Reduction In Diurnal Temperature Range Research Articles

Wildfires affect tree growth and resilience in Northeastern China natural Dahurian larch forests: A dendrochronological perspective

Wildfires are natural and ubiquitous disturbances in boreal forests. Assessing their impacts on tree growth and resilience are particularly important to recognize the adaptation strategies of fire-tolerant species and forest succession in fire conditions. To date, the growth resilience of fire-tolerant species in boreal forests remains largely unquantified, and the drivers of resilience are poorly understood. Here, we measured the tree-ring widths of 99 fire-scarred trees from three sites in natural Dahurian larch (Larix gmelinii) forests. Three moderate-severity fire events in years 1987, 1990, and 2000 occurring at three sites were detected from the records of local forestry bureau. Based on tree-ring width data, we calculated resilience components (i.e., resistance, recovery, resilience and relative resilience) to quantify the responses of growth resilience in the larch trees to fires and analyzed their drivers at three sites. Results indicated that fires significantly reduced the tree growth. With the increasing tree age, these reductions were more pronounced. As for resilience components, our study showed a limited resistance but high recovery of tree growth against fires, and resistance tended to increase northwards but recovery showed the opposite, suggesting a growth-survival tradeoff was exhibited in Dahurian larch trees. With an increasing tree age, regional resistance and resilience showed a decreasing trend, whereas recovery and relative resilience showed an increasing trend. Resilience components were mainly affected by the climatic factors in spring. An increase in moisture availability enhanced resistance, a reduction in diurnal temperature range enhanced recovery, and an increase in mean temperature enhanced resilience and relative resilience. This study reveals that Dahurian larch could be even less favorable when faced with moderate or severe fire events, but a high capacity of recovery enables this species to adapt to the fire-prone condition. Moreover, this work highlights that the resilience of tree growth should be considered to understand tree behaviors and survival strategies of boreal forests following fires across fire-prone regions under future climate warming.

Tree‐ring reconstructed diurnal temperature range on the eastern Tibetan plateau and its linkage to El Niño‐Southern Oscillation

AbstractThe decreasing trend in diurnal temperature range (DTR) since the 1950s has been widely observed in many regions of the world, including the Tibetan Plateau (TP). However, scarce instrumental records on the TP before the 1950s limit the understanding of DTR variation on a longer timescale, and its internal forcing mechanisms remain unclear. Here, we present two regional records of May–June DTR since 1753 reconstructed from tree rings on the northeastern TP (NETP) and southeastern TP (SETP), respectively. The decreasing trend in DTR in the second half of the twentieth century also occurred in the time earlier than the 1950s, indicating that the reduction in DTR is not unique to global warming. Spatially, both the instrumental and reconstructed DTR show different modes on the NETP and SETP. Composite analysis and superposed epoch analysis reveal the linkage between El Niño‐Southern Oscillation (ENSO) and the DTR on the SETP. La Niña (El Niño) winters are generally followed by the stronger (weaker) early Indian summer monsoon so that may lead to the decrease (increase) in May–June DTR. The positive correlation between Niño 3.4 index and the DTR on the SETP over the past two and a half centuries is accompanied by a stable response of the decreased DTR to La Niña events. These results suggest that ENSO is a crucial driver for the DTR variation on the SETP through oceanic‐atmospheric modulation.

