So I spotted this article in the Guardian, by one Damian Carrington, who gives us an example of how not to write about new research. The article is about the release of this paper in Science, by Gerland et al.
Let's take a little walk through the article to see how Mr. Carrington mangles nearly everything important about this research.
- The title of the article is "World population to hit 11bn in 2100". The Gerland et al article is about using Bayesian techniques to arrive at confidence intervals for the size of global population, meaning that their article is about how much uncertainty there is in a population projection. The entire point of their work is that statements like "World population to hit 11bn in 2100" are stupid because they do not tell you about the uncertainty in that estimate.
- "A ground-breaking analysis...." is how the Gerland et al article is introduced. I'm sure Gerland and his co-authors are very capable scholars. But this is not ground-breaking analysis. How do I know that? Because they base all their work on the existing 2012 United Nations Population Projections, so they do not fundamentally change our estimates of future population. What they do add is the Bayesian analysis to give more accurate confidence intervals to those United Nations projections. This technique was developed by some of the co-authors a while ago, see this paper. *That* technique could arguably called ground-breaking, but the current Science paper is not.
- "The work overturns 20 years of consensus that global population, and the stresses it brings, will peak by 2050 at about 9bn people." What consensus? The UN's 2012 population projection that this Science article is based on predicts that population will be 11 billion by 2100, and that it will still be growing at that point. The UN population projection in 2010 also predicted population would be 11 billion in 2100. Population projects by the UN from around 2000 suggest that population would hit 9 billion in 2050, but never said it would max out there. The UN just didn't project out populations past 2050 back then.
- "Lack of healthcare, poverty, pollution and rising unrest and crime are all problems linked to booming populations, he [Prof. Adrian Raftery, U. of Washington] said." Mr. Carrington does not feel compelled to support these statements by citing any evidence that (a) the links exist and (b) are causal. I'd like to think that Prof. Raftery at least tried to provide this kind of evidence, but we don't know.
- "The research, conducted by an international team including UN experts, is published in the journal Science and for the first time uses advanced statistics to place convincing upper and lower limits on future population growth." Statistics? No - advanced statistics. See the difference? One is more advanced. Convincing? Convincing of what? That upper and lower limits exist? Of what relevance is it that the team was international? Do the advanced statistics require people with different passports to run the code? This is just such a ridiculous sentence. The stupid, it burns us.
- "But the new research narrows the future range to between 9.6bn and 12.3bn by 2100. This greatly increased certainty – 80% – allowed the researchers to be confident that global population would not peak any time during in the 21st century." They didn't increase certainty at all. The prior UN projections were mechanical, and had no uncertainty associated with them at all. Gerland et al have created confidence intervals where none existed. This didn't increase certainty, it quantified it.
By the way, it took me all of about 10 minutes on the Google machine to find the references I just cited here, and to look up the old UN projections. And I didn't use any special PhD kung-fu to do this. So I don't want to hear "well, science is hard for the layman to understand". This is click-bait crap reporting, period.