Wolfgang Knorr

• Senior Researcher at Lund University

Advances in Earth observation capabilities mean that there is now a multitude of spatially resolved data sets available that can support the quantification of water and carbon pools and fluxes at the land surface. However, such quantification ideally requires efficient synergistic exploitation of those data, which in turn requires carbon and water...

Advances in Earth Observation capabilities mean that there is now a multitude of spatially resolved data sets available that can support the quantification of water and carbon pools and fluxes at the land surface. However, such quantification ideally requires efficient synergistic exploitation of those data, which in turn requires carbon and water...

The European Copernicus programme plans to install a constellation of multiple polar orbiting satellites (Copernicus Anthropogenic CO2 Monitoring Mission, CO2M mission) for observing atmospheric CO2 content with the aim to estimate fossil fuel CO2 emissions. We explore the impact of potential CO2M observations of column-averaged CO2 (XCO2), nitroge...

The Paris Agreement establishes a transparency framework for anthropogenic carbon dioxide (CO2) emissions. It's core component are inventory-based national greenhouse gas emission reports, which are complemented by independent estimates derived from atmospheric CO2 measurements combined with inverse modelling. It is, however, not known whether such...

The northern land biosphere is believed to be the main global sink of CO2, but the contribution of Europe is uncertain. While bottom-up estimates and inverse atmospheric transport studies based on atmospheric CO2 observed in situ or from space by OCO-2 point to a moderate rate of uptake, some other inversions based on remotely sensed atmospheric CO...

The ongoing ESA funded 'SMOS + Vegetation' project combines a retrieval component that aims at further improving the SMOS VOD product with an assimilation component that aims at demonstrating the added value of this product in constraining simulated land surface fluxes of carbon dioxide. This contribution focuses on the project's modelling and assi...

The ongoing ESA funded `SMOS + Vegetation' project combines a retrieval component that aims at further improving the SMOS VOD product with an assimilation component that aims at demonstrating the added value of this product in constraining simulated land surface fluxes of carbon dioxide. This contribution focuses on the project's modelling and assi...

Fires have influenced atmospheric composition and climate since the rise of vascular plants, and satellite data have shown the overall global extent of fires. Our knowledge of historic fire emissions has progressively improved over the past decades due mostly to the development of new proxies and the improvement of fire models. Currently, there is...

We present two novel earth observation products derived from the BESD and EMMA XCO2 products which were respectively retrieved from SCIAMACHY and GOSAT observations within the GreenHouse Gas project of ESA's Climate Change Initiative (GHG-CCI). These products are inferred by a Carbon Cycle Data Assimilation System (CCDAS) and consist of net and gro...

Wildfires pose a significant risk to human livelihoods and are a substantial health hazard due to emissions of toxic smoke. Previous studies have shown that climate change, increasing atmospheric CO2, and human demographic dynamics can lead to substantially altered wildfire risk in the future, with fire activity increasing in some regions and decre...

The important role of fire in regulating vegetation community composition and contributions to emissions of greenhouse gases and aerosols make it a critical component of dynamic global vegetation models and Earth system models. Over 2 decades of development, a wide variety of model structures and mechanisms have been designed and incorporated into...

Fires have influenced atmospheric composition and climate since the rise of vascular plants, and satellite data has shown the overall global extent of fires. Our knowledge of historic fire emissions has progressively improved over the past decades due mostly to the development of new proxies and the improvement of fire models. Currently there is a...

The important role of fire in regulating vegetation community composition and contributions to emissions of greenhouse gases and aerosols make it a critical component of dynamic global vegetation models and Earth system models. Over two decades of development, a wide variety of model structures and mechanisms have been designed and incorporated int...

HIGHLIGHTS About 500 million hectares of tropical forests have been degraded due primarily to overexploitation Preventing premature re-entry into harvested areas can retain up to 34% of carbon stocks in the forests Adoption of reduced-impact logging and wood processing technologies (RIL+) along with financial incentives can reduce forest fires, for...

Wildfires pose a significant risk to human livelihoods and are a substantial health hazard due to emissions of toxic smoke. It is widely believed that climate change, through increasing the frequency of hot weather conditions, will also lead to an increase in wildfire activity. More recently, however, new research has shown that trends in populatio...

Biomass burning impacts vegetation dynamics, biogeochemical cycling, atmospheric chemistry, and climate, with sometimes deleterious socio-economic impacts. Under future climate projections it is often expected that the risk of wildfires will increase. Our ability to predict the magnitude and geographic pattern of future fire impacts rests on our ab...

