<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><div>On Dec 21, 2010, at 10:32 PM, Keith Henson wrote:</div><blockquote type="cite"><div><font class="Apple-style-span" color="#000000"><br></font>The best way I see is to come up with an energy source considerably<br>less expensive than fossil fuels. </div></blockquote><div><br></div>That would be a great way to cure global warming but unfortunately nobody has figured out how to make a cheap clean substitute for fossil fuels yet, nobody has figured out a cure for CO2 emissions (if that is indeed the cause of the problem) that is not worse than the disease. So until somebody dose figure that out and if the problem is really as catastrophic as the doomsayers say it is then we'd better have another idea; and Nathan Myhrvold, the former chief technical officer at Microsoft, may have one, build an artificial volcano. </div><div><br></div><div>Mt Pinatubo in 1991 became the best studied large volcanic eruption in history, it put more sulphur dioxide into the stratosphere than any volcano since Krakatoa in 1883. There is no longer any dispute that stratospheric sulphur dioxide leads to more diffuse sunlight, a decrease in the ozone layer, and a general cooling of the planet. What was astonishing was how little stratospheric sulphur dioxide was needed. If you injected it in the arctic where it would be about 4 times more effective, about 100,000 tons a year would reverse global warming in the northern hemisphere. That works out to 34 gallons per minute, a bit more than what a standard garden hose could deliver but much less than a fire hose. We already spew out over 200,000,000 tons of sulphur dioxide into the atmosphere each year, but all of that is in the lower troposphere where it has little or no cooling effect, the additional 100,000 tons is a drop in the bucket if you're looking at the tonnage, but it's in the stratosphere where its vastly more effective.</div><div><br></div><div>Myhrvold wasn't suggesting anything as ambitious as a space elevator, just a light hose about 2 inches in diameter going up about 18 miles. In one design he burns sulfur to make sulphur dioxide, he then liquefies it and injects it into the stratosphere with a hose supported every 500 to 1000 feet with helium balloons. Myhrvold thinks this design would cost about 150 million dollars to build and about 100 million a year to operate. In another design that would probably be even cheaper he just slips a sleeve over the smokestack of any existing small to midsize coal power plant in the higher latitudes and uses the hot exhaust to fill hot air balloons to support the hose. </div><div><br></div><div>If Myhrvold's cost estimate is correct that means it would take 50 million dollars less to cure global warming than it cost Al Gore to just advertise the evils of climate change. But even if Myhrvold's estimate is ten times or a hundred times too low it hardly matters, it's still chump change. In a report to the British government economist Nicholas Stern said that to reduce carbon emissions enough to stabilize global warming by the end of this century we would need to spend 1.5% of global GDP each year, that works out to 1.2 trillion (trillion with a t) dollars EACH YEAR.</div><div><br></div><div>One great thing about Myhrvold's idea is that you're not doing anything irreparable, if for whatever reason you want to stop you just turn a valve on a hose and in about a year all the sulphur dioxide you injected will settle out of the atmosphere. And Myhrvold isn't the only fan of this idea, Paul Crutzen won a Nobel prize for his work on ozone depletion, in 2006 he said efforts to solve the problem by reducing greenhouse gases were doomed to be “grossly unsuccessful” and that an injection of sulphur in the stratosphere “is the only option available to rapidly reduce temperature rises and counteract other climatic effects”. Crutzen acknowledged that it would reduce the ozone layer but the change would be small and the the benefit would be much greater than the harm.</div><div><br></div><div>And by the way, diffuse sunlight, another of the allegedly dreadful things associated with sulphur dioxide high up in the atmosphere, well..., plant photosynthesis is more efficient under diffuse light. Plants grow better in air with lots of CO2 in it too, but that's another story.</div><div><br></div><div> John K Clark </div><div><br></div><div><br></div><div><i><span class="Apple-style-span" style="font-style: normal; "><br></span></i></div><div><br></div><div><p><br></p></div><div><br></div><div><br></div><div><br></div><div> </div><div><p><br></p></div></body></html>