The size of the global human population is clearly an important driver of climate change both through our use of energy, which is principally generated by burning fossil fuels, and deforestation, driven for example by a trend away from staple foods to meat eating.  However, gross domestic product (GDP) is also closely correlated with energy use and over the last 40 years increases in the scale of global economy activity can be shown to have been an even bigger factor in the increase in energy use (and consequently the growth in greenhouse gas emissions) than population growth.  The growth in both GDP and global population needs to be reined back if climate change and its damaging consequences are to be avoided.

Since the Industrial Revolution climate change has been dominated by humanity’s use of fossil fuels and land, and the consequent emission of greenhouse gases into the atmosphere. This situation continues today as the global population grows, becomes more affluent, and demands more energy.

Population growth is often assumed to be the principal cause of rising greenhouse gas emissions. But on closer inspection another more important factor is seen to have been at work, growth in income. In the last 40 years global carbon dioxide emissions and gross domestic product (GDP) per head has grown irregularly, but more or less together, whereas population increased inexorably, at roughly the same rate, until about 2002. Since 2002 global emissions and GDP per person have grown much faster than population.

When primary energy use per person is plotted against GDP per person, it is seen that lower GDP countries tend to use less energy while richer ones use more. This relationship is distorted partly because the energy use per person of some moderate GDP countries, such as China, is larger than it would otherwise because they manufacture goods for export to higher GDP countries.

Even so, since the economic recession which hit the developed countries in 2008, the rapidly increasing pooled consumption emissions of the developing countries have overtaken those of the developed ones.

Population growth in many high GDP countries has stalled or is even negative in contrast to the relatively high rates of growth  in both population and income per person in some but not all of the developing ones. This leads to the conclusion that although average energy use per person in the developed countries taken as a whole is currently higher than that in the developing ones, the combination of increasing per capita income  in some of the developing countries and their relatively high rate of population growth is   likely to have an  important future impact on climate change if trends continue.

In conclusion, the high GDP and disposable income of individuals in developed countries, exhibited by a huge demand for meat, food from abroad, consumer items, car use and foreign travel, has been responsible for driving climate change in the recent past and this is likely to continue. In the 21st century an important secondary factor is likely to be the emissions from the rapidly growing populations of developing countries which aspire to raise their standard of living to that of developed ones.

Dr. David Knight of WinACC's Science and Technology Advisory Panel has written an in-depth paper on the links between population, economic growth and climate change: full papersummary. He also gave a talk on population and its impact on climate change compared with other thjngs such as consumption and energy efficiency, with slides and a published text.

You may be interested in Chris Nelder's provocative blog post on population issues, The 21st Century Population Crash, dispite omiting the impact of income and wealth on resource use.

24 March 2014 - 'Is it the answer?' A lecture on climate change,  population growth and economic growth.