Archive for 4 febbraio 2013


sn-erosion

Who says Earth’s not flat? Even though more than half of the planet’s ice-free terrain has a slope of 0.6° or less, where water flow is generally languid, a significant part of the world’s erosion takes place there, a new study reveals. By analyzing river sediments collected at thousands of locations worldwide and estimating their concentration of the isotope beryllium-10 (which is produced when cosmic rays strike rocks at or near Earth’s surface), researchers could assess rates of erosion in those watersheds. For watersheds with areas ranging between 1 and 10,000 square kilometers, rates of erosion were strongly correlated with the average steepness of the watershed when that slope exceeded 11.3° (a rise of 200 meters for every horizontal kilometer). Rates of erosion were less predictable in more gently sloping landscapes, but data suggest that the breakdown of rocks in ice-free terrain creates about 5.5 billion tons of sediment worldwide each year, the researchers report in a forthcoming issue of Geology. Although erosion can remove as much as 6 meters of material in mountainous areas (such as in the Grand Tetons in the above background) each millennium, in gently sloping areas (foreground) wind and water may strip away as little as 0.5 millimeters per year. Overall, at least half Earth’s surface loses about 12 millimeters or more to erosion every 1000 years, the team estimates. Altogether, about 80% of the world’s sediment is produced by erosion of terrain with a slope of 6° or less.

credits: Science by Sid Perkins on 1 February 2013

photo credit : Jon Sullivan

Interesting paper that shows a positive impact of warming up to 2.0C and a negative impact afterwards, suggesting that some warming is beneficial, but a lot of warming is not. tnx to WUWT and Richard T. and Lomborg B.

Watts Up With That?

I thought this paper was interesting, and it was (as part of a Twitter exchange) sent to me by request (thanks to Both Richard Tol and Bjørn Lomborg). I found figure 8 (shown below as part of the preview on Science Direct) to be interesting because it shows a positive impact of warming up to 2.0C and a negative impact afterwards, suggesting that some warming is beneficial, but a lot of warming is not. All things in moderation I suppose. – Anthony.

Abstract

A survey of the economic impact of climate change and the marginal damage costs shows that carbon dioxide emissions are a negative externality. The estimated Pigou tax and its growth rate are too low to justify the climate policy targets set by political leaders. A lower discount rate or greater concern for the global distribution of income would justify more stringent climate policy, but would imply an…

View original post 925 altre parole