The spread amongst ENSEMBLES regional scenarios: regional climate models, driving general circulation models and interannual variability

Various combinations of thirteen regional climate models (RCM) and six general circulation models (GCM) were used in FP6-ENSEMBLES. The response to the SRES-A1B greenhouse gas concentration scenario over Europe, calculated as the difference between the 2021–2050 and the 1961–1990 means can be viewed as an expected value about which various uncertainties exist. Uncertainties are measured here by variance explained for temperature and precipitation changes over eight European sub-areas. Three sources of uncertainty can be evaluated from the ENSEMBLES database. Sampling uncertainty is due to the fact that the model climate is estimated as an average over a finite number of years (30) despite a non-negligible interannual variability. Regional model uncertainty is due to the fact that the RCMs use different techniques to discretize the equations and to represent sub-grid effects. Global model uncertainty is due to the fact that the RCMs have been driven by different GCMs. Two methods are presented to fill the many empty cells of the ENSEMBLES RCM?×?GCM matrix. The first one is based on the same approach as in FP5-PRUDENCE. The second one uses the concept of weather regimes to attempt to separate the contribution of the GCM and the RCM. The variance of the climate response is analyzed with respect to the contribution of the GCM and the RCM. The two filling methods agree that the main contributor to the spread is the choice of the GCM, except for summer precipitation where the choice of the RCM dominates the uncertainty. Of course the implication of the GCM to the spread varies with the region, being maximum in the South-western part of Europe, whereas the continental parts are more sensitive to the choice of the RCM. The third cause of spread is systematically the interannual variability. The total uncertainty about temperature is not large enough to mask the 2021–2050 response which shows a similar pattern to the one obtained for 2071–2100 in PRUDENCE. The uncertainty about precipitation prevents any quantitative assessment on the response at grid point level for the 2021–2050 period. One can however see, as in PRUDENCE, a positive response in winter (more rain in the scenario than in the reference) in northern Europe and a negative summer response in southern Europe.     

Thermal Emission Spectrometer Observations of Martian Planet-Encircling Dust Storm 2001A

The initiation and evolution of a planet-encircling dust storm on Mars have been observed in unprecedented detail by the Thermal Emission Spectrometer (TES) on board the Mars Global Surveyor. A local dust storm began to expand quickly on 26 June 2001 (areo-centric longitude, L_s=185°), becoming a planet-encircling dust storm by 11 July 2001. The dust storm had dust optical depth >2 over wide areas and caused atmospheric temperatures over a large vertical range to warm by >40 K from 20°N latitude to the south pole.     

A lateral model parameter correlation procedure for one-dimensional inverse modelling

We present a new, fast and versatile method, the lateral parameter correlation method, of invoking lateral smoothness in model sections of one-dimensional (1D) models. Modern, continuous electrical and electromagnetic methods are capable of recording very large data sets and except for a few cases, standard inversion methodology still relies on 1D models. In environments where the lateral rate of change of resistivity is small, 1D inversion can be justified but model sections of concatenated 1D models do not necessarily display the expected lateral smoothness.
The lateral parameter correlation method has three steps. First, all sounding data are inverted individually. Next, a laterally smooth version of each model parameter, one at a time, is found by solving a simple constrained inversion problem. Identity is postulated between the uncorrelated and correlated parameters and the equations are solved including a model covariance matrix. As a last step, all sounding data are inverted again to produce models that better fit the data, now subject to constraints by including the correlated parameter values as a priori values. Because the method separates the inversion from the correlation it is much faster than methods where the inversion and correlation are solved simultaneously, typically with a factor of 200–500.
Theoretical examples show that the method produces laterally smooth model sections where the main influence comes from the well-determined parameters in such a way that problems with equivalence and poor resolution are alleviated. A field example is presented, demonstrating the improved resolution obtained with the lateral parameter correlation method. The method is very flexible and is capable of coupling models from inversion of different data types and information from boreholes.     

Surficial properties in Melas Chasma, Mars, from Mars Odyssey THEMIS data

We examine the nature of the surface layer in a small area of the Melas Chasma region as determined from high-resolution thermal and visible Mars Odyssey Thermal Emission Imaging System (THEMIS) data as well as how our conclusions compare to past analyses. At THEMIS resolution, the thermal structure is dominated by local control and all significant thermal variations can be linked to morphology. Thus, THEMIS provides us with detailed images that contain thermophysical information as well, allowing us to create a surficial geologic map intended to reflect the surface structure of the region. Eight units have been defined: (i) blanketed plateaus with thermally distinct craters and fractures, (ii) blanketed canyon walls with rocky edges, (iii) indurated and/or rocky canyon wall slide material partially covered by aeolian material, (iv) an anomalous wall region with fluvial-like depressions partially filled with particulate material, (v) indurated and/or rocky ridged and non-ridged canyon floor landslide material mingled with aeolian material, (vi) sand sheets, (vii) indurated and/or rocky rounded blocks intermingled with small areas of aeolian material, and (viii) transverse dunes. The THEMIS thermal data support conclusions from previous studies but also reveal much more structure than was seen in the past. We have found that all significant thermal variations in this region can be linked to morphology but all morphological variations cannot be linked to significant thermal variations. THEMIS visible images provide an intermediate resolution that bridges the gap between MOC and Viking and allow for a more meaningful interpretation of the geologic context of a region. Surfaces indicate that landslides were an important geologic process long ago, shaping the canyon walls and floor, while aeolian processes have subsequently altered the surface layer in many locations and may still be active.     

