2004

[Bartlett et al. 2004]
Abstract:Borehole temperature-depth profiles contain a record of surface ground temperature (SGT) changes with time and complement surface air temperature (SAT) analysis to infer climate change over multiple centuries. Ground temperatures are generally warmer than air temperatures due to solar radiation effects in the summer and the insulating effect of snow cover during the winter. The low thermal diffusivity of snow damps surface temperature variations; snow effectively acts as an insulator of the ground during the coldest part of the year. A numerical model of snow-ground thermal interactions is developed to investigate the effect of seasonal snow cover on annual ground temperatures. The model is parameterized in terms of three snow event parameters: onset time of the annual snow event, duration of the event, and depth of snow during the event. These parameters are commonly available from meteorological and remotely sensed data making the model broadly applicable. The model is validated using SAT, subsurface temperature from a depth of 10 cm, and snow depth data from the 6 years of observations at Emigrant Pass climate observatory in northwestern Utah and 217 station years of National Weather Service data from sites across North America. Measured subsurface temperature-time series are compared to changes predicted by the model. The model consistently predicts ground temperature changes that compare well with those observed. Sensitivity analysis of the model leads to a nonlinear relationship between the three snow event parameters (onset, duration, and depth of the annual snow event) and the influence snow has on mean annual SGT.
Borehole temperatures, influece of snow cover
[Barring and von Storch 2004]
We study the history of storminess in Northern Europe, as derived from local pressure observations in Lund since 1780 and Stockholm since 1820 (Sweden). At both stations barometer readings were made three times per day, morning, midday and evening, and after about 1850 at fixed observation hours. We use four common storminess indices: annual number of deep lows (p<980 hPa), the annual 95th and 99th percentile of pressure changes between two observations, and the annual number of fast absolute pressure changes (|ûp|/ût > 16 hPa/12 h). It turns out that the 1980 s mid 1990 s were a period of enhanced storminess, mainly seen in the Stockholm record, but his period is within the natural variability of the records. Thus, there are no robust signs of any long-term trend in the storminess indices. Storminess is during the entire historical period remarkably stable, with no systematic change and little transient variability.
Paleoclimate, storminess.
[Beltrami and Bourlon 2004]
Inversion of borehole temperaturees for the NH. Use gridding and appropriate approach. Warming has been of at least 1K. They derive 50 yr trends. Most of 1K warming in the last 50 years. Nice methodological description. Also in [Nitoiu and Beltrami 2005]
Paleoclimate, borehole reconstructions, NH temperature, proxies.
[Bense and Kooi 2004]
In the present paper it is shown how profiles consisting of closely spaced ( 10 m) temperature measurements at shallow depth, obtained at several instances during one season, provide a detailed record of lateral variations in vertical groundwater flow. This is illustrated by a field study around the Peel Boundary Fault zone that cuts through the unconsolidated, siliciclastic deposits that occur in the southeastern part of Netherlands. This regionally important fault forms at many locations a strong barrier to horizontal groundwater flow and therefore induces complex groundwater flow patterns. Temperature anomalies (over 2olsiC) are observed over short distances. These anomalies reverse over the season. Numerical modeling of coupled groundwater flow and heat transport demonstrates how the temporal and spatial variations of subsurface temperature are the result of the interaction between seasonal fluctuations in surface temperature and spatial variations in groundwater flow. In addition to the horizontal profiles, temperature-depth profiles obtained in groundwater observation wells were used to constrain the larger-scale characteristics of the groundwater flow system. In order to simulate the observed geothermal patterns it appeared to be essential to account for the long-term changes in surface temperature. Although groundwater temperature data are commonly used to constrain groundwater flow fields on regional scale or to calculate vertical groundwater velocities at point locations beneath small streams, the present study is one of the first to integrate these different scales and incorporate the impact of recent climate change.
Paleoclimate, borehole reconstructions,hidrology influence, NH temperature, proxies.
[Betts et al. 2004]
A suite of simulations with the HadCM3LC coupled climate-carbon cycle model is used to examine the various forcings and feedbacks involved in the simulated precipitation decrease and forest dieback. Rising atmospheric CO2 is found to contribute 20through the physiological forcing of stomatal closure, with 80excluded and only radiative forcing by CO2 was included. The forest dieback exerts two positive feedbacks on the precipitation reduction; a biogeophysical feedback through reduced forest cover suppressing local evaporative water recycling, and a biogeochemical feedback through the release of CO2 contributing to an accelerated global warming. The precipitation reduction is enhanced by 20biogeophysical feedback, and 5from the forest dieback. This analysis helps to explain why the Amazonian precipitation reduction simulated by HadCM3LC is more extreme than that simulated in other GCMs; in the fully-coupled, climate-carbon cycle simulation, approximately half of the precipitation reduction in Amazonia is attributable to a combination of physiological forcing and biogeophysical and global carbon cycle feedbacks, which are generally not included in other GCM simulations of future climate change. The analysis also demonstrates the potential contribution of regional-scale climate and ecosystem change to uncertainties in global CO2 and climate change projections. Moreover, the importance of feedbacks suggests that a human-induced increase in forest vulnerability to climate change may have implications for regional and global scale climate sensitivity.
Vegetation model, climate vegetation feedbacks, Amazonian forest
[Brandefelt and Kallén 2004]
Response of AAO and SH dynamics/cyclones in ECHAM4/opyc scenario simulations.
Scenario Simulations, AAO climate change, ECHAM4/OPYC3.
