Policy Analysis pubs.acs.org/est
Drivers of the Growth in Global Greenhouse Gas Emissions Iñaki Arto*,†,‡ and Erik Dietzenbacher§ †
Basque Centre for Climate Change (BC3), C/Alameda Urquijo 4, 4°,48006, Bilbao, Spain European Commission, Joint Research Centre, IPTS − Institute for Prospective Technological Studies, Edificio EXPO, C/ Inca Garcilaso 3, 41092, Seville, Spain § Faculty of Economics and Business, University of Groningen, P. O. Box 800, 9700 AV Groningen, The Netherlands ‡
S Supporting Information *
ABSTRACT: Greenhouse gas emissions increased by 8.9 Gigatons CO2 equivalent (Gt) in the period 1995−2008. A phenomenon that has received due attention is the upsurge of emission transfers via international trade. A question that has remained unanswered is whether trade changes have affected global emissions. For each of five factors (one of which is trade changes) in 40 countries we quantify its contribution to the growth in global emissions. We find that the changes in the levels of consumption per capita have led to an enormous growth in emissions (+14.0 Gt). This effect was partly offset by the changes in technology (−8.4 Gt). Smaller effects are found for population growth (+4.2 Gt) and changes in the composition of the consumption (−1.5 Gt). Changes in the trade structure had a very moderate effect on global emissions (+0.6 Gt). Looking at the geographical distribution, changes in the emerging economies (Brazil, Russia, India, Indonesia and China) have caused 44% of emission growth whereas the increase in their national emissions accounted for 59% of emission growth. This means that 15% (1.4 Gt) of all extra GHG emissions between 1995 and 2008 have been emitted in emerging countries but were caused by changes in other countries.
1. INTRODUCTION In recent years, due attention has been paid to the effects of the growing importance of international trade on CO2 emissions.1−4 Also the use of land,4−6 water,4,7,8 and materials,9 and even biodiversity threats10 have been considered in this respect. In the case of CO2, for example, most developed countries have stabilized their increase in national emissions, but substantially increased the global emissions embedded in their consumption. In developing countries, the global emissions attributable to their consumers have drastically increased but their national emissions have grown even more. Developing countries thus generated emissions that were embodied in their exports to developed countries (which is also known as weak carbon leakage11). As a consequence, the net imports of emissions by most developed countries increased and so did the net exports of emissions by most developing countries. These studies have become possible only recently when the methodology was developed and when data became available. With respect to the methodology, a shift has taken place from answering the question “Who emits?” to “For whom is emitted?”. The first question is answered by the national emissions of a country. Next to the emissions due to the actual consumption of goods and services, it includes the emissions in the production processes (hence production-based emission accounting). The second question takes the ultimate consumer as starting point and includes, again next to emissions due to the actual consumption, all emissions involved in producing the consumed goods and services (hence consumption-based © 2014 American Chemical Society
emission accounting) and yields a country’s footprint. For example, someone who drives a German car in the U.S. causes emissions in the U.S. (due to the actual driving), in Germany (due to the assembly of the car), and in the UK (due to producing the motor parts that went into the German car). The two accounting approaches are linked to the discussion on the responsibility for emissions and have therefore also been termed producer-responsibility and consumer-responsibility. The difference between the two concepts is laid in the trade in emissions (i.e., emissions in one country that are ultimately attributed to consumption in another country). Regarding the data issue, the consumption-based perspective requires detailed information on national production processes that are internationally linked through trade. That is, global multiregional input-output (GMRIO) tables that cover many countries, distinguish many industries and are appended by socalled environmental accounts (using the same industry classification). Such GMRIO tables have become available only recently.12 As indicated above, various studies have emphasized the growth in emission transfers via international trade.3,13 It has been argued that trade could contribute to increase GHG emissions in the less-developed nations (and reduce them in Received: Revised: Accepted: Published: 5388
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Figure 1. Cumulative change in global GHG emissions by driving factor, 1995−2008 (Gigatons CO2 equivalent).
understanding of the drivers of environmental pressures by applying decomposition techniques based on input−output analysis (i.e., structural decomposition analysis).23−28 However, these approaches analyze the change in the emissions in an aggregate way and ignore the role of the trade linkages between countries. That is, the changes in the emissions of one country due to the changes in other countries are not taken into account. An example is the changes in U.S. emissions attributed to an increase of its exports to India resulting from the growth of India’s population. Thus, a fundamental question is what have been the drivers of the growth in global GHG emissions from a multiregional perspective?
developed ones) as energy-intensive and highly polluting activities move there from developed nations.14 As a result, many developed countries in Annex B of the Kyoto Protocol have been able to report decreasing emissions, and some have officially fulfilled their mitigation commitments.15 Some authors have found that the specialization can only explain a fraction of the emission transfers between countries (with differences in energy intensity, carbon intensity and trade balances as other important explanatory factors).16 However, it has not been assessed whether the changes in the international trade structure have resulted in change of global GHG emissions. This question is of special relevance for the analysis of the environmental consequences of trade. In the current context of globalization, one might be inclined to think that we would have been better offin terms of global emissionsif we had traded less. That is, if we had produced a larger share of products at home rather than importing them. The key question is what has been the role of changes in trade structure for the growth in global greenhouse gas (GHG) emissions? In order to monitor the progress toward the stabilization of GHG concentrations in the atmosphere, the United Nations Framework Convention on Climate Change reports periodically emissions inventories.17 These inventories compile information on the evolution of the major sources of GHG over time. However, they fail to explain the driving forces behind these trends, which is essential for the definition of climate policies. The identification of the drivers of the growth in global GHG emissions is a key task in the construction of mitigation scenarios.18 In recent years, different decomposition techniques have been used to analyze the changes in the aggregate GHG emissions into the factors underlying their evolution. One of the first systematic explications of the idea of driving forces is represented by the IPAT equation,14,19 which decomposes the environmental impact as the product of three factors: population, GDP per capita (affluence), and technology (defined as the environmental impact per unit of GDP). Similarly, some authors have used the Kaya identity,20 which decomposes the change in global or regional emissions into four factors: population, GDP per capita, energy intensity, and carbon intensity of energy.21,22 Other studies have enriched the
2. MATERIALS AND METHODS To answer this question, we will carry out a so-called structural decomposition analysis (SDA) within a GMRIO framework. SDAs decompose the change in one variable (here global GHG emissions) into the changes of its constituent parts. In our study, these are consumption per capita, the product mix of the consumption bundle, population size, technology, and trade structure. For the sake of brevity, we use the term consumption for the sum of private and government consumption and investments. In other words, consumption in this paper includes all goods and services that are not used as inputs in any production process (i.e., final demands in input-output parlance). The typical outcome of an SDA tells by how much the global GHG emissions would have increased if only population, for example, had increased as it actually has while anything else had remained the same (i.e., the ceteris paribus clause that is common in economics). For a full description of the methodology see the Supporting Information (SI). Recently, also Xu and Dietzenbacher29 applied a similar SDA approach within a GMRIO framework, albeit with an entirely different focus. They decomposed only the emissions embodied in trade and answered the question: how come that, for example, China’s emissions embodied in exports have risen? The present paper focuses on global emissions and asks: how much of the changes in global emissions are due to changes in China? Clearly, emissions embodied in trade play an increasing role in a globalizing world (with fragmenting production processes) and are thus taken into full account in our analysis. 5389
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Figure 2. Change in global GHG emissions by driving factor and driving country, 1995−2008 (Gigatons CO2 equivalent). Region codes: AUS: Australia; BRA: Brazil; CAN: Canada; CHN: China; EAS: East Asia (Japan, South Korea and Taiwan); EU-27: European Union 27 Member States; IND: India; IDN: Indonesia; MEX: Mexico; RUS: Russia; TUR: Turkey; USA: United States of America; RoW: Rest of the World. Note: data sorted by change in a country’s national emissions.