Wildfires are not only a threat to human property and a vital element of many ecosystems, but also an important source of air pollution. In this study, we first review the available evidence for a past or possible future climate-driven increase in wildfire emissions in Europe. We then introduce an ensemble of model simulations with a coupled wildfi...

Wildfires are an important component of terrestrial ecosystem ecology but also a major natural hazard to societies, and their frequency and spatial distribution must be better understood. At a given location, risk from wildfire is associated with the annual fraction of burned area, which is expected to increase in response to climate warming. Until...

Carbon dioxide (CO 2) is the most important anthropogenic greenhouse gas contributing to about half of the total anthropogenic change in the Earth's radiation budget. And about half of the anthropogenic CO2 emissions stay in the atmosphere, the remainder is taken up by the biosphere. It is of paramount importance to better understand CO2 sources an...

Key Points Appreciation of Peer Reviewers for 2015

Wildfires are not only a threat to human property and a vital element of many ecosystems, but also an important source of air pollution. In this study, we first review the available evidence for a past or possible future climate-driven increase in wildfire emissions in Europe. We then introduce an ensemble of model simulations with a coupled wildfi...

Biomass burning impacts vegetation dynamics, biogeochemical cycling, atmospheric chemistry, and climate, with sometimes deleterious socio-economic impacts. Under future climate projections it is often expected that the risk of wildfires will increase. Our ability to predict the magnitude and geographic pattern of future fire impacts rests on our ab...

Wildfires are by far the largest contributor to global biomass burning and constitute a large global source of atmospheric traces gases and aerosols. Such emissions have a considerable impact on air quality and constitute a major health hazard. Biomass burning also influences the radiative balance of the atmosphere and is thus not only of societal,...

Global environmental changes and human activity influence wildland fires worldwide, but the relative importance of the individual factors varies regionally and their interplay can be difficult to disentangle. Here we evaluate projected future changes in burned area at the European and sub-European scale, and we investigate uncertainties in the rela...

Wildfires are by far the largest contributor to global biomass burning and constitute a large global source of atmospheric traces gases and aerosols. Such emissions have a considerable impact on air quality and constitute a major health hazard. Biomass burning also influences the radiative balance of the atmosphere and is thus not only of societal,...

The Model of Emissions of Gases and Aerosols from Nature (MEGANv2.1) together with the Modern-Era Retrospective Analysis for Research and Applications (MERRA) meteorological fields were used to create a global emission dataset of biogenic volatile organic compounds (BVOC) available on a monthly basis for the time period of 1980–2010. This dataset i...

The Model of Emissions of Gases and Aerosols from Nature (MEGANv2.1) together with the Modern-Era Retrospective Analysis for Research and Applications (MERRA) meteorological fields were used to create a global emission dataset of biogenic volatile organic compounds (BVOC) available on a monthly basis for the time period of 1980–2010. This dataset i...

Human impact on wildfires, a major earth system component, remains poorly understood. While local studies have found more fires close to settlements and roads, assimilated charcoal records and analyses of regional fire patterns from remote-sensing observations point to a decline in fire frequency with increasing human population. Here, we present a...

We present the concept of the Carbon Cycle Data Assimilation System and describe its evolution over the last two decades from an assimilation system around a simple diagnostic model of the terrestrial biosphere to a system for the calibration and initialization of the land component of a comprehensive Earth system model. We critically review the ca...

In this study we compare monthly gross primary productivity (GPP) time series (2000–2007), computed for Europe with the Biosphere Energy Transfer Hydrology (BETHY/DLR) model with monthly data from the eddy covariance measurements network FLUXNET. BETHY/DLR with a spatial resolution of 1 km2 is designed for regional and continental applications (her...

Fires are expected to change under future climate change, climatic fire is is increasing due to increase in droughts and heat waves affecting vegetation productivity and ecosystem function. Vegetation productivity influences fuel production, but can also limit fire spread. Vegetation-fire models allow investigating the interaction between wildfires...

Widlfires are a major component of most terrestrial ecosystems, and constitute a major hazard for humans. However, the way people influence fire occurrence remains poorly understood, in particular at the global scale. While local studies have found increasing numbers of fires near settlements and roads, a few regional studies for Africa have found...