[Briffa et al. 2004]
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).
NH land temperature reconstructions, tree ring
[Burns et al. 2002]
Meteorological records of monsoon rainfall in the Indian Ocean are generally less than 100 years long. The relative brevity of these records makes it difficult to investigate monsoon variation on decadal and centennial timescales, to determine what factors influence the intensity of rainfall on these timescales, or to place possible changes in the twentieth century into a broader historical context. Development of a geologic proxy for rainfall that records annual variation in the monsoon over much longer time periods than are covered by instrumental records would be a significant step forward. We have developed an annually resolved record of monsoon rainfall variation for the past 780 years based on annual layer thickness and stable isotope analyses of a laminated stalagmite from southern Arabia. Our results show that monsoon variation over the past century is not outside of the range of the past 800 years. Decreasing monsoon rainfall over the past century is related to increasing sea surface temperature in the Indian Ocean. Spectral analyses of the record are dominated by cycles that are similar to those observed in records of solar activity on centurial timescales. Decadal to interannual cycles in the record appear to originate in the tropical Pacific Ocean.
Paleoclimate reconstructions, speleothems, monsoon, coral
[Caussinus and Mestre 2004]
ABSTRACT: Many long instrumental climate records are available and might provide useful infor- mation in climate research.These series are usually affected by artificial shifts, due to changes in the conditions of measurement and various kinds of spurious data. A comparison with surround- ing weather-stations by means of a suitable two-factor model allows us to check the reliability of the series. An adapted penalized log-likelihood procedure is used to detect an unknown number of breaks and outliers. An example concerning temperature series from France confirms that a systematic comparison of the series together is valuable and allows us to correct the data even when no reliable series can be taken as a reference.
Homogeneity, pairwise, penalized log likelihood procedure.
[Celik 2004]
ABSTRACT: Probability density functions,such as the Weibull and Rayleigh,are often used in wind speed and wind energy analyses.It is important to establish the goodness of their suitability in modelling a particular measured distribution. The parameters obtained from the distributions (distributional parameters)are required to assess the suitability of the functions.Such distributional parameters that are commonly used are the following:the parameters of the function itself (such as the parameters of the Weibull function),the wind energy output and the correlation coe cient of the probability density distributions.It is shown in the present article that these parameters alone are not su cient to determine the suitability of a given function. Additional parameters are required to have a complete statistical assessment of the function,such as the standard deviation or, alternatively,the correlation coe cient of the power density distributions.In the present study, the suitability of the Weibull and Rayleigh functions is assessed based on a total of six parameters ( of the probability density and power density distributions),calculated from 12 months of hourly time series wind speed data.It is shown that the degree of suitability of a given function changes to a great extent with the parameter on which the judgement is based.
Wind Energy, weibull, wind power.
[Chapman et al. 2004]
Comment to [Mann and Schmidt 2003].
Paleoclimate, temperature reconstructions, borehole reconstructions.
[Chuine et al. 2004]
French records of grape harvest dates are used to reconstruct spring-summer temperatures from 1370 to 2003 using a process based phenology model developed from the Pinot Noir grape. Summer 2003 is the most extreme.
Paleoclimate, temperature reconstructions, borehole reconstructions, Grape harvest.
[Cook et al. 2004]
The Northern Hemisphere (NH) temperature reconstruction published by Esper, Cook, and Schweingruber (ECS) in 2002 is revisited in order to strengthen and clarify its interpretation. This reconstruction, based on tree-ring data from 14 temperaturesensitive sites, is best interpreted as a land-only, extra-tropical expression of NH temperature variability. Its strongly expressed multi-centennial variability is highly robust over the AD 1200 1950 interval, with strongly expressed periods of Little Ice Age cooling indicated prior to AD 1900. Persistently above-average temperatures in the AD 960 1050 interval also suggest the largescale occurrence of a Medieval Warm Period in the NH extra-tropics. However, declining site availability and low withinchronology tree-ring replication prior to AD 1200 weakens this interpretation considerably. The temperature signal in the ECS reconstruction is shown to be restricted to periods longer than 20 years in duration. After recalibration to take this property into account, annual temperatures up to AD 2000 over extra-tropical NH land areas have probably exceeded by about 0.3 1C the warmest previous interval over the past 1162 years. This estimate is based on comparing instrumental temperature data available up to AD 2000 with the reconstruction that ends in AD 1992 and does not take into account the mutual uncertainties in those data sets.
NH land temperature reconstruction
[Cox et al. 2004]
The first GCM climate change projections to include dynamic vegetation and an interactive carbon cycle produced a very significant amplification of global warming over the 21st century. Under the IS92a business as usual emissions scenario CO2 concentrations reached about 980 ppmv by 2100, which is about 280 ppmv higher than when these feedbacks were ignored. The major contribution to the increased CO2 arose from reductions in soil carbon because global warming is assumed to accelerate respiration. However, there was also a lesser contribution from an alarming loss of the Amazonian rainforest. This paper describes the phenomenon of Amazonian forest dieback under elevated CO2 in the Hadley Centre climate-carbon cycle model.
