I thought I'd make my first post about the event that
inspired this blog. In April 2010 the Eyjafjallajökull Volcano in Iceland erupted, spewing millions of tonnes of
ash into the air. The ensuing ash cloud which engulfed northern Europe forced
twenty countries to close their airspace, grounding hundreds of thousands of
flights.
What was bad news
for tourists was a once in a lifetime opportunity for scientists. Previously
they could only postulate the effects of such a large scale change to aviation
– now they could observe it firsthand.
David McCandless produced this marvelous diagram for his information is
beautiful website to illustrate the
carbon dioxide offset by all those grounded flights. He references his sources
here.
Let's take the
idea one step further. Instead of European flights, what would be the impact of
grounding all the flights in the world? (on a side note, the video below- an animation of all the flights in the world - makes fascinating viewing).
Each year, 165
member countries report their greenhouse gas emissions the United Nations
Framework Convention on Climate Change. The World Resources Institute (WRI), a
global environmental think tank, compile this data to produce a comprehensive
database of global emissions. According to the WRI, 1.6% of global greenhouse gas
emissions are from aviation. So the impact of not flying would be
relatively small right?
Not quite.
Aviation emissions have a threefold effect. Firstly, there's the direct emissions.
Next, the high concentrations of nitrous oxides emitted by planes induce the
formation of ozone, another greenhouse gas, which causes further warming. Finally,
aircraft contrails - water vapour tracks drawn in their wake - are thought to
induce clouds which further enhance warming. Once these two additional effects
are taken into account, the IPCC estimates
aviation accounts for 3.5% of total global emissions.
It's still only 3.5% - so why all the fuss about aviation?
It's because of the rate at which aviation emissions are
increasing. The aviation industry has grown 9% year on year since 1960. So stop
aviation now and you'll be stubbing out a major future emissions source.
There's so much more I wanted to cover in this post. In reality - grounding flights would have far too detrimental an effect on the economy to seriously be considered. The Department for Transport estimates the aviation industry empolys 220,000 people and contributes £16 billion to the UK economy alone.
ReplyDeleteI also spotted this paper
(http://www.sciencedirect.com.libproxy.ucl.ac.uk/science/article/pii/S1352231012001355)
The Eyjafjallajökull eruption had a measurably positive impact on air quality near Heathrow.
What's the paper reference? The link you posted tries to go through the UCL portal.
DeleteSorry Simon - here's the correct link http://www.sciencedirect.com/science/article/pii/S1352231012001355
DeleteI remember reading some research about the effect of the closure of US airspace after 9/11....the lack of planes in the sky (and the reflective contrails/clouds they produced) temporary increased temperatures. Here's the story:
ReplyDeletehttp://www.nature.com/news/2002/020808/full/news020805-7.html#B1
Great article Alex - thanks for posting.
DeleteIt's interesting that the article states contrails have a greater warming effect than cooling effect. If this was the case you'd expect the absence of contrails to have an overall cooling effect no?
My suspicion (and I'm no expert) is that it's down to the difference in timescales between the cooling and warming effects. I reckon the cooling effect of reflecting sunlight acts on a much shorter timescale than the long term warming effect of additional clouds.
So, remove the cooling effect and they'll be an immediate, noticeable warming. Remove the warming effect and a steady cooling will occur that might not be measurable on such short timescales. I'll have a dig around, see if I can find some papers that might hint either way.
First of all, fantastic blog. Really fascinating to read. In reference to your point about aircraft contrails inducing clouds which are thought to enhance warming, I just wanted to quote something I read in the 22 September 2012 edition of New Scientist:
ReplyDelete"Clouds have complex effects on Earth's heat budget, reflecting some incoming sunlight and trapping a lot of outgoing infrared radiation. Lower-altitude clouds such as marine stratus also radiate a lot of heat from their tops out into space, so overall they cool the planet. Icy cirrus clouds radiate much less heat, so their net effect is to warm us up."
Do you know what sort of clouds planes induce?
Thanks Jess - perhaps you might like to post a link to your blog too...
DeletePlanes produce cirrus clouds. As you say above... "cirrus clouds radiate much less heat, so their net effect is to warm us up."