Table of contents

Biofuels from land-rich tropical countries may help displace foreign petroleum imports for many industrialized nations, providing a possible solution to the twin challenges of energy security and climate change. But concern is mounting that crop-based biofuels will increase net greenhouse gas emissions if feedstocks are produced by expanding agricultural lands. Here we quantify the 'carbon payback time' for a range of biofuel crop expansion pathways in the tropics. We use a new, geographically detailed database of crop locations and yields, along with updated vegetation and soil biomass estimates, to provide carbon payback estimates that are more regionally specific than those in previous studies. Using this cropland database, we also estimate carbon payback times under different scenarios of future crop yields, biofuel technologies, and petroleum sources. Under current conditions, the expansion of biofuels into productive tropical ecosystems will always lead to net carbon emissions for decades to centuries, while expanding into degraded or already cultivated land will provide almost immediate carbon savings. Future crop yield improvements and technology advances, coupled with unconventional petroleum supplies, will increase biofuel carbon offsets, but clearing carbon-rich land still requires several decades or more for carbon payback. No foreseeable changes in agricultural or energy technology will be able to achieve meaningful carbon benefits if crop-based biofuels are produced at the expense of tropical forests.

This report consists of a top-level aggregate analysis of the total potential for converting livestock manure into a domestic renewable fuel source (biogas) that could be used to help states meet renewable portfolio standard requirements and reduce greenhouse gas (GHG) emissions. In the US, livestock agriculture produces over one billion tons of manure annually on a renewable basis. Most of this manure is disposed of in lagoons or stored outdoors to decompose. Such disposal methods emit methane and nitrous oxide, two important GHGs with 21 and 310 times the global warming potential of carbon dioxide, respectively. In total, GHG emissions from the agricultural sector in the US amounted to 536 million metric tons (MMT) of carbon dioxide equivalent, or 7% of the total US emissions in 2005. Of this agricultural contribution, 51 to 118 MMT of carbon dioxide equivalent resulted from livestock manure emissions alone, with trends showing this contribution increasing from 1990 to 2005. Thus, limiting GHG emissions from manure represents a valuable starting point for mitigating agricultural contributions to global climate change.

Anaerobic digestion, a process that converts manure to methane-rich biogas, can lower GHG emissions from manure significantly. Using biogas as a substitute for other fossil fuels, such as coal for electricity generation, replaces two GHG sources—manure and coal combustion—with a less carbon-intensive source, namely biogas combustion.

The biogas energy potential was calculated using values for the amount of biogas energy that can be produced per animal unit (defined as 1000 pounds of animal) per day and the number of animal units in the US. The 95 million animal units in the country could produce nearly 1 quad of renewable energy per year, amounting to approximately 1% of the US total energy consumption. Converting the biogas into electricity using standard microturbines could produce 88 ± 20 billion kWh, or 2.4 ± 0.6% of annual electricity consumption in the US. Replacing coal and manure GHG emissions with the emissions from biogas would produce a net potential GHG emissions reduction of 99 ± 59 million metric tons or 3.9 ± 2.3% of the annual GHG emissions from electricity generation in the US.

The US Corn Belt supports agroecosystems that flourish in a temperate climate regime that could see significant changes in the next few decades. Because Wisconsin is situated on the northern, cooler fringes of this region, it may be the beneficiary of a warmer climate that could help support higher corn and soybean yields. Here we show that trends in precipitation and temperature during the growing season from 1976–2006 explained 40% and 35% of county corn and soybean yield trends, respectively. Using county level yield information combined with climate data, we determined that both corn and soybean yield trends were enhanced in counties that experienced a trend towards cooler and wetter conditions during the summer. Our results suggest that for each additional degree ( °C) of future warming during summer months, corn and soybean yields could potentially decrease by 13% and 16%, respectively, whereas if modest increases in total summer precipitation (i.e. 50 mm) were to occur, yields may be boosted by 5–10%, counteracting a portion of the negative effects associated with increased temperature. While northern US Corn Belt regions such as Wisconsin may benefit from a warmer climate regime and management changes that lengthen the crop-growing period in spring and autumn, mid- to high-latitude crop productivity may be challenged by additional summertime warming unless adaptive measures are taken.