Vegetation model, climate vegetation feedbacks, Amazonian forest
[Felis et al. 2004]
The last interglacial period (about 125,000 years ago) is thought to have been at least as warm as the present climate1. Owing to changes in the Earth s orbit around the Sun, it is thought that insolation in the Northern Hemisphere varied more strongly than today on seasonal timescales2, which would have led to corresponding changes in the seasonal temperature cycle3. Here we present seasonally resolved proxy records using corals from the northernmost Red Sea, which record climate during the last interglacial period, the late Holocene epoch and the present. We find an increased seasonality in the temperature recorded in the last interglacial coral. Today, climate in the northern Red Sea is sensitive to the North Atlantic Oscillation4,5, a climate oscillation that strongly influences winter temperatures and precipitation in the North Atlantic region. From our coral records and simulations with a coupled atmosphere ocean circulation model, we conclude that a tendency towards the high-index state of the North Atlantic Oscillation during the last interglacial period, which is consistent with European proxy records6 8, contributed to the larger amplitude of the seasonal cycle in the Middle East.
Coral records Holocene, Last Interglacial, ECHO-G, asynchronous coupling.
[Ferguson and Woodbury 2004]
Influence of urban environment and buildings on the subsurface temperatures. Focus on Winnipeg area. Heat loss from buildings in addition to ohter lesser sources of increased heat flow to the subsurface, such as changes in the surface cover and cliamte change do the the urban heat island effect, make subsurface temperatures in urban areas higher than surrounding rural areas.
Paleoclimate, urban climate, temperature reconstructions, borehole reconstructions.
[Fleitmann et al. 2004]
High-resolution stable isotope pro les of three contemporaneously deposited stalagmites from a shallow cave in Southern Oman provide an annually resolved record of Indian Ocean monsoon rainfall variability for the past 780 years.Uranium-series age dating and counts of annual growth bands enable an excellent age calibration.Although modern speleothems do not grow in perfect isotopic equilibrium,oxygen isotope ratios (d 18 O)are a proxy for the amount of monsoon rainfall.This is supported by the statistically signi cant correlation between d 18 O and the thickness of annual bands,whereas d 18 O is inversely correlated with annual band thickness.Additionally,overlapping d 18 O pro les are very similar in pattern and range,indicating that sample speci c noise did not blur the climatic signal.The longest oxygen isotope pro le,derived from stalagmite S3,clearly shows the transition at B AD from a generally wetter Medieval Warm Period to a drier Little Ice Age that lasted from approximately AD 1320 1660 in Southern Oman.The decrease in monsoon rainfall since the 1960s is also obvious in meteorological records from Northern Africa and India,indicatingthat our speleothem-based rainfall records do not only re ect local monsoon rainfall variability.
Paleoclimate, speleothems, proxy reconstructions, coral, Monsoon.
[Foukal et al. 2004]
Variations of solar irradiance as in [Lean et al. 1995] are unlikely. The authors mostly come with a battery of arguments (past publications) against the feasibility of such reconstructions of multi decadal/centennial solar irradiance. Complementary to [Lean et al. 2002]
Paleoclimate, temperature reconstructions over europe, documentary data.
[Goodwin et al. 2004]
Abstract Mid-latitude winter atmospheric variability in the South Indian Ocean and southwest Pacific Ocean regions of the circum-Antarctic are reconstructed using sea-salt aerosol concentrations measured in the high resolution Law Dome (DSS) ice core from East Antarctica. The sea-salt aerosol concentration data, as sodium (Na), were measured at approximately monthly resolution spanning the past 700 years. Analyses of covariations between Na concentrations in Law Dome ice, and mean sea-level pressure (MSLP) and wind field data were conducted to define the mid-latitude and sub- Antarctic atmospheric circulation patterns associated with variations in Na delivery. High Na concentrations in Law Dome snow are associated with increased meridional aerosol transport from mid-latitude sources. The seasonal average Na concentration for early winter (May, June, July (MJJ)) is strongly correlated to the mid-latitude MSLP field in the South Indian and southwest Pacific Oceans, and southern Australian regions. In addition, the average MJJ Na concentrations display a strong association with the stationary Rossby wave number 3 circulation, and are anti-correlated to the Southern Annular Mode (SAM) index of climate variability: high (low) Na concentrations occurring during negative (positive) SAM phases. This observed relationship is used to derive a proxy record for earlywinter MSLP anomalies and the SAM in the South Indian and southwest Pacific Ocean regions over the period 1300 1995 AD. The proxy SAM index from 1300 to 1995 AD shows pronounced decadal-scale variability throughout. The period after 1500 AD is marked by a tendency toward slower variations and a weakly-positive mean SAM (enhanced westerlies in the 50 to 65S zone) compared to the early part of the record
Paleoclimate, temperature reconstructions over europe, documentary data.
[Gutierrez et al. 2005b]
Downscaling method for short term forecast using a clustering technique: weighting clustering downscaling method. They use it for precipitation and extreme wind on 98 stations on the Iberian Peninsula. Similar in concept to cart analysis.