The data to decompose the annual change of GHG emissions, at the country and global level, were taken from the World Input−Output Database (WIOD).30 Although the WIOD tables are perhaps not the most detailed in terms of numbers of countries and products, they have a unique feature that is necessary for our study: the WIOD includes tables in constant prices of the previous year, which are required to properly measure changes in technology. This database comprises time series of harmonized supply and use tables and symmetric input-output tables, valued both at current and previous year’s prices. It also includes data on international trade and satellite accounts related to environmental and socio-economic indicators (including the emissions of greenhouse gases). The WIOD comprises information for 35 industries and 59 products in 40 countries and the Rest of the World (RoW) (which is a single, aggregated region mainly including less developed countries). All data can be downloaded free of charge at www.wiod.org; for a description of the construction of the world input-output tables see.30 For the sake of simplicity we have aggregated the detailed country results to 13 regions: Australia, Brazil, Canada, China, East Asia (Japan, South Korea, and Taiwan), the European Union (27 member states, EU-27), India, Indonesia, Mexico, Russia, Turkey, the U.S., and the RoW.
equivalent (Gt) from 30.45 Gt to 39.31 Gt which was an increase of 29.1%. As shown by Figure 1, the change in consumption per capita was the main driver for the growth in global GHG emissions (detailed results for all 40 countries are given in Table S1 of SI). If only consumption per capita had increased in the way it actually did, while anything else had remained the same, global GHG emissions would have increased by 46.0% (14.01 Gt) when compared to the 1995 level. The growth in population was the second main factor adding 4.16 Gt to global emissions (an increase of 13.7%). The effects of the changes in the structure of international trade were relatively small. Trade changes only increased global GHG emissions by 0.58 Gt. More people and more consumption by each of them would thus have led to an almost 60% increase in GHG emissions. This was partly offset by the remaining two factors. The changes in technologywhich includes a shift to cleaner energy sources, efficiency gains and changes in the input structure of the different sectorsreduced global emissions by 27.6% (−8.40 Gt). Finally, the change in the commodity composition of the consumption bundle reduced the emissions by 4.8% (−1.50Gt). The product mix of consumption and investments has shifted toward goods (and services) that embody less GHG emissions. GDP per capita increased over time and consumers had more money to spend. This brought along a shift in their consumption pattern, because higher incomes have different consumption profiles. It is, however, not the case that consumers bought less emission-intensive goods.
3. RESULTS 3.1. Drivers of Global Emissions: Factors. Between 1995 and 2008, global GHG emissions grew by 8.86 Gigatons CO2 5390
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Figure 3. Changes in global emissions attributed to a country’s changes and changes in a country’s national emissions (Gigatons CO2 equivalent). Region codes: BRA: Brazil; CAN: Canada; CHN: China; EAS: East Asia (Japan, South Korea and Taiwan); EU-27: European Union 27 Member States; IDN: Indonesia; IND: India; MEX: Mexico; RUS: Russia; RoW: Rest of the World; USA: United States of America.
They increased their spending on emission-intensive products but increased their spending on products with lower emissions intensity even more. Figure 1 clearly shows that the evolution of global GHG emissions can be divided into two periods. Emissions grew at an average rate of 1.0% per year in the first period (1995− 2002) which increased to 3.1% per year on average in the second period (2002−2008). In both periods, consumption per capita and population growth were the main drivers of the increase in global emissions while the change in technology was the primary factor that had a lowering effect on emissions. The enhanced growth of emissions in the second period was mainly driven by the expansion of the growth in consumption per capita (from 1.6% per year to 4.6%). Also the annual emission reduction attributed to technological change accelerated in the second period (from an average growth rate of −1.4% in the period 1995−2002, to −3.7% between 2002 and 2008). Observe that the annual growth rate of the emissions as caused by the other factors remained more or less constant through the entire period 1995−2008. Figure 2 shows detailed results for a selected group of countries (Table S1 of SI shows detailed results for all 40 countries). For example, if only the consumption per capita in China had increased as it actually did, while anything else had remained the same, global GHG emissions would have increased by 4.88 Gt. Similar interpretations hold for the effects of: changes in the Chinese technology and emission intensities; changes in China’s import structure; changes in the product mix of the Chinese consumption bundle; and the growth of China’s population. The effect on global emissions of all the changes that have taken place in a country is given by the green cross (e.g., 2.77 Gt of the increase in global emissions is attributed to changes in China). In all regions, the growth in consumption per capita was the main driver for the growth of global emissions. In the BRIIC countries (Brazil, Russia, India, Indonesia, and China) and in
the RoW this factor boosted global emissions by 7.26 and 2.49 Gt, respectively. From the detailed annual results, it follows that the growth in GHG emissions attributed to changes in consumption per capita accelerated from 2002 onward for the BRIIC countries and the RoW. The U.S., and the EU-27 changes in consumption per capita increased global emissions by 1.63 and 1.58 Gt, respectively. The second factor that caused large increases in emissions was population growth. Particularly, the development of the population in the RoW had a substantial effect (generating an additional 1.58 Gt worldwide). Technological changes have limited the growth of global emissions, in particular the changes in China (−2.53 Gt), the RoW (−1.90 Gt), the EU-27 (−1.37 Gt), and the U.S. (−0.95 Gt) caused considerable reductions. Also the shifts in the countries’ product mix of the consumption bundle have decreased global emissions, except for the RoW and Indonesia. With respect the category “import structure”, it should be emphasized that these are the impacts on global emissions from changes in a country’s import structure. That is, given a country’s input requirements it may havefor the production of its goods or services substituted some domestically produced inputs for imported inputs (or the other way around) or substituted imported inputs from one country for those from another country. The same applies for the products that are consumed or bought for investment purposes. If producers and consumers shift to buying goods and services that are produced in a more (less) emission-friendly fashion, global GHG emissions will decrease (increase). Changes in a country’s import structure are complex and the outcome for global emissions can go either way. It has been argued in the literature that developing countries have been used as pollution havens by developed countries.31 In that case, we would expect that import structure changes in developed countries induce a large positive effect. This is because goods that are produced domestically in a relatively clean way are expected to be substituted for goods that are 5391
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from) other countries. The remaining countries (RoW, Mexico, and Turkey) imported extra emissions to the amount of 0.29 Gt. From the annual results it also follows that the role of BRIIC countries as drivers for the growth of global GHG emissions has become more important over the years. Changes in the BRIIC countries induced 51% of the change in the global emissions between 2002 and 2008, whereas this was 44% of the total growth in the entire 1995−2008 period (the results for the two subperiods are given in Tables S2 and S3 of SI). The growth in their national emissions amounted to 67% of the total emission growth over 2002−2008 and was 59% of the total growth of GHG emissions between 1995 and 2008. The redistribution to BRIIC countries of extra emissions driven by other countries was approximately 15% of the total growth in emissions in both periods. Finally, the change in national emissions (red line in Figure 3) can further be decomposed to distinguish the variation driven by domestic changes (dark gray bar in Figure 3) and foreign changes (light gray bar in Figure 3). In all the developed regions analyzed (Australia, Canada, East Asia, the EU-27, and the U.S.), foreign changes contributed to increase national emissions more than domestic changes. Moreover, in the case of East Asia and the EU-27, while domestic changes contributed to reduce national emissions, foreign changes drove their national emissions upward. That was also the case of Russia; on the contrary, in the rest of the BRIIC countries (i.e., Brazil, India, Indonesia, and China), the domestic changes were the main drivers for the growth in national emissions. Nevertheless, in these emerging economies the share of the increase in national emissions attributed to foreign changes was also significant (37% in Brazil, 26% in India, 30% in Indonesia, and 44% in China).