Access to and availability of accurate information has often been stated to play an important role in sustainable environmental management. There is a growing trend of setting up internet-based information services to support the availability of relevant information. The current initiatives that aim to facilitate such information sharing through the web are still, however, often premature and unable to ensure constant flow of data from producers to users. We examine these common challenges by using as an example a network-based facility of biodiversity and environmental information about the Peruvian Amazon region called SIAMAZONIA. Launched in 2001, the service includes data provided by 13 different nodes. The experiences of this initiative have been both encouraging and confusing. A good professional level has been reached, but participation by large information holders is impeded. Participation is obviously considered an additional task rather than an attractive option for enhanced performance at the individual or institutional levels. This dilemma reflects a genuine problem in the modern scientific community, which still lacks agreed ways to reward those who share their data and results through the web. If these problems are solved, internet-based information sharing may become a vital resource for environmental management in Amazonia and also elsewhere.

The amplitude and inter-model spread (IMS) of late 21st century changes in temperature and precipitation extremes in 21 Coupled Model Intercomparison Project 3 models are analyzed using the recently introduced climate change index (CCI) and its components. Strong changes in extremes are found which are similar to those found using older data. Large IMS is found mostly in regions where the multi-model mean CCI values are large (tropics land, polar regions) or small (El Niño Southern Oscillation (ENSO) region, North Atlantic Ocean). The two regions with large IMS in the tropics (ENSO region, Amazon basin) are mainly related to different model changes in precipitation extremes. In the polar regions the large IMS is linked to the IMS in both temperature and precipitation changes. Although the multi-model mean CCI values are average and the IMS is smallest in the subtropics, considerable change but also IMS is found as regards the changes of extremely dry events in this region. In this and other cases, a detailed analysis of the CCI components is important for getting a more complete picture of the changes and IMS of extreme temperature and precipitation events.

Data on rainfall patterns only weakly corroborate the claim that climate change explains the Darfur conflict that began in 2003 and has claimed more than 200 000 lives and displaced more than two million persons. Rainfall in Darfur did not decline significantly in the years prior to the eruption of major conflict in 2003; rainfall exhibited a flat trend in the thirty years preceding the conflict (1972–2002). The rainfall evidence suggests instead a break around 1971. Rainfall is basically stationary over the pre- and post-1971 sub-periods. The break is larger for the more northerly rainfall stations, and is less noticeable for En Nahud. Rainfall in Darfur did indeed decline, but the decline happened over 30 years before the conflict erupted. Preliminary analysis suggests little merit to the proposition that a structural break several decades earlier is a reasonable predictor of the outbreak of large-scale civil conflict in Africa.

Estimates of climate change impacts are often characterized by large uncertainties that reflect ignorance of many physical, biological, and socio-economic processes, and which hamper efforts to anticipate and adapt to climate change. A key to reducing these uncertainties is improved understanding of the relative contributions of individual factors. We evaluated uncertainties for projections of climate change impacts on crop production for 94 crop–region combinations that account for the bulk of calories consumed by malnourished populations. Specifically, we focused on the relative contributions of four factors: climate model projections of future temperature and precipitation, and the sensitivities of crops to temperature and precipitation changes. Surprisingly, uncertainties related to temperature represented a greater contribution to climate change impact uncertainty than those related to precipitation for most crops and regions, and in particular the sensitivity of crop yields to temperature was a critical source of uncertainty. These findings occurred despite rainfall's important contribution to year-to-year variability in crop yields and large disagreements among global climate models over the direction of future regional rainfall changes, and reflect the large magnitude of future warming relative to historical variability. We conclude that progress in understanding crop responses to temperature and the magnitude of regional temperature changes are two of the most important needs for climate change impact assessments and adaptation efforts for agriculture.

