>it is the _change_ in heat flux which is important to compare Yes. The simplest view of the situation would make you expect the change to partially offset regional warming: with a warmer arctic, you expect less of a temperature gradient, so less heat flowing in. Otoh, more evaporation might mean stronger air circulation, bringing in more heat. I sort of figure the change could be anything as long as it's not unreasonably large relative to the current amount.
> we certainly cannot rely on such a cycle to rescue us by reducing heat flux > into the Arctic and > switching off the sea ice retreat. ... Thus the urgency for geoengineering > is, if anything, increased, taking into account > the precautionary principle. Obviously I agree. However, we can count on opponents of geoengineering to grasp at every available straw. (Actually I do expect some of the surprises to be pleasant, since I think there will be a lot of them. I just don't know which ones.) On Feb 6, 2:07 pm, "John Nissen" <[email protected]> wrote: > Talk about unpleasant surprises (see my previous posting below), look at > this: > > 'Warm everywhere' in Arctic this winter > > While parts of North America have been in the icy grips of an unusually cold > and snowy winter recently, the Arctic has been downright balmy compared to > past winters. > > http://www.msnbc.msn.com/id/29038734/from/ET/ > > (with thanks to Albert Kallio for finding this) > ---- > > 'Warm everywhere' in Arctic this winter > Expert: Dec.-Jan. temps drop, both are 'crucial ice-growing months' > > By Andrea Thompson > updated 5:13 p.m. ET Feb. 5, 2009 > While parts of North America have been in the icy grips of an unusually cold > and snowy winter recently, the Arctic has been downright balmy compared to > past winters. > > These warmer-than-normal temperatures mean that the sea ice in the Arctic is > looking pretty anemic, despite the winter season. > > Arctic ice goes through a normal cycle of summer thaw and winter re-freeze. > In recent decades, however, sea ice has become overall less extensive and > thinner, leading to forecasts that in future decades the polar region will > be ice-free during summer. The trend looks to be continuing this winter, > scientists now say. > > Climate swings in any single season are part of Nature, of course. That's > why records - warm or cold, wet or dry - get broken. For much of the United > States, this winter has been an exceptionally chilly one. > > The average temperature for the United States in December, 32.5 F, was > almost 1 degree Fahrenheit below the average for the 20th century, according > to the National Oceanic and Atmospheric Administration. Much of the West and > Midwest had a particularly frigid month, with temperatures plunging several > degrees below average. > > This winter in the Arctic has been a completely different story. > > "It's warm everywhere in the Arctic. It's anomalously warm," said Julienne > Stroeve, of the National Snow & Ice Data Center (NSIDC) in Boulder, Colo. > > Both December and January have been abnormally warm months, which impacts > the cyclical re-freezing of sea ice over the years, because these are "two > crucial ice-growing months," Stroeve told LiveScience. > > Thinner ice, more melt > Arctic sea ice hasn't been reaching its former thicknesses and extents in > recent years, especially after the dramatic meltdown observed in the summer > of 2007, which opened up the fabled Northwest Passage. (This past summer saw > the second lowest summer ice area on record.) > > That record melting - which left 30 percent less ice in the Arctic than > there was at the previous record low - caused the loss of substantial > amounts of older ice, which is thicker and generally survives the summer. > Older, thicker ice is typically 6.5 to 10 feet (2 to 3 meters) thick, while > younger ice is closer to 3 feet (1 meter) in thickness. > > Melting exposes more areas of open ocean, which absorbs incoming sunlight > that the ice would normally reflect, so there is the potential for a > snowball effect, or what scientists call self-reinforcing or feedback. Come > winter, the ice that refreezes is thinner, first-year ice, which is more > susceptible to melt in the summer, potentially exposing even more open > ocean. > > "That [thinner ice] typically can all melt out in the summer," Stroeve said. > > This year, the future > That feedback seems to be kicking in, as now "the Arctic is just more > dominated by that thinner ice," Stroeve said, adding that unless February > and March are much colder than normal, this winter's ice could end up > covering less area than normal and be thinner than even in recent years. > > So far, this winter has been warmer than last, Stroeve said, and some odd > weather patterns cropped up in both December and January that brought ice > growth to a standstill. Pauses in the regrowth of ice aren't a new > phenomenon - they have happened before, even in much colder winters - but > they only exacerbate the current situation in the Arctic by adding yet > another mechanism that stagnates ice growth. > > In January, these weather patterns created different conditions in different > parts of the Arctic. While ice grew southwest of Greenland, it retreated in > areas east of Greenland and in parts of the Barents Sea, the NSIDC reported. > > While ice is still re-freezing, ice coverage area at the end of January was > still 293,000 square miles (760,000 square kilometers) less than the > 1979-2000 average, according to the NSIDC. This didn't break the record low > for January ice area (set in 2006), but it put January 2009 in the top six. > Including this year, January ice