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PubMed1994

On the arid margin: the relationship between climate, humans and the environment. A review of evidence from the highlands of central Mexico.

There has long been speculation as to the relationship between climate, humans and the environment. Until recently, however, it has proved difficult to establish the degree to which these factors are interlinked. Here we draw on evidence that has recently emerged from a series of investigations in central México to evaluate the long-term human impact on the environment and to establish the impact that late Holocene changes in the climate have had on the indigenous populations that lived on the arid frontier of Mesoamerica. Data from these studies indicate that: 1) the indigenous peoples of central México had a significant and often detrimental impact on the landscape, causing widespread land degradation; 2) The onset of anthropogenic accelerated erosion coincided with the introduction of sedentary agriculture in this region; 3) Fluctuations in the climate of central México over the last 4,000 years have had a significant impact on the subsistence strategies of the population which extended its territory into the northern arid lands during wetter periods, but rapidly abandoned these areas when the climate became drier.

Climate↗
PubMed1994

Effects of pre-industrial human activities on climate.

Pre-industrial human activities which changed the atmospheric greenhouse gas or aerosol loading, or which modified the properties of the earth's surface, such as albedo, roughness, or vegetation cover, had the potential to modify the regional or even global climate. The primary activities which could have produced these effects were deforestation, burning, and agriculture. These activities were not independent, and often occurred together. Deforestation could have produced warming or cooling at the surface, and different effects on different scales, depending on the fate of the biomass removed and the new use of the land. Burning is much less now than it was in the past in some regions, which would have produced warming as the burning decreased. This may be a partial explanation for the Little Ice Age. While a thorough survey of such pre-industrial human activities is called for, current information indicates that regional climatic effects were large in some regions, such as western North America, and hemispheric or global effects were possible. Once these pre-industrial human climatic forcing factors are better quantified, existing numerical models of the climate can be used to examine the impacts on regional and global scales.

Agriculture↗
PubMed2006

Implications of climate change for the stomatal flux of ozone: a case study for winter wheat.

Climate change factors such as elevated CO2 concentrations, warming and changes in precipitation affect the stomatal flux of ozone (O3) into leaves directly or indirectly by altering the stomatal conductance, atmospheric O3 concentrations, frequency and extent of pollution episodes and length of the growing season. Results of a case study for winter wheat indicate that in a future climate the exceedance of the flux-based critical level of O3 might be reduced across Europe, even when taking into account an increase in tropospheric background O3 concentration. In contrast, the exceedance of the concentration-based critical level of O3 will increase with the projected increase in tropospheric background O3 concentration. The influence of climate change should be considered when predicting the future effects of O3 on vegetation. There is a clear need for multi-factorial, open-air experiments to provide more realistic information for O3 flux-effect modelling in a future climate.

Atmosphere↗
PubMed2004

Downscaling climate change scenarios in an urban land use change model.

The objective of this paper is to describe the process through which climate change scenarios were downscaled in an urban land use model and the results of this experimentation. The land use models (Urban Growth Model [UGM] and the Land Cover Deltatron Model [LCDM]) utilized in the project are part of the SLEUTH program which uses a probabilistic cellular automata protocol. The land use change scenario experiments were developed for the 31-county New York Metropolitan Region (NYMR) of the US Mid-Atlantic Region. The Intergovernmental Panel on Climate Change (IPCC), regional greenhouse gas (GHG) emissions scenarios (Special Report on Emissions Scenarios (SRES) A2 and B2 scenarios) were used to define the narrative scenario conditions of future land use change. The specific research objectives of the land use modeling work involving the SLEUTH program were threefold: (1) Define the projected conversion probabilities and the amount of rural-to-urban land use change for the NYMR as derived by the UGM and LCDM for the years 2020 and 2050, as defined by the pattern of growth for the years 1960-1990; (2) Down-scale the IPCC SRES A2 and B2 scenarios as a narrative that could be translated into alternative growth projections; and, (3) Create two alternative future growth scenarios: A2 scenario which will be associated with more rapid land conversion than found in initial projections, and a B2 scenario which will be associated with a slower level of land conversion. The results of the modeling experiments successfully illustrate the spectrum of possible land use/land cover change scenarios for the years 2020 and 2050. The application of these results into the broader scale climate and health impact study is discussed, as is the general role of land use/land cover change models in climate change studies and associated environmental management strategies.

Cities↗
PubMed2006

Climate change and human health: impacts, vulnerability and public health.