How aerosols and greenhouse gases influence the diurnal temperature range

Abstract. The diurnal temperature range (DTR) (or difference between the maximum and minimum temperature within a day) is one of many climate parameters that affects health, agriculture and society. Understanding how DTR evolves under global warming is therefore crucial. Physically different drivers of climate change, such as greenhouse gases and aerosols, have distinct influences on global and regional climate. Therefore, predicting the future evolution of DTR requires knowledge of the effects of individual climate forcers, as well as of the future emissions mix, in particular in high-emission regions. Using global climate model simulations from the Precipitation Driver and Response Model Intercomparison Project (PDRMIP), we investigate how idealized changes in the atmospheric levels of a greenhouse gas (CO2) and aerosols (black carbon and sulfate) influence DTR (globally and in selected regions). We find broad geographical patterns of annual mean change that are similar between climate drivers, pointing to a generalized response to global warming which is not defined by the individual forcing agents. Seasonal and regional differences, however, are substantial, which highlights the potential importance of local background conditions and feedbacks. While differences in DTR responses among drivers are minor in Europe and North America, there are distinctly different DTR responses to aerosols and greenhouse gas perturbations over India and China, where present aerosol emissions are particularly high. BC induces substantial reductions in DTR, which we attribute to strong modeled BC-induced cloud responses in these regions.

Evaluating the impacts of climate change on the diurnal temperature range (DTR) in southeastern of Iran using the outputs of AOGCMs

Changes in global diurnal temperature range (DTR) areas are useful indicator of climate change. The present study aims at evaluating the impacts of climate change on DTR in southeastern of Iran by using 15 models of Atmospheric-Ocean General Circulation Model (AOGCM). Daily time series of parameters of minimum temperature and maximum temperature and the rainfall during the period were initially extracted. By making use of the aforementioned 48-year time series, the input for model LARS-WG was prepared. The model, then, was calibrated. By comparing changes in the next period to the previous one, impacts of climate change on variability of climate parameters affected by AOGCM were evaluated. Verification results of the minimum temperature and maximum temperature components showed that models HadGEM and GFCM21, respectively, are the most appropriate models for simulating the temperature components, with the least mean absolute error. Data analysis showed that the average hot days on the next period will increase then the base period and the average frost in the next climatic period will decrease in all months than the base which itself is a reason to increased average of minimum temperature component over the maximum one in the next climatic period. At the end, results obtained from investigating the impacts of average temperature components during the year showed that climate change in summer and autumn reduce the DTR on southeastern Iran. The maximum reduction in DTR occurs in late summer and mid-autumn.

Impacts of Small-Scale Urban Encroachment on Air Temperature Observations

AbstractA field experiment was performed in Oak Ridge, Tennessee, with four instrumented towers placed over grass at increasing distances (4, 30, 50, 124, and 300 m) from a built-up area. Stations were aligned in such a way to simulate the impact of small-scale encroachment on temperature observations. As expected, temperature observations were warmest for the site closest to the built environment with an average temperature difference of 0.31° and 0.24°C for aspirated and unaspirated sensors, respectively. Mean aspirated temperature differences were greater during the evening (0.47°C) than during the day (0.16°C). This was particularly true for evenings following greater daytime solar insolation (20+ MJ day−1) with surface winds from the direction of the built environment where mean differences exceeded 0.80°C. The impact of the built environment on air temperature diminished with distance with a warm bias only detectable out to tower B′ located 50 m away. The experimental findings were comparable to a known case of urban encroachment at a U.S. Climate Reference Network station in Kingston, Rhode Island. The experimental and operational results both lead to reductions in the diurnal temperature range of ~0.39°C for fan-aspirated sensors. Interestingly, the unaspirated sensor had a larger reduction in diurnal temperature range (DTR) of 0.48°C. These results suggest that small-scale urban encroachment within 50 m of a station can have important impacts on daily temperature extrema (maximum and minimum) with the magnitude of these differences dependent upon prevailing environmental conditions and sensing technology.

Effect of weakened diurnal evolution of atmospheric boundary layer to air pollution over eastern China associated to aerosol, cloud – ABL feedback