imported from developing countries where they are produced in a less clean fashion. For developing countries, a clear negative effect would be expected due to increased imports (from developed countries) of relatively clean products. The results do not support this version of the pollution haven hypothesis. The findings for some countries (Canada, East Asia, EU-27, and Russia) are in line with the expectation, but the findings for some other countries (China, U.S., Australia, and RoW) indicate the opposite. Moreover, changes in a country’s import structure only had a very modest effect on the growth in global GHG emissions, when compared to other changes in that country. These results are also consistent with the net emissions transfers from emerging to developed countries detected in previous studies.3,13 Consumption in developed countries has increased more than production, leading to rising current account deficits; these global imbalances in trade are also mirrored in imbalances in emissions. However, the production processes in the emerging economies are not particularly polluting compared to the ones in developed countries, as suggested by the pollution haven hypothesis. 3.2. Drivers of Global Emissions: Countries. The results at the country level can also be used to analyze which country has driven the growth of global emissions (black bars in Figure 3). For example, all the changes that have taken place in China have increased global GHG emissions by 2.77 Gt (which is 31.2% of the total growth of 8.86 Gt). This reflects the effect of all of a country’s (here China’s) changes on the growth in global emissions. It should be stressed that this differs from China’s consumer responsibility (which follows the consumption-based accounting approach and measures how much of the worldwide emissions are embodied in China’s consumption bundle). For example, the reduction in Chinese emission intensities is part of the impact of China’s changes on emission growth. At the same time, it will have reduced the amount of emissions in China that are ultimately embodied in, for instance, U.S. consumption (which is part of the change in the U.S. consumer responsibility). Comparing the effect of a country’s changes on the growth in global emissions with the change in the country’s national emissions (red line in Figure 3), provides information on the geographical redistribution of emissions. For example, all changes in China have increased global emissions by 2.77 Gt (black bar in Figure 3) but all changes in the world have increased Chinese national emissions by 3.88 Gt (the red line in Figure 3). The net effect is that China exports an extra 1.11 Gt of emissions which are caused by changes in other countries. The opposite holds for the U.S. and the EU-27: taken together their countries’ changes induce a growth in global emissions by 1.30 Gt, whereas their national emissions grow only by 0.24 Gt; the emission of an extra 1.06 Gt is thus imported from other countries. The results show a clear redistribution of the growth in emissions from developed to BRIIC countries. Changes in the BRIIC countries caused 44% (3.86 Gt) of the total growth in emissions but the growth of their national emissions accounted for 59% (5.22 Gt) of the total growth. The BRIIC countries thus have emitted an extra 1.35 Gt of emissions that have been caused by changes in other countries. Changes in the developed countries led to a growth in emissions of 1.81 Gt (20% of the total growth) but their extra national emissions were only 8% (0.74 Gt) of the total growth. Thus, 1.06 Gt of the extra emissions that they caused have been emitted by (i.e., imported
4. DISCUSSION Our first major finding was that growth in consumption per capita, the growth in population (capita), and technological change were the key drivers of the growth in global GHG emissions between 1995 and 2008. The first two factors have boosted emissions, which was dampened by the third factor. The changes in the trade structure have had a very minor effect on global emissions. Economic globalization caused goods, services and production factors to flow around the world and increased international trade. Between 1995 and 2008, world trade tripled from $6.3 trillion (21% of world GDP) to $19.5 trillion (32% of world GDP).32 A shift in the trade structure has taken place where domestically produced goods and services have been substituted for imported ones. It follows from our results that this has hardly affected global GHG emissions. If the 2008 consumption bundle would have been produced with the 1995 import structure, global emissions would only have been 0.6 Gt less than the actual 39.3 Gt in 2008. How does this result relate to earlier findings? For example, using the GTAP database, Peters et al.3 estimated that the CO2 emissions from the production of traded goods and services have increased from 20% of global emissions in 1990 to 26% in 2008. Using the WIOD database, Xu and Dietzenbacher29 report similar findings (24% in 1995 and 33% in 2007, for CO2) as do Arto et al.13 (19% in 1995 and 27% in 2008, for the three main GHG, that is, CO2, CH4 and N2O). Our study supports these findings but provides an alternative perspective. That is, more people and more consumption per person have pushed the demand for final goods and services upward 5392
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global emissions attributed to population is the high annual population growth in the RoW (close to 1.8% per year), which is expected to continue. In recent years, China and the U.S. have slowed down their demographic growth. That is, from around 1.0% per year in midnineties to 0.5% at the end of the period for China, and from 1.2% in 1996 to 0.9% in 2008% in case of the U.S. Compared to other regions, the population of the EU-27 has grown relatively little (0.3% per year). Comparing the effects of changes in consumption per capita and changes in population growth, it seems that there is more room, in terms of climate mitigation, for limiting a further growth in consumption per capita (especially in the richest countries) than for birth control. However, in the light of the current economic paradigm, the deployment of policies aimed at constraining the consumption in developed countries is not very likely to happen. Technological change has reduced the growth in GHG emissions, especially from 2004 onward due to the increase in energy prices. However, these improvements have been insufficient to offset the growth in the other factors. The reduction in global emissions attributed to technological change was driven by the BRIIC countries and the RoW (56%), the EU-27 (16%), and the U.S. (11%). Further reductions in GHG emissions through technological change seem possible, especially in terms of energy efficiency and a shift to cleaner energies,35 and in particular industries such as power generation and in transport. In addition, high energy prices will benefit a wider introduction of cleaner technologies and also climate policy may help to stimulate technological change. Nevertheless, even in such an optimistic scenario, it is questionable whether technological change can completely offset the consequences of the current pace of growth in per capita consumption and in population. The reduction of the emission intensity of emerging economies is one of the key elements for climate change mitigation. The growth in their national emissions may be expected to be enormous in the future. On the one hand, because BRIIC countries are expected to lead the worldwide growth in per capita consumption and population growth, and because they produce a large share of the extra production at home with their own technology and emission intensities. On the other hand, BRIIC countries continue to play a central role as suppliers of manufactured products to other countries. A considerable share of the extra production induced by changes in developed countries will continue to take place in BRIIC countries with their technology and emission intensities. At the same time, these countries have a huge potential for reducing emissions through cleaner technologies (e.g., the power generation industry in China35). A simple solution in terms of climate mitigation is to aim at getting the best value (i.e., the maximum reduction in emissions) for the money spent. That is, a dollar that is spent in the U.S. (or a euro spent in the EU-27) on further improving the emission intensity at home would generate a much larger effect if it were used to improve the emission intensity in China, for example. The implementation of such a solution is, of course, far from simple and would require a lot of international political co-ordination.
