Global warming is caused by the emission of greenhouse gases - 76.7% of the totally emitted greenhouse gases is carbon dioxide (CO2), 14.3% Methane and 7.9% Nitrous oxide (NOx). Carbon dioxide emissions therefore are the most important cause of global warming. CO2 is inevitably created by burning fuels like e.g. oil, natural gas, diesel, organic-diesel, petrol, organic-petrol, ethanol. The emissions of CO2 have been dramatically increased within the last 50 years and are still increasing by almost 3% each year.

In some countries, including Brazil and Indonesia, deforestation is the leading source of carbon dioxide emissions.

The world’s population is likely to increase from 7 billion to 9 billion over the next 40 years. This population growth, combined with rising incomes, will lead to a continual increasing demand for food, animal feed and fuel. And this, in turn, will lead to more destruction of rainforests, with devastating effects for everyone.  The graph below shows the tight relationship between population and CO2 emissions.
 
The graph below shows evolution of global population (red) and global carbon dioxide emissions (blue) since 1900. (Population data are from the U.S. Census Bureau, and CO2 emissions data are from the Carbon Dioxide Information Analysis Center (CDIAC).