Scenarios of land use and land cover change in the conterminous United States: Utilizing the special report on emission scenarios at ecoregional scales

Global environmental change scenarios have typically provided projections of land use and land cover for a relatively small number of regions or using a relatively coarse resolution spatial grid, and for only a few major sectors. The coarseness of global projections, in both spatial and thematic dimensions, often limits their direct utility at scales useful for environmental management. This paper describes methods to downscale projections of land-use and land-cover change from the Intergovernmental Panel on Climate Change's Special Report on Emission Scenarios to ecological regions of the conterminous United States, using an integrated assessment model, land-use histories, and expert knowledge. Downscaled projections span a wide range of future potential conditions across sixteen land use/land cover sectors and 84 ecological regions, and are logically consistent with both historical measurements and SRES characteristics. Results appear to provide a credible solution for connecting regionalized projections of land use and land cover with existing downscaled climate scenarios, under a common set of scenario-based socioeconomic assumptions.     

Land use and land cover tools for climate adaptation

Land use and land cover interact with atmospheric conditions to determine current climate conditions, as well, as the impact of climate change and environmental variability on ecological systems. Such interactions are ubiquitous, yet changes in LULC are generally made without regard to their biophysical implications. This review considers the potential for LULC to compound, confound, or even contradict changes expected from climate change alone. These properties give LULC the potential to be used as powerful tools capable of modifying local climate and contributing significantly to the net impact of climate change. Management practices based modifications of LULC patterns and processes could be applied strategically to increase the resilience of vulnerable ecological systems and facilitate climate adaptation. These interventions build on the traditional competencies of land management and land protection organizations and suggest that these institutions have a central role in determining the ecological impact of climate change and the development of strategies for adaptation. The practical limits to the use of LULC-based tools also suggest important inflection points between manageable and dangerous levels of climate change.     

Satellite monitoring of global land cover changes and their impact on climate

Land cover is a crucial, spatially and temporally varying component of global carbon and climate systems. Therefore accurate estimation and monitoring of land cover changes is important in global change research. Although, land cover has dramatically changed over the last few centuries, until now there has been no consistent way of quantifying the changes globally.In this study we used long-term climate, soils data along with coarse resolution satellite observations to quantify the magnitude and spatial extent of global land cover changes due to anthropogenic processes. Differences between potential leaf area index, derived from climate-soil-leaf area equilibrium and actual leaf area index obtained from satellite data were used to estimate changes in land cover.Forest clearing for agriculture and irrigated farming in arid and semi-arid lands are found to be two major sources of climatically important land cover changes. Satellite derived Spectral Vegetation indices (SV I) and surface temperatures (T s) show strong impact of land cover changes on climatic processes. Irrigated agriculture in dry areas increased energy absorption and evapotranspiration (ET) compared to natural vegetation. On the other hand, forest clearing for crops decreased energy absorption andET. A land cover classification and monitoring system is proposed using satellite derivedSV I andT s that simultaneously characterize energy absorption and exchange processes. This completely remote sensing based approach is useful for monitoring land cover changes as well as their impacts on climate. Monitoring the spatio-temporal dynamics of land cover is possible with current operational satellites, and could be substantially improved with the Earth Observing System (EOS) era satellite sensors.     

Numerical simulation of the impact of land cover change on regional climate in China

Land use and land cover change (LUCC) can modify the physical and thermodynamic characteristics of the land surface, including surface roughness, albedo, and vegetation fraction, among others. These direct changes can result in a series of impacts on regional climate. In this paper, the simulated results over China under the scenario of LUCC using weather research and forecasting model are presented. The period for the simulation is from December 2006 to December 2011. Two experiments are initialized by the LUCC datasets derived from the MODIS data of 2001 and 2008, respectively. The results show that the LUCC in most areas of China reduces the surface albedo and increases the surface temperature. Especially in the Hetao Plain, the magnitude of increased surface temperature is above 0.5 °C in winter, and the increase in winter is more obvious than in summer. The precipitation in the Hetao Plain increases. The sensible heat in most parts of East China is reduced, while the latent heat is increased in most areas of China.     

