Stock market crash hits EGU General Assembly shocker!

Here’s the second of my GeoLog guest blogs about the EGU General Assembly 2012, which originally appeared here on 2 May 2012.

It seems the global economic downturn is so pervasive that it has even hit the Earth sciences! I’ve been to a few talks now that have mentioned the downturn/recession/crisis/apocalypse (delete as appropriate), mainly with reference to emissions of pollutant species or greenhouse gases. I guess this is one of the few good-news stories to come from the bottom falling out of the world’s economy. With no money to burn, production and therefore emissions decreased, thus slowing emissions – ever so slightly.

On Tuesday, Jintai Lin presented some work on NO2 columns measured from space, which he used to back out the NO2 emissions coming from China. (NO2 is itself toxic, and a precursor for ozone, which is a greenhouse gas and is harmful for animal and plant health.) His analysis of the seasonal variation in NO2 showed that the emissions were dominated by anthropogenic sources. Presenting a time series of NO2 columns from satellites, he showed the unmistakable signal from the Chinese economic downturn in 2008-9 (see figure 3 in Lin and McElroy 2011, ACP), and he showed the same signal in aerosol optical depth (a marker for PM2.5 – see my immediately previous blog post for a definition). But this was not to last, as the NO2 caught up again after about a year and a half.

Gratuitous pretty satellite picture alert! Evidence of urbanisation is evident in these two images from 1999 acquired by the Landsat Thematic Mapper, and from 2008 acquired by ASTER. (Credit: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team )

Then on Wednesday, Patricia Castellanos showed a similarly striking graph of a stock index (I didn’t catch which one) on the same axes as measures of European industrial activity and road transport. As you might have guessed, they correlated perfectly, all dropping off the edge of a cliff over the space of a few months in 2008. By dropping off a cliff, I mean a 20% decrease in industrial activity and 15% decrease in commercial road transport. Castellanos summarised this effect with what I found to be a surprising finding: NOx is 10-50% lower now than it was in 2004 (that’s not the surprising bit), and at least half of this reduction was due to the recession.

So, for all the EU’s hard work in making policies and targets for air quality, in regulating vehicle emissions and all the other things they are doing to improve the air we breathe, it has at most been as “good” as the recession for reducing NO2 levels. If they are really serious about air quality, policy makers would be wise to reconsider their attitude to economic growth…

Megacities at EGU 2012

I recently attended the EGU’s General Assembly in Vienna (great conference, guys!), and wrote some posts for their GeoLog blog. Here’s the first, which originally appeared here on 26 April 2012.

Almost a whole day’s worth of sessions on megacities – where to begin? I certainly couldn’t pick just one talk to write about, so here’s a mish-mash of the session in general and a few talks in particular.

First things first: what is a megacity? Officially defined (by who, I don’t know) as a city of 5 million people or more, there are only two of them in Europe (London and Paris), and both are among the most polluted cities in Europe. There are other European places that embody megacity characteristics without adhering to the strict definition, so the MEGAPOLI project has focused on two of these alongside the two bona-fide megacities. The Po Valley in Italy, surrounded by mountains on three sides, is populated by 16 million people and contains 37% of the country’s industry. The mountains disrupt the large-scale meteorology so that local winds are often slack, which combines with the high levels of industrial, agricultural and residential emissions to cause worse air quality than in either Paris or London.

Loss in life expectancy (months) attributable to exposure to anthropogenic PM2.5 for year 2000 emissions (Source: EC, IIASA)

The air quality is similarly poor in the Rhine-Ruhr valley in Germany, an industrial region with about 10 million inhabitants. This region suffers not only from local emissions, but often from pollution transported from London, Paris and the Netherlands in the prevailing winds. (Thanks to the MEGAPOLI website for the info about these locations).