Upon the effect of atmospheric stability on air pollution, this study highlights the weakened diurnal evolution of atmospheric boundary layer (ABL), which is crucial to the formation of regional fog-haze and air pollution episodes over eastern China (ECN). The decrease of atmospheric visibility (Vis) during 1973–2012 is found to be related to the more stable ABL with weakened diurnal evolution that is characterized by a concurrent weakening of surface wind, a decrease in ABL height, and a reduction of diurnal temperature range (DTR, – 0.26 and – 0.092 °C/10-years in the winter and summer, respectively). With a general synchronous variation, the increase in both aerosol loading and cloud cover might work in concert to reduce solar radiation reaching the surface, stabilize ABL and weaken the diurnal ABL evolution, thereby weakening the turbulent mixing of pollutants and enhancing air pollution. This conjecture of “aerosol, cloud – ABL – air pollution” feedback, with particular emphasis on the effect of cloud (in addition to the effect of aerosol) on the ABL evolution, is supported by our analysis of 40 years trends in the cloud, Vis and DTR from surface observation, the aerosol optical depth from MODIS, and the validated MERRA-2 reanalysis aerosol, cloud and boundary layer height (by surface observation and routine radiosonde sounding). Regarding the linkage between fog-haze and diurnal evolution of the ABL, the result emphasizes the effect of a persistent high relative humidity (RH), which is found to be important to the formation of regional persistent fog-haze episodes and must be carefully considered in future study. Therefore, a chain of processes is suggested to interpret the occurrence of regional persistent fog-haze episodes over ECN. First, during a polluted day, because of aerosol radiative effects, the high ABL stability and high RH can persist throughout the day, and consequently, favoring the accumulation of pollutants as well as the secondary formation and hygroscopic growth of aerosol. Second, the maintenance of such more stable, humid and polluted ABL is in contrast to a clear day when the ABL is more convective in the afternoon and facilitates the diffusion and dilution of pollutants. Third, under a persistent stable synoptic system, the increase of air pollution associated with the weakened diurnal evolution of ABL due to the “aerosol, cloud – ABL – air pollution” feedback, as described above, can be further strengthened, thereby renders more persistent and severe air pollution events. The DTR variation in relationship with the aerosol, cloud, ABL and air pollution is also discussed.

Diurnal temperature range in CMIP5 models and observations on the Tibetan Plateau

The diurnal temperature range (DTR), defined as the difference between the maximum and minimum temperature, is a useful diagnostic index for evaluating global climate models. In this study, the DTR from 17 GCMs available in the fifth phase of the Coupled Model Intercomparison Project (CMIP5) is evaluated on the Tibetan Plateau (TP) by comparison with the observations during 1961–2005. During the studied period, the observed maximum/minimum temperatures on the TP show statistically increasing trends with the annual rates of 0.19/0.36 °C decade−1, respectively, leading to the reduction of DTR (−0.22 °C decade−1). Compared with the observed DTR, most CMIP5 models generally underestimate DTR, with absolute error ranging from −4.58 °C (GFDL‐ESM2M) to −1.36 °C (CESM1‐BGC). Fifteen CMIP5 models have reproduced the overall negative trends of DTR on the TP, but their trend magnitudes are smaller. Furthermore, the CMIP5 model biases in DTR are investigated by means of correlative approach, to reveal the dominant variables. The differences between the surface downwelling short‐wave radiation (SDSR) with clear skies (SDSRcs) and the SDSR can be used to describe the surface short‐wave cloud radiative effect. Similarly, the differences between the surface downwelling long‐wave radiation (SDLR) and the SDLR with clear skies (SDLRcs) are defined to address the surface long‐wave cloud radiative effect. It is found that the mean DTR in the CMIP5 models has significantly negative correlations with both SDLR–SDLRcs and SDSRcs–SDSR, suggesting that the model differences in DTR on the TP are probably determined by radiation variables and total cloud fraction in the CMIP5 models.

The Influence of the Intermittent Behavior of the Nocturnal Atmospheric Flow on the Prediction of the Diurnal Temperature Range: A Simplified Model Analysis

The variation of the atmospheric temperature near the surface associated with anthropogenic effects is analyzed using a simplified atmospheric model. Local changes in cloud cover and four different scenarios of atmospheric concentration of carbon dioxide are considered. The results show that the highest temperature variability occurs in the weak wind and decoupled state and in the transition between flow regimes. In agreement with previous efforts, the results indicate that the reduction of diurnal temperature range is related to the existence of two distinct flow regimes in the stable boundary layer. However, in the decoupled state, the occurrence of intermittent bursts of turbulence may cause temperature variations among the different scenarios to become unpredictable. It implies that it is difficult to predict the diurnal temperature range in places where low winds are common.