Downscaling, som, analogs, seasonal predictions
[Hasanean 2004]
ABSTRACT: Mean wintertime temperatures (December, January, February) recorded during the period 1905 2000 at 18 weather stations distributed across Egypt were analysed to reveal spatial and temporal patterns of long-term trends. The relationship between winter atmospheric circulation indices and winter temperature in Egypt is examined using correlation analysis. The atmospheric circulation is represented by four indices: the well-known El Ni Ü no southern oscillation (ENSO), North Atlantic oscillation (NAO) index, East Atlantic West Russia (EAWR) index, and East Atlantic (EA) index. Surface temperature is a stable climatic element whose coefficient of variation (COV) is lower during winter. A statistically significant relation between COV and latitude indicates that stations in the south, Upper Egypt, are more variable than stations in the north, Lower Egypt. Increasing and decreasing winter surface temperature trends were found. In general, wintertime temperature has increased (warming) at most stations. Decreasing trends (cooling) are observed mainly over Upper Egypt. The upward trends in mean winter temperature during the 1910s 30s, mid 1970s, and early 1980s 2000 and the downward trends during the 1940s and 1960s are prominent features of the temporal distributions. The warming period that occurred early in the century may be explained by changes in circulation. Striking upward trends are most remarkable during the last 20 years. This could be attributed not only to human activities, but also to atmospheric circulation changes. No detectable connection between Egypt temperature and either ENSO or EA index was found during winter. A statistically significant negative relationship between winter temperature and winter NAO index can be observed. The NAO index is more dominant in determining winter temperature than ENSO circulation. A significantly stronger negative relationship between temperature over Egypt and the winter EAWR index values is detected. Copyright Ù2004 Royal Meteorological Society.
Winter temperature, Egipt
[Huang 2004]
Uses bayesian inversion method to produce an integrated reconstruction since 1500 AD in which as a priori hypothesis introduces the observations (20th century) and MBH99 reconstruction. What he inverts is the forward analytical solution of the borehole only reconstruction for the NH. The reconstructed Sat agrees well with estimates of joint forcing effects (solar and greenhouse gases, also volcanic) and allows for an estimation of climate sensitivity which places in the range of 0.4 to 0.7.
Paleoclimate, temperature reconstructions, borehole, multi proxy, climate change, climate sensitivity.
[Huth 2004]
Comparison of temeprature change estimates with the canadian model for central Europe using different methods (linear) and predictors. There is sensitivity to the choice of the method and to the set of predictors. Thermal are needed. SLP not enough. A good performance of a downsscaling model on the present climate conditions does notimply its applicability to climate change studies, mainly because climate change proceeds on muchlarger time scales than to which the downscaling model is fitted. The performance on observations cannot remain the only criterion of the quality of a model.
Statistical downscaling, daily temperature, central europe, cca, linear methods, cccm.
[Hu and Wu 2004]
Analisis of NAO response in echam4 scenario simulation. Propose modified nao index to account for northeastward movement of NAO center.s
NAO, echam4 scenario simulations, nao index.
[Jones and Mann 2004]
We review evidence for climate change over the past several millennia from instrumental and high-resolution climate ‘‘proxy’’ data sources and climate modeling studies. We focus on changes over the past 1 to 2 millennia. We assess reconstructions and modeling studies analyzing a number of different climate fields, including atmospheric circulation diagnostics, precipitation, and drought. We devote particular attention to proxy-based reconstructions of temperature patterns in past centuries, which place recent large-scale warming in an appropriate longer-term context. Our assessment affirms the conclusion that late 20th century warmth is unprecedented at hemispheric and, likely, global scales. There is more tentative evidence that particular modes of climate variability, such as the El Nino/Southern Oscillation and the North Atlantic Oscillation, may have exhibited late 20th century behavior that is anomalous in a long-term context. Regional conclusions, particularly for the Southern Hemisphere and parts of the tropics where high- resolution proxy data are sparse, are more circumspect. The dramatic differences between regional and hemispheric/ global past trends, and the distinction between changes in surface temperature and precipitation/drought fields, underscore the limited utility in the use of terms such as the Little Ice Age and Medieval Warm Period for describing past climate epochs during the last millennium. Comparison of empirical evidence with proxy-based reconstructions demonstrates that natural factors appear to explain relatively well the major surface temperature changes of the past millennium through the 19th century (including hemispheric means and some spatial patterns). Only anthropogenic forcing of climate, however, can explain the recent anomalous warming in the late 20th century.
AAO index, zonal circulation, climate reconstructions.
[Jones and Widmann 2004]
Reconstructions of the AAOIndex, indicate in comparison with reanalysis that the present AAO positive trend is not unprecedent but also similar values were attained around 1960 after a period of 20 years of positive trend. Thus, at the time no stratospheric ozone depletion, no GHGases could have produced such similar shift.
AAO index, zonal circulation, climate reconstructions.
[Kilbourne et al. 2004a]
Coral skeletal geochemistry offers the potential to reconstruct the sea surface salinity (SSS) history of the tropical oceans on seasonal to interannual and perhaps centennial timescales because of the strong link between variation in SSS and seawater d 18 O in tropical regions. We explore this potential using a monthly resolved, 65-year record of skeletal d 18 O and Sr/Ca variations in a Porites coral from Espiritu Santo, Vanuatu. We demonstrate that El Nino Southern Oscillation related climate variability strongly influences coral d 18 O at Santo through local salinity changes associated with the position of the South Pacific Convergence Zone and the movement of its associated salinity front. Such a demonstration provides the ground truth data that can be used to place paleoclimate variability estimated using existing fossil coral records from this region into a modern conceptual framework. We also evaluate different methods of combining coral d 18 O and Sr/Ca to reconstruct SSS and conclude that the coral d 18 O anomaly time series provides the best fit to recent in situ SSS data at Santo.
Paleoclimate reconstructions, coral.