In this study we compare monthly gross primary productivity (GPP) time series (2000-2007), computed for Europe with the Biosphere Energy Transfer Hydrology (BETHY/DLR) model with monthly data from the eddy covariance measurements network FLUXNET. BETHY/DLR with a spatial resolution of 1 km2 is designed for regional and continental applications (her...

Terrestrial productivity in semi-arid woodlands is strongly susceptible to changes in precipitation, and semi-arid woodlands constitute an important element of the global water and carbon cycles. Here, we use the Carbon Cycle Data Assimilation System (CCDAS) to investigate the key parameters controlling ecological and hydrological activities for a...

Terrestrial ecosystem models (TEMs) contain the coupling of many biogeochemical processes with a large number of parameters involved. In many cases those parameters are highly uncertain. In order to reduce those uncertainties, parameter estimation methods can be applied, which allow the model to be constrained against observations. We compare the p...

Biomass burning is one of the largest sources of atmospheric trace gases and aerosols globally. These emissions have a major impact on the radiative balance of the atmosphere and on air quality, and are thus of significant scientific and societal interest. Several datasets have been developed that quantify those emissions on a global grid and offer...

The study has developed an interactive mission benefit analysis (MBA) tool that allows instantaneous evaluation of a range of potential mission designs. The designs are evaluated in terms of their constraint on carbon and water fluxes through calibration of a terrestrial bisphere model. The constraint is quantified by methematically rigorous uncert...

Tackling the possible severe impacts of climate change on the carbon cycle and land water resources requires further development of simulation models and monitoring capabilities. Carbon cycle impacts can lead to further climate change through releases of CO2, and impacts on water resources are critical for human survival. A rapidly increasing monit...

Terrestrial productivity in semi-arid woodlands is strongly susceptible to changes in precipitation, and semi-arid woodlands constitute an important element of the global water and carbon cycles. Here, we use the Carbon Cycle Data Assimilation System (CCDAS) to investigate the mechanisms controlling ecological and hydrogical activities for a semi-a...

Biomass burning is one of the largest sources of atmospheric trace gases and aerosols globally. These emissions have a major impact on the radiative balance of the atmosphere and on air quality, and are thus of significant scientific and societal interest. Several datasets have been developed that quantify those emissions on a global grid and offer...

Accurate modelling of the carbon cycle strongly depends on the parametrization of its underlying processes. The Carbon Cycle Data Assimilation System (CCDAS) can be used as an estimator algorithm to derive posterior parameter values and uncertainties for the Biosphere Energy Transfer and Hydrology scheme (BETHY). However, the simultaneous optimizat...

The terrestrial biosphere is currently a strong sink for anthropogenic CO2 emissions. Through the radiative properties of CO2 the strength of this sink has a direct influence on the radiative budget of the global climate system. The accurate assessment of this sink and its evolution under a changing climate is, hence, paramount for any efficient ma...

Accurate modelling of the carbon cycle strongly depends on the parametrization of its underlying processes. The Carbon Cycle Data Assimilation System (CCDAS) can be used as an estimator algorithm to derive posterior parameter values and uncertainties for the Biosphere Energy Transfer and Hydrology scheme (BETHY). However, the simultaneous optimizat...

The restoration of fire-affected forest areas needs to be combined with their future protection from renewed catastrophic fires, such as those that occurred in Greece during the 2007 summer season. The present work demonstrates that the use of various sources of satellite data in conjunction with weather forecast information is capable of providing...

Better estimates of the net exchange of CO 2 between the atmosphere and the terrestrial biosphere are urgently needed to improve predictions of future CO 2 levels in the atmosphere. The carbon cycle data assimilation system (CCDAS) offers the capability of inversion, while it is at the same time based on a process model that can be used independent...

Feedbacks between the terrestrial carbon cycle and the atmosphere have the potential to greatly modify expected rates of future climate change. This makes it all the more urgent to exploit all existing data for the purpose of accurate modelling of the underlying processes. Here we use a Bayesian random sampling method to constrain parameters of the...

Inclusion of improved forest management as a way to enhance carbon sinks in the Copenhagen Accord of the United Nations Framework Convention on Climate Change (December 2009) suggests that forest restoration will play a role in global climate change mitigation under the post-Kyoto agreement. Although discussions about restoration strategies often p...

Photosynthesis by terrestrial plants is the main driver of the global carbon cycle, and the presence of actively photosynthesizing vegetation can now be observed from space. However, challenges remain when translating remotely sensed data into carbon fluxes. One reason is that the Fraction of Absorbed Photosynthetically Active Radiation (FAPAR), wh...

