Old 13th Oct 2019, 13:06
  #23 (permalink)  
Lord Farringdon
 
Join Date: Mar 2014
Location: Auckland nz
Posts: 95
Originally Posted by tdracer View Post
The data is very limited and largely circumstantial, however there is some evidence that - in the immediate aftermath of 9/11 - the grounding of virtually all commercial air traffic over the continental US resulted in slightly lower temperatures. Some researchers suspect the reduction in water vapor being injected into the upper atmosphere by all those grounded aircraft was responsible.
That the average ground temperatures dropped slightly is pretty much certain, cause and effect is rather more questionable (particularly with a single data point).
Interesting stuff td. Perhaps worthy of more research by scientists.

Aircraft and engine manufacturers have come a long way in reducing emissions but the capability to keep doing this without some radical new technology that is both practical and economically viable, means any future reductions are likely to incrementally much smaller than has currently been the case. But despite all that has been done to reduce engine emissions the contribution to greenhouse gases from aviation continues to climb as a result of increasing demand for air travel. Calls by the environmentalists to effectively ban air travel or heavily tax it are just not the answer. You cant un-invent the wheel (or in the case the wing!). Asking business and liesure sectors to limit their travel is more sensible and more doable. However voluntary buy-in is hard and limited. So, if scientists could actually prove a connection between the 9/11 grounding event and reduced temperatures, and could quantify what that would actually mean to temperatures across the big emitters of China, the USA and Europe, then aviation could in fact be part of the climate change solution. How? By mandating flightless days!

Imagine no fly days across the world on for example Wednesday and Sundays. In big hairy audacious numbers that's about a 30 percent reduction in greenhouse gasses caused by aviation activity. This doesn't require new technology, alternative fuels, onerous carbon taxes, elimination of incentives to fly such as air points programmes or complete bans on flying. It would of course have an impact on world economies and certainly airline economies. But that would be in the form of a one off adjustment, albeit a bit painful in places. Yes, all the Wednesday and Sunday travelers would book on the other days and initially create chaos but adjustments would eventually be made. That thrice weekly meeting that required air travel would eventual settle down to Monday and Friday meetings with a video conference on Wednesdays. The world and it's economies would slow but not stop because they would simply adapt to the longer leads times. That Fedex carton is going to be six days away, not four!

Asking business and holiday makers to reduce their travel is not new. But realistically, relying on voluntary personal choices and social pressure just doesn't seem to do it. So this cannot be voluntary and it cannot be done unilaterally since that would give immediate economic advantage to non-participants. It must be a UN agreed solution and then implemented by ICAO and its treaties. It's either everyone, or no one.

So, huge political hurdles and many practical issues to overcome if this was to work but, we are either serious about human activity causing undesirable climate change .. or we're not.

Other than offering a cloudless night which is always a little cooler, I'm not sure how the 9/11 event would achieve measurable cooling in 1 day across the US when aviation is only contributing about 4 percent of carbon emissions globally. But whether this is true or not, and in answer to the question that the title of this thread raises, mandated flightless days would almost instantly create and achieve significant contributions to the reduction of aviation induced greenhouse gases.There is nothing else radical enough to do it.

But if the question is, what cost to our economies would such a radical action be, then the answer may be in a corollary question. What is the cost to the planet if we don't take such action?
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