Surface Air Temperature Time Series Research Articles

Comment on “Unresolved issues with the assessment of multidecadal global land surface temperature trends” by Roger A. Pielke Sr. et al.

[2] According to Pielke et al. [2007], the similarity of the different global surface temperature trends is unsurprising, in view of an estimated overlap of 90% to 95% in the raw data. Regional temperature trends are considered to be less robust in data-sparse regions such as parts of Africa and the Arctic and Antarctic. [3] Effectively independent analyses of land surface global temperature trends have already been carried out. Peterson et al.’s [1999] subset of rural stations showed very similar trends to those derived from the full GHCN data set. Using a worldwide network of about 270 stations, Parker [2006] obtained very similar trends to those produced by Jones and Moberg [2003] from their full network. The sensitivity of estimated land surface global temperature trends to analysis technique was estimated by Vose et al. [2005]. This paper showed that the Smith and Reynolds [2005] and the Jones and Moberg [2003] analyses yield comparable trends but the Hansen et al. [2001] and K. M. Lugina et al. (Monthly surface air temperature time series area averaged over the 30-degree latitudinal belts of the globe, 1881–2005, in Trends: A Compendium of Data on Global Change, 2006, an online report available at http:// cdiac.ornl.gov/trends/temp/lugina/lugina.html) analyses yield reduced trends in recent decades because of the greater oceanic influence on the former and the damping influence of optimal interpolation on the latter [Trenberth et al., 2007]. The generally good agreement between the global trends of land surface global temperature and the independent sea surface temperature and marine air temperature is also illustrated clearly by Trenberth et al. [2007]. Here we conduct an extra experiment: the CRUTEM3 land surface air temperatures [Jones and Moberg, 2003; Brohan et al., 2006] have been subsampled by taking, in each month, alternate 5 5 areas in alternate 5 latitude belts. Figure 1 shows annual global (Figure 1a) and hemispheric (Figures 1b and 1c) average land surface air temperature anomalies for 1850–2007 based on the full database, with uncertainty estimates as in work by Brohan et al. [2006], along with series based on the two sets of locations in Figure 1d. The subsampled series, despite being based on essentially independent data, lie well within the uncertainty estimates since 1900, and are usually within the uncertainty estimates even in the sparsely sampled 19th century, confirming the robustness of all the series. Not only do these analyses use completely different stations, but any adjustments applied are also independent owing to the distances between the stations that contributed to the two sets of 5 5 areas. In essence, the independence of the station data in the subsampled 5 5 areas cannot be compromised by the homogeneity adjustments reported in earlier papers (see sources given by Jones et al. [1986a, 1986b]), or through the inclusion of many additional adjusted data sets by Jones and Moberg [2003]. This is because adjustments were made to only a limited number of stations ( 20%), and almost all of these adjustments will have been based on stations within the same or surrounding 5 5 areas, not on remoter stations. Furthermore the sum total of the adjustments has a near zero effect on large-scale temperature averages [see Brohan et al., 2006, Figure 4]. [4] The spatial coherence of mapped temperature trends, transcending international borders as illustrated for example in Figures 3.9 and 3.10 of Trenberth et al. [2007], suggests strongly that recent global and regional trends are not severely affected by national biases or incomplete coverage. The latter inference can also be drawn from the relatively small numbers of spatial degrees of freedom estimated by Jones et al. [1997]. Brohan et al. [2006] estimated global and hemispheric incomplete-coverage errors by subsampling complete reanalysis fields; since the mid-20th century the 95% confidence range for decadally smoothed global land surface air temperature anomalies has been about 0.25 C and this is mainly due to incomplete-coverage error [Brohan et al., 2006, Figure 12]. However, the robustness of estimated trends for earlier periods and smaller regions is JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 114, D05104, doi:10.1029/2008JD010450, 2009 Click Here for Full Article

Detecting urbanization effects on surface and subsurface thermal environment — A case study of Osaka

Tremendous efforts have been devoted to improve our understanding of the anthropogenic effects on the atmospheric temperature change. In comparison, little has been done in the study of the human impacts on the subsurface thermal environment. The objective of this study is to analyze surface air temperature records and borehole subsurface temperature records for a better understanding of the urban heat island effects across the ground surface. The annual surface air temperature time series from six meteorological stations and six deep borehole temperature profiles of high qualities show that Osaka has been undergoing excess warming since late 19th century. The mean warming rate in Osaka surface air temperature is about 2.0 °C/100a over the period from 1883 to 2006, at least half of which can be attributed to the urban heat island effects. However, this surface air temperature warming is not as strong as the ground warming recorded in the subsurface temperature profiles. The surface temperature anomaly from the Osaka meteorological record can only account for part of the temperature anomaly recorded in the borehole temperature profiles. Surface air temperature is conventionally measured around 1.5 m above the ground; whereas borehole temperatures are measured from rocks in the subsurface. Heat conduction in the subsurface is much less efficient than the heat convection of the air above the ground surface. Therefore, the anthropogenic thermal impacts on the subsurface can be more persistent and profound than the impacts on the atmosphere. This study suggests that the surface air temperature records alone might underestimate the full extent of urban heat island effects on the subsurface environment.

