Showing papers in "Climatic Change in 1988"

The explosive volcanic eruption signal in northern hemisphere continental temperature records

Abstract: Several catalogs of explosive volcanic eruptions are reviewed and their limitations assessed. A new, homogeneous set of high quality gridded temperature data for continental regions of the northern hemisphere is then examined in relation to the timing of major explosive eruptions. Several of the largest eruptions are associated with significant drops in summer and fall temperatures, whereas pronounced negative anomalies in winter and spring temperatures are generally unrelated to volcanic activity. The effect of explosive eruptions on temperature decreases latitudinally away from the location of the eruption. High latitude eruptions have the greatest impact on high and mid latitudes; low latitude eruptions mainly influence low and mid latitudes. Temperature depressions following major eruptions are very abrupt but short-lived (1 to 3 months) decreasing in magnitude over the course of the subsequent 1 to 3 years. Generally any signal is indistinguishable from noise after 12 months but a small recurrent drop in temperature is evident about 12 to 24 months after the initial anomaly. Considering all known eruptions which injected material into the stratosphere over the last 100 years (except the 5 largest eruptions) a significant temperature depression is observed over the continents only in the month immediately following the eruption. There is no evidence that large eruptions over the last 100 years have had a significant effect on low frequency temperature changes.

Paleoclimatic variability at frequencies ranging from 1 cycle per 10 000 years to 1 cycle per 1000 years: Evidence for nonlinear behaviour of the climate system

Abstract: The paleoclimatic variability at frequencies ranging from 10−4 cycle per year (cpy) to 10−3 cpy is investigated using a set of three deep-sea cores from the Indian Ocean Three frequency bands of high paleoclimatic variability are first defined using upper and lower limits of the significant spectral power concentrations: the bands are centered around the spectral maxima located at 103, 47, and 25 kyr The localisation of spectral lines is then refined by high-resolution spectral analysis

The climatic impact of a Sonoran vegetation discontinuity

Abstract: The international fence separating Mexico and the United States is marked by a sharp vegetation discontinuity in the Sonoran Desert. Due to overgrazing, the Mexican side of the border has shorter grasses, more bare soil, and a higher albedo compared to the adjacent lands in the United States. In this investigation, long-term climate records are analyzed to determine the magnitude of any climatic differences associated with the spatial variation in the vegetation regime. The results suggest that summertime maximum temperatures recorded at the Mexican stations are significantly higher (by nearly 2.5 °C) than the Arizona stations when latitude and elevation are held constant. When only elevation is held constant, the difference in the maximum temperature jumps to approximately 4 dgC. No discernible changes in monthly and/or summer season precipitation could be identified in the records. These findings add support to other site-specific field measurements suggesting warming in desert areas where vegetation cover is decreasing and albedo is increasing.

Long-term variations of surface air temperature at major industrial cities of India

Abstract: Local temperature is one of the major climatic elements to record the changes in the atmospheric environment brought about by industrialization and urbanization. Long-term variations of seasonal and annual surface air temperature at six major industrial cities of India (Calcutta, Bombay, Madras, Bangalore, Pune and Delhi) have been studied, using data for the past 86 to 112 yr. Comparative analysis of the temperature data of six nonindustrial stations has also been done. The long-term change in the temperature has been evaluated by linear trend. Calcutta, Bombay and Bangalore have shown significant warning trend, while Delhi has shown a cooling trend. The trends at Madras and Pune are not significant. The nonindustrial stations did not show significant trends. In general, there was either a cooling tendency or cessation of warming, after the late 1950s at most of the industrial cities.

On the role of high latitude ice, snow, and vegetation feedbacks in the climatic response to external forcing changes

Abstract: A seasonal energy balance climate model containing a detailed treatment of surface and planetary albedo, and in which seasonally varying land snow and sea ice amounts are simulated in terms of a number of explicit physical processes, is used to investigate the role of high latitude ice, snow, and vegetation feedback processes. Feedback processes are quantified by computing changes in radiative forcing and feedback factors associated with individual processes. Global sea ice albedo feedback is 5–8 times stronger than global land snowcover albedo feedback for a 2% solar constant increase or decrease, with Southern Hemisphere cryosphere feedback being 2–5 times stronger than Northern Hemisphere cryosphere feedback.

