U.S. Energy Information Administration - EIA - Independent Statistics and Analysis
International Energy Outlook 2014
Energy-related carbon dioxide emissions
Energy-related carbon dioxide emissions—those emissions produced through the combustion of liquid fuels, natural gas, and coal—account for much of the world's anthropogenic greenhouse gas emissions. As a result, energy consumption is an important component of the global climate change debate. In the IEO2013 Reference case, which does not assume new policies to limit greenhouse gas emissions, world energy-related carbon dioxide emissions47 increase from 31.2 billion metric tons in 2010 to 36.4 billion metric tons in 2020 and 45.5 billion metric tons in 2040. Much of the growth in emissions is attributed to the developing non-OECD nations that continue to rely heavily on fossil fuels to meet fast-paced growth in energy demand. Non-OECD carbon dioxide emissions total 31.6 billion metric tons in 2040, or 69 percent of the world total. In comparison, OECD emissions total 13.9 billion metric tons in 2040—31 percent of the world total (Table 20 and Figure 140).
Near-term events can have a substantial impact on year-to-year changes in energy use and the corresponding carbon dioxide emissions. For instance, recent years have seen fluctuations in economic growth and, as a result, energy demand and emissions. During the 2008-2009 global economic recession, world energy consumption contracted, and as a result total world carbon dioxide emissions in 2009 were about 1 percent lower than in 2008. In 2010, as the world economy rebounded—especially among the emerging economies—total emissions increased by about 5.1 percent. In the longer term, conservation, improved technology, and increased use of energy sources with low or no emissions moderate the growth of energy-related carbon dioxide emissions in the Reference case.
The IEO2013 Reference case projections are, to the extent possible, based on existing laws and policies. Projections for carbon dioxide emissions could change significantly if new laws and policies aimed at reducing greenhouse gas emissions were implemented in the future. For example, emissions capand-trade programs, fees, and credits for meeting energy efficiency standards could facilitate global efforts to curb emissions that contribute to global warming. In addition, beyond energy-related carbon dioxide, other greenhouse gases (such as methane) and other activities that influence carbon dioxide levels (such as deforestation) contribute to anthropogenic influences on the climate but are not included in the IEO2013 Reference case projections.
Emissions by fuel
Carbon dioxide emissions from the use of liquid fuels, natural gas, and coal all increase in the IEO2013 Reference case, but the relative contributions of the individual fuels shift over time (Figure 141). Carbon dioxide emissions from liquid fuels consumption accounted for 43 percent of the world total in 1990 and 36 percent in 2010, and in the Reference case they are 34 percent of the 2020 total and 32 percent of the 2040 total. Emissions from coal use accounted for 39 percent of total emissions in 1990 and 44 percent in 2010, and their share increases to 47 percent in 2020 and 2030 before dropping slightly to 45 percent in 2040. Coal, the most carbon-intensive fossil fuel, became the leading source of world energy-related carbon dioxide emissions in 2004 and remains the leading source through 2040. Carbon dioxide emissions from natural gas increase from 19 percent of the total in 1990 to 22 percent in 2040.
Emissions from coal use show the largest increment in the Reference case, from about 14 billion metric tons in 2010 to 21 billion metric tons in 2040 (Figure 142). Coal is the largest contributor to emissions growth in the non-OECD economies, accounting for 52 percent of the increase in non-OECD carbon dioxide emissions from 2010 to 2040. For the entire world, coal-related carbon dioxide emissions grow by an average of 1.3 percent per year from 2010 to 2040, with 1.8-percent average annual increases in the non-OECD countries accounting for all of the growth. For the OECD countries, coal-related emissions decline by an average of 0.2 percent per year from 2010 to 2040.
Energy-related carbon dioxide emissions from natural gas use increase in both the OECD and non-OECD countries, by average annual rates of 1.1 percent and 2.2 percent, respectively. In percentage terms, world natural gas consumption grows more rapidly than consumption of coal or liquid fuels from 2010 to 2040 and accounts for 30 percent of world fossil fuel use in 2040. However, because of its relatively low carbon intensity, the natural gas share of energy-related carbon dioxide emissions in 2040 is only 22 percent.
Carbon dioxide emissions from the consumption of liquid fuels worldwide show the slowest growth, averaging 0.9 percent per year, resulting in an increment of 3.5 billion metric tons in liquids-related carbon dioxide emission from 2010 to 2040. As is the case for coal, carbon dioxide emissions related to liquid fuels decline in the OECD countries (by an average of 0.1 percent per year) but increase in non-OECD countries, where growing demand for transportation and industrial uses of liquid fuels contributes to an average growth rate of 1.7 percent per year. As a result, the OECD share of carbon dioxide emissions from liquid fuels declines from 52 percent in 2010 to 39 percent in 2040.