affecting production and global GHG emissions. At the same time, the process of globalization has led to phenomenal surges in international trade and, therefore, in the emissions embodied in trade. Earlier studies have convincingly shown that trade has led to a redistribution of emissions from producers to consumers (who emits for whom) and large shifts have taken place. This is confirmed by our results; but they also indicate that the increase in the emissions embedded in trade has not been a determinant of the growth in global emissions. Moreover, this result also holds for the individual regions analyzed: for most countries, the effect of the change in trade structure is an order of magnitude below the one of consumption per capita. In other words, emissions would have increased irrespective of the trade structure (i.e., the structure of 1995, 2008, or any year in-between). Even a stronger reliance on imported inputs in 2008 than in 1995 has had little effect on the global emissions. Although domestically produced goods have been substituted by imports, the production abroad was on average as emission intensive as the production at home. Import substitution therefore has not much changed global emissions. Trade in emissions is an interesting issue, but not when analyzing the growth of global emissions. At the global level, imports (exports) are basically a substitute for emissions that otherwise would have taken place at home (abroad). Of course, trade has been relevant for certain policy issues, such as the transfer of emissions between countries through international trade,10 the environmental load−displacement,33 or the debate on sharing the responsibility for emissions among countries.34 For instance, in recent years, the growth in national emissions slowed down in developed countries but increased significantly in emerging countries. For the entire period 1995− 2008, we found that changes in the BRIIC countries caused 44% of the growth in GHG emissions while changes in developed countries (the EU-27, the U.S., Canada, Japan, South Korea, Taiwan, and Australia) contributed to 20%. These figures differ substantially from the growth in national emissions: 59% of the total emission growth took place in BRIIC countries and 8% in the developed countries. The net transfers of emissions have thus further increased. BRIIC countries became larger net exporters of emissions and developed countries increased their net imports. The identification of the driving forces and countries of the change in GHG emissions is essential for the definition of climate policies, especially for the design of emission scenarios. The main driver for the growth in global GHG emissions between 1995 and 2008 was the change in consumption per capita, especially in BRIIC countries, the U.S., and the EU-27. In the latest years, the growth in consumption per capita accelerated in the BRIIC countries and other emerging economies due to a long period of economic growth, whereas it slowed down in developed economies. The financial crisis of 2008 and the subsequent recession will probably strengthen these trends. In the future, growth of per capita consumption in emerging economies is likely to continue being the main driver for the increase in global emissions. Also the growth in population has substantially contributed to the increase of global emissions, although not as much as growth in per capita consumption. Population growth caused global emissions to grow by 1.0% per year on average. This rate was fairly stable over time and might be expected not to change much in the future. Changes are likely to occur, however, in the localization of the drivers. The main driver of the change in 5393
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(15) Kanemoto, K.; Moran, D.; Lenzen, M.; Geschke, A. International trade undermines national emission reduction targets: New evidence from air pollution. Glob. Environ. Change 2014, 24, 52−59. (16) Jakob, M.; Marschinski, R. Interpreting trade-related CO2 emission transfers. Nat. Clim Change 2013, 3, 19−23. (17) United Nations Framework Convention on Climate Change. National Greenhouse Gas Inventory Data for the Period 1990−2009.; UNFCCC Thirty-fifth session. Durban, 28 November to 3 December 2011., 2011. (18) Intergovernmental Panel on Climate Change. Climate change 2007: Mitigation of Climate Change; IPCC: Geneva, Switzerland, 2007. (19) Chertow, M. R. The IPAT Equation and Its Variants. J. Ind. Ecol. 2000, 4, 13−29. (20) KayaY.Impact of carbon dioxide emission control on GNP growth: Interpretation of proposed scenarios. Presented to the IPCC Energy and Industry Subgroup, Response Strategies Working Group, 1989 (21) Raupach, M. R.; Marland, G.; Ciais, P.; Le Quéré, C.; Canadell, J. G.; Klepper, G.; Field, C. B. Global and regional drivers of accelerating CO2 emissions. Proc. Natl. Acad. Sci. U. S. A. 2007, 104, 10288−10293. (22) Jotzo, F.; Burke, P. J.; Wood, P. J.; Macintosh, A.; Stern, D. I. Decomposing the 2010 global carbon dioxide emissions rebound. Nat. Clim Change 2012, 2, 213−214. (23) Peters, G. P.; Weber, C. L.; Guan, D.; Hubacek, K. China’s growing CO2 emissions: A race between increasing consumption and efficiency gains. Environ. Sci. Technol. 2007, 41, 5939−5944. (24) Baiocchi, G.; Minx, J. C. Understanding changes in the UK’s CO2 emissions: A global perspective. Environ. Sci. Technol. 2010, 44, 1177−1184. (25) Minx, J. C.; Baiocchi, G.; Peters, G. P.; Weber, C. L.; Guan, D.; Hubacek, K. A “Carbonizing dragon”: China’s fast growing CO2 emissions revisited. Environ. Sci. Technol. 2011, 45, 9144−9153. (26) Liang, S.; Xu, M.; Liu, Z.; Suh, S.; Zhang, T. Socioeconomic drivers of mercury emissions in China from 1992 to 2007. Environ. Sci. Technol. 2013, 47, 3234−3240. (27) Liang, S.; Liu, Z.; Crawford-Brown, D.; Wang, Y.; Xu, M. Decoupling analysis and socioeconomic drivers of environmental pressure in China. Environ. Sci. Technol. 2013, 48, 1103−1113. (28) Zhang, Z.; Shi, M.; Yang, H. Understanding Beijing’s water challenge: A decomposition analysis of changes in Beijing’s water footprint between 1997 and 2007. Environ. Sci. Technol. 2012, 46, 12373−12380. (29) Xu, Y.; Dietzenbacher, E. A structural decomposition analysis of the emissions embodied in trade. Ecol. Econ. 2014, 101, 10−20. (30) Dietzenbacher, E.; Los, B.; Stehrer, R.; Timmer, M.; de Vries, G. The construction of world input-output tables in the WIOD project. Econ. Syst. Res. 2013, 25, 71−98. (31) Levinson, A.; Taylor, M. S. Unmasking the pollution have effect. Int. Econ. Rev. 2008, 49, 223−254. (32) International Monetary Fund. World Economic Outlook Database, April 2013., 2013. (33) Muradian, R.; O’Connor, M.; Martinez-Alier, J. Embodied pollution in trade: Estimating the “environmental load displacement” of industrialised countries. Ecol. Econ. 2002, 41, 51−67. (34) Peters, G. P. From production-based to consumption-based national emission inventories. Ecol. Econ. 2008, 65, 13−23. (35) Arto, I.; Rueda-Cantuche, J. M.; Andreoni, V.; Mongelli, I.; Genty, A. The game of trading jobs for emissions. Energy Policy 2014, 66, 517−525.