It is now widely accepted that climate change is occurring as a result of the accumulation of greenhouse gases in the atmosphere arising from the combustion of fossil fuels. Climate change may affect health through a range of pathways, for example as a result of increased frequency and intensity of heat waves, reduction in cold related deaths, increased floods and droughts, changes in the distribution of vector-borne diseases and effects on the risk of disasters and malnutrition. The overall balance of effects on health is likely to be negative and populations in low-income countries are likely to be particularly vulnerable to the adverse effects. The experience of the 2003 heat wave in Europe shows that high-income countries may also be adversely affected. Adaptation to climate change requires public health strategies and improved surveillance. Mitigation of climate change by reducing the use of fossil fuels and increasing a number of uses of the renewable energy technologies should improve health in the near-term by reducing exposure to air pollution.

Atmosphere↗
PubMed2006

Climate-change impacts on hydrology and nutrients in a Danish lowland river basin.

The Mike 11-TRANS modelling system was applied to the lowland Gjern river basin in Denmark to assess climate-change impacts on hydrology and nitrogen retention processes in watercourses, lakes and riparian wetlands. Nutrient losses from land to surface waters were assessed using statistical models incorporating the effect of changed hydrology. Climate-change was predicted by the ECHAM4/OPYC General Circulation Model (IPCC A2 scenario) dynamically downscaled by the Danish HIRHAM regional climate model (25 km grid) for two time slices: 1961-1990 (control) and 2071-2100 (scenario). HIRHAM predicts an increase in mean annual precipitation of 47 mm (5%) and an increase in mean annual air temperature of 3.2 degrees C (43%). The HIRHAM predictions were used as external forcings to the rainfall-runoff model NAM, which was set up and run for 6 subcatchments within and for the entire, Gjern river basin. Mean annual runoff from the river basin increases 27 mm (7.5%, p<0.05) when comparing the scenario to the control. Larger changes, however, were found regarding the extremes; runoff during the wettest year in the 30-year period increased by 58 mm (12.3%). The seasonal pattern is expected to change with significantly higher runoff during winter. Summer runoff is expected to increase in predominantly groundwater fed streams and decrease in streams with a low base-flow index. The modelled change in the seasonal hydrological pattern is most pronounced in first- or second-order streams draining loamy catchments, which currently have a low base-flow during the summer period. Reductions of 40-70% in summer runoff are predicted for this stream type. A statistical nutrient loss model was developed for simulating the impact of changed hydrology on diffuse nutrient losses (i.e. losses from land to surface waters) and applied to the river basin. The simulated mean annual changes in TN loads in a loamy and a sandy subcatchment were, respectively, +2.3 kg N ha(-1) (8.5%) and +1.6 kg N ha(-1) (6.9%). The rainfall-runoff model and the nutrient loss model were chained with Mike 11-TRANS to simulate the combined effects of climate-change on hydrology, nutrient losses and nitrogen retention processes at the scale of the river basin. The mean annual TN export from the river basin increased from the control to the scenario period by 7.7%. Even though an increase in nitrogen retention in the river system of 4.2% was simulated in the scenario period, an increased in-stream TN export resulted because of the simulated increase in the diffuse TN transfer from the land to the surface-waters.

Chemical Precipitation↗
PubMed2006

The influence of terrestrial ecosystems on climate.

Terrestrial ecosystems influence climate by affecting how much solar energy is absorbed by the land surface and by exchanging climatically important gases with the atmosphere. Recent model analyses show widespread qualitative agreement that terrestrial ecological processes will have a net positive feedback effect on 21st-century global warming, and, therefore, cannot be ignored in climate-change projections. However, the quantitative uncertainty in the net feedback is large. The uncertainty in 21st-century carbon dioxide emissions resulting from terrestrial carbon cycle-climate feedbacks is second in magnitude only to the uncertainty in anthropogenic emissions. We estimate that this translates into an uncertainty in global warming owing to the land surface of 1.5 degrees C by 2100. We also emphasise the need to improve our understanding of terrestrial ecological processes that influence land-atmosphere interactions at relatively long timescales (decadal-century) as well as at shorter intervals (e.g. hourly).

Climate↗
PubMed2001

Comparison of laboratory studies with predictions of the required sweat rate index (ISO 7933) for climates with moderate to high thermal radiation.