[Kilbourne et al. 2004b]
The nature of tropical climate variability 350 ka is addressed usingd18 O and Sr/Ca records from a modern and a fossil coral from Vanuatu (southwestern tropical Pacific Ocean). Modern El Nin Ü o events at Vanuatu produce positive coral d 18 O and Sr/Ca anomalies; similar anomalies observed in the fossil coral records suggest that El NinÜo was operative 350 kyr ago. Seasonal variations in coral Sr/Ca, a sea surface temperature (SST) proxy, have the same amplitude in both corals, whereas seasonal d 18 O variations are smaller in the fossil coral than in the modern coral. This is consistent with displacement of the South Pacific Convergence Zone toward the southwest during the boreal summer 350 ka. Mathematical modeling results preclude warmer SST and higher SSS at Vanuatu during this time, but permit the surface ocean to be 2 cooler and 0 2 psu fresher than today. Assessing the potential of variations in late Quaternary seawater Sr/Ca remains the largest obstacle to accurately reconstructing tropical SST using pristine fossil corals.
Paleoclimate reconstructions, coral.
[Laskar et al. 2004]
Abstract. We present here a new solution for the astronomical computation of the insolation quantities on Earth spanning from -250 Myr to 250 Myr. This solution has been improved with respect to La93 (Laskar et al, 1993) by using a direct integration of the gravitational equations for the orbital motion, and by improving the dissipative contributions, in particular in the evolution of the Earth-Moon System. The orbital solution has been used for the calibration of the Neogene period (Lourens et al., 2004), and is expected to be used for age calibrations of paleoclimatic data over 40 to 50 Myr, eventually over the full Palaeogene period (65 Myr) with caution. Beyond this time span, the chaotic evolution of the orbits prevents a precise determination of the Earth motion. However, the most regular components of the orbital solution could still be used over a much longer time span, which is why we provide here the solution over 250 Myr. Over this time interval, the most striking feature of the obliquity solution, apart from a secular global increase due to tidal dissipation, is a strong decrease of about 0.38 degree in the next few millions of years, due to the crossing of the s6 + g5 g6 resonance (Laskar et al, 1993). For the calibration of the Mesozoic time scale (about 65 to 250 Myr), we propose to use the term of largest amplitude in the eccentricity, related to g2 g5, with a fixed frequency of 3.200 /yr, corresponding to a period of 405000 yr. The uncertainty of this time scale over 100 Myr should be about 0.1
Paleoclimate, orbital changes.
[Lavallée and Beltrami 2004]
Adjust stochastic process to four tree ring chronologies. The model that best fits to the pdf among Gauss, Levy and Cauchy is the Levy law. Potentiall usefulness to compare in climate change scenarios.
Paleoclimate, temperature reconstructions over europe, documentary data.
[Lorentz and Lohmann 2004]
Abstract A method is introduced which allows the calculation of long-term climate trends within the framework of a coupled atmosphere-ocean circulation model. The change in the seasonal cycle of incident solar radiation induced by varying orbital parameters has been accelerated by factors of 10 and 100 in order to allow transient simulations over the period from the mid- Holocene until today, covering the last 7,000 years. In contrast to conventional time-slice experiments, this approach is not restricted to equilibrium simulations and is capable to utilise all available data for validation. We find that opposing Holocene climate trends in tropics and extra-tropics are a robust feature in our experiments. Results from the transient simulations of the mid-Holocene climate at 6,000 years before present show considerable differences to atmosphere-alone model simulations, in particular at high latitudes, attributed to atmosphere-ocean-sea ice effects. The simulations were extended for the time period 1800 2000 AD, where, in contrast to the Holocene climate, increased concentrations of greenhouse gases in the atmosphere provide for the strongest driving mechanism. The experiments reveal that a Northern Hemisphere cooling trend over the Holocene is completely cancelled by the warming trend during the last century, which brings the recent global warming into a long-term context.
Echog, acceleration, holocene.
[Luterbacher et al. 2004]
Reconstruction of european temperature since 1500.
Paleoclimate, temperature reconstructions over europe, documentary data.
[Majorowicz et al. 2004]
They acknowledge errors in the original list of proxy records. This is a reaction to S. McIntyre and R. McKitrick critic, though they do not specify a reference for them.
Paleoclimate, global and hemispherical temperature reconstructions, borehole reconstructions,
[Mann et al. 2004]
They acknowledge errors in the original list of proxy records. This is a reaction to S. McIntyre and R. McKitrick critic, though they do not specify a reference for them.
Paleoclimate, global and hemispherical temperature reconstructions.
[Mann 2004]
They propose an easily implemented smoothing routine that yields objective estimates of the low-frequency variability of potentially non-stationary climate time series. Not worth the fuss.
Climate change, non stationarities, filter.
[Martínez-Peña et al. 2004]
En este trabajo se propone un modelo explicativo de la produccion de carpoforos de Boletus edulis Bull.: Fr. con el que contribuir a la ordenacion y gestion de este recurso forestal no lenoso de alto valor economico. El estudio se ha llevado a cabo en el monte Pinar Grande, masa natural y ordenada de Pinus sylvestris de la comarca soriana de Pinares. Durante el periodo de estudio (1995-2001) se ha podido observar una enorme variabilidad interanual en la produccion, que oscilo entre 8,3 y 87,7 kg/ha, con unas relaciones productivas 1:2:11:8:5:2:4. Utilizando metodos de analisis multivariante de regresion paso a paso, se comprobo que esta variabilidad productiva podia explicarse en parte debido a la influencia de la reserva de agua en el suelo, que fue la mejor variable explicativa del inicio de la fructificacion, mientras que la temperatura minima y la precipitacion condicionaron la dinamica pro- ductiva en los demas periodos considerados. El modelo propuesto permite explicar entre el 62 y 65 percent de la variabilidad de la produccion de esta especie, pero todavia queda una parte importante sin explicar y que reclama del estudio con detalle de otros parametros que inciden en la misma.