Reassessing changes in diurnal temperature range: A new data set and characterization of data biases

AbstractIt has been a decade since changes in diurnal temperature range (DTR) globally have been assessed in a stand‐alone data analysis. The present study takes advantage of substantively improved basic data holdings arising from the International Surface Temperature Initiative's databank effort and applies the National Centers for Environmental Information's automated pairwise homogeneity assessment algorithm to reassess DTR records. It is found that breakpoints are more prevalent in DTR than other temperature elements and that the resulting adjustments have a broader distribution. This strongly implies that there is an overarching tendency, across the global meteorological networks, for nonclimatic artifacts to impart either random or anticorrelated rather than correlated biases in maximum and minimum temperature series. Future homogenization efforts would likely benefit from simultaneous consideration of DTR and maximum and minimum temperatures, in addition to average temperatures. Estimates of change in DTR are relatively insensitive to whether adjustments are calculated directly or inferred from adjustments returned for the maximum and minimum temperature series. The homogenized series exhibit a reduction in DTR since the midtwentieth century globally (−0.044 K/decade). Adjustments serve to approximately halve the long‐term global reduction in DTR in the basic “raw” data. Most of the estimated DTR reduction occurred over 1960–1980. In several regions DTR has apparently increased over 1979–2012, while globally it has exhibited very little change (−0.016 K/decade). Estimated changes in DTR are an order of magnitude smaller than in maximum and minimum temperatures, which have both been increasing rapidly on multidecadal timescales (0.186 K/decade and 0.236 K/decade, respectively, since the midtwentieth century).

The interrelationship between dengue incidence and diurnal ranges of temperature and humidity in a Sri Lankan city and its potential applications

BackgroundTemperature, humidity, and other weather variables influence dengue transmission. Published studies show how the diurnal fluctuations of temperature around different mean temperatures influence dengue transmission. There are no published studies about the correlation between diurnal range of humidity and dengue transmission.ObjectiveThe goals of this study were to determine the correlation between dengue incidence and diurnal fluctuations of temperature and humidity in the Sri Lankan city of Kandy and to explore the possibilities of using that information for better control of dengue.DesignWe calculated the weekly dengue incidence in Kandy during the period 2003–2012, after collecting data on all of the reported dengue patients and estimated midyear populations. Data on daily maximum and minimum temperatures and night-time and daytime humidity were obtained from two weather stations, averaged, and converted into weekly data. The number of days per week with a diurnal temperature range (DTR) of >10°C and <10°C and the number of days per week with a diurnal humidity range (DHR) of >20 and <15% were calculated. Wavelet time series analysis was performed to determine the correlation between dengue incidence and diurnal ranges of temperature and humidity.ResultsThere were negative correlations between dengue incidence and a DTR >10°C and a DHR >20% with 3.3-week and 4-week lag periods, respectively. Additionally, positive correlations between dengue incidence and a DTR <10°C and a DHR <15% with 3- and 4-week lag periods, respectively, were discovered.ConclusionsThese findings are consistent with the results of previous entomological studies and theoretical models of DTR and dengue transmission correlation. It is important to conduct similar studies on diurnal fluctuations of humidity in the future. We suggest ways and means to use this information for local dengue control and to mitigate the potential effects of the ongoing global reduction of DTR on dengue incidence.