Carbon dioxide emissions in a methane economy

Abstract: Increasing reliance on natural gas (methane) to meet global energy demands holds implications for atmospheric CO2 concentrations. Analysis of these implications is presented, based on a logistic substitution model viewing energy technologies like biological species invading an econiche and substituting in case of superiority for existing species. This model suggests gas will become the dominant energy source and remain so for 50 years, peaking near 70 percent of world supply. Two scenarios of energy demand are explored, one holding per capita consumption at current levels, the second raising the global average in the year 2100 to the current U.S. level. In the first (‘efficiency’) scenario concentrations peak about 450 ppm, while in the second (‘long wave’) they near 600 ppm. Although projected CO2 concentrations in a ‘methane economy’ are low in relation to other scenarios, the projections confirm that global climate warming is likely to be a major planetary concern throughout the twenty-first century. A second finding is that data on past growth of world per capita energy consumption group neatly into two pulses consistent with longwave theories in economics.

Estimated annual regime of energy-balance components, evapotranspiration and soil moisture for a drainage basin in the case of a CO2 doubling

Abstract: Assuming a doubling of the atmospheric CO2 concentration, parameters of an empirical formula for calculating the daily net terrestrial radiation under the climatic conditions of Belgium are determined. The developed method takes into account information yielded by climate models about the CO2 impacts. Annual regimes of the energy-balance components are calculated for a drainage basin in Belgium. A daily step conceptual hydrological model (developed at the Royal Meteorological Institute of Belgium) was run to estimate the effective evapotranspiration and the soil moisture in the 2 × CO2 case; results of this simulation are compared with the present-day conditions.

Climatic change and great lakes levels the impact on shipping

Abstract: This paper represents an attempt to combine the output of several models that deal with future climatic, hydrologic and economic conditions in the Great Lakes and makes some predictions about the possible impact of one scenario of 2 × CO2 climate on Great Lakes shipping. It is realized that there is a great deal of uncertainty in all the models and that improvements are continually being made. Data from a General Circulation Model of future temperature and precipitation in the Great Lakes basin, a Great Lakes levels and flows model from the Canada Centre for Inland Waters and an International Joint Commision's Great Lakes economic model modified by the University of Wisconsin were used. The 1900–1976 period of lake levels and flows was used. The hydrologic model indicated that future mean lake levels may be reduced by one-half meter, and that the extreme low levels of the mid 1960's could occur 77% of the time in the future. No ice cover is predicted for any lake except Erie, permitting an eleven month shipping season. Five scenarios of future impact on shipping were evaluated. It was found that mean annual shipping costs may increase by 30% and the frequency of years when costs exceed those of the period of low lake levels (1963–65) could rise to 97%. Possible policy options in a future with climatically induced lower lake levels could include regulation to keep levels artificially high by diversions into the system, or increased dredging of the connecting channels.

Adjusting water resources management to climate change

Abstract: The nature of climate impacts and adjustment in water supply and flood management is discussed, and a case study of water manager response to climate fluctuation in California's Sacramento Basin is presented. The case illuminates the effect on climate impact and response of traditional management approaches, the dynamic qualities of maturing water systems, socially imposed constraints, and climate extremes. A dual pattern of crisisresponse and gradual adjustment emerges, and specific mechanisms for effecting adjustment of water management systems are identified. The case study, and broader trends in U.S. water development, suggest that oversized structural capacity, the traditional adjustment to climate variability in water resources, may prove less feasible in the future as projects become smaller and new facilities are delayed by economic and environmental concerns.

Cyclicity in the late Precambrian Elatina Formation, South Australia: Solar or tidal signature?