Setas Soria
[O'Hagan and Oakley 2004]
There are difficulties with probability as a representation of uncertainty. However, we argue that there is an important distinction between principle and practice. In principle, probability is uniquely appropriate for the representation and quantification of all forms of uncertainty; it is in this sense that we claim that probability is perfect . In practice, people find it difficult to express their knowledge and beliefs in probabilistic form, so that elicitation of probability distributions is a far from perfect process. We therefore argue that there is no need for alternative theories, but that any practical elicitation of expert knowledge must fully acknowledge imprecision in the resulting distribution. We outline a recently developed Bayesian technique that allows the imprecision in elicitation to be formulated explicitly, and apply it to some of the challenge problems. q 2004 Elsevier Ltd. All rights reserved.
Uncertainty, climate change predictions, Bayesian inference; Computer codes; Elicitaton; Epistemic probability; Sensitivity analysis; Sources of uncertainty; Uncertainty analysis
[Osborn 2004]
Comparison of control and scenario runs of 7 models. HADCM2 and echam scenario runs lead to different AO intensities because of behaviour of Aleutian low. Regional scale changes in winter atms circulation are very variable from model to model... what leads to uncertainties in downscaling. There is inter model agreement on the sign of NAO change (considering only north Atlantic). The observed nao variability can hardly be explained with interanal and forced variability from models.
NAO variability, simulations, climate change.
[Osborn and Briffa 2004]
Comment on the paper by [von Storch et al. 2004]. Ilustration of the deterioration of the red frequency spectrum in proxies.
Paloclimate, proxy reconstructions, model simulations.
[Parker 2004]
Urban heat islands occur mainly at nighhts and are reduced in windy conditions. Parker checks Tmin trends for global and NH winter and summer sites, segregating windy and calm conditions and finds no significant bias in results. The reality and magnitude of global-scale warming is supporte by the near-equality of temperature trends on windy nights with trends based on all data.
Urban effect, global warming.
[Pollack and Smerdon 2004]
Mostly reply to [Mann et al. 2003a]. They check the influence of agregation and weighting scheme on the GST reconstructions. They report coolings of the order of 1K. Spatial correlation among the GST 20th century trends and those of SAT are significant (order of 0.4) contrary to stated by Mann et al. The bias between the Mann et al reconstruction and the borehole based reconstructions persists. Logging dates, borehole site geography, seasonal snow effects and investigator bias are not likely contributing to this shift.
Paleoclimate, temperature reconstructions, gst, sat, borehole reconstructions.
[Raible et al. 2004]
Rainfall anomalies in a longterm integration of general circulation model highlight the non-stationarity of the ocean atmosphere coupling in the North Atlantic which becomes manifest in two regimes. Anti-correlations between the precipitation in the tropical and subtropical western Atlantic illustrate the changes of the Hadley cell with El NinÜo/Southern Oscillation (ENSO).The precipitation anomaly pattern in the north eastern Atlantic resembles variations of the North Atlantic storm track and the North Atlantic Oscillation (NAO). In the hemispheric regime, where 40 $\%$ of the NAO variability can be explained by ENSO, both precipitation pattern are connected, whereas in the regional regime the ENSO-link with the North Atlantic storm track and the subtropical 500 hPa geopotential height disappears.
Dynamics , North Atlantic, Echog.
[Raisanen et al. 2004]
Regional climate change simulations with the Rossby Centre coupled regional climate model forced with the Hadley and ECHAM model. Descriptions of climate change over Europe in A2 and B2 scenario runs.
Climate change. Regional climate models. Scenarios.
[Rutherford and Mann 2004]
Revise calculations in [Mann et al. 2003a] as a reaction to [Pollack and Smerdon 2004]. Optimal borehole hemispheric surface temperature (SAT) trend is slightly grater than shown in [Mann et al. 2003a]. The areally weighted, gridded borehole data display a larger trend than shown in [Mann et al. 2003a] and close in amplitude to [Huang et al. 2000]. There was an error in normalization of grid box weights used to form an areal hemisphere mean series.
Paleoclimate reconstructions, temperature, borehole, pseudoproxies, multiproxy.
[Rind et al. 2004]
Use GISS model to simulate climate since 1500 AD
Paleoclimate simulations.
[Schar et al. 2004]
The extrem warm summer 2003 falls well out of the range of variability of observations and fits with the idea of increased variability in summer temperature distribution which would follow increase of ghg concentration. For this test they use and assessment comparing observations in northern Switzerland and a chain of 3 models: HADCM3 + HadAM3H + CHRM in scenario A2. It is important to foucus on changes in the shape of the distribution.
Regional climate change, summer 2003.
[Schaeffer et al. 2004]
Abstract The mean state and variability of deep convection in the ocean influence the North Atlantic climate. Using an ensemble experiment with a coupled atmosphere ocean sea ice model, it is shown that cooling and subdued warming areas can occur over the North Atlantic Ocean and adjacent landmasses under global warming. Different present-day convection patterns in the Greenland Iceland Norway (GIN) Sea result in different future surfaceair temperature changes. At higher latitudes, the more effective positive sea ice feedback increases the likelihood of changes in convection causing a regional cooling that is larger than the warming brought about by the enhanced greenhouse effect. The modeled freshening of deep ocean layers in the North Atlantic in a time period preceding a reorganization of GIN Sea convection is consistent with recent observations. Low-frequency internal variability in the ocean model has relatively little impact on the response patterns.