A regional climate model for the western United States

A numerical approach to modeling climate on a regional scale is developed whereby large-scale weather systems are simulated with a global climate model (GCM) and the GCM output is used to provide the boundary conditions needed for high-resolution mesoscale model simulations over the region of interest. In our example, we use the National Center for Atmospheric Research (NCAR) community climate model (CCM1) and the Pennsylvania State University (PSU)/NCAR Mesoscale Model version 4 (MM4) to apply this approach over the western United States (U.S.). The topography, as resolved by the 500-km mesh of the CCM1, is necessarily highly distorted, but with the 60-km mesh of the MM4 the major mountain ranges are distinguished. To obtain adequate and consistent representations of surface climate, we use the same radiation and land surface treatments in both models, the latter being the recently developed Biosphere-Atmosphere Transfer Scheme (BATS). Our analysis emphasizes the simulation at four CCM1 points surrounding Yucca Mountain, NV, because of the need to determine its climatology prior to certification as a high-level nuclear waste repository.We simulate global climate for three years with CCM1/BATS and describe the resulting January surface climatology over the western U.S. The details of the precipitation patterns are unrealistic because of the smooth topography. Selecting five January CCM1 storms that occur over the western U.S. with a total duration of 20 days for simulation with the MM4, we demonstrate that the mesoscale model provides much improved wintertime precipitation patterns. The storms in MM4 are individually much more realistic than those in CCM1. A simple averaging procedure that infers a mean January rainfall climatology calculated from the 20 days of MM4 simulation is much closer to the observed than is the CCM1 climatology. The soil moisture and subsurface drainage simulated over 3–5 day integration periods of MM4, however, remain strongly dependent on the initial CCM1 soil moisture and thus are less realistic than the rainfall. Adequate simulation of surface soil water may require integrations of the mesoscale model over time periods.The National Center for Atmospheric Research is sponsored by the National Science Foundation. of up to several months or longer.     

Standardized estimates of climate change damages for the United States

Nordhaus (1991), Cline (1992), Fankhauser (1992), and Titus (1992) have published comprehensive estimates of annual climate change damages to the United States in about 2060 that vary from $55 billion to $111 billion ($1990). The estimates are comprehensive because they address market and nonmarket impacts. They based their estimates on different assumptions about the rates of climate change and sea level rise, rates of return on investment, and changes in population and income. In addition, many of the damage estimates, although reported for a 2.5–3.0 °C warming, were based on studies that assumed higher rates of warming. Thus, these studies may have overestimated damages associated with a 2.5–3.0 °C warming. In this paper, the results of these studies were standardized for a 2.5 °C warming, a 50-cm sea level rise, 1990 income and population, and a 4% real rate of return on investments. After standardization, the total damage estimates range from $42.3 billion to $52.8 billion, slightly less than 1% of United States GNP in 1990. Yet, within individual sectors, such as agriculture and electricity, standardized damages differ by more than an order of magnitude. In addition, a significant amount of speculation underlies the damage estimates. Thus, the small range of total standardized damages and apparent agreement about the magnitude of such damages should be interpreted with caution.     

Evaluation of satellite derived land cover characteristics for global climate modelling

A preliminary evaluation of the suitability of a currently operational satellite data archive, namely the NOAA global vegetation index (GVI) product, as a basis for providing information on land cover characteristics for global climate modelling has been undertaken by comparing it to several existing data bases of soil and vegetation cover. It is found that temporal composites of GVI values often continue to change beyond the accepted compositing period of three or four weeks. In extreme cases the addition of another week to the compositing period changes over 90% of the pixels. Selection of GVI class boundaries is found to be rather hard and is probably a strong function of the classification technique employed. The resulting GVI classes are generally explicable by reference to other archival material although this study identifies some specific cases of locational divergence from consensus classification. In these locations monitoring with the GVI may prove useful. More importantly GVI values for very similar ecotypes vary widely from region to region thus rendering global classification very dangerous despite the graphic appeal of coloured maps. In its present form the NOAA global vegetation index is not a useful data source for climate modellers.Now at the Institute of Hydrology, Wallingford, U.K.     

