As forecast, China has overtaken the U.S. in carbon-dioxide emissions  due largely to China’s heavy reliance on coal. Another factor is its well-publicized population of 1.3 billion. But per-capita emissions are much higher in developed countries, where populations are exploding due to immigration. The U.S. already releases four times the carbon per-capita each year as China. And the U.S. population, which has been doubling every 40 years, is headed for one billion by the end of this century!
A number of climate-change observers see population control as essential to arresting global warming.  They blame expansive immigration policies of the U.S., Canada and Europe for rising emissions because every immigrant from a tropical or semi-tropical climate requires huge additional amounts of carbon-based energy in the much-colder climate.
For example, the average annual per capita production of CO2 in Canada is 4.35 tons versus a mere .21 tons in Indonesia and 1.01 tons in Mexico. Even in highly industrialized Japan, where the climate is more moderate than in North America or Europe, production of CO2 per capita is only 2.34 tons or approximately 50% less than the same person's output in Canada.
Approximately 82,000,000 people have entered the U.S., Canada and Europe from warm climates in the last 40 years. Assuming only 3 additional tons of CO2 per person – a very conservative estimate – this transfer of population has added another 246,000,000 tons of greenhouse gases, annually, to the world's global-warming problems.
“Global warming is a subset of the overpopulation problem  ,” said Ric Oberlink of Californians for Population Stabilization. “If we had half as many people, we wouldn't have much of a climatic warming problem.
“Many have noted the disproportionate impact of America on greenhouse emissions and rightly called for reduced emissions. But it's hypocritical to say Americans consume too much and then say it doesn't matter how many Americans there are.”