Wilfried Winiwarter

Summary for policy makers

Over the past century humans have caused unprecedented • changes to the global nitrogen cycle, converting atmospheric di-nitrogen (N 2 ) into many reactive nitrogen (N r ) forms, doubling the total fi xation of N r globally and more than tripling it in Europe. Th e increased use of N • r as fertilizer allows a growing world population, but has considerable adverse eff ects on the environment and human health. Five key societal threats of N r can be identifi ed: to water quality, air quality, greenhouse balance, ecosystems and biodiversity, and soil quality. Cost–benefi t analysis highlights how the overall environ• mental costs of all N r losses in Europe (estimated at €70–€320 billion per year at current rates) outweigh the direct economic benefi ts of N r in agriculture. Th e highest societal costs are associated with loss of air quality and water quality, linked to impacts on ecosystems and especially on human health.

Inventorying emissions from nature in Europe

As part of the work of the Economic Commission for Europe of the United Nations Task Force on Emission Inventories, a new set of guidelines has been developed for assessing the emissions of sulphur, nitrogen oxides, NH3, CH4, and nonmethane volatile organic compounds (NMVOC) from biogenic and other natural sources in Europe. This paper gives the background to these guidelines, describes the sources, and gives our recommended methodologies for estimating emissions. We have assembled land use and other statistics from European or national compilations and present emission estimates for the various natural/biogenic source categories based on these. Total emissions from nature derived here amount to ∼1.1 Tg S yr−1, 6–8 Tg CH4 yr−1, 70 Gg NH3 (as N) yr−1, and 13 Tg NMVOC yr−1. Estimates of biogenic NO x emissions cover a wide range, from 140 to 1500 Gg NO x (as N) yr−1. In terms of relative contribution to total European emissions for different pollutants, then NMVOC from forests and vegetation are clearly the most important emissions source. Biogenic NO x emissions (although heavily influenced by nitrogen inputs from anthropogenic activities) are very important if the higher estimates are reliable. CH4 from wetlands and sulphur from volcanoes are also significant emissions in the European budgets. On a global scale, European biogenic emissions are not significant, a consequence of the climate and size (7% of global land area) of Europe and of the destruction of natural ecosystems since prehistoric times. However, for assessing local budgets and for photochemical oxidant modeling, natural/biogenic emissions can play an important role. The most important contributor in this regard is undoubtedly forest VOC emissions, although this paper also indicates that NMVOC emissions from nonforested areas also need to be further evaluated. This paper was originally conceived as a contribution to the collection of papers arising as a result of the Workshop on Biogenic Hydrocarbons in the Atmospheric Boundary Layer, August 24–27, 1997. (Several papers arising from this workshop have been published in Journal of Geophysical Research, 103(D19) 1998.)

Uncertainties in greenhouse gas emission inventories — evaluation, comparability and implications

Abstract This paper reviews quantitative assessments of uncertainty in level and trend in national greenhouse gas inventories. The reported uncertainty in the total emissions of high-quality greenhouse gas inventories ranges from ±5–20% in studies of five industrialised countries. The differences in uncertainty are, in particular, due to different subjective assessment of the uncertainty in emissions of nitrous oxide from agricultural soils. The fraction of CO2 in the inventory has little effect on the uncertainty. The uncertainties in trends are about ±4–5 percentage points for those countries that have made estimates. High uncertainties of emission levels indicate potential for improvements and, consequently, recalculations. Recalculations will reduce uncertainty, but might also cause practical problems. A high uncertainty in the emission level for large emission sources may be an obstacle for assessing cost-effective reduction strategies as well as for designing effective systems of emission trading. This could imply that the more uncertain emission sources should be excluded from emission trading. Alternatively, subjective uncertainty estimates may be expressed in terms of an economic risk of recalculation. The latter system may allow a market-based encouragement to reduce emission uncertainty. Reductions in uncertainties are anticipated in the future. However, it will be extremely difficult to reduce the trend uncertainty. Trend uncertainties may consequently remain high compared with the emission reduction targets in the Kyoto protocol.