Geophysical Research Letters (GRL) is the American Geophysical Union's premier journal of fast, groundbreaking communication. It rapidly publishes high-impact, letter-length articles, and it is the top-cited multidisciplinary geosciences journal over the past 10 years, with an impact factor that increased again in 2009, to 3.204. For manuscripts su...

Earth Observation from space offers the opportunity to produce time-series of geophysical products that can be used to assess the state and changes of land surfaces. The Fraction of Absorbed Photosynthetically Active Radiation (FAPAR) is used to monitor the state and evolution of terrestrial vegetation, and also constitutes a state variable in adva...

The study looks at forestry policies in India in conjunction with the Kyoto Protocol (KP) to assess the possibilities for synergy between them. It assesses how far existing national initiatives, namely the Joint Forest Management and the more recent Forest Rights Act, are able to contribute to the dual objectives of the Clean Development Mechanism...

The importance of understanding the impact of wildfires on natural ecosystems has given rise to the development of realistic computer models for the simulation of wildfires. Stochastic models based on simplified equations and local interactions, such as Cellular Automata (CA) models, are particularly popular as an alternative to more computationall...

The Carbon Cycle Data Assimilation System (CCDAS) allows the current fluxes of CO2 to the atmosphere to be mapped and the evolution of these fluxes into the future to be predicted. In this work we concentrate on the calibration mode of CCDAS where an optimal parameter set is derived from 10 years of atmospheric CO2 concentration observations using...

The response of land ecosystems to climate change and associated feedbacks are a key uncertainty in future climate prediction (Friedlingstein et al. 2006). However global models generally do not account for the acclimation of plant physiological processes to increased temperatures. Here we conduct a first global sensitivity study whereby we modify...

Space-based observations of terrestrial vegetation are one of the best means of characterizing vegetation status over the globe. The most suitable variable for this purpose is FAPAR, the fraction of plant-absorbed photosynthetically active radiation. Data assimilation offers an objective means for the utilization of FAPAR for improving estimates of...

The Clean Development Mechanism (CDM), Article 12 of the Kyoto Protocol allows Afforestation and Reforestation (A/R) projects as mitigation activities to offset the CO2 in the atmosphere whilst simultaneously seeking to ensure sustainable development for the host country. The Kyoto Protocol was ratified by the Government of India in August 2002 and...

Remote sensing is increasingly being used as a cost-effective and practical solution for the rapid evaluation of impacts from wildland fires. The present study investigates the use of the support vector machine (SVM) classification method with multispectral data from the Advanced Spectral Emission and Reflection Radiometer (ASTER) for obtaining a r...

Several recent studies have highlighted the possibility that the oceans and terrestrial ecosystems have started losing part of their ability to sequester a large proportion of the anthropogenic CO2 emissions. This is an important claim, because so far only about 40% of those emissions have stayed in the atmosphere, which has prevented additional cl...

Forests in Southeast Asia are important sources of timber and other forest products, of local energy for cooking and heading, and potentially as sources of bioenergy. Many of these forests have experienced deforestation and forest degradation over the last few decades. The potential flow of woody biomass for bioenergy from forests is uncertain and...

The present study investigates the use of support vector machine (SVM) classification methods with multispectral data from the Advanced Spectral Emission and Reflection Radiometer (ASTER) for obtaining rapid and cost effective cartography of fuel types and burn scars in a Mediterranean setting. A further objective is to perform a detailed intercomp...

Concern about the uncertainty on the current and future behaviour of the terrestrial carbon cycle has stimulated the research community to build complex observing systems for the terrestrial carbon cycle. These observations are of many forms and are made either at a point or with detailed spatial coverage. Improving our understanding requires incor...

Photosynthetic capacity is one of the most sensitive parameters of terrestrial biosphere models whose representation in global scale simulations has been severely hampered by a lack of systematic analyses using a sufficiently broad database. Due to its coupling to stomatal conductance changes in the parameterisation of photosynthetic capacity may p...

Abstract Photosynthetic capacity and its relationship to leaf nitrogen content are two of the most sensitive parameters of terrestrial biosphere models (TBM) whose representation in global-scale simulations has been severely hampered by a lack of systematic analyses using a sufficiently broad database. Here, we use data of qualitative traits, clima...

The present study investigates the use of support vector machine (SVM) classification methods with multispectral data from the Advanced Spectral Emission and Reflection Radiometer (ASTER) for obtaining rapid and cost effective cartography of fuel types and burn scars in a Mediterranean setting. A further objective is to perform a detailed intercomp...