Emissions by region
World energy-related carbon dioxide emissions increase at an average annual rate of 1.3 percent from 2010 to 2040 in the IEO2013 Reference case, with much of the overall increase occurring in the non-OECD nations (see Table 21). OECD emissions increase by 0.2 percent per year on average, while non-OECD emissions increase by an average of 1.9 percent per year.
In the OECD regions, the United States continues to be the largest source of energy-related carbon dioxide emissions through 2040, followed by OECD Europe and Japan. Those three OECD regions accounted for 84 percent of total OECD emissions in 2010. Carbon dioxide emissions in the United States and OECD Europe grow only slightly, and in Japan they decline over the long term (see "Effect of nuclear plant shutdowns on Japan's carbon dioxide emissions"). Thus, total emissions from the three largest OECD emitters increase by only 91 million metric tons over the 30-year period. For the other OECD countries combined, carbon dioxide emissions increase by a total of 727 million metric tons from 2010 to 2040.
Japan's energy-related carbon dioxide emissions decline in the IEO2013 Reference case by an average of 0.1 percent per year from 2010 to 2040. The 2040 total of 1.1 billion metric tons is 2.2 percent less than the 2010 total. In the IEO2011 Reference case, Japan's emissions declined by 0.4 percent annually from 2008 to 2035. However, following the March 2011 disaster at the Fukushima Daiichi nuclear facility, the country's nuclear power plants were shut down over a period extending to May 2012, and the resulting loss of nuclear electricity generation was replaced with generation from plants using coal, oil, and natural gas. While the IEO2013 Reference case anticipates that many of the reactors will be restarted, the projections for nuclear generation in Japan are lower than the IEO2011 estimates. Nuclear generation in 2035 is 50 percent lower in the IEO2013 Reference case than was projected in IEO2011, natural gas-fired generation in 2020 is 107 billion kilowatthours higher, and coal-fired generation is 44 billion kilowatthours higher.
From 2008 to 2035, the growth rates of Japan's population and GDP are similar in IEO2013 and IEO2011. However, Japan's total projected electricity generation is lower in this year's outlook, by 29 billion kilowatthours in 2020 and 67 billion kilowatthours in 2035, reflecting conservation efforts undertaken after the events at Fukushima forced the closure of all of the nation's nuclear reactors. Long-term conservation efforts help to offset some of the increase in emissions in the IEO2013 projection.
Total carbon dioxide emissions in Japan decline in the IEO2013 Reference case, from 1,243 million metric tons in 2015 to 1,223 million metric tons in 2025 and 1,194 million metric tons in 2035, but at a slightly lower rate than in IEO2011, where they were projected to be 1,136 million metric tons and 1,087 million metric tons in 2025 and 2035, respectively. Emissions from coal and natural gas combustion are higher in all years from 2015 to 2035 in the IEO2013 Reference case (Figure 143). For liquid fuels there is a spike in 2015 emissions, followed by declines in the subsequent years as oil-fired electricity generation that was brought on line to compensate for lost nuclear generation is displaced by increases in generation from coal and natural gas.
In the IEO2013 Reference case, the fastest rate of increase in carbon dioxide emissions in the OECD region is for Mexico/Chile, at 2.1 percent per year on average from 2010 to 2040, followed by South Korea at 0.8 percent per year (Figure 144). Mexico and Chile in combination have the highest economic growth rate in the OECD over the 2010-2040 period, averaging 3.7 percent per year, and South Korea's GDP growth averages 3.3 percent per year. For the OECD region as a whole, GDP growth averages 2.2 percent per year.
The non-OECD countries together account for 94 percent of
the total increase in world carbon dioxide emissions from 2010
to 2040, and non-OECD Asia alone accounts for 71 percent of
the total increase. China's emissions grow by an average of 2.1
percent per year (Figure 145) and account for 69 percent of
the increase for non-OECD Asia and 49 percent of the total
world increase in carbon dioxide emissions. India's emissions
increase by 2.3 percent per year, and emissions in the rest of
non-OECD Asia increase by an average of 1.9 percent per year.
The increases in non-OECD Asia, particularly China, are led by coal-related carbon dioxide emissions, and emissions from natural gas and liquid fuels use also increase substantially (Figure 146).