For International Standard ISO 7933 (Hot environments-analytical determination and interpretation of thermal stress using calculation of required sweat rate. International Organization for Standardization, Geneva, 1989) it has been questioned whether the heat stress index "required sweat rate" is applicable in environments where mean radiant temperature (t(r)) exceeds dry air temperature (t(a)). Based on a re-analysis of 556 climatic chamber experiments on 16 subjects the observed sweat rates were compared with required sweat rates predicted according to the ISO standard. Under climatic conditions with t(r) > t(a) the predictions overestimate the observed sweat rates on average by 86% in clothed subjects and by 25% in nude subjects. In climates with t(r) = t(a) the predictions highly agreed with the observed sweat rates in nude subjects and were slightly overestimated (13%) in clothed subjects. The misjudgement of the present ISO standard is obviously caused by an inappropriate calculation of radiative heat exchange. Corrections are proposed to improve the validity concerning climates with t(r) > t(a).

Adult↗
PubMed1998

Mosquito-borne arboviruses in Australia: the current scene and implications of climate change for human health.

Of the mosquito-borne arboviruses, the encephalitic Murray Valley encephalitis and Kunjin viruses are a major public health concern, but the arthritides Ross River and Barmah Forest viruses are more important in a public health sense, being responsible for a far greater number of infections. Reported cases of Ross River totalled approximately 30,000 during 1991-1996; there have been several widely separated outbreaks of Barmah Forest in recent years and case reports are increasing annually. Surveillance programmes have increased our understanding of the geographic regions, climatic conditions and vector factors associated with viruses. Virus activity is widespread but is often localised, is driven primarily by mosquito abundance and various species are involved; host factors are involved also, but are not well understood. Typically, mosquito populations are governed by availability of habitat and environmental conditions. Models of climate change predict increases in rainfall, tides and temperature for parts of Australia, and such changes have the potential to increase the risk of arbovirus transmission by increasing the distribution and abundance of vectors, and duration of mosquito and arbovirus seasons. However, the amplitude of climate change is uncertain and the ecology of arbovirus transmission is complex. It is likely that some areas will have increases in arbovirus activity and human infection with predicted climate change, but risk of increased transmission will vary with locality, vector, host and human factors.

Alphavirus Infections↗
PubMed2004

The influence of climate on the epidemiology of bartonellosis in Ancash, Peru.

The aim of this study was to evaluate the association between bartonellosis and selected climatic factors during the time periods 1983-1988 and 1995-99, which included two events of the El Niño phenomenon (1986-88, 1997-98), and to identify a reliable climate parameter to be used as an alert indicator for bartonellosis outbreaks in Ancash. The study site was Ancash and its province Carhuaz, Peru. Time-series cross-correlation analysis was used to assess the association between bartonellosis and climate parameters. A higher, almost 4-fold, monthly bartonellosis incidence risk in Ancash department was observed during the El Niño events of 1986-88 and 1997-98. At a regional (Ancash department) and local level (Carhuaz, Ancash), the best correlation was observed between bartonellosis and sea-surface temperature (SST). The results indicate that SST would be the best climate parameter to be used as an alert indicator for bartonellosis outbreaks in Ancash.

Bartonella Infections↗
PubMed2000

Climate change and forest fires.

This paper addresses the impacts of climate change on forest fires and describes how this, in turn, will impact on the forests of the United States. In addition to reviewing existing studies on climate change and forest fires we have used two transient general circulation models (GCMs), namely the Hadley Centre and the Canadian GCMs, to estimate fire season severity in the middle of the next century. Ratios of 2 x CO2 seasonal severity rating (SSR) over present day SSR were calculated for the means and maximums for North America. The results suggest that the SSR will increase by 10-50% over most of North America; although, there are regions of little change or where the SSR may decrease by the middle of the next century. Increased SSRs should translate into increased forest fire activity. Thus, forest fires could be viewed as an agent of change for US forests as the fire regime will respond rapidly to climate warming. This change in the fire regime has the potential to overshadow the direct effects of climate change on species distribution and migration.

Animals↗
PubMed2002

Living with uncertainty: climate change, river flows and water resource management in Scotland.

