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PubMed2004

A 'snowball Earth' climate triggered by continental break-up through changes in runoff.

Geological and palaeomagnetic studies indicate that ice sheets may have reached the Equator at the end of the Proterozoic eon, 800 to 550 million years ago, leading to the suggestion of a fully ice-covered 'snowball Earth'. Climate model simulations indicate that such a snowball state for the Earth depends on anomalously low atmospheric carbon dioxide concentrations, in addition to the Sun being 6 per cent fainter than it is today. However, the mechanisms producing such low carbon dioxide concentrations remain controversial. Here we assess the effect of the palaeogeographic changes preceding the Sturtian glacial period, 750 million years ago, on the long-term evolution of atmospheric carbon dioxide levels using the coupled climate-geochemical model GEOCLIM. In our simulation, the continental break-up of Rodinia leads to an increase in runoff and hence consumption of carbon dioxide through continental weathering that decreases atmospheric carbon dioxide concentrations by 1,320 p.p.m. This indicates that tectonic changes could have triggered a progressive transition from a 'greenhouse' to an 'icehouse' climate during the Neoproterozoic era. When we combine these results with the concomitant weathering effect of the voluminous basaltic traps erupted throughout the break-up of Rodinia, our simulation results in a snowball glaciation.

Journal Article↗
PubMed2004

Extreme climate of the global troposphere and stratosphere in 1940-42 related to El Niño.

Although the El Niño/Southern Oscillation phenomenon is the most prominent mode of climate variability and affects weather and climate in large parts of the world, its effects on Europe and the high-latitude stratosphere are controversial. Using historical observations and reconstruction techniques, we analyse the anomalous state of the troposphere and stratosphere in the Northern Hemisphere from 1940 to 1942 that occurred during a strong and long-lasting El Niño event. Exceptionally low surface temperatures in Europe and the north Pacific Ocean coincided with high temperatures in Alaska. In the lower stratosphere, our reconstructions show high temperatures over northern Eurasia and the north Pacific Ocean, and a weak polar vortex. In addition, there is observational evidence for frequent stratospheric warmings and high column ozone at Arctic and mid-latitude sites. We compare our historical data for the period 1940-42 with more recent data and a 650-year climate model simulation. We conclude that the observed anomalies constitute a recurring extreme state of the global troposphere-stratosphere system in northern winter that is related to strong El Niño events.

Journal Article↗
PubMed2006

Temperature sensitivity of soil carbon decomposition and feedbacks to climate change.

Significantly more carbon is stored in the world's soils--including peatlands, wetlands and permafrost--than is present in the atmosphere. Disagreement exists, however, regarding the effects of climate change on global soil carbon stocks. If carbon stored belowground is transferred to the atmosphere by a warming-induced acceleration of its decomposition, a positive feedback to climate change would occur. Conversely, if increases of plant-derived carbon inputs to soils exceed increases in decomposition, the feedback would be negative. Despite much research, a consensus has not yet emerged on the temperature sensitivity of soil carbon decomposition. Unravelling the feedback effect is particularly difficult, because the diverse soil organic compounds exhibit a wide range of kinetic properties, which determine the intrinsic temperature sensitivity of their decomposition. Moreover, several environmental constraints obscure the intrinsic temperature sensitivity of substrate decomposition, causing lower observed 'apparent' temperature sensitivity, and these constraints may, themselves, be sensitive to climate.

Carbon↗
PubMed2000

[School climate and psychological symptoms--correlations between school stress, sense of coherence and physical-psychological impairment in high school students].