Abstract: New observations from two late Precambrian (~800-650 Ma) sedimentary rhythmites in South Australia (Reynella Siltstone and Chambers Bluff Tillite) reveal cycles structurally similar to the ~12-laminae cycles of the ~650-Ma Elatina Formation but which comprise from 15 to 26 or more laminae. The new data are difficult to accomodate in depositional models for the Elatina Formation whereby its laminae are regarded as annual and the cyclicity ascribed to solar variability (Williams and Sonett, 1985) or to the combined influences of the sunspot cycle and the lunar nodal tide (Zahnle and Walker, 1987). If, however, the long-term ‘Elatina Cycle’ and not the individual lamina is taken as a yearly climatic signal, the Elatina and other rhythmites studied may be interpreted as the deposits of marine ebb-tidal deltas that record variability in the velocity and range of paleo-ebb tides. The basic laminae-cycles would represent lunar fortnightly cycles of diurnal and/or semidiurnal laminae, commonly truncated through non-deposition at neap tides. Despite numerous empirical similarities between the Elatina and sunspot series, the ebb-tidal model for deposition is preferred because it accounts plausibly for observations from all three rhythmites studied.

Estimating the consequences of CO2-induced climatic change on north american grain agriculture using general circulation model information

Abstract: A procedure to estimate the potential climatic effects of a doubling of atmospheric carbon dioxide concentration on agricultural production is illustrated. The method combines use of atmospheric general circulation models (GCMs) and process-oriented crop models. Wheat and corn (maize) yields in three important North American grain cropping regions are treated. Combined use of these two types of models can provide insights into the impacts of climate changes at the level of plant physiology, and potential means by which agricultural production practices may adapt to these changes. Specific agronomic predictions are found to depend critically on the details of the projected climate change. Uncertainties in the specification of the doubled-CO2 climate by the GCM, particularly with respect to precipitation, dictate that agricultural predictions derived from them at this time must be regarded only as illustrative of the impact assessment method.

Tropical deforestation: Important processes for climate models

Abstract: Tropical deforestation is a current anthropogenic change to the land surface. Tropical forests are known to be changing rapidly, but the rate and extent of deforestation and the resulting secondary cover, as would be needed for quantitative projections of future change, are difficult to establish now. Also necessary for climate simulations is a description of the micrometeorological processes within the forest canopy, including especially the processes of evapotranspiration and interception. Past General Circulation Model sensitivity studies have established the potential major significance of perturbation of surface energy processes. Climate modeling sensitivity studies and ecological systems studies have highlighted the importance of the surface energy balance and the hydrological cycle over continental areas. However, predicting even the local, immediate effects of replacing tropical broadleaved forest with impoverished grassland is difficult because the land-surface parameterization schemes used in most climate models have been inadequate. A wide range of parameterization schemes in past studies of the climate change with tropical deforestation have led to divergent conclusions as to the consequences. The most recent such study has attempted to include more realistic processes than past studies, including separate submodels for soil and forest canopy. Results from the simulations of this study are reviewed. With attempts to simulate realistically the climatic impact of tropical deforestation, several issues must be considered. What is the rate and extent of the deforestation? What land cover replaces the forest and what physical properties of the forest and its replacement are most important for the simulation? Are the parameterizations of these properties plausibly correct and are the model ‘predictions’ explicable in terms of these properties? A simulation methodology that treats these latter questions is proposed.

Multi-year fluctuations of temperature and precipitation: The gray area of climate change

Abstract: The issue of whether the secular climate (twentieth century) is stationary or changing to some new semi-permanent state is clouded by the presence of so-called ‘climate fluctuations’. The twentieth century climate record of the United States reveals a substantial number of decadal fluctuations which occur in all seasons for both temperature and precipitation. Recent examples of such behavior include changes in winter and summer temperature variability and increases in transition season precipitation. Statistical evidence suggests that a substantial portion of these fluctuations, even those which are remarkably unusual, are merely manifestations of a stochastic process which possesses weak year-to-year persistence as viewed from an a posteriori perspective. The implications of this result are particularly important with respect to the formulation of physical causes of the fluctuations. The results emphasize the desirability of well-founded clearly-stated a priori theories of climate change as well as the limited usefulness of widely used climate normals.