A universal model to characterize different multi-fractal behaviors of daily temperature records over China

The multi-fractal properties of surface air temperature over China are studied through Multi-fractal detrended fluctuation analysis (MF-DFA). It is shown that there indeed exists the multi-fractal phenomenon in daily surface air temperature time series, reflecting a great deal of fluctuations at various time scales. The multi-fractal properties can be characterized very well by a universal generalized binomial multiplicative cascade model with only two parameters a and b . For different stations, the width of singularity spectrum f ( α ) is different, indicating different strengths of temperature multi-fractal behavior from station to station.

Exceptional European warmth of autumn 2006 and winter 2007: Historical context, the underlying dynamics, and its phenological impacts

Updated European averaged autumn and winter surface air temperature (SAT) timeseries indicate that the autumn 2006 and winter 2007 were extremely likely (>95%) the warmest for more than 500 years. In both seasons, the European SAT anomaly is widespread with anomalies up to three standard deviations from normal. The anomalous warmth is associated with strong anticyclonic conditions and warm air advection from south west. Phenological impacts related to this warmth included some plant species having a partial second flowering or extended flowering till the beginning of winter. Species that typically flower in early spring were found to have a distinct earlier flowering after winter 2007.

Five centuries of climate change in Australia: the view from underground

AbstractFifty‐seven borehole temperature profiles from across Australia are analysed to reconstruct a ground surface temperature history for the past five centuries. The five‐hundred‐year reconstruction is characterised by a temperature increase of approximately 0.5 K, with most of the warming occurring in the 19th and 20th centuries. The 17th century was the coolest interval of the five‐century reconstruction. Comparison of the geothermal reconstruction to the Australian annual surface air temperature time series in their period of overlap shows excellent agreement. The full geothermal reconstruction also agrees well with the low‐frequency component of dendroclimatic reconstructions from Tasmania and New Zealand. The warming of Australia over the past five centuries is only about half that experienced by the continents of the Northern Hemisphere in the same time interval. Copyright © 2006 John Wiley & Sons, Ltd.

Urban heat island effect on annual mean temperature during the last 50 years in China

Based on China’s fifth population survey (2000) data and homogenized annual mean surface air temperature data, the urban heat island (UHI) effect on the warming during the last 50 years in China was analyzed in this study. In most cities with population over 104, where there are national reference stations and principal stations, most of the temperature series are inevitably affected by the UHI effect. To detect the UHI effect, the annual mean surface air temperature (SAT) time series were firstly classified into 5 subregions by using Rotated Principal Components Analysis (RPCA) according to its high and low frequency climatic change features. Then the average UHI effect on each subregion’s regional annual mean STA was studied. Results indicate that the UHI effect on the annual mean temperatures includes three aspects: increase of the average values, decrease of variances and change of the climatic trends. The effect on the climatic trends is different from region to region. In the Yangtze River Valley and South China, the UHI effect enhances the warming trends by about 0.011 °C/decade. In the other areas, such as Northeast, North-China, and Northwest, UHI has little impact on the warming trends of the regional annual temperature; while in the Southwest of China, introducing UHI stations slows down the warming trend by −0.006 °C/decade. But no matter what subregion it is, the total warming/cooling of these effects is much smaller than the background change in regional temperature. The average UHI effect for the entire country, during the last 50 years is less than 0.06 °C, which agrees well with the IPCC (2001). This suggests that we cannot conclude that urbanization during the last 50 years has had much obvious effect on the observed warming in China.

FICKIAN DIFFUSION AND NEWTONIAN COOLING: A CONCEPT FOR NOISE INDUCED CLIMATE VARIABILITY WITH LONG-TERM MEMORY?

Observed near surface air and soil temperature time series reveal a long-term memory, which is associated with a power-law scaling of the frequency spectra, S(ω) ~ ω- β with β ~ 0.6, lying between white and flicker noise, 0 < β < 1. As this power law scaling is not consistent with the Brownian motion concept of climate variability, Fickian diffusion is added to a Newtonian cooling relaxation to provide a more suitable analog of climatic fluctuations: (i) Diffusive plus random heat fluxes parametrise the turbulent mixing by synoptic scale eddy life cycles, affect tropospheric and near surface temperatures and excite a long-term memory regime with a β ~ 0.5 scaling. (ii) Newtonian cooling describes the near surface temperatures relaxing towards a global mean deep soil temperature and stabilises the system to a white noise response at very low frequencies. The long-term memory regime emerges from the high frequency scaling (β ~ 1.5), once temperatures become correlated in space due to diffusion, so that spatially averaged fluctuations correlate for times beyond the diffusion time scale. The long-term memory regime disappears into a white noise plateau (β ~ 0), when low frequencies exceed the damping time scale of Newtonian cooling. This system may be interpreted as a diffusive system relaxing towards the deep soil restoration temperature with an almost infinitely large time scale.