Non-OECD Europe and Eurasia has the slowest growth in carbon dioxide emissions among the non-OECD regions, at 1.0 percent per year in the IEO2013 Reference case. Natural gas is the region's leading source of emissions from fossil fuel use, accounting for 51 percent of total carbon dioxide emissions in Russia in 2010 and 36 percent in the other non-OECD Europe and Eurasia nations. Total carbon dioxide emissions in non-OECD Europe and Eurasia increase from 2.6 billion metric tons in 2010 to 3.5 billion metric tons in 2040.
Measures of trends and comparisons of energy-related carbon dioxide emissions
Many factors influence national levels of carbon dioxide emissions, as reflected in the relationships among a country's economy, its energy demand, and the fuel mix used to meet that demand. Three measures provide useful insights for the analysis of trends in energy-related emissions:
1. The energy intensity of economic activity is a measure of energy consumption per unit of economic activity as measured by GDP. It relates changes in energy consumption to changes in economic output. Increased energy use and economic growth generally occur together, although the degree to which they are linked varies across regions and stages of economic development.
Energy intensity can be indicative of the energy efficiency of an economy's capital stock (vehicles, appliances, manufacturing equipment, power plants, etc.). For example, if an old power plant is replaced with a more thermally efficient unit, then it is possible to supply the same amount of electricity with a lower level of primary energy use, thereby decreasing energy intensity. If the sector that consumes the electricity also achieves gains in energy efficiency (for example, through more efficient refrigerators), then there is an additional reduction in energy intensity to meet the same level of energy service demand.
Energy intensity is acutely affected by structural changes within an economy—in particular, the relative shares of its output
sectors (manufacturing versus service, for example). Higher concentrations of energy-intensive industries, such as oil and gas
extraction, yield higher overall energy intensities, whereas countries with proportionately larger service sectors tend to have
lower energy intensities. For example, the Middle East had a relatively high energy intensity of 12.1 thousand Btu per dollar of GDP in 2010, in part because of the important role played by hydrocarbon production (an energy-intensive activity) and exports in most Middle East economies. On a worldwide basis, shifting energy-intensive industries such as steel production from one country to another does little to lower global energy demand and related emissions unless the countries to which the industries are shifted possess more efficient industrial capacity than the original country or substitute labor for energy.
2. The carbon intensity of energy supply is a measure of the amount of carbon dioxide associated with each unit of energy used.
It directly links changes in carbon dioxide emissions levels with changes in energy usage. Carbon emissions vary by energy
source, with coal being the most carbon-intensive fuel, followed by oil and natural gas. Nuclear power and some renewable
energy sources (i.e., solar and wind) do not directly generate carbon dioxide emissions. Consequently, changes in the fuel mix alter overall carbon intensity. Over time, declining carbon intensity can offset increasing energy consumption to some extent. If energy consumption increases and carbon intensity declines by an equivalent factor, carbon dioxide emissions will remain constant. A decline in carbon intensity can indicate a shift away from fossil fuels, a shift toward less carbon-intensive fossil fuels, or both.
Carbon intensities, like energy intensities, do not necessarily remain constant over time. However, carbon intensities historically have varied less than energy intensities (Figure 147) because they reflect the energy endowment of a country or region or are dependent on major shifts in energy technologies, such as the introduction of nuclear power, that occur relatively slowly over time.
3. The carbon intensity of economic output is a measure of carbon dioxide emissions per dollar of GDP (CO2/GDP), which can be
calculated by multiplying the carbon intensity of energy supply (CO2/E) by the energy intensity of economy activity (E/GDP).
The carbon intensity of economic output is commonly used
in analysis of changes in carbon dioxide emissions, and it
is sometimes used as a stand-alone measure for tracking progress in relative emissions reductions.
Historically, carbon intensity of economic output has declined
over time (Figure 148), and it continues to decline worldwide
from 2010 to 2040 in the Reference case. In the non-OECD
countries, where national and regional economies are growing more rapidly than in the OECD countries, the rate of decline in carbon intensity of economic output is slower than the rate
of economic growth, leading to net increases in emissions over time. For the world as a whole, if the carbon intensity of economic output declines faster than the world economy grows, emissions will decline over time.
The Kaya decomposition of emissions trends
The Kaya Identity provides an approach to the interpretation
of historical trends and future projections of energy-related
carbon dioxide emissions. It can be used to decompose total carbon dioxide emissions as the product of individual factors that explicitly link energy-related carbon dioxide emissions to energy consumption, the level of economic output as measured by
GDP, and population size.