The impacts of long‐lived jet contrail ‘outbreaks’ on surface station diurnal temperature range

ABSTRACTMultiple persistent jet aviation contrails – contrail ‘outbreaks’ – occur frequently over certain portions of the Continental United States (CONUS). The artificial cloudiness generated by contrail outbreaks alters the atmospheric radiation budget, potentially impacting the surface air temperature, particularly the diurnal temperature range (DTR), or difference between daytime maximum and nighttime minimum temperatures. This study evaluates the hypothesis that contrail outbreaks reduce the DTR relative to clear‐sky conditions. We utilize a database of longer‐lived (&gt;4 h duration) jet contrail outbreaks for the CONUS previously determined from interpretation of high‐resolution satellite imagery, for the January and April months of 2008 and 2009. The outbreak impact on DTR was determined by comparing maximum and minimum temperatures at pairs of surface weather stations (one outbreak and one non‐outbreak) across two regions of climatologically high outbreak frequency; the South in January, and Midwest in April. We ensured that each station pair selected had broadly similar land use‐land cover, soil moisture, and synoptic air mass conditions. For outbreaks in the South (January), there was a statistically significant reduction of DTR at the outbreak versus non‐outbreak stations. This result was similar to that obtained for a smaller subset of outbreaks for which lower‐level clouds could be confirmed as being absent (from North American Regional Reanalysis (NARR) output). For the Midwest (April), the results are mixed; statistically different for satellite‐retrieved outbreaks, but not significantly different for the NARR‐validated dataset. These results suggest that persistent jet contrails should be considered in short‐term weather forecasting, and for their potential influence on the climatology of more frequently impacted areas.

Impacts of Regional-Scale Land Use/Land Cover Change on Diurnal Temperature Range

The NCAR Community Atmosphere Model (CAM4.0) was used to investigate the climate effects of land use/land cover change (LUCC). Two simulations, one with potential land cover without significant human intervention and the other with current land use, were conducted. Results show that the impacts of LUCC on diurnal temperature range (DTR) are more significant than on mean surface air temperature. The global average annual DTR change due to LUCC is −0.1°C, which is three times as large as the mean temperature change. LUCC influences regional DTR as simulated by the model. In the mid-latitudes, LUCC leads to a decrease in DTR, which is mainly caused by the reduction in daily maximum temperature. However, there are some differences in the low latitudes. The reduction in DTR in East Asia is mainly the result of the decrease in daily maximum temperature, while in India, the decrease in DTR is due to the increase in daily minimum temperature. In general, the LUCC significantly controls the DTR change through the changes in canopy evaporation and transpiration. CitationHua, W.-J., and H.-S. Chen, 2013: Impacts of regional-scale land use/land cover change on diurnal temperature range. Adv. Clim. Change Res., 4(3), doi: 10.3724/SP.J.1248.2013.166.

Modeled rapid adjustments in diurnal temperature range response to CO2 and solar forcings

We used the National Center for Atmospheric Research single column climate model to determine if rapid adjustments to surface heat fluxes contribute to a change in skin surface or surface air diurnal temperature range (DTR) under 2 × CO2 and −2% solar forcings. An ensemble of model runs was employed with locations selected to represent a range of different climatic conditions and with forcing implemented hourly throughout the diurnal cycle. The change in skin surface DTR and surface energy fluxes during the 3 days after forcing were used to quantify the rapid adjustment response and temperature related feedback. Averaged over all locations, skin surface DTR reduced by 0.01°C after CO2 forcing and included a rapid adjustment to skin surface DTR of −0.12°C. Skin surface DTR reduced by 0.17°C after solar forcing and included a rapid adjustment of −0.01°C. The rapid adjustments in skin surface DTR were associated with rapid adjustments in surface sensible and latent heat fluxes necessary to balance the energy budget immediately after forcing. We find that the sensitivity of skin surface DTR to mean temperature related feedback is the same for CO2 and solar forcings when skin surface DTR rapid adjustments are allowed for. Rapid adjustments played a key role in the geographic variation of the skin surface DTR response to forcing. Our results suggest that diurnal variations in trends of downwelling longwave radiation and rapid reductions in DTR associated with CO2 forcing potentially contributed to the observed global trend in surface air DTR.

