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According to a new study from researchers from the United Nations by 2100, the global population could rise 70%  from its current  7.5 billion to 12.3 billion; a rise of 2 billion more then previous estimates.


Patrick Gerland runs  the United Nation’s Population Section. Gerland, who earned a Ph.D in Population Studies, has the job of projecting how many people will be born, will, die, and where they live: all of over the world,  and it would help if he could tell us,  when it  will happen. Gerland and his team of 13 other researchers have been working hard and this week they published a new population projection in  Science . They crunched information on national trends in fertility, mortality, migration and age patterns to build a more accurate understand of how our world will change in the next century.

Previous projections from the UN have been criticized for containing a great deal of uncertainty, with possible population scenarios of as many as 15.8 billion people, or as few as 6.2 billion. According to wired that wide range was a result of  the vast differences due to d itarations of  different outcomes in  human behavior.  Researchers calculated what would happen if women on average had 0.5 more or fewer children than expected. That’s not a bad rough guide, but is statistically rudimentary, failing to account for how those numbers will vary from country to country.

Raftery’s group took a finer grained look at the data, running population models on a country-by-country basis. “There is an 80 percent probability that world population, now 7.2 billion, will increase to between 9.6 and 12.3 billion in 2100,” they concluded. Population growth was found to vary by contient and regions, with growth in Asia and South America slowing at a much more rapid rate than Africa.


Projections of probable populations by continent.  Rafter et al./Science
Projections of probable populations by continent. Rafter et al./Science