Solar rotation, impulses of the torque in the Sun's motion, and climatic variation

Abstract: Running variance analysis and maximum entropy spectral analysis applied to Mount Wilson rotation data yield arguments in favor of a connection between variations in the Sun's rotation rate, energetic X-ray flares, and impulses of the torque (IOT) in the Sun's irregular motion about the barycenter of the planetary system. Such IOT, that have been shown to be related to the secular cycle of solar activity and excursions of the Maunder minimum type, also seem to be linked to outstanding peaks in geomagnetic activity, maxima in ozone concentration, incidence of blocking type circulation, as well as rainfall over Central Europe, England/Wales, eastern United States, and India. Statistical tests, that confirm these links, additionally point to IOT connection with temperature in Central Europe and the number of icebergs that pass south of latitude 48° N. IOT relationship with X-ray flares and strong geomagnetic storms was tested in successful long range forecasts.

Climate change in fact and in theory: Are we collecting the facts?

Abstract: For the past 100 years, a mostly volunteer group of observers has formed the backbone of the U.S. National Weather Service (NWS) Cooperative (CO-OP) network. These stations have provided most of the observations used to satisfy the Department of Commerce's statutory mandate of 1890... “to establish and record the climatic conditions of the United States” (15 USCA 313). Originally, this network was intended primarily for agriculture, but many other uses of the data have since emerged, such as the climatic planning of weather sensitive activities, input to engineering design studies, and input and verification for weather and river forecasts. In recent years, heightened awareness regarding climatic change and variability has challenged this network with yet another mission: the monitoring and detection of climate change. While not designed for that mission, the CO-OP network has proved useful in this respect. However, with some changes in operation, it could become even more valuable in monitoring for climatic change, and could do so in a most economical way. Similar practices instituted worldwide will be necessary for comprehensive study of climate change to the degrees of detail necessary to address specific policy issues and practical local-scale decision making.

Comment: On the need for validation of the Jones et al. temperature trends with respect to urban warming

Abstract: The Jones et al. hemispheric and global temperature trends and the methodology used to detect and correct for urban heat island effects are examined in detail. The results of this review suggest that there is still the possibility of significant urban warming bias remaining in the hemispheric and global averages. The actual extent of any such bias is unknown but warrants full investigation, since undetected and/or uncorrected urban warming could account for some of the hemispheric and global warming reported by Jones et al. Several research activities are suggested for resolving this uncertainty, including the rigorous application of urban warming correction factors to the data set used by Jones et al. and the development of geographically representative rural temperature series.

Quantifying how climatic factors affect variation in plant disease severity: A general method using a new way to analyze meteorological data

Abstract: A general method is presented for analyzing how climatic conditions affect plant disease severity. An example of its application is given for the analysis of stripe rust (caused by Puccinia striiformis) data on winter wheat cultivar Gaines and climatic data collected at Pullman, WA. for 1968–1986. A computer program WINDOW was written to identify the climatic factors most highly correlated with disease. This program is designed to utilize meteorological data for an entire growing season of a crop as well as to include climatic conditions preceding planting. This program uses an iterative process to examine variable-length segments of meteorological data in a more exhaustive analysis than previously possible. Climatic factors considered include: mean maximum, minimum, and average temperature; total and frequency of precipitation; consecutive days with and without precipitation; accumulation of negative and positive degree days; and number of days with extreme temperature events. Variables that were highly correlated with disease were the basis for regression models that were developed to predict disease severity index for each of the three cultivars. Two- and three-variable models explained, respectively, 75 and 76% of the variation in disease from year to year. Predictions (which could be made early enough in the growing season to allow application of chemical control) were evaluated on the basis of whether years with severe disease were accurately predicted. Models were validated using Allen's PRESS statistic and by application to new data. The method is potentially applicable to studies of how climatic conditions affect the populations or productivity of other types of organisms.

