What trees tell us: dendrochronological and statistical analysis of the data

Trees are a great bank of data, named sometimes for this reason as the "silentwitnesses" of the past. Due to annual formation of rings, which is normally influenced directly by of climate parameters (generally changes in temperature and moisture or precipitation) and other environmental factors; these changes, occurred in the past, are"written" in the tree "archives" and can be "decoded" in order to interpret what hadhappened before, mainly applied for the past climate reconstruction.Using dendrochronological methods for obtaining samples of Pinus nigra fromthe Catalonian PrePirineous region, the cores of 15 trees with total time spine of about 100 - 250 years were analyzed for the tree ring width (TRW) patterns and had quite high correlation between them (0.71 ¿ 0.84), corresponding to a common behaviour for the environmental changes in their annual growth.After different trials with raw TRW data for standardization in order to take outthe negative exponential growth curve dependency, the best method of doubledetrending (power transformation and smoothing line of 32 years) were selected for obtaining the indexes for further analysis.Analyzing the cross-correlations between obtained tree ring width indexes andclimate data, significant correlations (p<0.05) were observed in some lags, as forexample, annual precipitation in lag -1 (previous year) had negative correlation with TRW growth in the Pallars region. Significant correlation coefficients are between 0.27- 0.51 (with positive or negative signs) for many cases; as for recent (but very short period) climate data of Seu d¿Urgell meteorological station, some significant correlation coefficients were observed, of the order of 0.9.These results confirm the hypothesis of using dendrochronological data as aclimate signal for further analysis, such as reconstruction of climate in the past orprediction in the future for the same locality.

Estimating 750 years of temperature variations and uncertainties in the Pyrenees by tree-ring reconstructions and climate simulations.

Past temperature variations are usually inferred from proxy data or estimated using general circulation models. Comparisons between climate estimations derived from proxy records and from model simulations help to better understand mechanisms driving climate variations, and also offer the possibility to identify deficiencies in both approaches. This paper presents regional temperature reconstructions based on tree-ring maximum density series in the Pyrenees, and compares them with the output of global simulations for this region and with regional climate model simulations conducted for the target region. An ensemble of 24 reconstructions of May-to-September regional mean temperature was derived from 22 maximum density tree-ring site chronologies distributed over the larger Pyrenees area. Four different tree-ring series standardization procedures were applied, combining two detrending methods: 300-yr spline and the regional curve standardization (RCS). Additionally, different methodological variants for the regional chronology were generated by using three different aggregation methods. Calibration verification trials were performed in split periods and using two methods: regression and a simple variance matching. The resulting set of temperature reconstructions was compared with climate simulations performed with global (ECHO-G) and regional (MM5) climate models. The 24 variants of May-to-September temperature reconstructions reveal a generally coherent pattern of inter-annual to multi-centennial temperature variations in the Pyrenees region for the last 750 yr. However, some reconstructions display a marked positive trend for the entire length of the reconstruction, pointing out that the application of the RCS method to a suboptimal set of samples may lead to unreliable results. Climate model simulations agree with the tree-ring based reconstructions at multi-decadal time scales, suggesting solar variability and volcanism as the main factors controlling preindustrial mean temperature variations in the Pyrenees. Nevertheless, the comparison also highlights differences with the reconstructions, mainly in the amplitude of past temperature variations and in the 20th century trends. Neither proxy-based reconstructions nor model simulations are able to perfectly track the temperature variations of the instrumental record, suggesting that both approximations still need further improvements.

Limitations and biases of conventional analysis of climate change. Towards an analysis coherent with sustainable development

This paper shows the numerous problems of conventional economic analysis in the evaluation of climate change mitigation policies. The article points out the many limitations, omissions, and the arbitrariness that have characterized most evaluation models applied up until now. These shortcomings, in an almost overwhelming way, have biased the result towards the recommendation of a lower aggressiveness of emission mitigation policies. Consequently, this paper questions whether these results provide an appropriate answer to the problem. Finally, various points that an analysis coherent with sustainable development should take into account are presented.

Equity and CO2 emissions distribution in climate change integrated assessment

Emissions distribution is a focus variable for the design of future international agreements to tackle global warming. This paper specifically analyses the future path of emissions distribution and its determinants in different scenarios. Whereas our analysis is driven by tools which are typically applied in the income distribution literature and which have recently been applied to the analysis of CO2 emissions distribution, a new methodological approach is that our study is driven by simulations run with a popular regionalised optimal growth climate change model over the 1995-2105 period. We find that the architecture of environmental policies, the implementation of flexible mechanisms and income concentration are key determinants of emissions distribution over time. In particular we find a robust positive relationship between measures of inequalities.