The direct electricity used by data centers has become an important issue in recent years as demands for new Internet services (such as search, music downloads, video-on-demand, social networking, and telephony) have become more widespread. This study estimates historical electricity used by data centers worldwide and regionally on the basis of more detailed data than were available for previous assessments, including electricity used by servers, data center communications, and storage equipment.

Aggregate electricity use for data centers doubled worldwide from 2000 to 2005. Three quarters of this growth was the result of growth in the number of the least expensive (volume) servers. Data center communications and storage equipment each contributed about 10% of the growth. Total electricity use grew at an average annual rate of 16.7% per year, with the Asia Pacific region (without Japan) being the only major world region with growth significantly exceeding that average.

Direct electricity used by information technology equipment in data centers represented about 0.5% of total world electricity consumption in 2005. When electricity for cooling and power distribution is included, that figure is about 1%. Worldwide data center power demand in 2005 was equivalent (in capacity terms) to about seventeen 1000 MW power plants.

International attention is focused on Beijing's efforts to improve air quality. The number of days reported as attaining the daily Chinese National Ambient Air Quality Standard for cities, called 'Blue Sky' days, has increased yearly from 100 in 1998 to 246 in 2007. However, analysis of publicly reported daily air pollution index (API) values for fine particulate matter (diameter≤10 µm, PM₁₀), indicates a discrepancy between the reported 'Blue Sky' days (defined as API≤100, PM₁₀≤150 µg m⁻³) and published monitoring station data. Here I show that reported improvements in air quality for 2006–2007 over 2002 levels can be attributed to (a) a shift in reported daily PM₁₀ concentrations from just above to just below the national standard, and (b) a shift of monitoring stations in 2006 to less polluted areas. I found that calculating daily Beijing API for 2006 and 2007 using data from the original monitoring stations eliminates a bias in reported PM₁₀ concentrations near the 'Blue Sky' boundary, and results in a number of 'Blue Sky' days and annual PM₁₀ concentration near 2002 levels in 2006 and 2007 (203 days and ∼167 µg m⁻³ calculated for 2006—38 days fewer and a PM₁₀ concentration ∼6 µg m⁻³ higher than reported; 191 'Blue Sky' days and ∼161 µg m⁻³ calculated for 2007—55 days fewer and a PM₁₀ concentration ∼12 µg m⁻³ higher than reported; 203 days and 166 µg m⁻³ were reported in 2002). Furthermore, although different pollutants were monitored before daily reporting began and less stringent standards were implemented in June 2000, reported annual average concentrations of particulate (diameter≤100 µm, TSP) and nitrogen dioxide (NO₂) indicate no improvement between 1998 and 2002. This analysis highlights the sensitivity of monitoring data in the evaluation of air quality trends, and the potential for the misinterpretation or manipulation of these trends on the basis of inconsistent metrics.

The comprehensive model MAID (model for aerosol and ice dynamics) was developed to simulate condensation and freezing in aerosol particles residing in the UT/LS (upper troposphere/lower stratosphere). The exact balancing of trace gas components is a particular emphasis of MAID. MAID is applied to and verified by experiments in the aerosol chamber AIDA, and, moreover, it is adapted to Lagrangian atmospheric cirrus cloud simulations. Here, the model is introduced, and as an example for model applications the significant influence of homogeneous or heterogeneous freezing on ice cloud microphysics and the water and nitric acid partitioning in cirrus clouds is shown.

Water can represent a substantial fraction of the mass of tropospheric non-cloud particulate matter, and can also serve as a medium for aqueous-phase reactions in such particles. Aerosol water contents are highly dependent upon aerosol hygroscopicity and ambient relative humidities (RH). In this work we evaluate a recently proposed parameterization of composition-dependent aerosol hygroscopicity that predicts the volume of liquid water associated with a unit volume of dry aerosol. The predictions over the range 10%<RH<99% are compared with those from a rigorous thermodynamic model and shown to predict water volumes within ∼20% for the high water contents (RH>85%) expected to have the most significant effects on tropospheric chemistry and radiation balance. Water contents for most of the compounds studied are generally represented within experimental uncertainties over the entire range of relative humidity examined, with the exception of marine-type particles dominated by sodium chloride and sodium sulfate.