The research project "Health Promotion and School Culture" investigated associations between school climate, school stress, sense of coherence and physical/psychological symptoms in high school students. 565 students, aged 15 to 20 from two high schools (Gymnasium) in the canton of Zurich took part in the study. Assessment measures included questionnaires on school climate (FUK 7-10), school stress, sense of coherence (SOC-13), physical (GBB-24) and psychological symptomatology (SCL-90-R, ADS-K). 166 of the students also participated in a standardised psychiatric interview (DIA-X). Results revealed significant associations between 1. school climate and school stress, 2. biographical risk and protective factors and sense of coherence, 3. school stress and sense of coherence, and 4. school-stress and sense of coherence on the one side and symptomatology on the other. The results are discussed in terms of Karasek and Theorell's (1990) three dimensional stress model. Finally, the need for health promotion in school, especially in classes of high school, is addressed.

Adolescent↗
PubMed2001

Reducing relative humidity is a practical way to control dust mites and their allergens in homes in temperate climates.

BACKGROUND: Maintaining a relative humidity (RH) of less than 50% is one recommendation for reducing numbers of house dust mites and their allergens in homes. OBJECTIVE: The purpose of this study was to determine whether, in a humid temperate climate, indoor RH could be sufficiently lowered to control dust mites and their allergens. METHODS: During a period spanning 2 humid summers (May 1998 to October 1999), dust mite and allergen densities were determined in 3 groups of homes. One group (low RH group, n = 23) maintained an RH of less than 51%. Most of these homes used a high-efficiency dehumidifier and air conditioning. A second group of homes (group A) used air conditioning only (n = 19) or air conditioning and dehumidification (n = 5) but did not maintain an RH of less than 51%. A third group of homes (group C, n = 24) controlled climate by opening windows and had an RH of greater than 51%. Normal housecleaning was maintained in all homes during the study. RESULTS: The low RH group homes started in June with a mean +/- SE of 401 +/- 124 live mites and 17 +/- 3 microg of total Der 1 allergen per gram of dust. After 17 months of maintaining an RH of less than 51%, these declined significantly to 8 +/- 3 live mites per gram (P =. 004) and 4 +/- 1 microg of Der 1 per gram of dust (P <.001). In contrast, group A and C homes exhibited seasonal peaks of 500 to 1000 mites and 40 to 70 microg of Der 1 per gram of dust. At all time points after the baseline sample, the low RH group homes had significantly less (P <.001) allergen than the group A and C homes. After 17 months, allergen levels were more than 10 times lower in low RH homes compared with humid homes. CONCLUSION: This study showed that it is practical to maintain an indoor RH of less than 51% during the humid summer season in a temperate climate, and this resulted in significant reductions in mite and allergen levels.

Air Pollution, Indoor↗
PubMed2002

What might we learn from climate forecasts?

Most climate models are large dynamical systems involving a million (or more) variables on big computers. Given that they are nonlinear and not perfect, what can we expect to learn from them about the earth's climate? How can we determine which aspects of their output might be useful and which are noise? And how should we distribute resources between making them "better," estimating variables of true social and economic interest, and quantifying how good they are at the moment? Just as "chaos" prevents accurate weather forecasts, so model error precludes accurate forecasts of the distributions that define climate, yielding uncertainty of the second kind. Can we estimate the uncertainty in our uncertainty estimates? These questions are discussed. Ultimately, all uncertainty is quantified within a given modeling paradigm; our forecasts need never reflect the uncertainty in a physical system.

Journal Article↗
PubMed2003

Correlated terrestrial and marine evidence for global climate changes before mass extinction at the Cretaceous-Paleogene boundary.