The reasons why these non-megacities have been brought into the fold highlight the complexities of trying to understand what might happen in the coming years as the world becomes increasingly urbanised. It’s not only the amount of stuff being pumped into the atmosphere that causes air quality issues. It’s equally how much stuff gets vented out of the boundary layer (the lowest layer of the atmosphere, where people live), and how much gets washed out in rain. And what happens to the stuff before it gets removed? And this is not even considering the climate impacts of all this stuff is getting higher up into the atmosphere, where it has a longer lifetime and can be transported long distances, potentially also affecting air quality downwind. All these interactions could be broadly categorised into: emissions, boundary layer meteorology, deposition, chemistry, global transport, and climate.

Several talks in the session were related to emissions evaluations, as how can we hope to understand anything if we’re putting the wrong amount of stuff into the atmosphere? Any by “stuff”, I mean NOx (the sum of NO and NO2, which are pollutants emitted from both anthropogenic and natural sources, and can react to produce ozone, which has adverse health effects) and particulates (the shorthand for particulate matter is PM2.5/PM10 for those with a radius less than 2.5/10 microns, also bad for health), as these were the main topics in the session.

Generating emissions inventories is no trivial task, as is evidenced by the continual work going in to this area. In his talk, S Sahu described the development of an emissions inventory for Delhi and the surrounding areas, which is home to a staggering 30 million people in an area of 70 km x 65 km. For 6 months, an army of 250 students surveyed the residents and businesses to determine a sample of the emission-generating activity in the region. They combined this new data with the existing literature and government statistics to develop a GIS-based emissions inventory. Their results showed that there are 5.7 million vehicles on the roads, and 1.5 million living in slums and cooking with wood, kerosene or LPG (in order of decreasing precedence). The PM2.5 emissions total was 68.1 Gg/year, the largest portion of which was from transport at 30.25 Gg/year. Wind-blown dust and residential emissions were also large contributors. The inventory was used to forecast for the Commonwealth games in 2010 and is currently available for both science and policy uses.

Policy issues were the driver behind R Friedrich’s talk, which directly addressed questions of whether air quality policies could result in the desired policy outcome – surely an important factor in decision-making. As part of the EU MEGAPOLI project, his work took a “full chain approach”, whereby the scenario with and without the policy measure was modeled to determine the effectiveness of a policy. The reference scenario assumes the current EU energy and climate package was taken forward. Then each policy was added to the model, and the difference can be described in monetary terms or by DALYs (disability adjusted life years).

The study generated some surprising results. Twenty four policy measures were ranked in terms of avoided DALYs for Paris, and the best measure by this metric was to change to efficient combustion of gaseous fuels (which generate less PM than wood), followed by biomass fuels. However, different metrics paint a different picture. Calculating the efficiency of each measure in monetary terms put coke dry quenching (as opposed to wet quenching which generates PM) in the top spot, followed by use of biofuels, use of district-wide heating networks, an aviation kerosene tax and a switch to electric vehicles. The least efficient measure was a passenger car toll (which, for example, London has had since 2003). Interestingly, the implementation of a low emissions zone was shown to have a negative or neutral effect. On the other hand, the speaker recommended the improvement of traffic management as an efficient measure.

Another EU project, CityZEN, also linked the science with policy needs by producing some 2 page policy briefs on ozone, PM, observations and the East Mediterranean air pollution hotspot, and was discussed by several speakers. Other talks and poster covered the links between meteorology and chemistry, observations and models, but I’m afraid this is all I have time for… See you next time, on the GeoLog.

What do I do all day?

Science in action! Well, maybe "in progress" would be more accurate...

I ask myself this question frequently, usually when I review my to-do list, and wonder how I’ve managed to take so much longer to complete the tasks than I originally planned. Today, for example, I spent the whole day working on a program that will automatically plot some nice histograms of my data. I hadn’t intended to spend the whole day on doing just this, but once I started, it just seemed to eat up the whole day. Worse, the program still isn’t finished! Maybe it’s a problem peculiar to IDL (it is a rather long winded programming language, but you can make pretty plots with it). But I doubt it. IDL just makes it even easier for a small task to take up your whole life. But just think of the pretty pictures it makes!

