Water has been called life on earth. The climate extremes such as flooding, heatwaves, drought, storms, and wildfires are all linked to either scarcity or excess of water. It is imperative to understand the global water cycle that affects the terrestrial and atmospheric circulation of various water cycle components. In addition to the water cycle, energy and carbon cycles play an important role in determining the loss/gain of heat and assimilation of carbon by plants from the atmosphere. Increase in carbon dioxide in the atmosphere with the anthropogenic changes in land use/land cover (LULC) with other environmental factors leading to the intensification of the hydrological cycle and the climate change phenomenon. Land surface models (LSMs) provides a best possible approach to quantify the hydrological and carbon cycle components at the point, regional, and global scale. It can provide long term climate patterns of the past, and future projections for multiple representative concentration pathway (RCP) scenarios. Remote sensing and flux towers were also used to cross-validate the model results. In this study, we used the Community Land Model (CLM4.0), Variable Infiltration Capacity Model (VIC3L), and latest release CLM5.0. The satellite and observation datasets include MODerate-resolution Imaging Spectroradiometer (MODIS) evapotranspiration (ET), latent heat flux (LE), runoff, gross primary production (GPP) product. Firstly, we evaluated CLM4.0 and VIC3L parameterization for water and energy cycle at two flux tower sites in Texas and California, United States. Time series and statistical results showed better performance by CLM4.0 for energy fluxes. The modeled energy fluxes were analyzed at two sites: Freeman Ranch-2 (FR2) located in the lowland region of Texas (272 m), and Providence 301 (P301) located on the mountains of Sierra Nevada in California (2015 m) from 2003 to 2013. Net radiation (RN) was underestimated by CLM with bias −25.06 W m−2 due to its snow hydrology scheme at P301. LE was overestimated by the VIC during summer precipitation and had a positive bias of 5.51 W m−2, whereas CLM showed a negative bias of −6.58 W m−2 at the FR2 site. Ground heat flux (G) was considered as a residual term in CLM, which caused weak performance at P301, while VIC calculated G as a function of soil temperature, depth, and hydraulic conductivity. In addition, the MOD16 showed similar results with models at FR2; however, at P301, they yielded a correlation value of 0.85 and 0.21 for LSMs and MOD16, respectively. The later has lower correlation with in situ specifically in summer season caused by erroneous biophysical or meteorological inputs to the algorithms. The sensitivity analysis between soil moisture and turbulent fluxes, exhibited negative trend (especially for LE at P301) due to topography and snow cover. The results from this study are conducive to improvements in models and satellite-based characterization of water and energy fluxes, especially at rugged terrain with high elevation, where observational experiments are difficult to conduct. Second, the effect of changes in LULC in an East Asia ecosystem was studied using CLM4.0. The two experiments were conducted: 1) by using newly created high-resolution MODIS LULC data 2) by-default CLM4.0 LULC data to assess the impact of LULC changes on climate. Both experiments were evaluated at temperate, arid, continental, and tropical regions with the effect of LULC changes from 2001-2015. Anthropogenic LULC changes have considerable impacts on the climate and its extremes. For the whole East Asia region, area-averaged runoff decreased by 2.10%. The temperate region experienced a 3.16% decrease in runoff and a 4.22% increase in LE due to an increase in irrigation activities that could lead to the drying of soil moisture and drought in the future. In contrast, the arid region experienced a 6.30% increase in runoff despite dry conditions and a 5.70% reduction in LE, which ultimately increased H by 2.25% and caused an intensification of the climate in the form of strong heat waves and floods. The continental region followed the same trend as the temperate region with a noticeable decrease in winter H, which caused severe cold weather. The tropical region showed a slight impact of LULC change on energy fluxes due to high precipitation and intense solar radiations. Overall, the results of this research follow the ‘dry gets drier and wet gets wetter’ paradigm due to LULC changes in the study region. Third, the effect of climate, increase in atmospheric carbon dioxide (CO2), aerosol concentration, and nitrogen deposition on Water-use efficiency (WUE) was evaluated at forest, grassland, and cropland sites from 1981-2010. Ecosystem WUE (EWUE) and transpiration WUE (TWUE) increased at the forest site due to the CO2 fertilization effect but decreased at the grassland and cropland sites due to lower gross primary production and higher/lower (cropland/grassland) evapotranspiration as consequences of rising temperature and water availability. Inherent WUE confirmed that EWUE and TWUE trends were controlled by the rising temperature and CO2-induced warming through an increase in vapor pressure deficit. In this way, forest and cropland sites showed warming patterns, while the grassland site showed a drier climate. The later period (2001–2010) showed steeper trends in WUE compared with the earlier period at all sites, implying a change in climate. The results showed implications for rising temperature due to increased CO2 concentration at multiple land cover types. Further global and regional based studies are required to evaluate the effects of increasing CO2, climate variability, and other environmental factors such as nitrogen deposition and aerosols concentration in the atmosphere.