A Statistical Analysis of the North Atlantic Oscillation and its Impact on European Temperature

In this study the behaviour of the North Atlantic Oscillation (NAO) and its impact on the surface air temperature in Europe 1891-1990 is analysed using statistical time series analysis techniques. For this purpose, both the NAO index (NAOI) and the surface air temperature time series from 41 European stations are split up into typical variation components. Various measures of correlation indicate that the NAOI-temperature relationships are approximately linear and most pronounced in winter. The spatial correlation patterns show a correlation decrease from North West to South East (winter) exceeding correlation coefficients of 0.6 in the Scotland-South Norwegian area. In summer, these correlations are very weak, in spring and autumn stronger but smaller than in winter. These correlations change significantly in time indicating increasing correlations in Central and North Europe and decreasing correlations in the North West. Low-frequent episodic components represented by related polynomials of different or...

Evidence of climatic warming in the southern Urals region derived from borehole temperatures and meteorological data

Thirty borehole temperature–depth profiles in the central and southern Urals, Russia were scrutinized for evidence of ground surface temperature histories. We explored two inversion schemes: a simple ramp inversion in which solutions are parameterized in terms of an onset time and magnitude of change and a more sophisticated functional space inverse algorithm in which the functional form of the solution is left unspecified. To enhance and potentially identify latitudinal differences in the ground surface temperature signal, we subdivided the data into three groups based on geographic proximity and simultaneously inverted the borehole temperature–depth logs. The simultaneous inversions highlighted 13 temperature–depth logs that could not both fit a common ground surface temperature history and a priori models within reasonable bounds. Our results confirm that this is an effective way to reduce site-specific noise from an ensemble of boreholes. Each inversion scheme gives comparable results indicating locally variable warming on the order of 1°C starting between 1800 and 1900 AD. Similarly surface air temperature records from 12 nearby meteorological stations exhibit locally variable warming also on the order of 1°C of warming during the 20th century. To explore the degree to which borehole temperatures and surface air temperature (SAT) time series are responding to the same signal, we average the SAT data into the same three groups and used these averages as a forcing function at the Earth's surface to generate synthetic transient temperature profiles. Root mean square (RMS) misfits between these synthetic temperature profiles and averaged temperature–depth profiles are low, suggesting that first-order curvature in borehole temperatures and variations in SAT records are correlated.

Wavelet Analysis of Nonstationary and Chaotic Time Series with an Application to the Climate Change Problem

—Our aim here is to show merits of the so-called wavelet transform of time series as an analyzing tool of the simultaneously nonstationary and chaotic processes that usually appear in the Earth sciences. The merits are illustrated on some surrogate time series as well as the natural ones that are observed in the present-day climate change problem. As a result of a wavelet transform of the natural hemispheric averaged surface air temperature time series a crossover scale is recognized that cuts off the intra- and interdecadal temperature oscillations, which are obviously internally induced, from a secular trend-like component of unknown origin.

Multiscale Oscillations of the Global Climate System as Revealed by Wavelet Transform of Observational Data Time Series

The surface air temperature time series of both hemispheres and the North Atlantic European area as well as the Southern Oscillation (SO) index time series were analysed using a wavelet transform technique. The values of the so-called singularity exponents of these series were estimated and compared with such estimations for some surrogate time series artificially created from the observed temperature series. It was concluded that the climate dynamics on interannual and interdecadal scales may be considered as a kind of classical Brownian motion although its consideration as a flicker-noise is also possible. The extracted temperature variations were shown to be closely coupled with the SO process. The wavelet-transformed SO series reveals itself as a whole self-similar “tree” the main branches of which are the appearances of the strongest El-Ninos of 1898 – 1899, 1941 – 1942, and 1982 – 1983. Similar “trees” can be seen in the wavelet-transformed temperature series. Thus, the extracted temperature variations were shown to be closely coupled with the SO process, and a decomposition of the current global climate dynamics into three climatic epochs (of about 40-year long) seems to be appropriate.