Terrestrial climates near the time of the end-Cretaceous mass extinction are poorly known, limiting understanding of environmentally driven changes in biodiversity that occurred before bolide impact. We estimate paleotemperatures for the last approximately 1.1 million years of the Cretaceous ( approximately 66.6-65.5 million years ago, Ma) by using fossil plants from North Dakota and employ paleomagnetic stratigraphy to correlate the results to foraminiferal paleoclimatic data from four middle- and high-latitude sites. Both plants and foraminifera indicate warming near 66.0 Ma, a warming peak from approximately 65.8 to 65.6 Ma, and cooling near 65.6 Ma, suggesting that these were global climate shifts. The warming peak coincides with the immigration of a thermophilic flora, maximum plant diversity, and the poleward range expansion of thermophilic foraminifera. Plant data indicate the continuation of relatively cool temperatures across the Cretaceous-Paleogene boundary; there is no indication of a major warming immediately after the boundary as previously reported. Our temperature proxies correspond well with recent pCO(2) data from paleosol carbonate, suggesting a coupling of pCO(2) and temperature. To the extent that biodiversity is correlated with temperature, estimates of the severity of end-Cretaceous extinctions that are based on occurrence data from the warming peak are probably inflated, as we illustrate for North Dakota plants. However, our analysis of climate and facies considerations shows that the effects of bolide impact should be regarded as the most significant contributor to these plant extinctions.

Journal Article↗
PubMed2005

Effects of seasonal climate forecasts and participatory workshops among subsistence farmers in Zimbabwe.

Improvements in the ability to model El Niño and other large-scale interannual climate variations have allowed for the development of seasonal climate forecasts, predicting rainfall and temperature anomalies for many places around the world. These forecasts have allowed developing countries to predict shortfalls in grain yields, with benefits for food security. Several countries communicate the forecasts to subsistence farmers, which could allow them to mitigate the effects of drought on their harvests by adapting their cropping decisions accordingly. However, it has not been demonstrated that subsistence farmers benefit from having access to the forecasts. Here we present evidence of subsistence farmers using the forecasts over multiple years to make different decisions and significantly improving their harvests when they do so. In a controlled study, farmers in Zimbabwe who reported adapting their farming methods to seasonal climate forecasts significantly improved their harvests over baseline amounts. Moreover, farmers who had attended a brief workshop and learned more about the forecasts were significantly more likely to use the forecasts than were farmers who learned of the forecasts through nonparticipatory channels.

Journal Article↗
PubMed2001

Trends of measured climate forcing agents.

The growth rate of climate forcing by measured greenhouse gases peaked near 1980 at almost 5 W/m(2) per century. This growth rate has since declined to approximately 3 W/m(2) per century, largely because of cooperative international actions. We argue that trends can be reduced to the level needed for the moderate "alternative" climate scenario ( approximately 2 W/m(2) per century for the next 50 years) by means of concerted actions that have other benefits, but the forcing reductions are not automatic "co-benefits" of actions that slow CO(2) emissions. Current trends of climate forcings by aerosols remain very uncertain. Nevertheless, practical constraints on changes in emission levels suggest that global warming at a rate +0.15 +/- 0.05 degrees C per decade will occur over the next several decades.

Journal Article↗
PubMed1997

Geochemistry of corals: proxies of past ocean chemistry, ocean circulation, and climate.

This paper presents a discussion of the status of the field of coral geochemistry as it relates to the recovery of past records of ocean chemistry, ocean circulation, and climate. The first part is a brief review of coral biology, density banding, and other important factors involved in understanding corals as proxies of environmental variables. The second part is a synthesis of the information available to date on extracting records of the carbon cycle and climate change. It is clear from these proxy records that decade time-scale variability of mixing processes in the oceans is a dominant signal. That Western and Eastern tropical Pacific El Niño-Southern Oscillation (ENSO) records differ is an important piece of the puzzle for understanding regional and global climate change. Input of anthropogenic CO2 to the oceans as observed by 13C and 14C isotopes in corals is partially obscured by natural variability. Nonetheless, the general trend over time toward lower delta18O values at numerous sites in the world's tropical oceans suggests a gradual warming and/or freshening of the surface ocean over the past century.

Journal Article↗
PubMed2000

As climate changes, so do glaciers.

Understanding abrupt climate changes requires detailed spatial/temporal records of such changes, and to make these records, we need rapidly responding, geographically widespread climate trackers. Glacial systems are such trackers, and recent additions to the stratigraphic record show overall synchronous response of glacial systems to climate change reflecting global atmosphere conditions.