Climate and economic competitiveness: Florida freezes and the global citrus processing industry

Abstract: Casual observers of the impacts associated with four recent freezes in Florida's citrus producing areas might be inclined to agree with an assessment by Miami Herald reporters that these freezes had caused the ‘king of citrus’ to be toppled from its throne, enabling Brazil to take its place. Research on the citrus industry, however, reveals that the impacts of these recent freezes only explain part of the story of the interaction between climate variability and the relationship between the citrus industries of Florida and Brazil. Climate characteristics and their variability have directly as well as indirectly affected the economic competitiveness of citrus producers whose output is in large measure climate-dependent. Climate variability has had direct impacts on Florida's citrus industry by adversely affecting the productivity of citrus groves in some areas, by altering growers' perceptions of freeze probabilities and, occasionally, by suddenly reducing output, thus elevating the price that consumers must pay for that commodity. Indirectly, competition can be affected by climate as a potential producer identifies a weakness in the supply system of an existing industry and seeks to ‘fill the gap’.

Application of solar max ACRIM data to analysis of solar-driven climatic variability on Earth

Abstract: Climatic change caused by solar variability has been proposed for at least a century, but could not be assessed reliably in the past because the uncertainty in solar irradiance measured from the Earth's surface is too large. Now satellite measurements by such instruments as the Active Cavity Radiometer Irradiance Monitor (ACRIM) permit a preliminary assessment. The satellite data exhibit irradiance variations over a spectrum of shorter timescales, but the first 5-yr overall trend indicates slightly decreasing luminosity. The global temperature response to monthly-mean ACRIM-measured fluctuations from 1980–1984 was computed from the NYU 1D transient climate model - which includes thermal inertia effects of the world oceans - starting from an assumed pre-existing steady state, and the results compared with observations of recent global temperature trends. The modeled surface temperature evolution exhibited a complex history-dependent behavior whose fluctuations were an order of magnitude smaller than observed, primarily owing to oceanic thermal damping. Thus solar variability appears unlikely to have been an important factor in global-scale climate change over this period. The possibility of using the measurements to develop simple correlations for irradiance with longer term solar activity observable from the surface, and therefore to analyze historical effects, was considered, but is not supported by the satellite data. However, we have used a model of solar irradiance variation with time (Schatten, 1988), covering the period 1976–1997 in order to assess our model's response to forcing whose fluctuation timescale is comparable to the thermal relaxation time of the upper ocean. Continuous monitoring of solar flux by space-based instruments over timescales of 20 yr or more, comparable to timescales for thermal relaxation of the oceans, and of the solar cycle itself, is probably needed to resolve issues of long-term solar variation effects on climate.

Spectral characteristics of the annual rainfall series for Northeast Brazil

Abstract: The rainfall series for Fortaleza (Ceara) is compared with similar series for several other locations in Northeast Brazil. It is shown that the correlations are high for distances up to about 600 km from Fortaleza. The Fortaleza series shows prominent periodicities at T = 2.1, 10.1, 12.9, 25.1, and 61.0 years, all significant at a 3σ a priori level. Amongst these, T = 12.9 and 25.1 years are significant at a 4σ a priori level. A master Curve (for 1912–1978 only), obtained by averaging rainfall data for 93 stations having good correlations with Fortaleza, shows very prominent periodicities at T = 5.6, 12.3 and 47.3 years, significant at a 3σ a priori level. T = 12.3 is significant at a 4σ a priori level. Predictions from both the Fortaleza series (1849–1976) and the Master Curve (1912–1978) indicated droughts during 1979–1983. This prediction seems to have come true. In the future, droughts during 1992–1994 and 2002–2006 are indicated.

Atmospheric and oceanic heat transport: Simulations versus observations

Abstract: Poleward transport of heat by the atmosphere as simulated by a recently developed general circulation model (GCM) is consistent with earlier GCM studies in being significantly greater than indicated from radiosonde (weather balloon) observations. However, total heat transport by the combined ocean-atmosphere system appears to be approximately the same in the models and in satellite observations of irradiances at the top of the atmosphere: in the models most of this transport takes place in the atmosphere whereas the combined satellite and radiosonde observations indicate that half or more of the transport takes place in the oceans. It is argued here that the atmospheric model results are generally closer to the truth than the radiosonde observations. If this is true, then the oceans transport less heat than often supposed, and conventional ideas about the genesis of climatic change through alterations in oceanic heat transport must be reexamined.