This article was submitted without an abstract, please refer to the full-text PDF file.

This article was submitted without an abstract, please refer to the full-text PDF file.

This article was submitted without an abstract, please refer to the full-text PDF file.

Global policy targets for greenhouse gas emissions reductions are being negotiated. The amount of emitted carbon dioxide remaining in the atmosphere is controlled by carbon cycle processes in the ocean and on land. These processes are themselves affected by climate. The resulting 'climate–carbon cycle feedback' has recently been quantified, but the...

The present study investigates the use of support vector machine (SVM) classification methods with multispectral data from the Advanced Spectral Emission and Reflection Radiometer (ASTER) for obtaining rapid and cost effective cartography of fuel types and burn scars in a Mediterranean setting. A further objective is to perform a detailed intercomp...

Approaches combining satellite-based remote sensing data with ecosystem modelling offer potential for the accurate assessment of changes in forest carbon balances, for example, in support of emission credits under the Kyoto Protocol. We investigate the feasibility of two alternative methods of using satellite-derived data to constrain the behaviour...

The use of information from climate model simulations by policy makers and other potential users poses great challenges. On the one hand, researchers are rightly cautious about prediction, as the uncertainties are large. On the other hand, policy makers may be used to dealing with great uncertainties, and may be quite prepared to use assessments of...

We quantify the risks of climate-induced changes in key ecosystem processes during the 21st century by forcing a dynamic global vegetation model with multiple scenarios from the IPCC AR4 data archive using 16 climate models and mapping the proportions of model runs showing exceedance of natural variability in wildfire frequency and freshwater suppl...

The Farquhar et al. model of C(3) photosynthesis is frequently used to study the effect of global changes on the biosphere. Its two main parameters representing photosynthetic capacity, V(cmax) and J(max), have been observed to acclimate to plant growth temperature for single species, but a general formulation has never been derived. Here, we prese...

1] One of the major advantages of carbon cycle data assimilation is the possibility to estimate carbon fluxes with uncertainties in a prognostic mode, that is beyond the time period of carbon dioxide (CO 2) observations. The carbon cycle data assimilation system is built around the Biosphere Energy Transfer Hydrology Scheme (BETHY) model, coupled t...

Global warming caused by anthropogenic CO2 emissions is expected to reduce the capability of the ocean and the land biosphere to take up carbon. This will enlarge the fraction of the CO2 emissions remaining in the atmosphere, which in turn will reinforce future climate change. Recent model studies agree in the existence of such a positive climate–c...

A long-term global modeling study of tropospheric chemistry funded under the 5th EU framework programme Project Number: EVK2-CT-2002-00170 (RETRO) Call identifier: EESD-ESD-3 (JO 2000/C 324/09)

A long-term global modeling study of tropospheric chemistry funded under the 5th EU framework programme Project Number: EVK2-CT-2002-00170 (RETRO) Call identifier: EESD-ESD-3 (JO 2000/C 324/09)

A long-term global modeling study of tropospheric chemistry funded under the 5th EU framework programme Project Number: EVK2-CT-2002-00170 (RETRO) Call identifier: EESD-ESD-3 (JO 2000/C 324/09)

This contribution gives an overview of the Medium Resolution Imaging Spectrometer (MERIS) global land product corresponding to the biophysical variable of the Fraction of Absorbed Photosynthetically Active Radiation (FAPAR). This product can be used in large-scale biosphere modeling for better estimating the carbon fluxes since they directly repres...

Understanding the carbon dynamics of the terrestrial biosphere during climate fluctuations is a prerequisite for any reliable modeling of the climate-carbon cycle feedback. We drive a terrestrial vegetation model with observed climate data to show that most of the fluctuations in atmospheric CO2 are consistent with the modeled shift in the balance...

The current and future strength of the terrestrial car- bon sink has a crucial influence on the expected climate warming on Earth. Usually, Earth Observation (EO) by its very nature focusses on diagnosing the current state of the planet. However, it is possible to use EO products in data assimilation systems to improve not only the diag- nosis of t...

The impact of the European drought event in 2003 on water and carbon fluxes between atmosphere and terrestrial biosphere has been well described and vegetation stress has been documented by time series of the fraction of absorbed photosynthetically active radiation (FAPAR). Still the response of terrestrial biosphere characteristics, like canopy ph...