Journal Article↗
PubMed2000

Two terrestrial records of rapid climatic change during the glacial-Holocene transition (14,000- 9,000 calendar years B.P.) from Europe.

Two independent multidisciplinary studies of climatic change during the glacial-Holocene transition (ca. 14,000-9,000 calendar yr B.P.) from Norway and Switzerland have assessed organism responses to the rapid climatic changes and made quantitative temperature reconstructions with modern calibration data sets (transfer functions). Chronology at Krakenes, western Norway, was derived from calibration of a high-resolution series of 14C dates. Chronologies at Gerzensee and Leysin, Switzerland, were derived by comparison of delta18O in lake carbonates with the delta18O record from the Greenland Ice Core Project. Both studies demonstrate the sensitivity of terrestrial and aquatic organisms to rapid temperature changes and their value for quantitative reconstruction of the magnitudes and rates of the climatic changes. The rates in these two terrestrial records are comparable to those in Greenland ice cores, but the actual temperatures inferred apply to the terrestrial environments of the two regions.

Journal Article↗
PubMed2000

Twentieth century climate change: evidence from small glaciers.

The relation between changes in modern glaciers, not including the ice sheets of Greenland and Antarctica, and their climatic environment is investigated to shed light on paleoglacier evidence of past climate change and for projecting the effects of future climate warming on cold regions of the world. Loss of glacier volume has been more or less continuous since the 19th century, but it is not a simple adjustment to the end of an "anomalous" Little Ice Age. We address the 1961-1997 period, which provides the most observational data on volume changes. These data show trends that are highly variable with time as well as within and between regions; trends in the Arctic are consistent with global averages but are quantitatively smaller. The averaged annual volume loss is 147 mm.yr(-1) in water equivalent, totaling 3.7 x 10(3) km(3) over 37 yr. The time series shows a shift during the mid-1970s, followed by more rapid loss of ice volume and further acceleration in the last decade; this is consistent with climatologic data. Perhaps most significant is an increase in annual accumulation along with an increase in melting; these produce a marked increase in the annual turnover or amplitude. The rise in air temperature suggested by the temperature sensitivities of glaciers in cold regions is somewhat greater than the global average temperature rise derived largely from low altitude gauges, and the warming is accelerating.

Journal Article↗
PubMed2006

Climate change, parasitism and the structure of intertidal ecosystems.

Evidence is accumulating rapidly showing that temperature and other climatic variables are driving many ecological processes. At the same time, recent research has highlighted the role of parasitism in the dynamics of animal populations and the structure of animal communities. Here, the likely interactions between climate change and parasitism are discussed in the context of intertidal ecosystems. Firstly, using the soft-sediment intertidal communities of Otago Harbour, New Zealand, as a case study, parasites are shown to be ubiquitous components of intertidal communities, found in practically all major animal species in the system. With the help of specific examples from Otago Harbour, it is demonstrated that parasites can regulate host population density, influence the diversity of the entire benthic community, and affect the structure of the intertidal food web. Secondly, we document the extreme sensitivity of cercarial production in parasitic trematodes to increases in temperature, and discuss how global warming could lead to enhanced trematode infections. Thirdly, the results of a simulation model are used to argue that parasite-mediated local extinctions of intertidal animals are a likely outcome of global warming. Specifically, the model predicts that following a temperature increase of less than 4 degrees C, populations of the amphipod Corophium volutator, a hugely abundant tube-building amphipod on the mudflats of the Danish Wadden Sea, are likely to crash repeatedly due to mortality induced by microphallid trematodes. The available evidence indicates that climate-mediated changes in local parasite abundance will have significant repercussions for intertidal ecosystems. On the bright side, the marked effects of even slight increases in temperature on cercarial production in trematodes could form the basis for monitoring programmes, with these sensitive parasites providing early warning signals of the environmental impacts of global warming.

Animals↗
PubMed2006

Climate warming and disease risks in temperate regions--Argulus coregoni and Diplostomum spathaceum as case studies.