Urban and Regional Temperature Trends in Las Vegas and Southern Nevada

Urban and regional temperature trends in southern Nevada, including the rapidly growing Las Vegas metropolitan area, were analyzed over two periods, 1940–2009 and 1977–2009. The data show that minimum temperatures in Las Vegas increased by more than 4°C above the regional trend since 1940 and by approximately 3°C more than the regional average since 1977, which demonstrates that urbanization has significantly altered the nighttime climate of the city and that the changes were most pronounced in the last 30 years. In contrast, regional minimum temperature increases were not widespread and generally limited to spring and summer with a regional annual average minimum temperature increase of about 1°C since 1940 and 0.6°C since 1977. Notably, there is little evidence of winter temperature moderation throughout rural southern Nevada in either time period investigated. The analysis also suggests maximum temperature trends in Las Vegas have been moderated by urbanization, as daytime temperatures across southern Nevada increased by approximately 1°C in the last 30 years, but no increase was observed within the city suggesting that Las Vegas has developed a moderate daytime urban cool island. While no absolute change in Las Vegas dewpoint temperatures was found, a relative increase of up to 3°C was observed when the city was compared to a rural control station. The relative increase in urban dewpoint temperature is significantly correlated to the daytime urban cooling trend, minimum temperature increase, and the significant reduction in diurnal temperature range, suggesting that increased latent heat flux in Las Vegas may be a primary cause of observed urban climate changes.

Diurnally Asymmetric Trends of Temperature, Humidity, and Precipitation in Taiwan

AbstractIn this work, 45 years (1961–2005) of hourly meteorological data in Taiwan, including temperature, humidity, and precipitation, have been analyzed with emphasis on their diurnal asymmetries. A long-term decreasing trend for relative humidity (RH) is found, and the trend is significantly greater in the nighttime than in the daytime, apparently resulting from a greater warming at night. The warming at night in three large urban centers is large enough to impact the average temperature trend in Taiwan significantly between 1910 and 2005. There is a decrease in the diurnal temperature range (DTR) that is largest in major urban areas, and it becomes smaller but does not disappear in smaller cities and offshore islands. The nighttime reduction in RH is likely the main cause of a significant reduction of fog events over Taiwan. The smaller but consistent reductions in DTR and RH in the three off-coast islands suggests that, in addition to local land use changes, a regional-scale process such as the indirect effect of anthropogenic aerosols may also contribute to these trends. A reduction in light precipitation (&amp;lt;4 mm h−1) and an increase in heavy precipitation (&amp;gt;10 mm h−1) are found over Taiwan and the offshore islands. The changes in precipitation are similar to the changes of other areas in Asia, but they are different from those of the United States, Europe, and the tropical oceans. The latter do not show any reduction in light precipitation.

Detection and attribution of anthropogenic forcing to diurnal temperature range changes from 1950 to 1999: comparing multi-model simulations with observations

Observations show that the surface diurnal temperature range (DTR) has decreased since 1950s over most global land areas due to a smaller warming in maximum temperatures (T max) than in minimum temperatures (T min). This paper analyzes the trends and variability in T max, T min, and DTR over land in observations and 48 simulations from 12 global coupled atmosphere-ocean general circulation models for the later half of the 20th century. It uses the modeled changes in surface downward solar and longwave radiation to interpret the modeled temperature changes. When anthropogenic and natural forcings are included, the models generally reproduce observed major features of the warming of T max and T min and the reduction of DTR. As expected the greenhouse gases enhanced surface downward longwave radiation (DLW) explains most of the warming of T max and T min while decreased surface downward shortwave radiation (DSW) due to increasing aerosols and water vapor contributes most to the decreases in DTR in the models. When only natural forcings are used, none of the observed trends are simulated. The simulated DTR decreases are much smaller than the observed (mainly due to the small simulated T min trend) but still outside the range of natural internal variability estimated from the models. The much larger observed decrease in DTR suggests the possibility of additional regional effects of anthropogenic forcing that the models can not realistically simulate, likely connected to changes in cloud cover, precipitation, and soil moisture. The small magnitude of the simulated DTR trends may be attributed to the lack of an increasing trend in cloud cover and deficiencies in charactering aerosols and important surface and boundary-layer processes in the models.