Climate Change Impact on Snow Coverage, Evaporation and River Discharge in the Sub-Arctic Tana Basin, Northern Fennoscandia

Arctic environments are generally believed to be highly sensitive to human-induced climatic change. In this paper, we explore the impacts on the hydrological system of the sub-arctic Tana Basin in Northernmost Finland and Norway. In contrast with previous studies, attention is not only given to river discharge, but also to the spatial patterns in snow coverage and evapotranspiration. We used a distributed water balance model that was coupled to a regional climate model in order to calculate a scenario of climate change by the end of this century. Three different model experiments were performed, adopting different approaches to using the climate model output in the hydrological model runs. The results were largely consistent, indicating a much shorter snow season and, accordingly, decreased sublimation, an increase in evapotranspiration, and a shift in the annual runoff peak. As the snow-free season is extended, the amount of solar radiation that is received during this period increases significantly. The results also show important local differences in the hydrological response to climate change. For example, in the scenario runs, the snow season was more than 30 days shorter at higher elevations, but in some of the river valleys, this was up to 70 days.     

A framework for testing the ability of models to project climate change and its impacts

Models used for climate change impact projections are typically not tested for simulation beyond current climate conditions. Since we have no data truly reflecting future conditions, a key challenge in this respect is to rigorously test models using proxies of future conditions. This paper presents a validation framework and guiding principles applicable across earth science disciplines for testing the capability of models to project future climate change and its impacts. Model test schemes comprising split-sample tests, differential split-sample tests and proxy site tests are discussed in relation to their application for projections by use of single models, ensemble modelling and space-time-substitution and in relation to use of different data from historical time series, paleo data and controlled experiments. We recommend that differential-split sample tests should be performed with best available proxy data in order to build further confidence in model projections.     

Fugitive emissions from Norwegian oil and gas production

Fugitive hydrocarbon emissions from oil and gas production, always a safety concern, are currently a growing environmental and economic concern. Fugitive emissions from the offshore industry comprise mainly methane, which has an atmospheric warming contribution of approximately 14 times that of CO₂, and Volatile Organic Compounds (VOCs), which have an atmospheric warming contribution of around twice that of CO₂.

Current studies indicate that fugitive emissions are approximately equivalent to 0.02% of the total gas produced in 1992 on the Norwegian Continental Shelf. A positive downward trend in fugitive emissions from oil and gas production has been identified and attributed to advances in technology and changes in design and operating philosophy.     

Exploration of the high-redshift universe enabled by THESEUS

Experimental Astronomy - At peak, long-duration gamma-ray bursts are the most luminous sources of electromagnetic radiation known. Since their progenitors are massive stars, they provide a tracer...     

Evaluation of water and energy budgets in regional climate models applied over Europe

This study presents a model intercomparison of four regional climate models (RCMs) and one variable resolution atmospheric general circulation model (AGCM) applied over Europe with special focus on the hydrological cycle and the surface energy budget. The models simulated the 15 years from 1979 to 1993 by using quasi-observed boundary conditions derived from ECMWF re-analyses (ERA). The model intercomparison focuses on two large atchments representing two different climate conditions covering two areas of major research interest within Europe. The first is the Danube catchment which represents a continental climate dominated by advection from the surrounding land areas. It is used to analyse the common model error of a too dry and too warm simulation of the summertime climate of southeastern Europe. This summer warming and drying problem is seen in many RCMs, and to a less extent in GCMs. The second area is the Baltic Sea catchment which represents maritime climate dominated by advection from the ocean and from the Baltic Sea. This catchment is a research area of many studies within Europe and also covered by the BALTEX program. The observed data used are monthly mean surface air temperature, precipitation and river discharge. For all models, these are used to estimate mean monthly biases of all components of the hydrological cycle over land. In addition, the mean monthly deviations of the surface energy fluxes from ERA data are computed. Atmospheric moisture fluxes from ERA are compared with those of one model to provide an independent estimate of the convergence bias derived from the observed data. These help to add weight to some of the inferred estimates and explain some of the discrepancies between them. An evaluation of these biases and deviations suggests possible sources of error in each of the models. For the Danube catchment, systematic errors in the dynamics cause the prominent summer drying problem for three of the RCMs, while for the fourth RCM this is related to deficiencies in the land surface parametrization. The AGCM does not show this drying problem. For the Baltic Sea catchment, all models similarily overestimate the precipitation throughout the year except during the summer. This model deficit is probably caused by the internal model parametrizations, such as the large-scale condensation and the convection schemes.