area is declining by about 3 percent per > decade, the NSIDC reported. > > Looking further into the future, unless there are several very cold winters > and mild summers, Arctic sea ice is unlikely to bounce back in the coming > decades. > > "The idea of recovery right now seems pretty slim," Stroeve said. "You just > don't get very cold temperatures like you used to." > > Eventually, the sea ice is expected to melt out entirely in the summer, > leaving only a cover of winter seasonal ice. The NSIDC predicts that this > will happen around 2030, though Stroeve says it could happen earlier, as > indeed some other scientists predict. That it will happen seems fairly > certain: "There's no doubt in my mind about that," Stroeve said. > > ---- > > Cheers from Chiswick, where it has been unusually cold and snowy, as in > parts of N America, > > John > > ----- Original Message ----- > From: "John Nissen" <[email protected]> > To: <[email protected]> > > Cc: "geoengineering" <[email protected]> > Sent: Friday, February 06, 2009 6:43 PM > Subject: Re: [geo] Re: runaway arguments ripped to bits > > > Hi dsw_s, > > > You are right about the relative size of heat flux compared to albedo > > effect, but it is the _change_ in heat flux which is important to compare, > > e.g. any increased heat flux from the Gulf Stream entering the Arctic > > Ocean. > > > Anyway, whatever is the root cause of Arctic shrinkage, it is happening a > > lot fast than IPCC predicted only a couple of years ago, and the trend > > shows no signs of reversing. Exactly the opposite - it has shown signs of > > accelerating this decade. There are recognised to be various cycles of > > the northern hemisphere ocean-atmosphere system, but we certainly cannot > > rely on such a cycle to rescue us by reducing heat flux into the Arctic > > and switching off the sea ice retreat. > > > We can indeed expect surprises, but we cannot rely on them being pleasant > > ones! Indeed, most have been extremely unpleasant, of late. Thus the > > urgency for geoengineering is, if anything, increased, taking into account > > the precautionary principle. > > > Cheers, > > > John > > > ----- Original Message ----- > > From: "dsw_s" <[email protected]> > > To: "geoengineering" <[email protected]> > > Sent: Friday, February 06, 2009 1:04 PM > > Subject: [geo] Re: runaway arguments ripped to bits > > >>The "forcing" from the sea ice albedo effect is of the order of 30 Watts > >>per square metre, so you expect this to drive regional warming.< > > > I expect surprises. How does the total number of watts of forcing > > compare with variability in heat fluxes into and out of the region? > > What other feedbacks are there that we haven't thought about? The > > vapor pressure over ice is less than over water at the same > > temperature, and the surface of ice can be cooler than the water > > below. So evaporation will presumably be greater over open water than > > it has been historically over the sea ice. If that water condenses > > elsewhere, that's a heat flux out of the region. > > > Let's say we lose ten million square km of sea ice: that's 30 > > terawatts of forcing. But it looks as though there's over a petawatt > > of annually-averaged heat flux into the region, just by eyeballing a > > figure in a badly-out-of-date textbook. So with even a modest > > relative change in heat fluxes, the effects of the forcing could show > > up somewhere else rather than regionally. Or the regional effects > > could be an order of magnitude greater than the forcing would produce > > directly. For a conclusion about that, I would be more convinced by a > > peer-reviewed analysis of a detailed model than by the simple-and- > > obvious argument. > > > On Feb 6, 6:49 am, "John Nissen" <[email protected]> wrote: > >> Hi Andrew, > > >> It depends what kind of proof you want. I myself am convinced of things > >> if there is a logical argument based on established facts. > > >> I am convinced by anthropogenic global warming because if you put an > >> extra 100 ppm CO2 in the atmosphere, you EXPECT to have greenhouse > >> warming. I don't need "proof" to be convinced. To be persuaded otherwise, > >> I would need a convincing explanation of why the CO2 wasn't causing > >> global warming, or how this was somehow neutralised. I would need to be > >> PROVED WRONG. > > >> Similarly with methane runaway feedback. There's a vast amount of methane > >> trapped in frozen structures. Nobody disputes this fact. If you put > >> enough of this methane in the atmosphere, you expect global warming. You > >> then expect positive feedback as a result of this, as the frozen > >> structures unfreeze to release more methane until it's all gone. Unless > >> there is an argument against this logic, I will remain convinced by it. > > >> Similarly with the Arctic sea ice and domino effects. The "forcing" from > >> the sea ice albedo effect is of the order of 30 Watts per square metre, > >> so you expect this to drive regional warming. Nobody is suggesting how > >> this warming would reverse naturally. So, as the region continues to > >> warm, you expect the domino effects of methane release and Greenland ice > >> sheet accelerated discharge. > > >> This is all highly uncomfortable to contemplate, and I'd like to be > >> proved wrong. However we do have a possible way out of this situation > >> with geoengineering. So all is not lost. > > >> Please can we now persuade politicians and potential funding bodies of > >> the inescapable logic of this situation, so that > > ... > > read more » --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en -~----------~----~----~----~------~----~------~--~---