Supersaturations, microphysics and nitric acid partitioning in a very cold subvisible tropical cirrus cloud observed on 2 February 2006, during the field campaign CR-AVE, are studied by comparing a simulated set of possible cloud development scenarios with the in situ observations. The scenario that best matches the observations is a cirrus cloud forming by heterogeneous freezing of a small number of ice nuclei with subsequent unimpeded mass accommodation of water on ice. Variation of the freezing process, the accommodation coefficient or the amount of available water leads to simulated clouds that differ microphysically from the observed cloud in important respects. In particular, the simulations suggest that heterogeneous ice nucleation or another freezing mechanism producing only a low number of ice crystals could be an important process for cold cirrus cloud formation, possibly explaining the frequent observations of high supersaturations inside the cirrus cloud in this temperature regime.

This work recompiles studies that have been done with respect to hygroscopic growth in the regime of high relative humidities and with respect to activation for different kinds of particle at LACIS (Leipzig Aerosol Cloud Interaction Simulator) during the last few years. The particles examined consisted of a mixture of succinic acid and ammonium sulfate, seawater samples, soot coated with an organic and/or an inorganic substance, and two different atmospheric HULIS (HUmic LIke Substance) samples. An influence of changing non-ideal behavior and of slightly soluble substances on the hygroscopic growth was found in varying degrees in the subsaturation regime. The measured hygroscopic growth was extrapolated towards supersaturation, using a simple form of the Köhler equation, and assuming a constant number of molecules/ions in solution for high relative humidities (≥95% or ≥98%, depending on the particles). When the surface tension of water was used, the modeled critical supersaturations reproduced the measured ones for the seawater samples and for the coated soot particles. To reach agreement between measured and modeled critical supersaturations for the HULIS particles, a concentration-dependent surface tension had to be used, with values of the surface tension that were lower than that of water, but larger than those that had been reported for bulk measurements in the past.

A common paradigm when the reduction of emissions from deforestations is estimated for the purpose of promoting it as a mitigation option in the context of the United Nations Framework Convention on Climate Change (UNFCCC) is that high uncertainties in input data—i.e., area change and C stock change/area—may seriously undermine the credibility of the estimates and therefore of reduced deforestation as a mitigation option.

In this paper, we show how a series of concepts and methodological tools—already existing in UNFCCC decisions and IPCC guidance documents—may greatly help to deal with the uncertainties of the estimates of reduced emissions from deforestation.

International discussions on reducing emissions from deforestation and degradation (REDD) as a greenhouse gas (GHG) abatement strategy are ongoing under the United Nations Framework Convention on Climate Change (UNFCCC). In the light of these discussions, it behooves countries to be able to determine the relative likelihood of deforestation over a landscape and perform a first order estimation of the potential reduction in GHGs associated with various protection scenarios. This would allow countries to plan their interventions accordingly to maximize carbon benefits, alongside other environmental and socioeconomic benefits, because forest protection programs might be chosen in places where the perceived threat of deforestation is high whereas in reality the threat is low. In this case study, we illustrate a method for creating deforestation threat maps and estimating potential reductions in GHGs from eighteen protected areas in East Kalimantan, Indonesia, that would occur if protection of these areas was well enforced. Results from our analysis indicate that a further 230 720 ha of East Kalimantan's forest area would be lost and approximately 305 million t CO₂ would be emitted from existing protected areas between 2003 and 2013 if the historical rate of deforestation continued unabated. In other words, the emission of 305 million t CO₂ into the atmosphere would be avoided during this period if protection of the existing areas was well enforced. At a price of $4 per ton of CO₂ (approximate price on the Chicago Climate Exchange in August 2008), this represents an estimated gross income stream of about $120 million per year. We also identified additional areas with high carbon stocks under high deforestation threat that would be important to protect if the carbon benefits of avoided deforestation activities are to be maximized in this region.