Attribution of Recent Temperature Changes in the Australian Region

Abstract Variations of Australian-average mean temperature and diurnal temperature range over the twentieth century are investigated. The observed interannual variability of both is simulated reasonably well by a number of climate models, but they do not simulate the observed relationship between the two. Comparison of the observed warming and reduction in diurnal temperature range with climate model simulations shows that Australian temperature changes over the twentieth century were very unlikely to be due to natural climate variations alone. It is likely that there has been a significant contribution to the observed warming during the second half of the century from increasing atmospheric greenhouse gases and sulfate aerosols.

Diurnal temperature range as an index of global climate change during the twentieth century

The usefulness of global‐average diurnal temperature range (DTR) as an index of climate change and variability is evaluated using observations and climate model simulations representing unforced climate variability and anthropogenic climate change. On decadal timescales, modelled and observed intrinsic variability of DTR compare well and are independent of variations in global mean temperature. Observed reductions in DTR over the last century are large and unlikely to be due to natural variability alone. Comparison of observed and anthropogenic‐forced model changes in DTR over the last 50 years show much less reduction in DTR in the model simulations due to greater warming of maximum temperatures in the models than observed. This difference is likely attributed to increases in cloud cover that are observed over the same period and are absent in model simulations.

Climate Change and its Consequences

Most General Circulation Models (GCMs) realistically simulate large-scale circulation patterns, particularly monsoonal winds over the Asian and Australian regions and their related rainfall patterns, but they underestimate observed magnitudes of these variables. The consistency between model-predicted and observed changes in surface temperature during the last 100 years is good, particularly when these models include the combined effects of increases in carbon dioxide (CO2), sulfate aerosols and solar influences. However, these models underestimate the degree of variability in daily weather phenomena that are associated with local- and meso-scale circulation patterns and daily rainfall. Cyclones and storms which produce heavy rain events, and droughts and floods associated with the El Nino-Southern Oscillation phenomenon, are not well simulated. Observational studies indicate an increasing trend in heavy rainfall intensity and frequency in Australia, Japan and the United States, but the results are mixed (increasing and decreasing trends or no trends) in the former Soviet Union and China. All GCMs simulate an increase in global mean temperature for increased greenhouse gas concentrations, and minimum temperatures tend to increase more than maximum temperatures, leading to a reduction in diurnal temperature range. All GCMs simulate an increase in global mean rainfall but decreases and increases occur on a regional scale, with little agreement between models. In regions which become wetter, some models indicate an increase in heavy rainfall events and a decrease in light rainfall events under enhanced greenhouse conditions. Links between climate change, agriculture, industry and socio-economic factors are very complex in nature. There will be winners and losers, and adaptation to climate change associated with an approximate doubling of present CO2 concentrations will be unavoidable.

Analysis of satellite‐based estimates of tropospheric diurnal temperature range

A decrease in the diurnal temperature range has been identified throughout this century in many of the world's land‐based climate records. However, documentation of the seasonality, magnitude, and geography of these changes has been hampered by the lack of homogeneous maximum and minimum temperature measurements over most of the planet. In this investigation, we attempt to use satellite‐based measurements of tropospheric temperatures to assess spatial and temporal trends in the diurnal temperature range over the period 1979 to 1994. Although quite exploratory and preliminary in nature, we find that the satellite‐based estimates of the diurnal temperature range are (1) larger over land areas than ocean areas, (2) high in summer, particularly in low latitudes, and low in winter, especially in the higher latitudes, and (3) decreasing substantially in the winter season for the land areas between 30°N and 60°N. The results are potentially compromised by many factors including orbital drift problems and changes in satellites. Despite the potential pitfalls of the satellite‐based measurements in this investigation our findings support other results showing a reduction in diurnal temperature range in the midlatitudes of the northern hemisphere during the low‐sun season.