EU Energy, Transport and GHG Emissions: Trends to 2050, Reference Scenario 2013

This report is an update and extension of the previous trend scenarios for development of energy systems taking account of transport and greenhouse gas (GHG) emissions developments. The purpose of this publication is to present the new European Union (EU) Reference scenario 2013. It focuses on energy, transport and climate dimensions of EU developments and the various interactions among policies, including specific sections on emission trends not related to energy. The Reference scenario was elaborated by a consortium led by the National Technical University of Athens (E3MLab) using the PRIMES model for energy and CO2 emission projections, the GAINS model for non-CO2 emission projections and the GLOBIOM-G4M models for LULUCF emission and removal projections. The scenarios are available for the EU and each of its 28 Member States simulating the energy balances and GHG emission trends for future years under current trends and policies as adopted in the Member States by spring 2012.

Assessing the uncertainty associated with national greenhouse gas emission inventories : a case study for Austria

The uncertainty associated with the Austrian Greenhouse Gas emission inventory has been determined for the gases CO2, CH4 and N2O and for the overall greenhouse potential. Expert interviews were conducted to obtain uncertainties in inventory input data. Based on these interviews, error distributions were developed and combined using Monte-Carlo analysis. Results for all sources and gases combined indicate an overall uncertainty between 10.5% and 12% depending on the base year considered. Excluding emissions and the uncertainty associated with forest sinks and natural sources, overall uncertainty decreased by 2% points. The mere ‘random error’, which is considered the level of uncertainty to be achieved with the current methodology (excluding all systematic errors) is 5% points lower. Detailed evaluation shows that much of the overall uncertainty derives from a lack of understanding the processes associated with N2O emissions from soils. Other important contributors to GHG emission uncertainties are CH4 from landfills and forests as CO2 sinks. The uncertainty of the trend has been determined at near 5% points, with solid waste production (landfills) having the strongest contribution. Theoretical considerations do not permit a decrease of the trend uncertainty—even when forest sinks are not considered—below 3% points.

Nitrogen footprints: past, present and future

The human alteration of the nitrogen cycle has evolved from minimal in the mid-19th century to extensive in the present time. The consequences to human and environmental health are significant. While much attention has been given to the extent and impacts of the alteration, little attention has been given to those entities (i.e., consumers, institutions) that use the resources that result in extensive reactive nitrogen (Nr) creation. One strategy for assessment is the use of nitrogen footprint tools. A nitrogen footprint is generally defined as the total amount of Nr released to the environment as a result of an entitys consumption patterns. This paper reviews a number of nitrogen footprint tools (N-Calculator, N-Institution, N-Label, N-Neutrality, N-Indicator) that are designed to provide that attention. It reviews N-footprint tools for consumers as a function of the country that they live in (N-Calculator, N-Indicator) and the products they buy (N-Label), for the institutions that people work in and are educated in (N-Institution), and for events and decision-making regarding offsets (N-Neutrality). N footprint tools provide a framework for people to make decisions about their resource use and show them how offsets can be coupled with behavior change to decrease consumer/institution contributions to N-related problems.

The role of N2O derived from crop-based biofuels, and from agriculture in general, in Earth's climate

In earlier work, we compared the amount of newly fixed nitrogen (N, as synthetic fertilizer and biologically fixed N) entering agricultural systems globally to the total emission of nitrous oxide (N2O). We obtained an N2O emission factor (EF) of 3–5%, and applied it to biofuel production. For ‘first-generation’ biofuels, e.g. biodiesel from rapeseed and bioethanol from corn (maize), that require N fertilizer, N2O from biofuel production could cause (depending on N uptake efficiency) as much or more global warming as that avoided by replacement of fossil fuel by the biofuel. Our subsequent calculations in a follow-up paper, using published life cycle analysis (LCA) models, led to broadly similar conclusions. The N2O EF applies to agricultural crops in general, not just to biofuel crops, and has made possible a top-down estimate of global emissions from agriculture. Independent modelling by another group using bottom-up IPCC inventory methodology has shown good agreement at the global scale with our top-down estimate. Work by Davidson showed that the rate of accumulation of N2O in the atmosphere in the late nineteenth and twentieth centuries was greater than that predicted from agricultural inputs limited to fertilizer N and biologically fixed N (Davidson, E. A. 2009 Nat. Geosci. 2, 659–662.). However, by also including soil organic N mineralized following land-use change and NOx deposited from the atmosphere in our estimates of the reactive N entering the agricultural cycle, we have now obtained a good fit between the observed atmospheric N2O concentrations from 1860 to 2000 and those calculated on the basis of a 4 per cent EF for the reactive N.