ASSOCIATED CONTENT
S Supporting Information *
Additional material concerning methods and detailed results are available. This material is available free of charge via the Internet at http://pubs.acs.org.
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AUTHOR INFORMATION
Corresponding Author
*Phone: + 34 944 014 690; e-mail: [email protected]. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This research was carried out in the frame of the project WIOD, World Input−Output Database: Construction and Applications funded by the European Commission Seventh Framework Programme (FP7). We would like to thank Miriam Diamond and two anonymous referees for their comments and suggestions. The views expressed in this paper belong to the authors and should not be attributed to the European Commission or its services.
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REFERENCES
(1) Davis, S. J.; Caldeira, K. Consumption-based accounting of CO2 emissions. Proc. Natl. Acad. Sci. U. S. A. 2010, 107, 5687−5692. (2) Davis, S. J.; Peters, G. P.; Caldeira, K. The supply chain of CO2 emissions. Proc. Natl. Acad. Sci. U. S. A. 2011, 108, 18554−18559. (3) Peters, G. P.; Minx, J. C.; Weber, C. L.; Edenhofer, O. Growth in emission transfers via international trade from 1990 to 2008. Proc. Natl. Acad. Sci. U. S. A. 2011, 108, 8903−8908. (4) Steen-Olsen, K.; Weinzettel, J.; Cranston, G.; Ercin, A. E.; Hertwich, E. G. Carbon, land, and water footprint accounts for the European Union: Consumption, production, and displacements through international trade. Environ. Sci. Technol. 2012, 46, 10883− 10891. (5) Weinzettel, J.; Hertwich, E. G.; Peters, G. P.; Steen-Olsen, K.; Galli, A. Affluence drives the global displacement of land use. Glob. Environ. Change 2013, 23, 433−438. (6) Yu, Y.; Feng, K.; Hubacek, K. Tele-connecting local consumption to global land use. Glob. Environ. Change 2013, 23, 1178−1186. (7) Feng, K.; Chapagain, A.; Suh, S.; Pfister, S.; Hubacek, K. Comparison of bottom-up and top-down approaches to calculating the water footprints of nations. Econ. Syst. Res. 2011, 23, 371−385. (8) Lenzen, M.; Moran, D.; Bhaduri, A.; Kanemoto, K.; Bekchanov, M.; Geschke, A.; Foran, B. International trade of scarce water. Ecol. Econ. 2013, 94, 78−85. (9) Wiedmann, T. O.; Schandl, H.; Lenzen, M.; Moran, D.; Suh, S.; West, J.; Kanemoto, K. The material footprint of nations. Proc. Natl. Acad. Sci. U. S. A. 2013, DOI: 0.1073/pnas.1220362110. (10) Lenzen, M.; Moran, D.; Kanemoto, K.; Foran, B.; Lobefaro, L.; Geschke, A. International trade drives biodiversity threats in developing nations. Nature 2012, 486, 109−112. (11) Peters, G. P.; Hertwich, E. G. CO2 embodied in international trade with implications for global climate policy. Environ. Sci. Technol. 2008, 42, 1401−1407. (12) Tukker, A.; Dietzenbacher, E. Global multiregional input-output frameworks: An introduction and outlook. Econ. Syst. Res. 2013, 25, 1− 19. (13) Arto, I.; Genty, A.; Rueda-Cantuche, J. M.; Villanueva, A.; Andreoni, V. Global Resources Use and Pollution, Vol. 1/Production, Consumption and Trade (1995−2008); Publication Office of the European Union: Luxembourg, 2012. (14) Rosa, E. A.; Dietz, T. Human drivers of national greenhouse-gas emissions. Nat. Clim Change 2012, 2, 581−586. 5394
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Drivers of the Growth in Global Greenhouse Gas Emissions Iñaki Arto*,†,‡ and Erik Dietzenbacher§ †
Basque Centre for Climate Change (BC3), C/Alameda Urquijo 4, 4°,48006, Bilbao, Spain European Commission, Joint Research Centre, IPTS − Institute for Prospective Technological Studies, Edificio EXPO, C/ Inca Garcilaso 3, 41092, Seville, Spain § Faculty of Economics and Business, University of Groningen, P. O. Box 800, 9700 AV Groningen, The Netherlands ‡
S Supporting Information *
ABSTRACT: Greenhouse gas emissions increased by 8.9 Gigatons CO2 equivalent (Gt) in the period 1995−2008. A phenomenon that has received due attention is the upsurge of emission transfers via international trade. A question that has remained unanswered is whether trade changes have affected global emissions. For each of five factors (one of which is trade changes) in 40 countries we quantify its contribution to the growth in global emissions. We find that the changes in the levels of consumption per capita have led to an enormous growth in emissions (+14.0 Gt). This effect was partly offset by the changes in technology (−8.4 Gt). Smaller effects are found for population growth (+4.2 Gt) and changes in the composition of the consumption (−1.5 Gt). Changes in the trade structure had a very moderate effect on global emissions (+0.6 Gt). Looking at the geographical distribution, changes in the emerging economies (Brazil, Russia, India, Indonesia and China) have caused 44% of emission growth whereas the increase in their national emissions accounted for 59% of emission growth. This means that 15% (1.4 Gt) of all extra GHG emissions between 1995 and 2008 have been emitted in emerging countries but were caused by changes in other countries.
1. INTRODUCTION In recent years, due attention has been paid to the effects of the growing importance of international trade on CO2 emissions.1−4 Also the use of land,4−6 water,4,7,8 and materials,9 and even biodiversity threats10 have been considered in this respect. In the case of CO2, for example, most developed countries have stabilized their increase in national emissions, but substantially increased the global emissions embedded in their consumption. In developing countries, the global emissions attributable to their consumers have drastically increased but their national emissions have grown even more. Developing countries thus generated emissions that were embodied in their exports to developed countries (which is also known as weak carbon leakage11). As a consequence, the net imports of emissions by most developed countries increased and so did the net exports of emissions by most developing countries. These studies have become possible only recently when the methodology was developed and when data became available. With respect to the methodology, a shift has taken place from answering the question “Who emits?” to “For whom is emitted?”. The first question is answered by the national emissions of a country. Next to the emissions due to the actual consumption of goods and services, it includes the emissions in the production processes (hence production-based emission accounting). The second question takes the ultimate consumer as starting point and includes, again next to emissions due to the actual consumption, all emissions involved in producing the consumed goods and services (hence consumption-based © 2014 American Chemical Society
emission accounting) and yields a country’s footprint. For example, someone who drives a German car in the U.S. causes emissions in the U.S. (due to the actual driving), in Germany (due to the assembly of the car), and in the UK (due to producing the motor parts that went into the German car). The two accounting approaches are linked to the discussion on the responsibility for emissions and have therefore also been termed producer-responsibility and consumer-responsibility. The difference between the two concepts is laid in the trade in emissions (i.e., emissions in one country that are ultimately attributed to consumption in another country). Regarding the data issue, the consumption-based perspective requires detailed information on national production processes that are internationally linked through trade. That is, global multiregional input-output (GMRIO) tables that cover many countries, distinguish many industries and are appended by socalled environmental accounts (using the same industry classification). Such GMRIO tables have become available only recently.12 As indicated above, various studies have emphasized the growth in emission transfers via international trade.3,13 It has been argued that trade could contribute to increase GHG emissions in the less-developed nations (and reduce them in Received: Revised: Accepted: Published: 5388
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Figure 1. Cumulative change in global GHG emissions by driving factor, 1995−2008 (Gigatons CO2 equivalent).