The Kaya Identity expresses total carbon dioxide emissions as the product of (1) carbon intensity of energy supply (CO2/E), (2) energy intensity of economic activity (E/GDP), (3) economic output per capita, and (4) population:
|CO2 = (CO2/E) (E/GDP) x (GDP/POP) x POP .|
Using 2010 data as an example, world energy-related carbon dioxide emissions totaled 31.2 billion metric tons in 2010, world energy consumption totaled 524 quadrillion Btu, world GDP totaled $70.5 trillion, and the world population was 6,880 million. Using those figures in the Kaya equation yields the following: 59.5 metric tons of carbon dioxide per billion Btu of energy (CO2/E), 7,400 Btu of energy per dollar of GDP (E/GDP), and $10,247 of income per person (GDP/POP). Appendix H delineates the Kaya factors for all IEO regions over the IEO2013 projection period.
Of the four Kaya components, policymakers generally focus on developing programs that can change, in various energy-consuming sectors, the energy intensity of economic output (E/GDP) and carbon dioxide intensity of the energy supply (CO2/E). Reducing growth in output per capita may have a mitigating influence on emissions, but governments generally pursue policies to increase rather than reduce output per capita in order to advance objectives other than greenhouse gas mitigation.
Policies related to energy intensity of GDP typically involve improvements in energy efficiency. However, the measure is also sensitive to shifts in the energy-intensive portion of a country's trade balance, and improvements may simply reflect a greater reliance on imports of manufactured goods, which may decrease one country's energy intensity but, if the country producing the imported goods is less energy efficient, could lead to a worldwide increase in energy consumption and related carbon dioxide emissions. Policies related to the carbon dioxide intensity of energy supply typically focus on promotion of low-carbon or zerocarbon sources of energy.
Conveniently, the percentage rate of change in carbon dioxide emission levels approximates the sum of the percentage rate of change across the four Kaya components. Table 22 shows the average rate of change of total carbon dioxide emissions and each individual Kaya component for the projection period from 2010 to 2040 in the IEO2013 Reference case. The most significant factor for the growth of energy-related carbon dioxide emissions is economic output per capita. The average annual growth rate of output per capita for non-OECD countries (3.8 percent from 2010 to 2040) in particular dominates all other Kaya components in the 30-year projection. For OECD countries, on the other hand, the 1.8-percent average annual increase in output per capita is nearly offset by the 1.6-percent annual decline in energy intensity.
Population growth is another important determinant in the rate of emissions change. However, as mentioned above, the
population effect is less pronounced than the effect of output per capita. For non-OECD countries, increases in output per
capita coupled with population growth overwhelm improvements in energy intensity and carbon intensity, yielding 1.9-percent
average annual growth in emissions. The projection horizon shows OECD growth in output per capita and growth in population mostly balanced by improvements in energy intensity and carbon intensity, yielding average emissions growth of 0.2 percent per year.
Over the 2010-2040 period, the energy intensity of economic output declines in all the IEO2013 regions. The trend is particularly pronounced in the non-OECD countries, where energy intensity of output decreases on average by 2.5 percent per year, compared with 1.6 percent per year in the OECD countries. Worldwide, the largest declines in energy intensity of output are projected for India, at 3.2 percent per year, while declines in other non- OECD Europe and Eurasia nations and in China both average 2.9 percent annually. However, output per capita increases by averages of more than 5 percent per year in and India and China and by 4 percent per year in the other non-OECD Europe and Eurasia nations.
The carbon intensity of energy supply also is projected to
decline in all the IEO2013 regions from 2010 to 2040. In the
OECD region, the largest decline in carbon intensity of energy
supply is for South Korea (0.5 percent per year), and several
countries and regions—Australia/New Zealand, Canada,
Mexico/Chile, and OECD Europe—have annual decreases
in carbon intensity that average 0.4 percent. In the non-OECD economies, both China and India have 0.5-percent
average annual declines in carbon intensity. Decreases or only
moderate increases in the consumption of liquid fuels and coal
(the most carbon-intensive fuels) in those regions, combined
with increases in consumption of renewable energy, nuclear
power (except for Australia/New Zealand), and natural gas (the least carbon-intensive fossil fuel), reduce the carbon intensity of the energy supply. For the OECD region as a whole, the
average rate of decline in carbon intensity of energy supply over the 2010-2040 period is 0.3 percent per year, the same as the
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