Simulated impacts of historical land cover changes on global climate in northern winter

This ten-year general circulation model experiment compared a simulation where land surface boundary conditions were represented by observed, present day land cover to a simulation where the surface was represented by natural, potential land cover conditions. As a result of these estimated changes in historical land cover, significant temperature and hydrology changes affected tropical land surfaces, where some of the largest historical disruptions in total vegetation biomass have occurred. Also of considerable interest because of their broad scope and magnitude were changes in high-latitude Northern Hemisphere winter climate which resulted from changes in tropical convection, upper-level tropical outflow, and the generation of low-frequency tropical waves which propagated to the extratropics. These effects combined to move the Northern Hemisphere zonally averaged westerly jet to higher latitudes, broaden it, and reduce its maximum intensity. Low-level easterlies were also reduced over much of the tropical Pacific basin while positive anomalies in convective precipitation occurred in the central Pacific. Globally averaged changes were small. Comparisons of recent, observed trends in tropical and Northern Hemisphere, mid-latitude climate with these simulations suggests an interaction between the climatic effects of historical land cover changes and other modes of climate variability. Received: 8 September 1998 / Accepted: 31 July 1999     

Urbanization, climate change and flood policy in the United States

The average annual cost of floods in the United States has been estimated at about $2 billion (current US dollars). The federal government, through the creation of the National Flood Insurance Program (NFIP), has assumed responsibility for mitigating the societal and economic impacts of flooding by establishing a national policy that provides subsidized flood insurance. Increased flood costs during the past two decades have made the NFIP operate at a deficit. This paper argues that our current understanding of climate change and of the sensitivity of the urban environment to floods call for changes to the flood policy scheme. Conclusions are drawn on specific examples from cities along the heavily urbanized corridor of northeastern United States. Mesoscale and global models along with urbanization and economic growth statistics are used to provide insights and recommendations for future flood costs under different emissions scenarios. Mesoscale modeling and future projections from global models suggest, for example, that under a high emissions scenario, New York City could experience almost twice as many days of extreme precipitation that cause flood damage and are disruptive to business as today. The results of the paper suggest that annual flood costs in the United States will increase sharply by the end of the 21st Century, ranging from about $7 to $19 billion current US dollars, depending on the economic growth rate and the emissions scenarios. Hydrologic, hydraulic and other related uncertainties are addressed and a revised version of the NFIP is suggested.     

Estimating climate change effects on net primary production of rangelands in the United States

The potential effects of climate change on net primary productivity (NPP) of U.S. rangelands were evaluated using estimated climate regimes from the A1B, A2 and B2 global change scenarios imposed on the biogeochemical cycling model, Biome-BGC from 2001 to 2100. Temperature, precipitation, vapor pressure deficit, day length, solar radiation, CO₂ enrichment and nitrogen deposition were evaluated as drivers of NPP. Across all three scenarios, rangeland NPP increased by 0.26 % year^?1 (7 kg C ha^?1 year^?1) but increases were not apparent until after 2030 and significant regional variation in NPP was revealed. The Desert Southwest and Southwest assessment regions exhibited declines in NPP of about 7 % by 2100, while the Northern and Southern Great Plains, Interior West and Eastern Prairies all experienced increases over 25 %. Grasslands dominated by warm season (C4 photosynthetic pathway) species showed the greatest response to temperature while cool season (C3 photosynthetic pathway) dominated regions responded most strongly to CO₂ enrichment. Modeled NPP responses compared favorably with experimental results from CO₂ manipulation experiments and to NPP estimates from the Moderate Resolution Imaging Spectroradiometer (MODIS). Collectively, these results indicate significant and asymmetric changes in NPP for U.S. rangelands may be expected.     

Sensitivity of carbon cycling in the European Alps to changes of climate and land cover

Assessments of the impacts of global change on carbon stocks in mountain regions have received little attention to date, in spite of the considerable role of these areas for the global carbon cycle. We used the regional hydro-ecological simulation system RHESSys in five case study catchments from different climatic zones in the European Alps to investigate the behavior of the carbon cycle under changing climatic and land cover conditions derived from the SRES scenarios of the IPCC. The focus of this study was on analyzing the differences in carbon cycling across various climatic zones of the Alps, and to explore the differences between the impacts of various SRES scenarios (A1FI, A2, B1, B2), and between several global circulation models (GCMs, i.e., HadCM3, CGCM2, CSIRO2, PCM). The simulation results indicate that the warming trend generally enhances carbon sequestration in these catchments over the first half of the twenty-first century, particularly in forests just below treeline. Thereafter, forests at low elevations increasingly release carbon as a consequence of the changed balance between growth and respiration processes, resulting in a net carbon source at the catchment scale. Land cover changes have a strong modifying effect on these climate-induced patterns. While the simulated temporal pattern of carbon cycling is qualitatively similar across the five catchments, quantitative differences exist due to the regional differences of the climate and land cover scenarios, with land cover exerting a stronger influence. The differences in the simulations with scenarios derived from several GCMs under one SRES scenario are of the same magnitude as the differences between various SRES scenarios derived from one single GCM, suggesting that the uncertainty in climate model projections needs to be narrowed before accurate impact assessments under the various SRES scenarios can be made at the local to regional scale. We conclude that the carbon balance of the European Alps is likely to shift strongly in the future, driven mainly by land cover changes, but also by changes of the climate. We recommend that assessments of carbon cycling at regional to continental scales should make sure to adequately include sub-regional differences of changes in climate and land cover, particularly in areas with a complex topography.     