understanding of the drivers of environmental pressures by applying decomposition techniques based on input−output analysis (i.e., structural decomposition analysis).23−28 However, these approaches analyze the change in the emissions in an aggregate way and ignore the role of the trade linkages between countries. That is, the changes in the emissions of one country due to the changes in other countries are not taken into account. An example is the changes in U.S. emissions attributed to an increase of its exports to India resulting from the growth of India’s population. Thus, a fundamental question is what have been the drivers of the growth in global GHG emissions from a multiregional perspective?
developed ones) as energy-intensive and highly polluting activities move there from developed nations.14 As a result, many developed countries in Annex B of the Kyoto Protocol have been able to report decreasing emissions, and some have officially fulfilled their mitigation commitments.15 Some authors have found that the specialization can only explain a fraction of the emission transfers between countries (with differences in energy intensity, carbon intensity and trade balances as other important explanatory factors).16 However, it has not been assessed whether the changes in the international trade structure have resulted in change of global GHG emissions. This question is of special relevance for the analysis of the environmental consequences of trade. In the current context of globalization, one might be inclined to think that we would have been better offin terms of global emissionsif we had traded less. That is, if we had produced a larger share of products at home rather than importing them. The key question is what has been the role of changes in trade structure for the growth in global greenhouse gas (GHG) emissions? In order to monitor the progress toward the stabilization of GHG concentrations in the atmosphere, the United Nations Framework Convention on Climate Change reports periodically emissions inventories.17 These inventories compile information on the evolution of the major sources of GHG over time. However, they fail to explain the driving forces behind these trends, which is essential for the definition of climate policies. The identification of the drivers of the growth in global GHG emissions is a key task in the construction of mitigation scenarios.18 In recent years, different decomposition techniques have been used to analyze the changes in the aggregate GHG emissions into the factors underlying their evolution. One of the first systematic explications of the idea of driving forces is represented by the IPAT equation,14,19 which decomposes the environmental impact as the product of three factors: population, GDP per capita (affluence), and technology (defined as the environmental impact per unit of GDP). Similarly, some authors have used the Kaya identity,20 which decomposes the change in global or regional emissions into four factors: population, GDP per capita, energy intensity, and carbon intensity of energy.21,22 Other studies have enriched the
2. MATERIALS AND METHODS To answer this question, we will carry out a so-called structural decomposition analysis (SDA) within a GMRIO framework. SDAs decompose the change in one variable (here global GHG emissions) into the changes of its constituent parts. In our study, these are consumption per capita, the product mix of the consumption bundle, population size, technology, and trade structure. For the sake of brevity, we use the term consumption for the sum of private and government consumption and investments. In other words, consumption in this paper includes all goods and services that are not used as inputs in any production process (i.e., final demands in input-output parlance). The typical outcome of an SDA tells by how much the global GHG emissions would have increased if only population, for example, had increased as it actually has while anything else had remained the same (i.e., the ceteris paribus clause that is common in economics). For a full description of the methodology see the Supporting Information (SI). Recently, also Xu and Dietzenbacher29 applied a similar SDA approach within a GMRIO framework, albeit with an entirely different focus. They decomposed only the emissions embodied in trade and answered the question: how come that, for example, China’s emissions embodied in exports have risen? The present paper focuses on global emissions and asks: how much of the changes in global emissions are due to changes in China? Clearly, emissions embodied in trade play an increasing role in a globalizing world (with fragmenting production processes) and are thus taken into full account in our analysis. 5389
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Figure 2. Change in global GHG emissions by driving factor and driving country, 1995−2008 (Gigatons CO2 equivalent). Region codes: AUS: Australia; BRA: Brazil; CAN: Canada; CHN: China; EAS: East Asia (Japan, South Korea and Taiwan); EU-27: European Union 27 Member States; IND: India; IDN: Indonesia; MEX: Mexico; RUS: Russia; TUR: Turkey; USA: United States of America; RoW: Rest of the World. Note: data sorted by change in a country’s national emissions.
The data to decompose the annual change of GHG emissions, at the country and global level, were taken from the World Input−Output Database (WIOD).30 Although the WIOD tables are perhaps not the most detailed in terms of numbers of countries and products, they have a unique feature that is necessary for our study: the WIOD includes tables in constant prices of the previous year, which are required to properly measure changes in technology. This database comprises time series of harmonized supply and use tables and symmetric input-output tables, valued both at current and previous year’s prices. It also includes data on international trade and satellite accounts related to environmental and socio-economic indicators (including the emissions of greenhouse gases). The WIOD comprises information for 35 industries and 59 products in 40 countries and the Rest of the World (RoW) (which is a single, aggregated region mainly including less developed countries). All data can be downloaded free of charge at www.wiod.org; for a description of the construction of the world input-output tables see.30 For the sake of simplicity we have aggregated the detailed country results to 13 regions: Australia, Brazil, Canada, China, East Asia (Japan, South Korea, and Taiwan), the European Union (27 member states, EU-27), India, Indonesia, Mexico, Russia, Turkey, the U.S., and the RoW.
equivalent (Gt) from 30.45 Gt to 39.31 Gt which was an increase of 29.1%. As shown by Figure 1, the change in consumption per capita was the main driver for the growth in global GHG emissions (detailed results for all 40 countries are given in Table S1 of SI). If only consumption per capita had increased in the way it actually did, while anything else had remained the same, global GHG emissions would have increased by 46.0% (14.01 Gt) when compared to the 1995 level. The growth in population was the second main factor adding 4.16 Gt to global emissions (an increase of 13.7%). The effects of the changes in the structure of international trade were relatively small. Trade changes only increased global GHG emissions by 0.58 Gt. More people and more consumption by each of them would thus have led to an almost 60% increase in GHG emissions. This was partly offset by the remaining two factors. The changes in technologywhich includes a shift to cleaner energy sources, efficiency gains and changes in the input structure of the different sectorsreduced global emissions by 27.6% (−8.40 Gt). Finally, the change in the commodity composition of the consumption bundle reduced the emissions by 4.8% (−1.50Gt). The product mix of consumption and investments has shifted toward goods (and services) that embody less GHG emissions. GDP per capita increased over time and consumers had more money to spend. This brought along a shift in their consumption pattern, because higher incomes have different consumption profiles. It is, however, not the case that consumers bought less emission-intensive goods.
3. RESULTS 3.1. Drivers of Global Emissions: Factors. Between 1995 and 2008, global GHG emissions grew by 8.86 Gigatons CO2 5390
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Figure 3. Changes in global emissions attributed to a country’s changes and changes in a country’s national emissions (Gigatons CO2 equivalent). Region codes: BRA: Brazil; CAN: Canada; CHN: China; EAS: East Asia (Japan, South Korea and Taiwan); EU-27: European Union 27 Member States; IDN: Indonesia; IND: India; MEX: Mexico; RUS: Russia; RoW: Rest of the World; USA: United States of America.
