The interactions of three variables underlie debates on the issue of climate change and what responses might be justified: the magnitude and rates of change of (1) population, (2) incomes, and (3) intensity of greenhouse gas emissions relative to economic activities. This report examines the interrelationships of the variables to explore their implications for policies that address climate change. Both internationally and domestically, initiatives are underway both to better understand climate change and to take steps to slow, stop, and reverse the overall growth in greenhouse gas emissions, the most important of which is carbon dioxide (CO 2 ), emitted by the combustion of fossil fuels. These initiatives include the following bulleted items. The United Nations Framework Convention on Climate Change (UNFCCC), to which the United States and almost all other nations are Parties. Its stated objective is to stabilize greenhouse gas concentrations in the atmosphere at levels that "would prevent dangerous interference with the climate system." It established the principle that all nations should take action, and that developed nations should take the lead in reducing emissions. It required Parties to prepare national action plans to achieve reductions, with developed countries aiming to reduce year 2000 emissions to 1990 levels. It required preparation of inventories of emissions and annual reports. And it set up a process for the Parties to continue meeting. The Kyoto Protocol, an agreement negotiated under the auspices of the UNFCCC; 169 nations—but not the United States—are Parties to the Protocol. Even as the Framework Convention was going into force, it was recognized that most nations would not meet their 2000 aims of holding emissions at 1990 levels. Ensuing negotiations, in which the United States participated, led to the Kyoto Protocol, which called for mandatory reductions in greenhouse gases for the period 2008-2012 by developed nations—but not by developing ones. With the United States not participating, and with developing nations not required to make GHG reductions (and China became the world's largest emitter in about 2005), the reductions mandated by Kyoto will not significantly slow the accumulation of GHG in the atmosphere, although much is being learned of the institutional structures, such as the European Union's "cap and trade" mechanism, for handling reductions. Even as the Kyoto process began, negotiations on next steps resumed. The Asia-Pacific Partnership on Clean Development and Climate (APP), composed of the United States, China, India, Japan, Australia, and South Korea. The purposes of the Partnership are to create a voluntary, non-legally binding framework for international cooperation to facilitate the development, diffusion, deployment, and transfer of existing, emerging, and longer-term cost-effective, cleaner, more efficient technologies and practices among the Partners through concrete and substantial cooperation, so as to achieve practical results. It has the goal of meeting "national pollution reduction, energy security and climate change concerns, consistent with the principles of the U.N. Framework Convention on Climate Change (UNFCCC)." The Copenhagen Accord is an agreement of the Parties to the UNFCCC to begin establishing actions to follow on the Kyoto Protocol. The Copenhagen Accord does not mandate specific reductions, but sets a goal of reducing global emissions "so as to hold the increase in global temperature below 2 degrees C, and take action to meet this objective consistent with science and on the basis of equity." Annex I nations commit to implement "quantified economy-wide emissions targets for 2020" and non-Annex I nations commit to implement "mitigation actions." Both sets of nations commit to reporting and verification procedures "in accordance with guidelines adopted by the Conference of the Parties." (Monitoring, reporting, and verification were a key demand of the United States of developing nations.) Also, the accord contained the promise that developed countries would make available $100 billion a year by 2020 "to address the needs of developing countries." However, these several, related efforts have had to struggle with substantive economic, technical, and political differences among regional, national, and local circumstances. Foremost among these differences is the divide between developed and less-developed nations. Conflict arises because any pressure to reduce emissions comes up against increases in emissions likely to result from energy use fueling economic development and raising standards of living in developing economies, which contain a large share of the world's population. Even in many developed nations, efforts to constrain emissions by, for example, conservation, increased energy efficiency, and use of energy sources that emit less or no CO 2 , have been outstripped by increases in total energy use associated with population and economic growth. For example, between 1990 and 2005, in the United States, the greenhouse gas intensity of the economy declined at a rate of -1.9% per year, but total emissions increased at the rate of 1.0% per year. Although some countries have experienced declines in emissions—either through economic contraction or deliberate policies—the overall