A group of 13 marine scientists* from 12 different institutions in the United States and Germany have in Science criticised a January publication in that same journal, which stated ‘almost all’ of the spilled methane had been consumed by microbes, within 120 days of the spill.

Although their criticism of that research is quite wide-ranging, in their comments, published on Thursday, the scientists especially disagree with the interpretation of [low] oxygen levels as an indicator of [large] amounts of converted methane – as they say low oxygen levels are typical for large parts of the deep water of the Gulf of Mexico.

Methane feedback relevance

It is an important debate, the authors say, because it has ramifications for other scenarios with methane leakages from the deep sea bottoms, as could for instance be the case with a possible ‘melting’ of gas hydrates due to ocean warming.

If microorganisms consume methane, most of the carbon will eventually reach the atmosphere as [relatively harmless] CO2. If not, over time the methane bubbles will break through to the surface and act as a much more powerfull atmospheric greenhouse gas themselves.

PETM methane warning

Paleoclimate studies show this positive feedback to climate change can be important and devastating, as it is held responsible for the mass extinction that followed a ‘sharp’ [some 6 degrees over 10,000 years 20,000 years] temperature rise known as the Paleocene Eocene Thermal Maximum (PETM), 55 million years ago.

(The PETM case is convincing and should present a clear warning about the possibility of methane escalation. That does not mean methane is always the driver of ‘natural climate forcing’ events. A theory about another possible methane-induced climate warming 635 million ago, so almost out of geological sight, has recently been debunked.)

[*) The lead author of the critical post in Science is Samantha Joye of the Department of Marine Sciences of the University of Georgia. We have to admit we don’t have all our articles peer-reviewed – but to compensate for that we can be a good deal faster in providing Joye with a platform for her critical notes.]

© Rolf Schuttenhelm | www.bitsofscience.org