They increased their spending on emission-intensive products but increased their spending on products with lower emissions intensity even more. Figure 1 clearly shows that the evolution of global GHG emissions can be divided into two periods. Emissions grew at an average rate of 1.0% per year in the first period (1995− 2002) which increased to 3.1% per year on average in the second period (2002−2008). In both periods, consumption per capita and population growth were the main drivers of the increase in global emissions while the change in technology was the primary factor that had a lowering effect on emissions. The enhanced growth of emissions in the second period was mainly driven by the expansion of the growth in consumption per capita (from 1.6% per year to 4.6%). Also the annual emission reduction attributed to technological change accelerated in the second period (from an average growth rate of −1.4% in the period 1995−2002, to −3.7% between 2002 and 2008). Observe that the annual growth rate of the emissions as caused by the other factors remained more or less constant through the entire period 1995−2008. Figure 2 shows detailed results for a selected group of countries (Table S1 of SI shows detailed results for all 40 countries). For example, if only the consumption per capita in China had increased as it actually did, while anything else had remained the same, global GHG emissions would have increased by 4.88 Gt. Similar interpretations hold for the effects of: changes in the Chinese technology and emission intensities; changes in China’s import structure; changes in the product mix of the Chinese consumption bundle; and the growth of China’s population. The effect on global emissions of all the changes that have taken place in a country is given by the green cross (e.g., 2.77 Gt of the increase in global emissions is attributed to changes in China). In all regions, the growth in consumption per capita was the main driver for the growth of global emissions. In the BRIIC countries (Brazil, Russia, India, Indonesia, and China) and in
the RoW this factor boosted global emissions by 7.26 and 2.49 Gt, respectively. From the detailed annual results, it follows that the growth in GHG emissions attributed to changes in consumption per capita accelerated from 2002 onward for the BRIIC countries and the RoW. The U.S., and the EU-27 changes in consumption per capita increased global emissions by 1.63 and 1.58 Gt, respectively. The second factor that caused large increases in emissions was population growth. Particularly, the development of the population in the RoW had a substantial effect (generating an additional 1.58 Gt worldwide). Technological changes have limited the growth of global emissions, in particular the changes in China (−2.53 Gt), the RoW (−1.90 Gt), the EU-27 (−1.37 Gt), and the U.S. (−0.95 Gt) caused considerable reductions. Also the shifts in the countries’ product mix of the consumption bundle have decreased global emissions, except for the RoW and Indonesia. With respect the category “import structure”, it should be emphasized that these are the impacts on global emissions from changes in a country’s import structure. That is, given a country’s input requirements it may havefor the production of its goods or services substituted some domestically produced inputs for imported inputs (or the other way around) or substituted imported inputs from one country for those from another country. The same applies for the products that are consumed or bought for investment purposes. If producers and consumers shift to buying goods and services that are produced in a more (less) emission-friendly fashion, global GHG emissions will decrease (increase). Changes in a country’s import structure are complex and the outcome for global emissions can go either way. It has been argued in the literature that developing countries have been used as pollution havens by developed countries.31 In that case, we would expect that import structure changes in developed countries induce a large positive effect. This is because goods that are produced domestically in a relatively clean way are expected to be substituted for goods that are 5391
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from) other countries. The remaining countries (RoW, Mexico, and Turkey) imported extra emissions to the amount of 0.29 Gt. From the annual results it also follows that the role of BRIIC countries as drivers for the growth of global GHG emissions has become more important over the years. Changes in the BRIIC countries induced 51% of the change in the global emissions between 2002 and 2008, whereas this was 44% of the total growth in the entire 1995−2008 period (the results for the two subperiods are given in Tables S2 and S3 of SI). The growth in their national emissions amounted to 67% of the total emission growth over 2002−2008 and was 59% of the total growth of GHG emissions between 1995 and 2008. The redistribution to BRIIC countries of extra emissions driven by other countries was approximately 15% of the total growth in emissions in both periods. Finally, the change in national emissions (red line in Figure 3) can further be decomposed to distinguish the variation driven by domestic changes (dark gray bar in Figure 3) and foreign changes (light gray bar in Figure 3). In all the developed regions analyzed (Australia, Canada, East Asia, the EU-27, and the U.S.), foreign changes contributed to increase national emissions more than domestic changes. Moreover, in the case of East Asia and the EU-27, while domestic changes contributed to reduce national emissions, foreign changes drove their national emissions upward. That was also the case of Russia; on the contrary, in the rest of the BRIIC countries (i.e., Brazil, India, Indonesia, and China), the domestic changes were the main drivers for the growth in national emissions. Nevertheless, in these emerging economies the share of the increase in national emissions attributed to foreign changes was also significant (37% in Brazil, 26% in India, 30% in Indonesia, and 44% in China).
imported from developing countries where they are produced in a less clean fashion. For developing countries, a clear negative effect would be expected due to increased imports (from developed countries) of relatively clean products. The results do not support this version of the pollution haven hypothesis. The findings for some countries (Canada, East Asia, EU-27, and Russia) are in line with the expectation, but the findings for some other countries (China, U.S., Australia, and RoW) indicate the opposite. Moreover, changes in a country’s import structure only had a very modest effect on the growth in global GHG emissions, when compared to other changes in that country. These results are also consistent with the net emissions transfers from emerging to developed countries detected in previous studies.3,13 Consumption in developed countries has increased more than production, leading to rising current account deficits; these global imbalances in trade are also mirrored in imbalances in emissions. However, the production processes in the emerging economies are not particularly polluting compared to the ones in developed countries, as suggested by the pollution haven hypothesis. 3.2. Drivers of Global Emissions: Countries. The results at the country level can also be used to analyze which country has driven the growth of global emissions (black bars in Figure 3). For example, all the changes that have taken place in China have increased global GHG emissions by 2.77 Gt (which is 31.2% of the total growth of 8.86 Gt). This reflects the effect of all of a country’s (here China’s) changes on the growth in global emissions. It should be stressed that this differs from China’s consumer responsibility (which follows the consumption-based accounting approach and measures how much of the worldwide emissions are embodied in China’s consumption bundle). For example, the reduction in Chinese emission intensities is part of the impact of China’s changes on emission growth. At the same time, it will have reduced the amount of emissions in China that are ultimately embodied in, for instance, U.S. consumption (which is part of the change in the U.S. consumer responsibility). Comparing the effect of a country’s changes on the growth in global emissions with the change in the country’s national emissions (red line in Figure 3), provides information on the geographical redistribution of emissions. For example, all changes in China have increased global emissions by 2.77 Gt (black bar in Figure 3) but all changes in the world have increased Chinese national emissions by 3.88 Gt (the red line in Figure 3). The net effect is that China exports an extra 1.11 Gt of emissions which are caused by changes in other countries. The opposite holds for the U.S. and the EU-27: taken together their countries’ changes induce a growth in global emissions by 1.30 Gt, whereas their national emissions grow only by 0.24 Gt; the emission of an extra 1.06 Gt is thus imported from other countries. The results show a clear redistribution of the growth in emissions from developed to BRIIC countries. Changes in the BRIIC countries caused 44% (3.86 Gt) of the total growth in emissions but the growth of their national emissions accounted for 59% (5.22 Gt) of the total growth. The BRIIC countries thus have emitted an extra 1.35 Gt of emissions that have been caused by changes in other countries. Changes in the developed countries led to a growth in emissions of 1.81 Gt (20% of the total growth) but their extra national emissions were only 8% (0.74 Gt) of the total growth. Thus, 1.06 Gt of the extra emissions that they caused have been emitted by (i.e., imported