trend, both globally and for most individual nations, reflects increasing emissions. This upward trend in greenhouse gas emissions runs counter to the long-term objectives of these climate change initiatives. This report identifies drivers of the increase in emissions and explores their implications for efforts to reduce emissions. During this exploration, it is useful to bear in mind that although short-term efforts may not achieve emissions reductions that immediately meet goals to prevent dangerous interference with the climate system, such endeavors may nevertheless establish a basis for longer-term efforts. The analysis below, which uses data from the World Resources Institute's Climate Analysis Indicators Tool (CAIT), is based on the following relationships: The CAIT database includes 185 nations (plus a separate entry for the European Union) with a 2005 population of 6.462 billion, compared with 191 members of the United Nations and with a 2005 world population count of 6.470 billion by the U.S. Census Bureau. Average income is measured as per capita Gross Domestic Product (GDP), in international dollars of purchasing power parity ($PPP). (Note that population times per capita GDP equals GDP.) Greenhouse gas intensity is measured as tons of emissions in carbon equivalents per million dollars of GDP. Table 1 provides a snapshot of the equation 1 variables for the top 20 greenhouse gas emitters in the year 2005, plus for the European Union 27, and for the world. The data reflect the wide range of circumstances faced by any initiative to address GHGs. However, it is the way those variables are changing that illuminates both the seemingly inexorable rise in GHG emissions and the challenge of reducing them. A variable changing at an annual rate of 6.9% doubles in 10 years; at an annual rate of 3%, it doubles in 23 years. The growth rate of each of the variables of equation 1 can be expressed as an exponent, the annual percentage rate of change over some time period (see Growth Relationship of Greenhouse Gas Drivers ). As exponents of multiplicands are added, relationship among the variables can be simply expressed: the growth rates of the three variable on the left side of the equation sum to the growth rate of the variable (emissions) on the right side. Thus, if the sum of the three growth rate variables on the left is positive, emissions are rising; if the sum is negative, emissions are declining; and if the sum is zero, emissions are constant. This growth relationship among the variables makes explicit why there is upward pressure on GHG emissions. For nearly all nations, population is increasing, with developing nations typically having the highest rate. Thus population growth rate is positive globally and for most nations; it is zero or negative for only a few nations. The economic development of less-developed nations is a global objective acknowledged by the UNFCCC; developed nations also promote economic growth to raise living standards. Thus economies are growing globally and for most nations. With the population and economic activity variables positive, emissions will be rising unless the decline in intensity exceeds the growth in population and economic activity, which has seldom been the case. If the goal is to reduce GHG emissions, the larger the negative change in intensity, the better. Table 2 shows the changes in these variables for 1990 - 2005. (The figures in the right-most column are taken from the CAIT database. ) As the table shows, global growth rates for population and per capita income outpaced the rate of decline in intensity—so GHG emissions rose; this is also true of the majority of nations, including the United States. Circumstances in several individual countries highlight some important points about GHG emissions and their potential control. First, for many nations, population growth is an important contributor to the increase in GHG emissions. For Brazil, Mexico, Indonesia, Iran, Australia, Spain, South Africa, and Turkey, any improvements in intensity were annulled by increases in population alone. Second, developing countries, focused on developing their economies, have increasing GHG emissions even when they manage to improve intensity (e.g., China, India, Mexico, Indonesia, South Korea, and South Africa). For these countries, population growth combined with per capita GDP growth overwhelmed whatever intensity improvements they achieved. Third, lower emissions can be associated with decreasing economic activity. For the Russian Federation and Ukraine, economic contraction following the dissolution of the Soviet Union contributed to decreases in their emissions. During 2008-2009,GHG emission reductions occurred in many if not most nations as a result of the global recession, and almost certainly declined globally. Fourth, several developed countries improved per capita GDP while holding their GHG emissions to a 1% increase or less: the United States, Japan, Germany, the United Kingdom, Italy, and France. Germany and the United Kingdom (and also the European Union 27) actually decreased their emissions. Fifth, in some developed countries, income growth alone exceeded the decline in intensity (e.g., Japan, Italy, Canada, Australia, and Spain). Stabilizing emissions would require an accelerated decline in intensity.