An assessment of the influence of land cover uncertainties on the simulation of global climate in the early Holocene

Six and 21 kyear BP represent the extreme states of climate since the last glacial maximum. The early Holocene, in contrast, was a time of transition, experiencing rapidly melting continental ice sheets, rising sea-level, and increasing summer insolation. Key features of the climate, illustrated by an NCAR CCM3 general circulation model experiment representing 11 kyr BP, include enhanced continentality and seasonality, and an enhanced northern monsoon. The principal circulation responses to the 11 kyr BP boundary conditions can be summarized as an intensification and northward shift of the mean meridional circulation and an intensification of the planetary wave structure of the Northern Hemisphere in northern summer, and a slight intensification of the mean meridional circulation coupled with a southward shift in the planetary wave structure in northern winter. These changes are manifest in the enhancement of the typical seasonal cycle of sea-level pressure in the Northern Hemisphere relative to that of the present day, and enhancement and equatorward shift of the Aleutian and Icelandic lows in northern winter. Over the period 15-8 kyr BP, within the current boreal forest zone, herbaceous tundra was replaced by shrub tundra, and subsequently by evergreen or deciduous forest, but there is uncertainty in the location, timing, and exact nature of these transitions. The specific location of the relatively small area of the Asian boreal forest-tundra transition can have an impact on regional climate, primarily in the net shortwave radiation component of the surface energy budget in spring, and in the cloudiness, net shortwave radiation, and turbulent heat fluxes in summer. These changes also have an impact on global climate. Our results suggest that the additional northern heating leads to a reduced equator-pole heat transport in the Northern Hemisphere which then influences heat and momentum transport in the Southern Hemisphere.     

Uncertainties in solar radiation assessment in the United States using climate models

Climate Dynamics - Solar energy is abundant and offers significant potential for future climate change mitigation. This study investigates the impacts of climate change on surface solar radiation...     

Consequences of climate change for the soil climate in Central Europe and the central plains of the United States

This study aims to evaluate soil climate quantitatively under present and projected climatic conditions across Central Europe (12.1°–18.9° E and 46.8°–51.1° N) and the U.S. Central Plains (90°–104° W and 37°–49° N), with a special focus on soil temperature, hydric regime, drought risk and potential productivity (assessed as a period suitable for crop growth). The analysis was completed for the baselines (1961–1990 for Europe and 1985–2005 for the U.S.) and time horizons of 2025, 2050 and 2100 based on the outputs of three global circulation models using two levels of climate sensitivity. The results indicate that the soil climate (soil temperature and hydric soil regimes) will change dramatically in both regions, with significant consequences for soil genesis. However, the predicted changes of the pathways are very uncertain because of the range of future climate systems predicted by climate models. Nevertheless, our findings suggest that the risk of unfavourable dry years will increase, resulting in greater risk of soil erosion and lower productivity. The projected increase in the variability of dry and wet events combined with the uncertainty (particularly in the U.S.) poses a challenge for selecting the most appropriate adaptation strategies and for setting adequate policies. The results also suggest that the soil resources are likely be under increased pressure from changes in climate.     

Evaluation of climate change over the continental United States using a moisture index

This paper uses a modified form of Thornthwaite’s moisture index to better quantify climate variability by integrating the effects of temperature and precipitation. Using the moisture index, trends were evaluated over the last 112 years (1895–2006), when unique changes in temperature and precipitation have been documented to have occurred. In addition, data on potential evapotranspiration and the moisture index were used to investigate changing climate and vegetation regions. The results show that the eastern half of the country has been getting wetter, even as temperatures have continued to increase in many areas. In particular, conditions have become wetter in the South, Northeast, and East North Central regions. The changing climate is illustrated by computing climate and vegetation regions for three 30-year periods (1910–1939, 1940–1969, and 1970–1999). Climate regions based on the moisture index show an expansion of the Humid region (where precipitation vastly exceeds climatic demands for water) across the East as well as a westward shift in the zero moisture index line. In terms of vegetation zones, the most dramatic change occurs across the Midwestern prairie peninsula where the wetter conditions lead to a westward expansion of conditions favorable for oak–hickory–pine vegetation.     