The recent increased variability of Scotland's hydroclimate poses major problems for water resource managers charged with making informed investment decisions given the likely impact of future climate change. Two strategies are developed in this paper to assist managers faced with this environmental uncertainty. The first involves trend analysis of precipitation and runoff since the 1960s and 1970s viewed against longer-term variability reported from instrumental records. The second strategy is based upon current climate change scenarios coupled with GCMs, and downscaling of precipitation and temperature to provide inputs to rainfall-runoff models. The long-term records of precipitation (back to the 1860s) and runoff (back to the 1930s) reveal the late 1980s and early 1990s as the wettest period on record for the west but not for the east. Over the period 1961-1996 the precipitation gradient has intensified across Scotland: wetter west; relatively dry east. Changes in runoff over the period 1970-1996 are also reported with increases in annual flows at 33 out of 38 stations (significantly at 12 stations) and decreases in low flows at 21 out of 38 stations (significantly at one station). The bulk of these flow increases occurred in the south and west especially in the autumn and spring. In terms of high flows over the period 1970-1996, four out of 44 stations reported a change in magnitude and 15 reported an increase in the frequency of POT events. In terms of future climate change, Hulme and Jenkins (1998) predict annual precipitation increases of 6-16% (Scotland) and 6-14% (Scottish Borders) from the 2020s to the 2080s based on the Hadley Centre model (HadCM2) medium-high scenario. Seasonal changes are concentrated in the autumn (SON) and winter (DJF) with increases as high as 24 and 29% for the autumn by the 2080s. (Arnell NW, et al. Institute of Hydrology Report No. 107, Wallingford, 1996), using an earlier transient Hadley experiment (IS92a), predict a 5-15% increase in annual runoff across Scotland by the 2050s, locally rising to 25%. Simulation flow duration curves for the 2050s generate Q95 values up by 5% or less (Rivers Don, Almond and Nith) and Q5 up by 10-24% (Rivers Don, Almond, Nith and Lyne Water). In terms of water resource planning, these predicted changes should be regarded as first order approximations, as they take no account of natural climatic variability, and could generate different absolute values if other scenarios were used. The predictions are, however, broadly consistent with trends in precipitation and runoff for Scotland since the 1970s. Major issues of concern to water resource managers are identified and commented upon in the light of these predictions.

Climate↗
PubMed2001

Tick-borne encephalitis in Sweden and climate change.

BACKGROUND: The incidence of tick-borne encephalitis (TBE) in Sweden has substantially increased since the mid-1980s. During the same period the climate has become milder and ticks have become more abundant. We investigated whether there is a link between the change in climate and the increase in incidence of TBE. METHODS: Since the late 1950s all cases of encephalitis admitted in Stockholm County have been serologically tested for TBE. We analysed the period 1960-98 with multiple regressions. The number of days per season with temperatures of known importance for tick prevalence and pathogen transmission were studied. 2 years of temperature data were related to each TBE incidence rate to account for the tick's long life-span. FINDINGS: Increases in disease incidence was significantly related (R(2)=0.58; p<0.0001) to a combination of two consecutive mild winters, temperatures favouring spring development (8-10 degrees C) and extended autumn activity (5-8 degrees C) in the year prior to the incidence year, and temperatures allowing tick activity (5-8 degrees C) early in the incidence year. INTERPRETATIONS: The findings indicate that the increase in TBE incidence since the mid-1980s is related to the period's change towards milder winters and early arrival of spring. Other factors may have influenced TBE incidence such as more people in endemic locations, and increases in host animal populations; factors which are partly climate related. Access to TBE vaccination since 1986 and increased awareness of ticks might have caused an underestimation of the links found. Our findings also suggest that the incidence of other tick-borne zoonoses might have been affected by the milder climate.

Animals↗
PubMed2006

Climate change and human health: impacts, vulnerability, and mitigation.

It is now widely accepted that climate change is occurring as a result of the accumulation of greenhouse gases in the atmosphere arising from the combustion of fossil fuels. Climate change may affect health through a range of pathways--eg, as a result of increased frequency and intensity of heat waves, reduction in cold-related deaths, increased floods and droughts, changes in the distribution of vector-borne diseases, and effects on the risk of disasters and malnutrition. The overall balance of effects on health is likely to be negative and populations in low-income countries are likely to be particularly vulnerable to the adverse effects. The experience of the 2003 heat wave in Europe shows that high-income countries might also be adversely affected. Adaptation to climate change requires public-health strategies and improved surveillance. Mitigation of climate change by reducing the use of fossil fuels and increasing the use of a number of renewable energy technologies should improve health in the near term by reducing exposure to air pollution.

Aged↗
PubMed2003

Influence of climatic conditions and soil type on 99TcO4- uptake by rye grass.

