The majority of informed scientific opinion is that human activities – primarily the combustion of fossil fuels and changes in land use – are having a discernible impact on global climate. This impact results from emissions of "greenhouse gases" that modify the heat gain/loss balance from solar radiation. The Environmental Protection Agency has projected impacts of climate changes on the states, including Rhode Island. In 1992 the United Nations General Assembly adopted a Framework Convention on Climate Change (UNFCCC), which was signed by President Clinton and ratified by the U.S. Senate.   The UNFCCC took 1990 as a base year, to provide a common reference against which emissions in subsequent years could be compared. In order to establish the 1990 baseline, national and state level inventories of greenhouse gas emissions have been prepared in this country. To provide information on the changes in these emissions since 1990, these inventories generally also include emissions estimates for the most recent year for which data are available.  

This report provides estimates of greenhouse gas emissions for Rhode Island for 1990 and 1996, and in the case of fossil fuel combustion, for the 1986 – 1996 period. The Introduction explains the format of the report and provides links to the rest of the report.. The inventory process followed the instructions in the EIIP Document Series, Volume VIII: Estimating Greenhouse Gas Emissions, December 1998 Review Draft (referred to in this report as Workbook). The emissions of three greenhouse gases are estimated: carbon dioxide, methane and nitrous oxide, and following Workbook instructions, these are converted into Metric Tons of Carbon Equivalent (MTCE), which takes into account the different warming potential of each gas. The Summary table displays the contribution from all significant sources.  Table entries have been rounded (compared to numbers in the remainder of this report) to give a rough approximation of the certainty with which the values are known.

In order to avoid double-counting, the Workbook procedures do not include in the inventory the emissions from fossil fuel combustion used to generate imported electricity . Because Rhode Island imports most of its electricity, the greenhouse gas emissions from energy consumed in-state are understated. The emissions from imported electricity are reported separately in the Summary table, to give a more realistic picture of the total impacts of energy consumption in Rhode Island.

Fossil fuel combustion dominates the emission inventory for both years. The 48% increase in fossil fuel emissions between 1990 and 1996 results in large part from a significant increase in the amount of electricity generated in-state (from 2% in 1990 to 20% in 1996). Significant increases in natural gas consumption occurred when the Ocean State Power facility came online in 1991 and when the repowered Manchester Street station began production in 1996.  The details of these calculations are presented in the chapters on Fossil Fuels and on Electricity Imports.

Because most solid waste produced in-state is landfilled at the Central Landfill, and because ca. 80% of the methane emissions from anerobic decomposition of this waste is collected and burned, solid waste disposal leads to a net sequestration of carbon (all organic materials in landfills do not decompose in the thirty-year period covered by Workbook procedures). Because the amount of waste landfilled increased between the two inventory years, so did the amount of carbon sequestered. Sequestration is shown as a negative emission in the Summary table.

Estimates of changes in the amount of carbon sequestered in forests and forest lands are based on forest inventories conducted in 1985 and 1998.  Decrease in forest acreage was only partially offset by tree biomass increase during this period, leading to net emissions of carbon dioxide.  The emission reported in the Summary Table is the annual average emission.  Some of the Workbook assumptions (e.g. that land converted to non-forest use loses all plant biomass and all soil carbon) lead to a systematic underestimate of the amount of carbon sequestered.  It is likely that between 1990 and 1996 more carbon was sequestered than released, but in any case, because of relatively slow changes in land use over such a short period, the change, whatever the direction, surely was small.

The only other source of greenhouse gas emissions of any significance is nitrous oxide emissions from mobile sources, primarily resulting from cold starts from catalytically equipped vehicles.  All other sources of greenhouse gas emissions in Rhode Island are believed to contribute insignificantly to the overall emissions in the state.

 The draft Inventory of U.S. Greenhouse Gas, Emissions and Sinks: 1990 – 1998 allows a comparison of Rhode Island and national emissions data.  In interpreting these comparisons, it may be helpful to keep in mind that during the 1990 to 1996 period, Rhode Island's population declined by 1.7% while national population increased by 6.3%.  

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