The link between climate changes and disease risks from various pathogens has been increasingly recognized. The effect of climatic factors on host-parasite population dynamics is particularly evident in northern latitudes where the occurrence and transmission of parasites are strongly regulated by seasonality-driven changes in environmental temperatures. Shortened winter periods would increase growth potential of many parasite populations. The ways in which climate warming could affect life history dynamics of the directly transmitted crustacean ectoparasite Argulus coregoni and complex life cycle trematode Diplostomum spathaceum, which frequently cause problems in northern fish farming, are discussed. Increased problems for fish farming are predicted in terms of increased infection pressure from these parasites in future. This would increase problems associated with infections and increase the use of expensive management protocols with high environmental impact.

Animals↗
PubMed1998

Evaluating functional clothing in climatic chamber tests versus field tests: a comparison of quantitative and qualitative methods in product development.

For the evaluation of clothing by human beings, two different approaches can be identified--laboratory tests (i.e. climatic chamber tests) or field trials/wear trials. It has been suggested that the performance of clothing can be adequately predicted on the basis of the data obtained from climatic chamber tests and that field trials may be expendable altogether. From a product development perspective, this paper discusses the information provided by standard data collection methods and tools for the assessment of thermal comfort used in laboratory settings and compares this information with that acquired in field trials. When assessing the information provided in the laboratory test against those questions posed in a development process, the results highlight the insufficiency of objectively measurable criteria. Therefore, objective measurements alone cannot verify the adequacy of stated requirements for thermal comfort. The use of appropriate and sensitive tools for collecting subjective votes should also be noted, since small differences in thermal sensation affected the individual's preference for clothing. Exposed differences between subjects, in terms of thermophysiological as well as subjective responses, illustrate the importance of studying individual values and deviations as opposed to strict mean values for large populations in order to satisfy a potential user group. It is argued that complementary interviews form a basis for further understanding of ratings and preferences and that they should also be included in the climatic chamber evaluation 'tool box'. User satisfaction is based on a simultaneous assessment of partly opposing properties into a satisfying use value. Although laboratory test procedures can be developed and improved in relation to design issues, field evaluations must be regarded as an integrated part of an iterative development process. Only the actual use situation can provide the total spectrum of conditions on which basis requirements and/or properties can be prioritized or downgraded. This information forms the prerequisite for successful product development.

Acclimatization↗
PubMed1989

Predicting positive goal attainment and symptom reduction from early group climate dimensions.

The general thesis of this paper is that interactional variables are the most promising way to forecast the results of psychological treatment. In particular we believe that perceived group climate dimensions early in group psychotherapy might be valuable predictors. The group atmosphere-climate dimensions, cohesion and relationship, were significant predictors of positive goal attainment and/or symptom reduction (affiliation, involvement-engagement) and so was the subscale, submission-conformity. In addition, the dimensions avoidance and anxiety were negatively correlated with the same outcome indexes. A multiple linear regression analysis suggests, however, that these significant predictions reflect the pretherapy levels of therapy projects-targets and symptoms to be reduced. This study is so promising that group therapy researchers and clinicians are recommended to exploit group climate dimensions to predict outcome.

Adaptation, Psychological↗
PubMed1983

Effect of relaxation training on personal adjustment and perceptions of organizational climate.

The chief aim of the present study was to investigate the effect of relaxation training on personal adjustment and perceptions of organizational climate. The Stern Activity Index and Organizational Climate Index along with the Bendig Manifest Anxiety Scale were administered to 71 volunteer Ss (28 males and 43 females) as pre- and post-test measures. The Ss were randomly assigned to three groups, seminar and relaxation training, seminar and a placebo condition, and no treatment. A one-way multivariate analysis showed a significant mean difference. Results obtained from t tests indicated a significant reduction in anxiety and an increase in personal adjustment. Changes in perceptions of organizational climate, although in the predicted direction, were not statistically significant.

Adaptation, Psychological↗