Modeling the hydroclimatology of the midwestern United States. Part 1: current climate

An ensemble of six 22-year numerical experiments was conducted to evaluate the ability of Regional Climate Model version 3 (RegCM3) to simulate the energy and water budgets of the midwestern United States. RegCM3 was run using two surface physics schemes: Integrated Biosphere Simulator (IBIS) and Biosphere-Atmosphere Transfer Scheme 1e (BATS1e), and two convective closure assumptions: Fritsch & Chappell (FC80) and Arakawa & Schubert (AS74). Boundary conditions were provided by the National Centers for Environmental Prediction-Department of Energy Reanalysis 2 dataset and the ECHAM5 general circulation model. A companion paper examines the American Midwest under future climate scenarios. Overall, the model that reproduces the observed seasonal cycles of the midwestern United States climate system best is RegCM3 using IBIS and the AS74 convective closure assumption. IBIS simulates shortwave radiation more accurately, while BATS1e simulates longwave radiation more accurately. Summer two-meter air temperature is overestimated by the combination of IBIS and the FC80 convective closure assumption. All models contain a wet bias and overestimate evapotranspiration during the spring. Total runoff, surface runoff, groundwater runoff, and root zone soil moisture are best simulated by RegCM3 using IBIS and the AS74 convective closure assumption. While BATS1e does capture the seasonal cycle of total runoff, gross errors in the partitioning of total runoff between surface runoff and groundwater runoff exist. The seasonal cycle of root zone soil moisture simulated by RegCM3 using IBIS and the AS74 convective closure assumption is dry, but agrees with observations during the summer. The rest of the models underestimate root zone soil moisture.     

Modeling the hydroclimatology of the midwestern United States. Part 2: future climate

An ensemble of six 22-year numerical experiments was conducted to quantify the response of soil moisture to multiple climate change scenarios over the American Midwest. Regional Climate Model version 3 (RegCM3) was run using two surface physics schemes: Integrated Biosphere Simulator (IBIS) and Biosphere-Atmosphere Transfer Scheme 1e (BATS1e); and two convective closure assumptions: Fritsch and Chappell and Arakawa and Schubert. Experiments were forced with a surrogate climate change scenario constructed using the National Centers for Environmental Prediction-Department of Energy Reanalysis 2 dataset and the ECHAM5 A1B climate change scenario. RegCM3-IBIS and RegCM3-BATS1e simulate increased two-meter air temperature and downward longwave radiation throughout the year under both climate change scenarios. While differences in shortwave radiation are relatively small; some model configurations and climate change scenarios produce additional precipitation, evapotranspiration, and total runoff during the spring and summer. Soil moisture is unchanged or increased throughout the growing season as enhanced rainfall offsets greater evaporative demand. Negligible drying in root zone soil moisture is found in all climate change experiments conducted, regardless of surface physics scheme, boundary conditions, or convective closure assumption.     

The Statistical Significance Test of Regional Climate Change Caused by Land Use and Land Cover Variation in West China

The West Development Policy being implemented in China is causing significant land use and land cover （LULC） changes in West China. With the up-to-date satellite database of the Global Land Cover Characteristics Database （GLCCD） that characterizes the lower boundary conditions, the regional climate model RIEMS-TEA is used to simulate possible impacts of the significant LULC variation. The model was run for five continuous three-month periods from 1 June to 1 September of 1993, 1994, 1995, 1996, and 1997, and the results of the five groups are examined by means of a student t-test to identify the statistical significance of regional climate variation. The main results are： （1） The regional climate is affected by the LULC variation because the equilibrium of water and heat transfer in the air-vegetation interface is changed. （2） The integrated impact of the LULC variation on regional climate is not only limited to West China where the LULC varies, but also to some areas in the model domain where the LULC does not vary at all. （3） The East Asian monsoon system and its vertical structure are adjusted by the large scale LULC variation in western China, where the consequences are the enhancement of the westward water vapor transfer from the east oast and the relevant increase of wet-hydrostatic energy in the middle-upper atmospheric layers. （4） The ecological engineering in West China affects significantly the regional climate in Northwest China, North China and the middle-lower reaches of the Yangtze River; there are obvious effects in South, Northeast, and Southwest China, but minor effects in Tibet.