Affichage des articles dont le libellé est population. Afficher tous les articles
Affichage des articles dont le libellé est population. Afficher tous les articles

2013/07/02

World population in 2050 : new revision but what about accuracy?

United Nations has released this month the 2012 revision of their demographic forecast :
the world population of 7.2 billion in mid-2013 is projected to increase by almost one billion people within the next twelve years, reaching 8.1 billion in 2025, and to further increase to 9.6 billion in 2050 and 10.9 billion by 2100. These results are based on the medium-variant projection.

Source : United Nations, Department of Economic and Social Affairs, Population Division (2013). World Population Prospects: The 2012 Revision, Key Findings and Advance Tables.

The "constant fertility" scenario assumes the current fertility rate in the different countries remains unchanged in the future. This rate is the most critical parameter in the U.N. projections, whereas there are many others important parameters.

This global trend is putting even further pressure on natural ressources, as described in our previous articles about the Global Ecological Crisis (MAP1MAP2).

But we would like here to challenge these U.N. projections. The authors speak about Medium (Median (50%) prediction interval), High (Higher 95% prediction interval) and Low (Lower 95% prediction interval) fertility scenarii but do not propose, define or estimate accuracy for each of them. We have first think to compare current data with past projections. We can observe in the figure that the different scenarii produce significant separate results 20 to 30 years in the future. What about comparing currently measured population sizes with U.N. projections made in the 70's ?

Well, this job has already been done, with much greater details I would have hope. In 2000, the Panel on Population Projections published "Beyond Six Billion: Forecasting the World's Population", a detailed scientific study to examine official population projections: to assess their assumptions, estimate their accuracy and uncertainty (past U.N. projections did not precise the prediction interval), and evaluate the implications of current demographic research for projection procedures. This study is freely available.
The results are in short: 



Using the ex post approach and an appropriate statistical model developed after analysis of errors in international forecasts, we estimated prediction intervals for the current U.N. forecast. These intervals are constructed on the assumption that errors in current projections resemble those in past projections made after 1970. Our results suggest that the uncertainty in country projections is quite variable and is dramatically greater than suggested by U.N. high-low scenarios, with a typical 95-percent range more than twice as wide as the U.N. high-low intervals.
Regional 95-percent intervals are similarly variable but generally much narrower than country intervals. For developing regions, however, they are still consistently wider than U.N. high-low intervals. Across regions, the median 95-percent interval in 50-year projections was 40 per-cent wider than the U.N.’s high-low interval. However, prediction intervals are proportionally narrower for industrial regions and for the world as a whole. In these cases, our estimated prediction intervals are narrower than the intervals defined by the U.N. high-low scenarios. The world prediction interval also suggests a greater possibility of a downside than an upside error, making sustained population decline appear quite unlikely during the next 50 years.

2011/05/21

World population in 2050 : new revision and even more pressure on ressources

 United Nations has released this month the 2010 revision of their demographic forecast :
 9 708 595 000 is the updated number of humans in 2050 using the standard/medium fertility variant, up from 9.1 billions in the last revision.
This trend is putting even more pressure on our ressources, as described into our previous writings (MAP1, MAP2)

2010/12/04

La crisi ecologica globale è iniziata

 "Nel corso della storia, i danni causati all’ambiente e il cambiamento climatico sono tra le cause principali del crollo delle società. Una crisi ecologica mette in discussione il modello di sviluppo socio-economico, ed è dunque una crisi del modello stesso. La scala temporale in questione ci riguarda in prima persona : i fenomeni hanno preso piede, ne vedremo i primi effetti di rottura strategica durante il corso della nostra vita. E se falliremo nel risolvere questa crisi ecologica, i nostri figli o nipoti non avranno altra possibilità che subire gli effetti devastanti di questa incapacità a trasformare il nostro modello di società."
I dati utilizzati in questo articolo, per il 2010 e lo scenario di anticipazione politica fino al 2020 e il 2050, e una bibliografia aggiuntiva sarà pubblicato in allegato a questo blog:
Il seguente articolo è stato pubblicato il MAP, la rivista di anticipazione politica, che è stata completamente tradotta in italiano. La presentazione di questo primo numero di MAP è disponibile sul web del LEAP, disponibile anche in tedesco e francese... e spagnolo (aggiornato 30/01).

Die weltweite Umweltkrise hat begonnen

 "Im Laufe der Geschichte sind die Beschädigungen der Umwelt und der Klimawandel mit die wichtig-sten Gründe für den Zusammenbruch von Gesellschaften. Eine ökologische oder Umweltkrise stellt das Modell der gesellschaftlichen und wirtschaftlichen Entwicklung in Frage, ist also eine Krise dieses Modells. Der in Frage stehende Zeitrahmen betrifft in erster Linie uns: die Phänomene sind schon da, wir werden die ersten strategischen Umbrüche sehend miterleben. Und wenn wir diese Umweltkrise nicht zu lösen vermögen, bleibt unseren Kindern oder Kindeskindern nichts als die zerstörerischen Folgen unserer Unfähigkeit zur Umformung unseres Gesellschaftsmodells zu erdulden."

Der folgende Artikel wurde in den M.A.P. #1, das Magazin für Politische Antizipation, veröffentlicht.

M.A.P. wird von Anfang an in drei Sprachen (Französisch Deutsch Italienisch) erscheinen. Wir gehen davon aus, dass andere bedeutende Sprachen wie Englisch, Spanisch (aktualisiert 30/01), Russisch, Chinesisch und Arabisch bald folgen können. Denn M.A.P. soll einen möglichst großen Leserkreis unmittelbar erreichen.
Die Angaben in diesem Artikel verwendet, für 2010 und die Vorfreude Szenario bis 2020 und 2050 und ausführliche Hinweise wird als Anhänge zu diesem Blog veröffentlicht werden:

2010/11/11

La crise écologique globale publiée dans le M.A.P.

 Je publie un premier article sur la crise écologique globale dans le premier numéro du Magazine d'Anticipation Politique (M.A.P.), disponible aujourd'hui.

La crise écologique, ce n'est pas simplement HOME, les pluies acides, la fonte des pôles... c'est bien plus important que cela et il est capital de bien comprendre le destin que nous nous forgeons aujourd'hui.

Les données utilisées dans cet article, pour 2010 et pour le scénario d'anticipation jusqu'en 2020 et 2050, ainsi qu'un complément de bibliographie sont publiés comme annexes sur ce blog : 
M.A.P. est un magazine diffusé gratuitement au format PDF, édité par le Laboratoire Européen d'Anticipation Politique (LEAP) et Newropeans Magazine.
Diffusé dès l'origine en trois langues (Français-Allemand-Italien), M.A.P. devrait rapidement être disponible en d’autres grandes langues comme l’Anglais (ajouté à partir du M.A.P. n2), l’Espagnol (ajouté le 30/01 pour le M.A.P. n1 et les suivants), le Russe, le Chinois et l’Arabe (ajoutés pour le M.A.P. n6) afin de toucher directement un lectorat global. Si vous voulez contribuer à la traduction, contactez-moi ou directement l'éditeur du MAP.

Aperçu du sommaire du MAP numéro 1 : 
  •  Impacts sociaux de la crise en Europe, par Jérôme Defaix 
  • Transferts Europe-Afrique : quand la manne se tarit, par Ludovic Follot 
  •  La crise écologique globale a commencé, par Bruno Paul 
  • Amérique Latine/USA : la décennie qui confirmera l’émancipation, par Sébastien Rouxel
Je ne peux que vous recommander de vous précipiter vers cette lecture du M.A.P. !