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BackgroundCities contribute more than 70% of global anthropogenic carbon dioxide (CO2) emissions and are leading the effort to reduce greenhouse gas (GHG) emissions through sustainable planning and development. However, urban greenhouse gas mitigation often relies on self-reported emissions estimates that may be incomplete and unverifiable via atmospheric monitoring of GHGs. We present the Hestia Scope 1 fossil fuel CO2(FFCO2) emissions for the city of Baltimore, Maryland—a gridded annual and hourly emissions data product for 2010 through 2015 (Hestia-Baltimore v1.6). We also compare the Hestia-Baltimore emissions to overlapping Scope 1 FFCO2emissions in Baltimore’s self-reported inventory for 2014.ResultsThe Hestia-Baltimore emissions in 2014 totaled 1487.3 kt C (95% confidence interval of 1158.9–1944.9 kt C), with the largest emissions coming from onroad (34.2% of total city emissions), commercial (19.9%), residential (19.0%), and industrial (11.8%) sectors. Scope 1 electricity production and marine shipping were each generally less than 10% of the city’s total emissions. Baltimore’s self-reported Scope 1 FFCO2emissions included onroad, natural gas consumption in buildings, and some electricity generating facilities within city limits. The self-reported Scope 1 FFCO2total of 1182.6 kt C was similar to the sum of matching emission sectors and fuels in Hestia-Baltimore v1.6. However, 20.5% of Hestia-Baltimore’s emissions were in sectors and fuels that were not included in the self-reported inventory. Petroleum use in buildings were omitted and all Scope 1 emissions from industrial point sources, marine shipping, nonroad vehicles, rail, and aircraft were categorically excluded.ConclusionsThe omission of petroleum combustion in buildings and categorical exclusions of several sectors resulted in an underestimate of total Scope 1 FFCO2emissions in Baltimore’s self-reported inventory. Accurate Scope 1 FFCO2emissions, along with Scope 2 and 3 emissions, are needed to inform effective urban policymaking for system-wide GHG mitigation. We emphasize the need for comprehensive Scope 1 emissions estimates for emissions verification and measuring progress towards Scope 1 GHG mitigation goals using atmospheric monitoring.

Past assessments of climate change impacts on building energy consumption have typically neglected spatial variations in the “balance point” temperature, population distribution effects, and the extremes at smaller spatiotemporal scales where the impacts of climate change are most pronounced. Here we test the impact of these limitations through a sensitivity analysis in the Contiguous United States. Though national/annual total source energy consumption differences between the 2080–99 time period and the present are less than 2 %, we find changes at the state/month scale that are much larger with summer electricity demand increases exceeding 50 % and spring non-electric energy declines of 48 % by the end of the century. The use of a fixed 18.3 °C (65 °F) balance point temperature, versus a more representative state-specific value, leads to an overestimate of the energy consumption changes in most states with a maximum change in the state of Oregon of almost 14 percentage points. Finally, projected population redistribution, when combined with the spatial pattern of climate change, exacerbates the building energy consumption impacts, further increasing source energy consumption in some states (max = +5.3 percentage points) and further diminishing energy consumption declines in others (max = −8.2 percentage points). When integrated over the U.S., the intersection of projected population distribution changes and climate change shifts future building energy consumption from a net decrease to a net increase.

Fossil fuel carbon dioxide (FFCO2) emissions are the largest driver of anthropogenic climate change. Approximately three-quarters of the world’s fossil fuels carbon dioxide emissions are generated in urban areas. We used the Hestia high resolution approach to quantify FFCO2 for Salt Lake County, Utah, USA and demonstrate the importance of high resolution quantification to urban emissions mitigation policymaking. We focus on the residential and onroad sectors across both urbanized and urbanizing parts of the valley. Stochastic Impact by Regression on Population, Affluence, and Technology (STIRPAT) regression models using sociodemographic data at the census block group level shows that population, per capita income, and building age exhibit positive relationships while household size shows a negative relationship with FFCO2 emissions. Compact development shows little effect on FFCO2 emissions in this domain. FFCO2 emissions in high income block groups is twice as sensitive to income than low income block groups. Emissions are four times as sensitive to household size in low-income versus high-income block groups. These results suggest that policy options targeting personal responsibility or knowledge feedback loops may be the most effective strategies. Examples include utility bill performance comparison or publicly available energy maps identifying high-emitting areas. Within the onroad sector, high emissions density (FFCO2/km) is associated with primary roads, while high emissions intensity (FFCO2/VMT) is associated with secondary roads. Opportunities exist for alignment of public transportation extension with remaining high emission road segments, offering a prioritization of new onroad transportation policy in Salt Lake County.

On June 2, 2014, the United States Environmental Protection Agency proposed goals and guidelines aimed at lowering carbon dioxide (CO2) emissions from existing power plants in the United States. Should it be successfully implemented, US power plant CO2 emissions would be reduced approximately 30 percent below 2005 levels by the year 2030. Rather than a single national reduction goal, the proposed rule specifies reduction targets unique to each US state but leaves the means by which states meet those targets, flexible to individual state conditions. Regardless of the policy mixture adopted in each US state, quantification of CO2 emissions at the level of individual power plants will be a critical need. Recent research examining power plant CO2 emissions has noted potentially large uncertainties at the individual facility level, uncertainty that remains poorly understood. At the same time, carbon scientists working on aspects of monitoring, reporting and verification of anthropogenic CO2 emissions have developed a mixture of measurement and modeling capabilities as part of the development of a “carbon monitoring system”, that could assist in assessing how well independent emissions quantification is performing currently and identify a path towards improved monitoring. Equally important is an assessment of uncertainty at the various space and time scales the EPA proposed rule implies. Application of these recent scientific capabilities to the needs of the EPA’s proposed rule could offer a cogent, near-term example of how scientific research can directly enable better decision-making. This paper provides a review of the proposed rule and what role scientific research could play in the evolution of the rulemaking and its application in the future.

In China, as in other nations that produce carbon dioxide from fossil fuels on a large scale, the terrestrial biosphere mops up a proportion of the emissions. Estimates of the amounts involved are now available. The publication of a comprehensive assessment of China's terrestrial carbon budget fills a major gap in the geographical spread of carbon balance data, and helps to further reduce uncertainties in the Northern Hemisphere carbon balance. Three different indicators were used to monitor China's carbon balance and its driving mechanisms during the 1980s and 1990s: biomass and soil carbon inventories extrapolated from satellite greenness measurements, ecosystem models and atmospheric inversions. The three methods produce similar estimates for the net carbon sink at 0.19 to 0.26 petagrams per year. Global terrestrial ecosystems, in comparison, have absorbed carbon at a rate of 1 to 4 Pg carbon per year during the 1980s and 1990s, which offsets 10–60% of fossil fuel emissions. Northeast China is a net source of CO2 to the atmosphere as a result over-harvesting and degradation of forests. In contrast, southern China accounts for over 65% of the carbon sink, attributable to regional climate change, tree planting and shrub recovery.