Climatic changes over the long term will modify significantly the biosphere, with glaciation events probably taking place in the next 100 000 years. This is important to safety assessments of nuclear waste disposal facilities that contain high-level and long-lived waste. The soils will evolve toward new situations, and their properties will be consequently modified (e.g. an increase of soil organic matter may be expected in a cooler climate). These changes in soil properties would affect the mobility and the soil-to-plant transfer of radionuclides such as (99)Tc. This study aimed at simulating the cooling of climatic conditions for soils representative of a Jurassic limestone plateau, and the effect on transfer parameters of (99)TcO(4)(-) in the soil-plant systems was investigated. The cooler conditions were simulated by increasing elevation, a surrogate for climate change. Soils were sampled in similar geological background and topography at different elevations in the north east of France (Lorraine and Jura). Soil/solution distribution coefficients (K(d)) of (99)TcO(4)(-) were measured on soil samples in short-term batch experiments with 1:10 soil:solution ratio. Rye grass was grown on the soils spiked with (99)TcO(4)(-) at temperature regimes adapted to each soil. Also, two different temperature regimes (cold and temperate) were applied to one soil to test the effect of plant physiology and evapotranspiration on (99)TcO(4)(-) uptake. K(d) values did not show significant differences among soils in aerobic conditions, and were not significantly different from 0. During plant culture, reduction of (99)Tc was never totally achieved in soils, including in a peaty OM soil. Concentration ratios (CR) were calculated on a dry weight basis and ranged from 20 to 370. CR were always higher in high temperature regimes than in cold temperatures. They were also inversely correlated with soil organic matter (OM) content. A decrease of CR values from 5 to 10-fold was observed with increasing soil OM. Results suggested that the water holding capacity, in which (99)Tc is diluted, the nitrification potential of the soils and the evapotranspiration of plants (efficiency of uptake of soluble (99)TcO(4)(-)) were strongly involved in these differences.

Biological Availability↗
PubMed1986

Distribution and management of cattle in relation to climatic zones within North America.

The United States has a diversity of climates, as noted earlier. Although one can describe, as was done here, a grid of zones based on average temperature, rainfall, and terrain, the complexity of climates within these zones based on elevation, rainfall, and temperature requires much closer evaluation. The practicing veterinarian or animal husbandman must evaluate the specific climatic conditions prevailing on the farm or ranch in question and integrate the components of that climate into the management or health practices to be recommended. There is no substitute for careful observation.

Animal Husbandry↗
PubMed2003

Climatic oscillations triggered post-Messinian speciation of Western Palearctic brown frogs (Amphibia, Ranidae).

Oscillating glacial cycles over the past 2.4 million years are proposed to have had a major impact on the diversity of contemporary species communities. We used mitochondrial and nuclear DNA sequence data to infer phylogenetic relationships within Western Palearctic brown frogs and to test the influence of Pliocene and Pleistocene climatic changes on their evolution. We sequenced 1976bp of the mitochondrial genes 16S rRNA and cytochrome b and of the nuclear rhodopsin gene for all current species and subspecies. Based on an established allozyme clock for Western Palearctic water frogs and substitution rate constancy among water frogs and brown frogs, we calibrated a molecular clock for 1425bp of the 16S and rhodopsin genes. We applied this clock to date speciation events among brown frogs. Western Palearctic brown frogs underwent a basal post-Messinian radiation about 4 million years ago (mya) into five major clades: three monotypic lineages (Rana dalmatina, Rana latastei, Rana graeca), an Anatolian lineage, and a lineage comprising Rana italica, Rana arvalis, and all Iberian taxa. Polytypic lineages radiated further in concordance with the onset of climatic oscillations ca. 3.2, 2.0, and 1.0-0.6 mya, respectively. The dated fossil record corroborates our paleobiogeographic scenario. We conclude that drastic climatic changes followed by successive temperature oscillations "trapped" most brown frog species in their southern European glacial refugia with enough time to speciate. Substantial dispersal was only possible during extensive interglacial periods of a constant subtropical climate.

Animals↗
PubMed2002

Hot topic or hot air? Climate change and malaria resurgence in East African highlands.

Climate has a significant impact on malaria incidence and we have predicted that forecast climate changes might cause some modifications to the present global distribution of malaria close to its present boundaries. However, it is quite another matter to attribute recent resurgences of malaria in the highlands of East Africa to climate change. Analyses of malaria time-series at such sites have shown that malaria incidence has increased in the absence of co-varying changes in climate. We find the widespread increase in resistance of the malaria parasite to drugs and the decrease in vector control activities to be more likely driving forces behind the malaria resurgence.

Africa, Eastern↗