{"id":4,"date":"2004-11-28T11:10:05","date_gmt":"2004-11-28T15:10:05","guid":{"rendered":"\/?p=4"},"modified":"2007-02-25T09:22:48","modified_gmt":"2007-02-25T14:22:48","slug":"forcings","status":"publish","type":"post","link":"https:\/\/www.realclimate.org\/index.php\/archives\/2004\/11\/forcings\/","title":{"rendered":"Forcings For\u00e7ages<\/lang_fr>"},"content":{"rendered":"
\n

Forcings in the climate sense are external boundary conditions or inputs to a climate model. Obviously changes to the sun’s radiation are external, and so that is always a forcing. The same is true for changes to the Earth’s orbit (“Milankovitch cycles”). Things get a little more ambigous as you get closer to the surface. In models that do not contain a carbon cycle (and that is most of them), the level of CO2<\/sub> is set externally, and so that can be considered a forcing too. However, in models that contain a carbon cycle, changes in CO2<\/sub> concentrations will occur as a function of the climate itself and in changes in emissions from industrial activity. In that case, CO2<\/sub> levels will be a feedback, and not a forcing. Almost all of the elements that make up the atmosphere can be considered feedbacks on some timescale, and so defining the forcing is really a function of what feedbacks you allow in the model and for what purpose you are using it. A good discussion of recent forcings can be found in Hansen et al (2002)<\/a> and in Schmidt et al (2004)<\/a>.<\/p>\n

Les for\u00e7ages aux sens climatique du terme, correspondent aux conditions aux limites ou “entr\u00e9es” (input<\/i> du mod\u00e8le climatique. Les changements de rayonnement solaire sont \u00e9videmment externes, de telle mani\u00e8re qu’ils forment toujours un for\u00e7age. C’est \u00e9galement vrai pour les changements de l’orbite terrestre (“Cycles de Milankovitch”). Par contre, cette d\u00e9finition est plus ambigu\u00eb quand on se rapproche de la surface de la plan\u00e8te. Dans les mod\u00e8les n’incluant pas le cycle du carbone (c’est a dire la majorit\u00e9), la concentration du CO2 est fix\u00e9e en externe, ce qui peut donc \u00eatre consid\u00e9r\u00e9 comme un for\u00e7age \u00e9galement. Par contre, dans les mod\u00e8les qui incluent le cycle du carbone, les changements de concentration en CO2 seront fonction du climat et des changements li\u00e9s a l’activit\u00e9 industrielle. Dans ce cas, les niveaux de CO2 seront des r\u00e9troactions, et non pas des for\u00e7ages. Presque tous les \u00e9l\u00e9ments constitutifs de l’atmosph\u00e8re peuvent \u00eatre consid\u00e9r\u00e9es comme des r\u00e9troactions, et donc d\u00e9finir un for\u00e7age est r\u00e9ellement d\u00e9pendant des r\u00e9troactions possibles dans le mod\u00e8le, et dans quel but il est utilis\u00e9. Une bonne discussion des for\u00e7ages r\u00e9cents peut \u00eatre trouv\u00e9e dans Hansen et al (2002)<\/a> et dans Schmidt et al (2004)<\/a>.<\/lang_fr><\/p>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

Forcings in the climate sense are external boundary conditions or inputs to a climate model. Obviously changes to the sun’s radiation are external, and so that is always a forcing. The same is true for changes to the Earth’s orbit (“Milankovitch cycles”). Things get a little more ambigous as you get closer to the surface. […]<\/p>\n","protected":false},"author":12,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"_genesis_hide_title":false,"_genesis_hide_breadcrumbs":false,"_genesis_hide_singular_image":false,"_genesis_hide_footer_widgets":false,"_genesis_custom_body_class":"","_genesis_custom_post_class":"","_genesis_layout":"","footnotes":""},"categories":[6],"tags":[],"class_list":{"0":"post-4","1":"post","2":"type-post","3":"status-publish","4":"format-standard","6":"category-glossary","7":"entry"},"aioseo_notices":[],"post_mailing_queue_ids":[],"_links":{"self":[{"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/posts\/4","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/users\/12"}],"replies":[{"embeddable":true,"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/comments?post=4"}],"version-history":[{"count":0,"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/posts\/4\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/media?parent=4"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/categories?post=4"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.realclimate.org\/index.php\/wp-json\/wp\/v2\/tags?post=4"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}