4. DISCUSSION Our first major finding was that growth in consumption per capita, the growth in population (capita), and technological change were the key drivers of the growth in global GHG emissions between 1995 and 2008. The first two factors have boosted emissions, which was dampened by the third factor. The changes in the trade structure have had a very minor effect on global emissions. Economic globalization caused goods, services and production factors to flow around the world and increased international trade. Between 1995 and 2008, world trade tripled from $6.3 trillion (21% of world GDP) to $19.5 trillion (32% of world GDP).32 A shift in the trade structure has taken place where domestically produced goods and services have been substituted for imported ones. It follows from our results that this has hardly affected global GHG emissions. If the 2008 consumption bundle would have been produced with the 1995 import structure, global emissions would only have been 0.6 Gt less than the actual 39.3 Gt in 2008. How does this result relate to earlier findings? For example, using the GTAP database, Peters et al.3 estimated that the CO2 emissions from the production of traded goods and services have increased from 20% of global emissions in 1990 to 26% in 2008. Using the WIOD database, Xu and Dietzenbacher29 report similar findings (24% in 1995 and 33% in 2007, for CO2) as do Arto et al.13 (19% in 1995 and 27% in 2008, for the three main GHG, that is, CO2, CH4 and N2O). Our study supports these findings but provides an alternative perspective. That is, more people and more consumption per person have pushed the demand for final goods and services upward 5392
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global emissions attributed to population is the high annual population growth in the RoW (close to 1.8% per year), which is expected to continue. In recent years, China and the U.S. have slowed down their demographic growth. That is, from around 1.0% per year in midnineties to 0.5% at the end of the period for China, and from 1.2% in 1996 to 0.9% in 2008% in case of the U.S. Compared to other regions, the population of the EU-27 has grown relatively little (0.3% per year). Comparing the effects of changes in consumption per capita and changes in population growth, it seems that there is more room, in terms of climate mitigation, for limiting a further growth in consumption per capita (especially in the richest countries) than for birth control. However, in the light of the current economic paradigm, the deployment of policies aimed at constraining the consumption in developed countries is not very likely to happen. Technological change has reduced the growth in GHG emissions, especially from 2004 onward due to the increase in energy prices. However, these improvements have been insufficient to offset the growth in the other factors. The reduction in global emissions attributed to technological change was driven by the BRIIC countries and the RoW (56%), the EU-27 (16%), and the U.S. (11%). Further reductions in GHG emissions through technological change seem possible, especially in terms of energy efficiency and a shift to cleaner energies,35 and in particular industries such as power generation and in transport. In addition, high energy prices will benefit a wider introduction of cleaner technologies and also climate policy may help to stimulate technological change. Nevertheless, even in such an optimistic scenario, it is questionable whether technological change can completely offset the consequences of the current pace of growth in per capita consumption and in population. The reduction of the emission intensity of emerging economies is one of the key elements for climate change mitigation. The growth in their national emissions may be expected to be enormous in the future. On the one hand, because BRIIC countries are expected to lead the worldwide growth in per capita consumption and population growth, and because they produce a large share of the extra production at home with their own technology and emission intensities. On the other hand, BRIIC countries continue to play a central role as suppliers of manufactured products to other countries. A considerable share of the extra production induced by changes in developed countries will continue to take place in BRIIC countries with their technology and emission intensities. At the same time, these countries have a huge potential for reducing emissions through cleaner technologies (e.g., the power generation industry in China35). A simple solution in terms of climate mitigation is to aim at getting the best value (i.e., the maximum reduction in emissions) for the money spent. That is, a dollar that is spent in the U.S. (or a euro spent in the EU-27) on further improving the emission intensity at home would generate a much larger effect if it were used to improve the emission intensity in China, for example. The implementation of such a solution is, of course, far from simple and would require a lot of international political co-ordination.
affecting production and global GHG emissions. At the same time, the process of globalization has led to phenomenal surges in international trade and, therefore, in the emissions embodied in trade. Earlier studies have convincingly shown that trade has led to a redistribution of emissions from producers to consumers (who emits for whom) and large shifts have taken place. This is confirmed by our results; but they also indicate that the increase in the emissions embedded in trade has not been a determinant of the growth in global emissions. Moreover, this result also holds for the individual regions analyzed: for most countries, the effect of the change in trade structure is an order of magnitude below the one of consumption per capita. In other words, emissions would have increased irrespective of the trade structure (i.e., the structure of 1995, 2008, or any year in-between). Even a stronger reliance on imported inputs in 2008 than in 1995 has had little effect on the global emissions. Although domestically produced goods have been substituted by imports, the production abroad was on average as emission intensive as the production at home. Import substitution therefore has not much changed global emissions. Trade in emissions is an interesting issue, but not when analyzing the growth of global emissions. At the global level, imports (exports) are basically a substitute for emissions that otherwise would have taken place at home (abroad). Of course, trade has been relevant for certain policy issues, such as the transfer of emissions between countries through international trade,10 the environmental load−displacement,33 or the debate on sharing the responsibility for emissions among countries.34 For instance, in recent years, the growth in national emissions slowed down in developed countries but increased significantly in emerging countries. For the entire period 1995− 2008, we found that changes in the BRIIC countries caused 44% of the growth in GHG emissions while changes in developed countries (the EU-27, the U.S., Canada, Japan, South Korea, Taiwan, and Australia) contributed to 20%. These figures differ substantially from the growth in national emissions: 59% of the total emission growth took place in BRIIC countries and 8% in the developed countries. The net transfers of emissions have thus further increased. BRIIC countries became larger net exporters of emissions and developed countries increased their net imports. The identification of the driving forces and countries of the change in GHG emissions is essential for the definition of climate policies, especially for the design of emission scenarios. The main driver for the growth in global GHG emissions between 1995 and 2008 was the change in consumption per capita, especially in BRIIC countries, the U.S., and the EU-27. In the latest years, the growth in consumption per capita accelerated in the BRIIC countries and other emerging economies due to a long period of economic growth, whereas it slowed down in developed economies. The financial crisis of 2008 and the subsequent recession will probably strengthen these trends. In the future, growth of per capita consumption in emerging economies is likely to continue being the main driver for the increase in global emissions. Also the growth in population has substantially contributed to the increase of global emissions, although not as much as growth in per capita consumption. Population growth caused global emissions to grow by 1.0% per year on average. This rate was fairly stable over time and might be expected not to change much in the future. Changes are likely to occur, however, in the localization of the drivers. The main driver of the change in 5393
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ASSOCIATED CONTENT
S Supporting Information *
Additional material concerning methods and detailed results are available. This material is available free of charge via the Internet at http://pubs.acs.org.
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AUTHOR INFORMATION
Corresponding Author
*Phone: + 34 944 014 690; e-mail: [email protected]. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This research was carried out in the frame of the project WIOD, World Input−Output Database: Construction and Applications funded by the European Commission Seventh Framework Programme (FP7). We would like to thank Miriam Diamond and two anonymous referees for their comments and suggestions. The views expressed in this paper belong to the authors and should not be attributed to the European Commission or its services.
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