Calculation of the variance in surveys of the economic climate

Public opinion surveys have become progressively incorporated into systems of official statistics. Surveys of the economic climate are usually qualitative because they collect opinions of businesspeople and/or experts about the long-term indicators described by a number of variables. In such cases the responses are expressed in ordinal numbers, that is, the respondents verbally report, for example, whether during a given trimester the sales or the new orders have increased, decreased or remained the same as in the previous trimester. These data allow to calculate the percent of respondents in the total population (results are extrapolated), who select every one of the three options. Data are often presented in the form of an index calculated as the difference between the percent of those who claim that a given variable has improved in value and of those who claim that it has deteriorated. As in any survey conducted on a sample the question of the measurement of the sample error of the results has to be addressed, since the error influences both the reliability of the results and the calculation of the sample size adequate for a desired confidence interval. The results presented here are based on data from the Survey of the Business Climate (Encuesta de Clima Empresarial) developed through the collaboration of the Statistical Institute of Catalonia (Institut d’Estadística de Catalunya) with the Chambers of Commerce (Cámaras de Comercio) of Sabadell and Terrassa.

Climate change in the Atlantic Ocean since the 1940's and the effects on the global climate

En aquest projecte s’ha estudiat la relació entre els canvis en les temperatures superficials de l’Oceà Atlàntic i els canvis en la circulació atmosfèrica en el segle XX. Concretament s’han analitzat dos períodes de estudi: el primer des del 1940 al 1960 i el segon des del 1980 fins al 2000. S’ha posat especial interès en les anomalies en les temperatures superficials del mar en la regió tropical de l’Oceà Atlàntic i la possible interconnexió amb els canvis climàtics observats i predits. Per a la realització de l’estudi s’han dut a terme una sèrie d’experiments utilitzant el model climàtic elaborat a la universitat d’UCLA (UCLA‐AGCM model). Els resultats obtinguts han estat analitzats en forma de mapes i figures per a cada variable d’estudi. També s’ha fet una comparació entre els resultats obtinguts i altres trobats en altres treballs publicats sobre el mateix tema de recerca. Els resultats obtinguts són molt amplis i poden tenir diverses interpretacions. Tot i així algunes de les conclusions a les quals s’ha arribat són: les diferències més significatives per a les variables estudiades i trobades a partir dels resultats obtinguts del model per als dos períodes d’estudi són en els mesos d’hivern i a la zona dels tròpics; concretament a parts del nord de sud Amèrica i a parts del nord d’Àfrica. S’han trobat també canvis significatius en els patrons de precipitació sobre aquestes mateixes zones. També s’ha observant un moviment cap al nord de la zona d’interconvergència tropical i pot ser degut a l’anòmal gradient trobat a la zona equatorial en les temperatures superficial de l’Oceà. Tot i així per a una definitiva discussió i conclusions sobre els resultats dels experiments, seria necessari un estudi més ampli i profund.

Risk Attitude And Wage Growth: Replication And Reconstruction

We replicate Shaw (1996) who found that individual wage growth is higher for individuals with greater preference for risk taking. Expanding her dataset with more American observations and data for Germany, Spain and Italy, we find mixed support for the earlier results. We present and estimate a new model and find that in particular the wage level is sensitive to attitudes towards risk taking. Comments given at the Labour Economics Conference in honour of Niels Westergaard (Nyborg, August 2008) and EALE 2008 (Amsterdam) and at seminars in Maastricht,Reus and Essen (RWI) are gratefully acknowledged. The authors also acknowledge financial support from the Spanish Ministry of Science and Innovation (grant number SEJ2007-66318) and from the Barcelona Economics Program of CREA. JEL code: J24; J30. Key words: wage growth, risk, post-school investment.

The Evolution of the Climate Change Regime: Beyond a North-South Divide?

This research primarily analyses relevant climate bargaining dynamics that have been informed by a North-South impasse. This working paper argues that the first stage of negotiations for a climate convention indeed witnessed a North-South divide which became institutionalized in the Framework Convention on Climate Change. However, in subsequent negotiation rounds the key loci of bargaining struggles was centered between developed countries, in which relevant North-South cooperation dynamics were also present. Finally, this paper assesses the unfinished post-Kyoto bargaining process in which two trends are already being observed: both the emergence of a new geopolitics between the United States and major developing countries, and a fragmentation process within the South, in which the Copenhagen Accord itself has begun to institutionalize such fragmentation.