AMOC, THC
[Schmidt and Mann 2004]
Reply to [Chapman et al. 2004] of their comment to [Mann and Schmidt 2003].
Paleoclimate, temperature reconstructions, borehole reconstructions.
[Silenzi et al. 2004]
The presence of Vermetid reefs in temperate waters, their diffusion in the Mediterranean Sea, and the possibility of performing 14 C ages allowed the use of Vermetids as an indicator of sea level changes. We present new data on sea climate trend fluctuations that could be interpreted as Sea Surface Temperature (SST) variations, recorded on Vermetid (Dendropoma petraeum) reefs, by means of isotopic analysis. The isotopic records show positive values of the d 18 O relative to present-day values in the period between 1600 and 1850 AD; this deviation occurs in association with the climatic cooling event known as Little Ice Age (LIA). Subsequently, we can observe the warming trend that characterized the last century. These preliminary results indicate that Vermetids could be considered a new SST proxy-data for the Mediterranean Sea and, more generally, for temperate areas.
Paleoclimate, temperature reconstructions, coral, vermetid.
[Smerdon et al. 2004]
Analyse four data sets of temperature data in the upper subsurface recorded over 7 years in 4 locations to examine heat transport in subsurface environments. The amplitude and phase shift of the sat signal transfers to gst accordingly with the one dimensional conductive model. The relation of annual SAT and GST signals can be understood from the different perturabations that occur in winter and summer involving snow cover variations and evaporation changes depending on the climate of each location.
Paleoclimate, temperature reconstructions, gst, sat, borehole reconstructions, annual variations.
[Solanki et al. 2004]
Reconstruction of sunspot numbers from treering C14 variations for the last 11400 years. They combine physics based models for each of the processes connecting the radiocarbon concentration with sunspot number. The level of solar activity in the last 70 years is exceptional. The previous period of similar activity ocurred about 8000 years ago.
Climate reconstructions, solar activity, sunspot numbers, c14, cosmogenic isotopes.
[Solanki and Krivova 2004]
Review on solar variability and climate reconstrucitons. Discusses [Lean et al. 2002] and [Foukal et al. 2004] with desagreement.
Climate reconstructions, solar activity, sunspot numbers, c14, cosmogenic isotopes.
[von Storch 2004]
The role and application of quasi-realistic climate models in paleocli-matic studies is reviewed. Conceptual aspects of modelling, such as the validation of positive analogs and the application of neutral analogs, are discussed. The math-ematical basis of quasi-realistic models and the major modes of applications are presented. An extended control run and a transient simulation of the Late Maun-der Minimum episode (1675-1710) are used as a demonstration of the general ideas.
Models, paleoclimate, surrogate reality
[von Storch et al. 2004]
Linear methods for reconstructing millennial global and hemispherical temperature from proxy databases infraestimate variance. Temperatures in the last 1000 yrs might have been larger than it is thought nowadays. The standard Mann et al. method is tested in the virtual world simulated with the ECHO-g model.
Climate reconstructions, hemispheric temperature, reconstruction methods validation using pseudoproxies.
[Stott et al. 2004]
ABSTRACT: In the present-day climate, surface water salinities are low in the western tropical Pacific Ocean and increase towards the eastern part of the basin 1 . The salinity of surface waters in the tropical Pacific Ocean is thought to be controlled by a combination of atmospheric convection, precipitation, evaporation and ocean dynamics 2 , and on interannual timescales significant variability is associated with the El NinÜo/Southern Oscillation cycles. How-ever, little is known about the variability of the coupled ocean atmosphere system on timescales of centuries to millennia. Here we combine oxygen isotope and Mg/Ca data from foraminifers retrieved from three sediment cores in the western tropical Pacific Ocean to reconstruct Holocene sea surface temperatures and salinities in the region. We find a decrease in sea surface temperatures of ,0.5 8 C over the past 10,000 yr, whereas sea surface salinities decreased by ,1.5 practical salinity units. Our data imply either that the Pacific basin as a whole has become progressively less salty or that the present salinity gradient along the Equator has developed relatively recently.
Holocene, western pacific, salinity, ocean circulation.
[Sun and Zhang 2004]
In this study, the effect of the lower boundary position selection for the Fourier equation on heat transfer and energy balance in soil is evaluated. A detailed numerical study shows that the proper position of the lower boundary is critical when solving the Fourier equation by using zero heat ux as the lower boundary condition. Since the position defines the capacity of soil as a heat sink or source, which absorbs and stores radiation energy from the sky in summer and then releases the energy to the atmosphere in winter, and regulates the deep soil temperature distribution, the depth of the position greatly in uences the heat balance within the soil as well as the interaction between the soil and the atmosphere. Based on physical reasoning and the results of numerical simulation, the proper depth of the position should be equal to approximately 3 times of the annual heat wave damping depth. For most soils, the proper lower boundary depth for the Fourier equation should be around 8 m to 15 m, depending on soil texture..
Boreholes, Land surface models, lower boundary position.
