Gary Lagerloef, earth, space, and ocean researcher, answers questions | Grist | InterActivist

Questions from Grist editors | Questions from readers

Are we seriously in danger of another mass extinction event from runaway global warming caused by the release of methane gas deposits beneath Canadian and Russian permafrost? -- Brooks Gracie, Miami, Fla.

Release of methane trapped in the permafrost is a legitimate concern as a potentially intense positive feedback that could rapidly accelerate global warming. Present atmospheric methane concentrations are less than 1 percent of carbon dioxide levels, but the methane greenhouse effect is much stronger per molecule. Additionally, methane concentrations have increased much more rapidly than CO2 since pre-industrial times, so the present net anthropogenic greenhouse forcing from methane is almost a third of that due to CO2.

The anthropogenic methane increase is mostly from agriculture and energy production. However, there are vast amounts of methane locked up in the permafrost and in sub-sea methane hydrates. Recent studies indicate early signs of increasing methane flux in areas where permafrost is now melting. These rates are apparently small relative to anthropogenic methane emissions, and the level of scientific understanding remains low regarding how quickly permafrost will melt and how quickly that will accelerate the methane flux to the atmosphere. I hope to see much more research develop on this topic because it is such an important area to watch. You can find some more background at the International Arctic Research Center, the American Geophysical Union, and these news stories.

I've heard about cities that just dump all their garbage and raw sewage right into the sea. How long before that kind of abuse affects the rest of the world's waters? Is there anything that can be done to stop this kind of behavior? -- Patti Scanlon, Simsbury, Conn.

U.S. laws enacted in the 1970s forced the regulation of raw sewage discharge and garbage dumping in our coastal waters, and have resulted in much-reduced pollution. However, these laws do not apply beyond our jurisdictions, and many other nations have no such legal restrictions. It is sad to say that this is already affecting the world's waters in profound ways. A good book to read on the subject of global ocean concerns and what might be done is Heal the Ocean by Rod Fujita.

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I truly appreciate the environmental work that you are doing. I have heard, however, that the launching of satellites and other spacecraft has very deleterious effects on the ozone layer. Can you speak to this? -- Joey Gates, Ithaca, N.Y.

It is true that launch rockets, including shuttles, spew chlorine into the stratosphere, which is the catalyst for ozone depletion. However, if you account for all the launches annually, this is a trace input (1 percent or less) relative to the flux of industrial chlorofluorocarbons (CFCs) that are depleting the stratospheric ozone.

One of the mechanisms being proposed for large-scale carbon capture and storage is a scheme that would compress carbon and inject it deep into the ocean. Is this feasible? What adverse effect could oceanic carbon sequestration have on ocean conditions such as pH and habitability? If oceanic CO2 sequestration was going to proceed anyway, what guidelines would you suggest they follow to minimize its adverse impacts? -- Jeff LeBrun, Ann Arbor, Mich.

The IPCC examined the whole range of options for CO2 sequestration, including the ocean, and the results are in a report published in 2005. The most important factor is that it must be done in a way that makes the CO2 chemically inert. Simple injection into the ocean where it can dissolve will ultimately be harmful because CO2 forms an acid when dissolved in seawater.

Already, through air-sea exchange, the ocean is absorbing about one-third to one-half the anthropogenic CO2 we put in the atmosphere. While this does slow the rate of CO2 accumulation in the atmosphere, and hence the rate of global warming, it is beginning to have a measurable effect on ocean pH levels. This has been dubbed "the other CO2 problem" and is potentially threatening to the marine ecosystem. Increased acidity impedes the ability of marine organisms to form shells, and many of the most vulnerable organisms are plankton at the base of the food chain. Learn more about ocean acidification at Real Climate and the National Oceanic and Atmospheric Administration's Pacific Marine Environmental Laboratory.

What do scientists currently know about the potential for climate change to disrupt large-scale ocean circulation, resulting in catastrophic changes for the planet? What do they forecast for the future? -- Steve Morales, Hayward, Wis.

The Atlantic Ocean meridional overturning circulation (MOC), which includes the Gulf Stream, is a major way that the ocean carries heat from the tropics to the high latitudes, moderating the climate of the Northern Hemisphere, particularly Europe. Abrupt climate cooling episodes in the geologic past have coincided with a shutting down of this circulation. However, these occurred when natural greenhouse-gas concentrations in the atmosphere were much lower than the anthropogenic levels we have today, so the overall climatic heat balance is quite different.

The model simulations being analyzed in the Fourth IPCC assessment predict that a slowing down of the MOC is very likely during the 21st century, perhaps by as much as 25 to 50 percent. However, temperatures in the Atlantic region are projected to increase despite the ocean circulation changes, because of the much more intense warming associated with projected anthropogenic GHG increases.

Oceanographic measurements of present changes in the MOC are not yet definitive. The models indicate a very low probability that the MOC will undergo a large abrupt transition during the 21st century. On the other hand, they do not factor in a catastrophic melting of the Greenland ice sheet, for example, which could supply enough freshwater to disrupt the MOC. Consequently, the IPCC concludes that longer-term changes in the MOC -- beyond the 21st century -- cannot be assessed with confidence.

If ice melt changes the North Atlantic Conveyor, what geographic areas would "benefit" based on the best model projections? -- Jim Keen, Chicago, Ill.

The issue of who will benefit depends very much on one's perspective. The impending loss of the Arctic Ocean ice cover, for example, will be a catastrophe for most Arctic species and the Native peoples, but if your only concern is open shipping lanes, it could be a boon.

Questions from Grist editors | Questions from readers

Devotion to the Ocean

Gary Lagerloef, earth, space, and ocean researcher, answers readers' questions