Do large-area-average temperature series have an urban warming bias?

Abstract: The arguments presented by Wood and his criticisms of the methods used by Jones et al. are largely fallacious and are generally based on misconceptions and unwarranted assumptions. This does not, of course, mean that the Jones et al. data are perfect. Jones et al. (1986a, b) have clearly stated that, at the regional level, there may be residual uncertainties in their gridded data set. Furthermore, they have noted that there is a residual uncertainty in the global-mean change since late last century of ±0.2 °C (Wigley et al., 1986), although the main reasons for this uncertainty do not relate to urban warming. Further studies of possible urban warming biases are certainly warranted, particularly at the regional scale. However, for averages over continental-scale areas upwards, it is unlikely that any significant urban warming bias remains.

Climatic warming and increased summer aridity in Florida, U.S.A.

Abstract: The impending trace-gas induced climatic warming is likely, at least in the near term, to result in a decrease in summertime convective activity in Florida, in turn producing a reduction in thunderstorm-derived precipitation. The phenomenon is expected to arise from the differential heating of continental land masses relative to the ocean resulting in a strengthening of the North Atlantic subtropical anticyclone. Precipitation shortfalls of 10–20% were recorded for some areas during Northern Hemispheric summer months a few tenths of a degree Celsius warmer than the normal for the period 1901–1980. Deficits somewhat greater than these may not be uncommon during a fullscale climatic warming depending on, among other factors, the rapidity of the warming. Precipitation resulting from tropical cyclones is not expected to have significant positive impact on the shortfall in the near term.

Assessing carbon emission control strategies: The case of China

Abstract: Scientists are now being asked to recommend measures to reduce the risks of climatic change due to anthropogenic greenhouse gases. Considerably less effort, however, has been allotted to understanding the efficacy of controlling these gases than to their effects. This paper briefly describes and applies an energy-economic model to assess the effectiveness of carbon dioxide control policies that theoretically could be enacted in China, a large, developing nation with an energy inefficient and ‘carbon-intensive’ economy. The paper also assesses the effectiveness of similar international efforts, as well as the effect of each initiative on Chinese income levels. Carbon dioxide control measures are contained in scenarios drawn to the year 2075 and include family planning, fossil fuel taxes, mandatory or technical energy efficiency improvements, and a combination of these.

Climate and regional resource analysis: The effect of scale on resource homogeneity

Abstract: General Circulation Models (GCMs) are currently used to project future climate. The output of the models is then used to evaluate the effect of a climatic change on resources such as agriculture, forestry, and water resources. The GCMs used in long-term climate studies vary widely in the geographic resolution of their predictions. The approximate matching of resource data to the geographic scale of GCMs is an important step in the evaluation of the effects of climatic change on resources. As gridcell size increases, however, the distribution of resources within cells becomes more heterogeneous, and it becomes more difficult to evaluate the regional effects of climatic change. We quantify the change in resource heterogeneity as a function of gridcell size. Four resource variables (wheat yield, percent forest cover, population density, and percent of land irrigated) are analyzed on the basis of county-averaged data, while assignment to major drainage basins is based on exact watershed boundaries. A major change in resource heterogeneity within gridcells occurs at a grid length of from 1.2° to 3°.

Historical variation in guano production from the Peruvian and Benguela upwelling ecosystems

Abstract: Analysis of the historical record shows that reductions in guano production in the eastern tropical Atlantic Ocean were not related to El Nino events in the Pacific. Guano production in the Atlantic was negatively correlated with guano production in the Pacific. Significant reductions in guano production in the Atlantic occurred 1 to 4 years after increases in guano production in the Pacific. Negative association is consistent with the hypothesis that global shifts in weather associated with the Southern Oscillation affect guano production.