temperature increase of approximately 0.6 K since 1900 (ref. 1), occurring from 1910 to 1940 and from 1970 to the present. The temperature change over the past 30–50 years is unlikely to be entirely due to internal climate variability2,3,4 and has been attributed to changes in the concentrations of greenhouse gases and sulphate aerosols5 due to human activity. Attribution of the warming early in the century has proved more elusive. Here we present a quantification of the possible contributions throughout the century from the four components most likely to be responsible for the large-scale temperature changes, of which two vary naturally (solar irradiance and stratospheric volcanic aerosols) and two have changed decisively due to anthropogenic influence (greenhouse gases and sulphate aerosols). The patterns of time/space changes in near-surface temperature due to the separate forcing components are simulated with a coupled atmosphere–ocean general circulation model, and a linear combination of these is fitted to observations. Thus our analysis is insensitive to errors in the simulated amplitude of these responses. We find that solar forcing may have contributed to the temperature changes early in the century, but anthropogenic causes combined with natural variability would also present a possible explanation. For the warming from 1946 to 1996 regardless of any possible amplification of solar or volcanic influence, we exclude purely natural forcing, and attribute it largely to the anthropogenic components.

THE NORTHERN HEMISPHERE TEMPERATURE CURVE: REPRESENTATIVENESS AND INTERPRETIVE FALLACIES

The Northern Hemisphere Temperature Curve has become one of the leading issues of modern climatology because it is not only considered to represent large-scale changes in temperature but is also used by some as a convenient indicator of changes in important derivatives of temperature. The development of the curve is reviewed and its representativeness of hemispheric climatic changes is discussed. Recently summarized marine temperature records and the tropospheric temperature record appear to confirm the general features of the curve. On the other hand, the curve's use as an indicator of local temperature changes and such derivatives as the length of the growing season and climatic variability is shown to be fallacious. This emphasizes the fact that local temperature trends are not necessarily similar to the hemispheric trend.

Large-Scale Temperature Changes in the Stratosphere Observed from Nimbus III

Abstract The radiances in the CO2 band centered at 669.3 cm−1 (15 μ), measured by the satellite infrared spectrometer on Nimbus III, are examined. These radiances are a measure of a weighted mean temperature of approximately the upper 100 mb of the atmosphere. A new result shows that stratospheric warmings in the winter hemisphere are accompanied by simultaneous coolings in the stratosphere of the tropics and the summer hemisphere. These out-of-phase changes of stratospheric temperature may be explained by heat transfer changes caused by variations of the meridional circulation and large-scale eddies. The out-of-phase relationship in stratospheric temperature is evident in the radiances when averaged around latitude circles, although the changes observed on certain dates do not occur at all longitudes. The isotherms in the stratosphere tend to be more nearly circumpolar on a day with minimum radiance. On a day when the warming reached its maximum, the higher radiances occur only in one part of the latitud...