New Delhi: The number of people on earth is likely to reach 11 billion by 2100, about 2 billion higher than widely cited previous estimates, reveals a study led by University of Washington and United Nations published in Science journal on Thursday.

Published ahead of the United Nations general assembly meeting in New York, the study reveals using new statistical tools that there is an 80% probability that the world’s population, which stands at 7.2 billion today, will increase to between 9.6 and 12.3 billion in 2100, led by a steep rise in Africa.

“The consensus over the past 20 years or so was that world population, which is currently around 7 billion, would go up to 9 billion and level off or probably decline," said corresponding author Adrian Raftery, a professor of statistics and of sociology at University of Washington. “We found there’s a 70% probability the world population will not stabilize this century. Population, which had sort of fallen off the world’s agenda, remains a very important issue."

According to the paper, this is the first UN population report to use modern statistics, known as Bayesian statistics, that combine all available information to produce better predictions.

World population projections are based mostly on future life expectancy and fertility rates, and expert opinions, while the new method uses a combination of government data and expert forecasts for such phenomena as mortality rates, fertility rates and international migration.

Most of the projected growth is in Africa, where the population is expected to increase four times from around 1 billion today to 4 billion by the end of the century. The primary reason attributed for this expected jump in population is higher fertility and a recent slowdown in the pace of fertility decline.

The study said that there is an 80% chance that the population in Africa at the end of the century will be between 3.5 billion and 5.1 billion. Asia, where the population is 4.4 billion, will peak at around 5 billion people in 2050 and then begin to decline. Populations in North America, Europe and Latin America and the Caribbean are projected to stay below 1 billion each.

“Rising population could exacerbate world problems such as climate change, infectious disease and poverty," said Raftery. “Studies show that the two things that decrease fertility rates are more access to contraceptives and education of girls and women, Africa could benefit greatly by acting now to lower its fertility rate."