Population and Climate Change

Key Facts & Trends

Population growth has been—and will continue to be—a major contributor to the increase in global greenhouse gas emissions in the decades ahead.

 

  • Leading scientists believe that greenhouse gas emissions are contributing to global warming and accelerating climate change. Greenhouse gas emissions, principally carbon dioxide emissions from the combustion of oil and other fossil fuels, have risen dramatically in the last half century and are projected to rise another 60 percent by 2030.
  • While some of the historic increase in greenhouse gas emissions is attributable to rising per capita emissions in the major industrialized nations, population growth has also played a leading role.
  • The U.S. is the leading emitter of greenhouse gas emissions in the world.  With five percent of the world’s population, it is generating 20 percent of energy-related emissions.  On a per capita basis, U.S. carbon emissions are about twice as high as Western Europe and Japan and five times higher than the world average.  During the past 40 years, U.S. population has grown by over 100 million, reaching the 300 million mark last year.  U.S. population is expected to grow to 420 million by 2050.
  • China, with 1.3 billion people, will soon surpass the U.S. as the largest emitter of greenhouse gases in the world. China’s population, like the U.S., has grown by over 50 percent in the past four decades. Around 2025, China’s population will reach a peak of nearly 1.5 billion people before stabilizing and then gradually declining.
  • India’s per capita output of carbon dioxide emissions is much lower than the U.S. or Western Europe, but its population is expected to grow from 1.1 billion today to almost 1.8 billion by 2050.  Its carbon dioxide emissions are expected to increase by 131 percent by 2030 and could quadruple by 2050.
  • Scientists believe that population pressures are also contributing to another major cause of global warming: deforestation. Trees, particularly in the tropics, act as a carbon sink, taking carbon dioxide out of the air, but in many developing countries wood is used as fuel. In some high-density countries, like Haiti and Madagascar, the land is almost entirely deforested. Global population pressures are also boosting the demand for timber, leading to the clear-cutting of tropical forests in places like Brazil and Southeast Asia. 
  •  An Organization for Economic Cooperation and Development (OECD) study of 136 of the world’s largest port cities concluded that the number of people that are currently exposed to a 1 in 100-year coastal flood event will more than triple by 2070. At present, about 40 million people are at risk. By 2070, the number will rise to about 150 million due to the “combined effects of climate change, population growth and urbanization.” Asset exposure could grow even more dramatically, reaching $35 trillion by the 2070s.

Policy Implications

Just as population growth is contributing to the increase in greenhouse gas emissions, it will also make it more difficult for many nations to reduce those emissions.

 

  • In an effort to mitigate the effects of global warming, many world leaders are talking about reducing carbon dioxide emissions by 60 to 80 percent below current levels by 2050. While it is anticipated that all industrialized nations, will be asked to lower carbon dioxide emissions, the burden of compliance may be harder on countries still experiencing significant population growth. Although population is stabilizing—or even contracting—in many industrialized nations, the U.S. and some rapidly developing nations such as India, Brazil, Mexico and Indonesia will have to achieve even greater per capita cuts in emissions in order to meet their targets.
  • With global population predicted to rise from 6.6 billion today 9.2 billion by 2050, the demand for timber is expected to soar, putting additional pressures on the world’s forests. Commercial tree farms can meet some of the increased demand for lumber, but efforts thus far to prevent clear-cutting of tropical forests have seen only limited success.  Nations and international institutions will have to step up enforcement of existing prohibitions on unauthorized logging.

·        In addition to reducing greenhouse gas emissions, policymakers may also need to take steps to mitigate the impact that climate change will have on people living in drought-impacted areas or in low-lying coastal areas susceptible to flooding.