Author: oliveridley

The Beeb does it again. Best use of simple graphics to clearly explain science.

1. Surface currents carry warm, salty water from the tropics.
2. The water cools, its density increases and it sinks to the deep ocean.
3. The cold water flows back to the equator, driving the “ocean conveyor” which in turn contributes to the Gulf Stream that warms northern Europe.
4. As ice melts, freshwater dilutes the warm salty water from the tropics.
5. The water becomes less dense so does not sink as fast, weakening the “conveyor” and therefore possibly disrupting the Gulf Stream.

Gulf Stream

Dramatic temperature shifts have happened in the past, driven partly by changes in a major ocean currents.

A “great ocean conveyor” helps transport heat around the globe via surface and deep-sea movements of water.

Scientists are exploring whether global warming might slow or shut it down – a scenario considered “low probability, high impact”.

This could disrupt mostly wind-driven surface currents such as the Gulf Stream, which brings milder weather to Northern Europe.

Low Probability, High impact indeed, aka the “Hell Freezes Over” Scenario. The Gulf Stream example is one of my favorites, check all the other animation out, it is great.

Check out this story from the January 26, 2006 LA Times.

In a rare move to phase out a widely used industrial compound, the Environmental Protection Agency announced Wednesday that it was asking all U.S. companies to virtually eliminate public exposure to a toxic chemical used to make Teflon cookware and thousands of other products.

EPA’s system of regulating chemicals leads to some really perverse incentives. The burden of proof shifts to the EPA to prove beyond reasonable doubt that a chemical has definite harmful effects on humans at ambient exposure levels. So the preferred route has been for the EPA to “suggest” to the companies to participate in a voluntary phaseout.

No one knows how the chemical is getting into people’s bloodstreams and in the bodies of polar bears and other animals. Although it is used in production of cookware, it is not found in the cookware, clothing and other fluoropolymers after manufacture.

Well, not quite. This from a paper published in the Environmental Science and Technology on January the 25th.

Polyfluorinated telomer alcohols and sulfonamides are classes of compounds recently identified as precursor molecules to the perfluorinated acids detected in the environment. Despite the detection and quantification of these volatile compounds in the atmosphere, their sources remain unknown. Both classes of compounds are used in the synthesis of various fluorosurfactants and incorporated in polymeric materials used extensively in the carpet, textile, and paper industries. This study has identified the presence of residual unbound fluoro telomer alcohols (FTOHs) in varying chain lengths (C6-C14) in several commercially available and industrially applied polymeric and surfactant materials…

This study suggests that elimination or reduction of these residual alcohols from all marketed fluorinated polymers and fluorosurfactants is key in reducing the prevalence of perfluorinated acids formed in the environment.

Well, that explains it a little better, this article from ES&T provides a nice executive summary like context.

An emerging theory that explains how PFOA (perfluorooctanoic acid) and other PFCAs (perfluorocarboxylic acids) have contaminated the Arctic has received a boost from a new modeling study published in this issue of ES&T (pp 924–930). The theory contends that Arctic contamination is due to atmospheric transport and breakdown of fluorotelomer alcohols, chemicals that are used in products that include stain protectors, microwave-popcorn bags, fast-food wrappers, polishes, and paints.

Well, it sure looks like we need to focus much more on the PFOA precursors rather than on the PFOA itself. Dupont and 3M are not going to be happy about that!