The 1 % per year exponential change in CO₂ concentration experiment is an idealized climate change scenario that has traditionally been used to facilitate comparison of different climate models and to create benchmark statistics. Here, we examine the limitations of this experiment for assessing the global carbon cycle and propose an alternative idealized experiment.

We present the automated method for recognizing atmospheric rivers in climate data, i.e., climate model output and reanalysis product. The method is based on topological data analysis and machine learning, both of which are powerful tools that the climate science community often does not use. An advantage of the proposed method is that it is free of selection of subjective threshold conditions on a physical variable. This method is also suitable for rapidly analyzing large amounts of data.

This work describes DATeS, a highly extensible data assimilation package. DATeS seeks to provide a unified testing suite for data assimilation applications that allows researchers to easily compare different methodologies in different settings with minimal coding effort. The core of DATeS is written in Python. The main functionalities, such as model propagation and assimilation, can however be written in low-level languages such as C or Fortran to attain high levels of computational efficiency.

We present a novel finite-volume dynamical core formulation considered for future numerical weather prediction at ECMWF. We demonstrate that this formulation can be competitive in terms of solution quality and computational efficiency to the proven spectral-transform dynamical core formulation currently operational at ECMWF, while providing a local, more scalable discretization, conservative and monotone advective transport, and flexible meshes.

This paper describes GCAM v5.1, an open source model that represents the linkages between energy, water, land, climate, and economic systems. GCAM examines the future evolution of these systems through the end of the 21st century. It can be used to examine, for example, how changes in population, income, or technology cost might alter crop production, energy demand, or water withdrawals, or how changes in one region’s demand for energy affect energy, water, and land in other regions.

We developed the GOTM–TOPAZ, a single-column ocean biogeochemistry model, which simulates the biogeochemical processes including carbon and nutrient cycles. The model contains the bio–physical feedback by incorporating the oceanic heating due to chlorophyll absorption of solar radiation. We evaluate the model performance against available observations and a global ocean simulation, and this shows that our model reproduces the magnitude of and variability in biogeochemical variables well.

We devised a system that simulates large ensembles of forecasts for European temperatures and the North Atlantic Oscillation index. This system is based on a stochastic weather generator that samples analogs of SLP. This paper provides statistical tests of temperature and NAO forecasts for timescales of days to months. We argue that the forecast skill of the system is significantly positive and could be used as a baseline for numerical weather forecast.

We present a methodological framework for the analysis of climate model uncertainty based on the functional data analysis approach, an emerging statistical field. The novel method investigates the multi-model spread, taking into account the behavior of entire simulated climatic time series, encompassing both past and future periods. We also introduce an innovative way of visualizing climate model similarities based on a network spatialization algorithm that enables an unambiguous interpretation.

A new framework was designed for the widely used Carbon Bond Mechanism Z (CBM-Z) gas-phase chemical kinetics kernel to adapt the single-instruction, multiple-data (SIMD) technology in next-generation processors like Knights Landing (KNL) to improve their calculation performance. The optimization is aimed at implementing the fine-grain level parallelization of CBM-Z. The test results showed significant acceleration with our optimization on both CPU and KNL platforms.

Land–surface interactions with the atmosphere are key for weather and climate modelling studies, both in research and in the operational systems that provide scientific tools for decision makers. Regional assessments will be influenced by the characteristics of the land. We improved the representation of river flows in Great Britain by including a dependency on the terrain slope. This development will be reflected not only in river flows, but in the whole water cycle represented by the model.

We present a simple model for assessing the cooling impacts of vegetation and water features (green and blue infrastructure) in urban environments. This model is designed to be computationally efficient so that those without technical knowledge or access to high-performance computers can use it. TARGET can be used to model average street-level air temperature at canyon to block scales (e.g. 100 m resolution). The model is carefully designed to provide reliable and accurate cooling estimates.

Accurate shortwave radiance computations are becoming increasingly important for some applications in atmospheric composition. In this work we propose a benchmark protocol and dataset to asses the accuracy and computing runtime of radiance calculations of radiative transfer models. It is applied to four models, showing the potential of this benchmark to evaluate the model performance under a variety of atmospheric conditions, viewing geometries, aerosol loading, and optical properties.

To enable fair comparisons of clouds between climate models and the ESA Cloud_cci climate data record (CDR), we present a tool called the Cloud_cci simulator. The tool takes into account the geometry and cloud detection capabilities of the Cloud_cci CDR to allow fair comparisons. We demonstrate the simulator on two climate models. We find the impact of time sampling has a large effect on simulated cloud water amount and that the simulator reduces the cloud cover by about 10 % globally.

Soils have been overlooked as a source of reactive nitrogen (N) emissions that are pronounced in the summer ozone season (growing season) and increasingly important as fertilizer use grows, while fossil fuel combustion sources of N decline. Mechanistic process models of soil N emissions are used in Earth science and soil biogeochemical modeling on a site scale. This work mechanistically models soil N emissions for the first time on a regional scale to better understand their air quality impacts.