Guest commentary by Alan Robock – Rutgers University
Bjorn Lomborg’s Climate Consensus Center just released an un-refereed report on geoengineering, An Analysis of Climate Engineering as a Response to Global Warming, by J Eric Bickel and Lee Lane. The “consensus” in the title of Lomborg’s center is based on a meeting of 50 economists last year. The problem with allowing economists to decide the proper response of society to global warming is that they base their analysis only on their own quantifications of the costs and benefits of different strategies. In this report, discussed below, they simply omit the costs of many of the potential negative aspects of producing a stratospheric cloud to block out sunlight or cloud brightening, and come to the conclusion that these strategies have a 25-5000 to 1 benefit/cost ratio. That the second author works for the American Enterprise Institute, a lobbying group that has been a leading global warming denier, is not surprising, except that now they are in favor of a solution to a problem they have claimed for years does not exist.
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.
Guest commentary by Ron Miller, NASA GISS
Several studies have shown that hurricane activity is generally reduced during years when there is a thick aerosol haze over the subtropical Atlantic. The haze is comprised mainly of soil particles, stripped by wind erosion from the barren ground over the Sahara and Sahel. These particles are lifted into the atmosphere and carried by the Trade winds as far as the Caribbean and Amazon basin. Plumes of dust streaming off the African coast are easily recognized in satellite imagery, and were even described by Charles Darwin during his voyage on the Beagle.
Guest post from Drew Shindell, NASA GISS
Our recent paper “Climate response to regional radiative forcing during the twentieth century”, has generated some interesting discussion (some of it very ‘interesting’ indeed). So this post is an attempt to give a better context to the methods and implications of the study.
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.
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.
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