Consumer populations and nutritional transition in Spain in the 20th century: a methodology for their reconstruction

One feature of the modern nutrition transition is the growing consumption of animal proteins. The most common approach in the quantitative analysis of this change used to be the study of averages of food consumption. But this kind of analysis seems to be incomplete without the knowledge of the number of consumers. Data about consumers are not usually published in historical statistics. This article introduces a methodological approach for reconstructing consumer populations. This methodology is based on some assumptions about the diffusion process of foodstuffs and the modeling of consumption patterns with a log-normal distribution. This estimating process is illustrated with the specific case of milk consumption in Spain between 1925 and 1981. These results fit quite well with other data and indirect sources available showing that this dietary change was a slow and late process. The reconstruction of consumer population could shed a new light in the study of nutritional transitions.

Reconstruction threshold for the hardcore model

"Vegeu el resum a l'inici del document del fitxer adjunt."

Impacte de la variabilitat climàtica ràpida de l'últim període glacial sobre la vegetació del sud-est de Nord Amèrica

Projecte de recerca elaborat a partir d’una estada a UMR-CNRS - Géologie et Océanographie, França, entre 2007 i 2009. Els canvis climàtics ràpids de l’últim període glacial (cicles Dansgaard/Oeschger i Heinrich Stadials-HS), han estat documentats en testimonis marins, de gel i dipòsits continentals, generalment de l’hemisferi nord. Mentre que la majoria dels estudis paleoclimàtics i paleoceanogràfics de l’Atlàntic Nord sobre l’últim període glacial s’han centrat en la part nord i est, les latituds mitjanes de la part occidental han estat menys estudiades. Particularment, els canvis de la vegetació de l’est de Nord Amèrica durant l’últim glacial es coneixen molt poc degut a la manca de seqüències pol.líniques llargues en aquesta regió. Només dues seqüències de pol.len del llac Tulane (Florida) mostren canvis de la vegetació significatius i interessants durant l’últim glacial, que suggereixen HS càlids i humits, que contrasta amb el que s’observa a l’altre costat de l’Atlàntic Nord. El treball realitzat al UMR-CNRS 5805 EPOC, Université Bordeaux 1, EPHE, des del 23 d’abril 2007 al 22 d’abril 2009, gràcies a la beca Beatriu de Pinós, implica una reconstrucció a alta resolució dels canvis de la vegetació a partir de l’anàlisi d’un testimoni marí, localitzat a l’oest de l’Atlàntic Nord subtropical (MD99-2203, 34º58’N, 75º12’W), durant l’Estadi Isotòpic Marí 3 (MIS 3). Les dades pal.linològiques del testimoni mostren una alternança entre Picea i Quercus. En general, les associacions pol.líniques indiquen que les variacions de la vegetació segueixen un patró bosc boreal/temperat durant l’últim glacial. El model d’edat preliminar basat en edats radiomètriques suggereix un augment del bosc temperat acompanyat d’una reducció del boreal entre el H4 i el H3. La comparació amb registres pol.línics marins d’alta resolució de la regió est subtropical, a latituds similars, mostren, per primer cop, que els canvis en les formacions forestals associats als canvis climàtics ràpids de l’últim glacial van ser menys intensos al sud-est de Nord Amèrica que a la Península Ibèrica.

Monocular-based 3-D seafloor reconstruction and ortho-mosaicing by piecewise planar representation

Photo-mosaicing techniques have become popular for seafloor mapping in various marine science applications. However, the common methods cannot accurately map regions with high relief and topographical variations. Ortho-mosaicing borrowed from photogrammetry is an alternative technique that enables taking into account the 3-D shape of the terrain. A serious bottleneck is the volume of elevation information that needs to be estimated from the video data, fused, and processed for the generation of a composite ortho-photo that covers a relatively large seafloor area. We present a framework that combines the advantages of dense depth-map and 3-D feature estimation techniques based on visual motion cues. The main goal is to identify and reconstruct certain key terrain feature points that adequately represent the surface with minimal complexity in the form of piecewise planar patches. The proposed implementation utilizes local depth maps for feature selection, while tracking over several views enables 3-D reconstruction by bundle adjustment. Experimental results with synthetic and real data validate the effectiveness of the proposed approach

Reconstruction of a superscheme from its derived category

The aim of this paper is to construct a "super" version of a tensor triangulated category, and to show that super-schemes can be reconstructed from its category of perfect complexes in a way similar to Balmer [Bal05] provided we consider this extra structure.

Reaction-diffusion wave fronts: Multigeneration biological species under climate change

A generalization of reaction-diffusion models to multigeneration biological species is presented. It is based on more complex random walks than those in previous approaches. The new model is developed analytically up to infinite order. Our predictions for the speed agree to experimental data for several butterfly species better than existing models. The predicted dependence for the speed on the number of generations per year allows us to explain the change in speed observed for a specific invasion