[Thorpe et al. 2004]
Abstract The Hadley Centre climate model HadCM3 simulates a stable thermohaline circulation driven by deep water formation in the Norwegian and Labrador Seas without the need for flux adjustments. It has however been suggested that this result is the fortuitous consequence of the local use of the Roussenov convection scheme in this region, and that the model simulation may depend sensitively on this parameterisation. Here we investigate the sensitivity of the thermohaline circulation (THC) to the models treatment of the overflows from the Nordic Seas for both pre-industrial and increasing greenhouse gas forcings.We find that although the density structure in the Labrador Sea does depend upon the specifics of how the overflows are modelled, the global thermohaline circulation and climate responses are not sensitive to these details. This result gives credibility to previously published modelling studies on the response of the thermohaline circulation to anthropogenic greenhouse gas forcing, and implies that research may profitably be focussed on the large scale transports, where models are known to disagree.
Ocean models, convection, GIN, GIS
[Valero et al. 2004]
Modes of large scale circulation and precipitation in the east of Iberian Peninsula using singular value decomposition. Analysis is made for Z300 and U and V wind components at 300 mb. East atlantic jet seems to be the pattern goberning long term trends.

Statistical downscaling, Iberian Precipitation, singular value decomposition.
[Vellinga and Wu 2004]
Abstract. Variability of the thermohaline circulation (THC) has been analyzed in a long control simulation by the Met Office¿s Third Hadley Centre Coupled Ocean¿Atmosphere General Circulation Model (HadCM3). It is shown that internal THC variability in the coupled climate system is concentrated at interannual and centennial time scales, with the centennial mode being dominant. Centennial oscillations of the THC can impact surface climate via an interhemispheric SST contrast of 0.18C in the Tropics and more than 0.58C in mid- and high latitudes. A mechanism is proposed based on detailed process analysis involving large-scale air¿sea interaction on multidecadal time scales. Anomalous northward ocean heat transport associated with a strong phase of the Atlantic THC generates a cross-equatorial SST gradient. This causes the ITCZ to move to a more northerly position with increased strength. The extra rainfall resulting from the anomalous ITCZ imposes a freshwater flux and produces a salinity anomaly in the tropical North Atlantic. Such sustained salinity anomalies slowly propagate toward the subpolar North Atlantic at a lag of 5¿6 decades. The accumulated low-salinity water lowers upper-ocean density, which causes the THC to slow down. The oscillation then enters the opposite phase.
THC, MOC, MOI, Hadcm3, control run,ocean modes
[Widmann and Tett 2004]
Comparison of the Columbus run and a Hadley Centre paleo run without anthropogenic forcing.
Paleoclimate simulations, AOGCM, forcing.
[Xoplaki et al. 2004]
Statistical downscalling of large scale fields to wet season precipitation over Mediterranean area. Reanalysis period. Interesting in combination with [Xoplaki et al. 2003b]. Inference back to 19th century of influence of large scale on surface temperature. NAO influence determines long term trends. Nice plot of predictability regions.
Precipitation, reanalysis, downscaling, precipitation, mediterranean.
[Weber et al. 2004]
Abstract Centennial climate variability during the Holocene has been simulated in two 10,000 year experiments using the intermediate-complexity ECBilt model. ECBilt contains a dynamic atmosphere, a global 3-D ocean model and a thermodynamic sea-ice model. One experiment uses orbital forcing and solar irradiance forcing, which is based on the Stuiver et al. residual 14C record spliced into the Lean et al. reconstruction. The other experiment uses orbital forcing alone. A glacier model is coupled off-line to the climate model. A time scale analysis shows that the response in atmospheric parameters to the irradiance forcing can be characterised as the direct response of a system with a large thermal inertia. This is evident in parameters like surface air temperature, monsoon precipitation and glacier length, which show a stronger response for longer time scales. The oceanic response, on the other hand, is strongly modified by internal feedback processes. The solar irradiance forcing excites a (damped) mode of the thermohaline circulation (THC) in the North Atlantic Ocean, similar to the loop-oscillator modes associated with random-noise freshwater forcing. This results in a significant peak (at time scales 200 250 year) in the THC spectrum which is absent in the reference run. The THC response diminishes the sea surface temperature response at high latitudes, while it gives rise to a signal in the sea surface salinity. A comparison of the model results with observations shows a number of encouraging similarities.
Solar irradiance forcing, holocene, ECBILTclio.
[Zheng and Frederiksen 2004]
We propose a method for studying the in u- ence of intraseasonal variability on the interannual variability of seasonal mean elds.The method,using monthly mean data,provides estimates of the interan- nual variance and covariance,in the seasonal mean eld, associated with intraseasonal variability.These esti- mates can be used to derive patterns of interannual variability associated with meteorological phenomena that vary signi cantly within a season,such as atmo- spheric blocking,or intraseasonal oscillations. By removing this intraseasonal component from the total interannual variance/covariance,one can de ne a slow component of interannual variability that is closely related to very slowly varying (interannual/su- pra-annual)external forcings and internal dynamics. Together these patterns may help in our understanding of the source of climate predictive skill,and also the in uence of intraseasonal variability on interannual variability.To show the e cacy of our methodology,we have tested it on synthetic data,using Monte Carlo simulations of the 500-hPa geopotential heights for boreal winter over the North Paci c/North American region.The synthetic data has been constructed in such a way that the intraseasonal and slow components of interannual variability are known a priori.It is demon- strated that our methodology can effectively separate the spatial patterns of both components of variability.The methodology is also applied to diagnose meteorological phenomena that play major roles in the variability and predictability of DJF New Zealand temperatures.
Downscaling, potential predictability, intraseasonal and interannual variability.