In a new GRL paper, Svensmark et al., claim that liquid water content in low clouds is reduced after Forbush decreases (FD), and for the most influential FD events, the liquid water content in the oceanic atmosphere can diminish by as much as 7%. In particular, they argue that there is a substantial decline in liquid water clouds, apparently tracking a declining flux of galactic cosmic rays (GCR), reaching a minimum days after the drop in GCR levels. The implication would be that GCR can affect climate through modulating the low-level cloudiness. The analysis is based on various remote sensing products.
Still not convincing
ACRIM vs PMOD
Classé dans: — rasmus @ 6 mai 2009 - (
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) () Two recent papers (Lockwood & Fröhlich, 2008 – ‘LF08′; Scafetta & Willson, 2009 – ‘SW09′) compare the analysis of total solar irradiance (TSI) and the way the TSI measurements are combined to form a long series consisting of data from several satellite missions. The two papers come to completely opposite conclusions regarding the long term trend. So which one (if either) is right, then? And does it really matter?
Aerosol effects and climate, Part II: the role of nucleation and cosmic rays
Guest post by Bart Verheggen, Department of Air Quality and Climate Change , Energy research Institute of the Netherlands (ECN)
In Part I, I discussed how aerosols nucleate and grow. In this post I’ll discuss how changes in nucleation and ionization might impact the net effects.
Cosmic rays
Galactic cosmic rays (GCR) are energetic particles originating from space entering Earth’s atmosphere. They are an important source of ionization in the atmosphere, besides terrestrial radioactivity from e.g. radon (naturally emitted by the Earth’s surface). Over the oceans and above 5 km altitude, GCR are the dominant source. Their intensity varies over the 11 year solar cycle, with a maximum near solar minimum. Carslaw et al. give a nice overview of potential relations between cosmic rays, clouds and climate. Over the first half of the 20th century solar irradiance has slightly increased, and cosmic rays have subsequently decreased. RC has had many previous posts on the purported links between GCR and climate, e.g. here, here and here.
The Younger Dryas comet-impact hypothesis: gem of an idea or fool’s gold?
There was a paper in Science last week that has gotten quite a bit of press. It reports further evidence in support of the idea that the Younger Dryas — a distinct period towards the end of the last ice age when the deglaciation in the Northern Hemisphere was interrupted for a period of about 1300 years — was caused by a barrage of comets hitting North America.
When the first papers on this came out last year, we expressed skepticism. We remain skeptical and our reasons remain unchanged. But we think it is worth saying a bit more on this, because the reporting on this issue has largely ignored just how big an idea this is, and therefore how much more work would need to be done before it could be taken very seriously.
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Ozone holes and cosmic rays
Browsing through the blogosphere recently, I came across an interesting little story about the scientific method, scientific progress, and un-scientific spin (h/t Hank Roberts). The subject concerns the polar ozone hole in Antarctica and a possible role for cosmic rays in its variability on solar cycle timescales. The proponents of this link are a small research group at the University of Sherbrooke in Canada, who find themselves up against the mainstream stratospheric chemistry community and whose ideas are twisted out of all recognition by the more foolish of the usual suspects.