Comparisons of borehole temperature-depth profiles and surface air temperatures in the northern plains of the USA

SUMMARY Temperature‐depth profiles measured in boreholes contain a record of temperature changes at the Earth’s surface. The degree to which these profiles and surface air temperature records track each other is quantitatively assessed for the northern plains of the USA. Surface air temperature records are used as a forcing function to generate synthetic transient temperature profiles which are compared with transient temperatures derived from borehole temperature‐depth data. These comparisons indicate that surface air and ground temperatures are correlated. Furthermore, these comparisons yield a long-term mean temperature tied to the meteorological record which provides a context for interpreting contemporary warming trends. Our results indicate that warming recorded in surface air temperature time series represents a positive departure above baseline temperature estimates.

Global rural temperature trends

Using rural/urban land surface classifications derived from maps and satellite observed nighttime surface lights, global mean land surface air temperature time series were created using data from all weather observing stations in a global temperature data base and from rural stations only. The global rural temperature time series and trends are very similar to those derived from the full data set. Therefore, the well‐known global temperature time series from in situ stations is not significantly impacted by urban warming.

Climate Dynamics as a Nonlinear Brownian Motion

Based on the heat balance equation of the global climate system the well-known surface air temperature time series of the Northern and Southern hemispheres were analyzed as realizations of a fractional Brownian motion. The technique of the so-called wavelet transform was used for this purpose. The technique easily admits splitting time series of interest to statistically stationary oscillations and a trend. Such temperature oscillations were extracted which include within themselves almost all differences between both hemispheric time series. As a result of subtraction of the oscillations from the primary hemispheric series a residual trend-like component was evaluated. The latter evidences a single warming trend of the global climate system that was started from the early 20th century.

Climate Change in the Urals, Russia, Inferred from Borehole Temperature Data

Borehole temperatures in the central and south Urals were analysed for the past ground surface temperature (GST) signal. 31 highquality temperature logs were selected for this purpose and inverted with algorithms based on the generalised least squares theory. The signal to noise ratio was improved by averaging the results of individual borehole inversions. No distinct regional trends were found in the studied region except for some indications of more pronounced warming in the south. The mean GST history (GSTH) was characterised by cooling down to −0.6 °C in the 18th century and subsequent warming to 0.5 °C above the longterm mean at the beginning of this century, and to 1 – 1.5 °C by 1980. The stability of the mean GSTH was tested in dependence on the number of holes used for the averaging. It showed that any subset of 15 holes yielded a GSTH similar to that obtained from the whole set. A surface air temperature (SAT) time series comprising the period 1832 – 1989 was combined from 17 meteorological records. Its least squares warming rate of 1.1 °C per 100 years is somewhat higher than that of the GST (0.7 – 0.8°C/100 years) in the same period.

Global Mean Sea Level: Indicator of Climate Change?

A critical discussion is presented on the use by Etkins and Epstein (1982) of combined surface air temperature and sea level time series to draw conclusions concerning the discharge of the polar ice sheets. It is objected by Robock that they used Northern Hemisphere land surface air temperature records which are unrepresentative of global sea surface temperature, and he suggests that externally imposed volcanic dust and CO2 forcings can adequately account for observed temperature changes over the last century, with global sea level changing in passive response to sea change as a result of thermal expansion. Hansen et al. adduce evidence for global cooling due to ice discharge that has not exceeded a few hundredths of a degree centigrade in the last century, precluding any importance of this phenomenon in the interpretation of global mean temperature trends for this period. Etkins and Epstein reply that since their 1982 report additional evidence has emerged for the hypothesis that the polar ice caps are diminishing. It is reasserted that each of the indices discussed, including global mean sea surface temperature and sea level, polar ice sheet mass balance, water mass characteristics, and the spin rate and axis of rotation displacement of the earth, are physically linked and can be systematically monitored, as is currently being planned under the auspices of the National Climate Program.

Global Mean Sea Level: Indicator of Climate Change?

A critical discussion is presented on the use by Etkins and Epstein (1982) of combined surface air temperature and sea level time series to draw conclusions concerning the discharge of the polar ice sheets. It is objected by Robock that they used Northern Hemisphere land surface air temperature records which are unrepresentative of global sea surface temperature, and he suggests that externally imposed volcanic dust and CO2 forcings can adequately account for observed temperature changes over the last century, with global sea level changing in passive response to sea change as a result of thermal expansion. Hansen et al. adduce evidence for global cooling due to ice discharge that has not exceeded a few hundredths of a degree centigrade in the last century, precluding any importance of this phenomenon in the interpretation of global mean temperature trends for this period. Etkins and Epstein reply that since their 1982 report additional evidence has emerged for the hypothesis that the polar ice caps are diminishing. It is reasserted that each of the indices discussed, including global mean sea surface temperature and sea level, polar ice sheet mass balance, water mass characteristics, and the spin rate and axis of rotation displacement of the earth, are physically linked and can be systematically monitored, as is currently being planned under the auspices of the National Climate Program.