Jordas albedo

Fra Judith Curry’s utmerkede vitenskapsblogg henter vi omtale av ny og viktig forskning. Albedo er andelen av innkommende lys eller stråling som er reflektert av en planets overflate. Albedo er et vitalt element av vårt klima og enda et element i en etterhvert bedrøvelig lang rekke som klimamodellene ikke fikser. Eksempler på at vi endrer albedoen på et lite stykke jordoverflate får vi hver gang vi hugger ned en skog og anlegger en flyplass – eller planter humle. I likhet med Judith Curry fikk redaksjonen seg noen overraskelser i løpet av gjennomlesningen.

image3Dette ble publisert i går i AGU-journalen Reviews of Geophysics og du finner orginalen her.

Forfattere er Graeme L. Stephens, Denis O’Brien, Peter J. Webster, Peter Pilewski, Seiji Kato, and Jui-lin Li.

Abstract. The fraction of the incoming solar energy scattered by Earth back to space is referred to as the planetary albedo. This reflected energy is a fundamental component of the Earth’s energy balance, and the processes that govern its magnitude, distribution, and variability shape Earth’s climate and climate change. We review our understanding of Earth’s albedo as it has progressed to the current time and provide a global perspective of our understanding of the processes that define it. Joint analyses of surface solar flux data that are a complicated mix of measurements and model calculations with top-of-atmosphere (TOA) flux measurements from current orbiting satellites yield a number of surprising results including (i) the Northern and Southern Hemispheres (NH, SH) reflect the same amount of sunlight within ~ 0.2Wm2. This symmetry is achieved by increased reflection from SH clouds offsetting precisely the greater reflection from the NH land masses. (ii) The albedo of Earth appears to be highly buffered on hemispheric and global scales as highlighted by both the hemispheric symmetry and a remarkably small interannual variability of reflected solar flux (~0.2% of the annual mean flux). We show how clouds provide the necessary degrees of freedom to modulate the Earth’s albedo setting the hemispheric symmetry. We also show that current climate models lack this same degree of hemispheric symmetry and regulation by clouds. The relevance of this hemispheric symmetry to the heat transport across the equator is discussed.

Dere vet hvor dere finner resten. For de som har tid, debatten raser hos Judith Curry.

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