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What does science say about the expected growth of the human population in the next decades?

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Currently we have over 7.7 billion people in the world (data from April 2019). In 2010 the UN made several projections for world population growth.

Picture from [wikipedia] World population estimates from 1800 to 2100, based on "high", "medium" and "low" United Nations projections in 2010 (source wikipedia).

The worst case scenario (red line) is that the world population will continue to grow and we’ll have about 10.5 billion people in 2050. The best case scenario (green line) is that the population will stop growing soon and we’ll have a peak of 8 billion people somewhere around 2045.

The UN scenario that is generally thought to be the most plausible is that the world population will continue to grow to around 9.3 in 2050 and 10.1 billion people at the end of the 21st century and then remain stable (the yellow line).

However the 2012 revision of these figures changed these 'most likely' numbers to 9.6 billion in 2050 and 10.9 billion in 2100, and in the 2015 revision the numbers were raised to 9.7 and 11.2 respectively. In the 2017 and 2019 revisions the numbers changed slightly (see table below).

                   2050    2100
--------------------------------
1994 revision  |   9.8           
2000 revision  |   9.3           
2002 revision  |   8.9          
2010 revision  |   9.306  10.125    
2012 revision  |   9.551  10.854 
2015 revision  |   9.725  11.213   
2017 revision  |   9.772  11.184 
2019 revision  |   9.7    10.9

Table 1: UN (medium) projections of the expected world population in billions of people

A statistical study published in 2014 says that the UN projections are inaccurate and claims that

There is an 80% probability that world population, now 7.2 billion people, will increase to between 9.6 billion and 12.3 billion in 2100

On the other hand, critics on this new study say that it doesn't take improvements to female education in Africa into account, which is a key driver in (slowing) population growth.

Sources:

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    Would be cool to include some older UN predictions in this (e.g. from the 80s or 90s) to see how they've panned out, and to compare the assumptions to the current projections.
    – naught101
    Commented Feb 12, 2015 at 0:32
  • The two extreme projections say essentially nothing, and are probably impossible. If numbers keep increasing, things are not looking good. How can we make the green line actually happen?
    – user2423
    Commented Jul 29, 2015 at 12:37
  • @naught101 I've been able to find data for 1994, 2000 and 2002 and added those to table 1
    – THelper
    Commented Jul 30, 2015 at 12:44

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