Integrating nitrogen fluxes at the European scale

Executive summary Nature of the problem • Environmental problems related to nitrogen concern all economic sectors and impact all media: atmosphere, pedosphere, hydrosphere and anthroposphere. • Therefore, the integration of fluxes allows an overall coverage of problems related to reactive nitrogen (Nr) in the environment, which is not accessible from sectoral approaches or by focusing on specific media. Approaches • This chapter presents a set of high resolution maps showing key elements of the N flux budget across Europe, including N2 and Nr fluxes. • Comparative nitrogen budgets are also presented for a range of European countries, highlighting the most efficient strategies for mitigating Nr problems at a national scale. A new European Nitrogen Budget (EU-27) is presented on the basis of state-of-the-art Europe-wide models and databases focusing on different segments of Europe’s society. Key findings • From c. 18 Tg Nr yr −1 input to agriculture in the EU-27, only about 7 Tg Nr yr− 1 find their way to the consumer or are further processed by industry. • Some 3.7 Tg Nr yr−1 is released by the burning of fossil fuels in the EU-27, whereby the contribution of the industry and energy sectors is equal to that of the transport sector. More than 8 Tg Nr yr−1 are disposed of to the hydrosphere, while the EU-27 is a net exporter of reactive nitrogen through atmospheric transport of c. 2.3 Tg Nr yr−1. • The largest single sink for Nr appears to be denitrifi cation to N2 in European coastal shelf regions (potentially as large as the input of mineral fertilizer, about 11 Tg N yr–1 for the EU-27); however, this sink is also the most uncertain, because of the uncertainty of Nr import from the open ocean. Major uncertainties • National nitrogen budgets are diffi cult to compile using a large range of data sources and are currently available only for a limited number of countries. • Modelling approaches have been used to fill in the data gaps in some of these budgets, but it became obvious during this study that further research is needed in order to collect necessary data and make national nitrogen budgets inter-comparable across Europe. • In some countries, due to inconsistent or contradictory information coming from different data sources, closure of the nitrogen budget was not possible. Recommendations • The large variety of problems associated with the excess of Nr in the European environment,including adverse impacts, requires an integrated nitrogen management approach that would allow for creation and closure of N budgets within European environments. • Development of nitrogen budgets nationwide, their assessment and management could become an effective tool to prioritize measures and prevent unwanted side effects.

Nitrogen as a threat to the European greenhouse balance

Reactive nitrogen (N_r) is of fundamental importance in biological and chemical processes in the atmosphere-biosphere system, altering the Earths climate balance in many ways. These include the direct and indirect emissions of nitrous oxide (N2O), atmospheric N_r deposition and tropospheric ozone formation (O3), both of which alter the biospheric CO2 sink, N_r supply effects on CH4 emissions, and the formation of secondary atmospheric aerosols resulting from the emissions of nitrogen oxides (NOx) and ammonia (NH3). Human production and release of N_r into the environment is thus expected to have been an important driver of European greenhouse balance. Until now, no assessment has been made of how much of an effect European N_r emissions are having on net warming or cooling.

Sectoral marginal abatement cost curves: implications for mitigation pledges and air pollution co-benefits for Annex I countries

Using the GAINS (Greenhouse Gas–Air Pollution Interactions and Synergies) model, we derived Annex I marginal abatement cost curves for the years 2020 and 2030 for three World Energy Outlook baseline scenarios (2007–2009) of the International Energy Agency. These cost curves are presented by country, by greenhouse gas and by sector. They are available for further inter-country comparisons in the GAINS Mitigation Efforts Calculator—a free online tool. We illustrate the influence of the baseline scenario on the shape of mitigation cost curves, and identify key low cost options as well as no-regret priority investment areas for the years 2010–2030. Finally, we show the co-effect of GHG mitigation on the emissions of local air pollutants and argue that these co-benefits offer strong local incentives for mitigation.