In fact, the pretty picture bit wasn’t taking the time. It’s the handling of the data, and making the code flexible so that I can feed it a whole bunch of different data, and ask it to sort it in different ways, and to plot it sensibly, all at the touch of a button. So I’m just spending my time up front, rather than later down the line.

So getting back to the question, “what do I do all day?”. Far from being a flippant remark, to anyone who is not me (or a post-doctoral researcher who works in a very similar area of work to me) it is a valid question. You might be curious about what do scientists do all day. You might even ask what scientists spend your taxes on. I can only speak for myself, but I thought I’d give it a go, seeing as I’ve had enough of IDL for one day. As my brain in almost a mush at this point in the day, I thought I’d go through the most mundane of tasks.

I run computer models. I edit the code of said models, to do little experiments and tests (this takes longer than it sounds). I find bugs in the code. I plot up the data from the models, often in comparison to observed data. Sometimes, I will process the data (eg using statistics to understand the data) before plotting the processed data. Hmm, that’s essentially it, I think. And I think that’s actually broadly similar to many other scientists in other disciplines, it’s just the specific methods that differ.

Why do I do all this sitting in front of a computer, writing code when I’m not actually a computer programmer? That’s a very good question, and one which is sometimes hard to answer when you’ve just spent hours, days or even weeks trying to get your code to work. It’s important to remember that these programs and models are just tools to use to try and understand the world around us, and to help answer scientific questions.

But what are the questions, you ask? Well, I think that’s a question for another blog post.

;-)

As light as a paper wasp nest

So a few months back, Dr Turnip (aka Mr Civiltalker) returned from the shed with a precious gift. It was the wonderfully delicate nest of a paper wasp, pictured below. I was quite astonished by it, as I had no idea what it was and had never seen one before. But luckily, Dr Turnip being a life-scientist, knew exactly what it was when he saw it attached to a folded up wooden chair.

Paper wasps make their honeycomb-shaped nests out of wood (or other fibres) mixed with their saliva — hence the name paper. They are very light and quite amazing to look at. Soon after we took the photos, our find blew out of the side hatch and landed in the water, it was quite literally (and I do mean “literally”) as light as a feather. When I reached down to the water to retrieve it before it floated away, the wet part had gone sticky and gluey — rehydrated wasp saliva!

The cells of this nest are open, and contained no eggs (this was back in May), so we may have robbed a potential wasp family of their home. As there were only a few cells, I am guessing that it was unfinished. Individual eggs are laid in each cell of the nest, and the larvae are fed other insects by the queen. When they are ready to pupate (turn into a pupa), they seal over their cell, from which they will emerge some weeks later as adult wasps.

We used to have a wooden garden table and chairs, which we left outdoors when we lived in London. That got stripped of its outer fibres by paper wasps, and it looks like wooden items in the shed might also be at risk of the same fate. If you notice wooden items going a bit splintery, and seem to have sectioned being stripped off, maybe it’s paper wasps harvesting your furniture too?

Thanks to Colorado State University for the background info on paper wasps. Dr Turnip knows a lot more interesting stuff about wasps and their social lives, but I’ll leave that for another time. If you know about paper wasps and wish to add anything, then post a comment below!

Contrails, digested

I’ve written a post on the NCAS Climate blog. Check it out here: http://ncas-climate.nerc.ac.uk/ncas-science-blog/237-science-blog-contrails-digested

Contrails and cirrus, as seen from the International Space Station, NASA/courtesy of nasaimages.org

Alternatively, read the text here. But do click through to the NCAS blog too, as there are some other interesting posts about climate science (including oceans, crops, blue blobs of death…) by other climate scientists.

I noticed that a new journal has just been launched - Nature Climate Change - and thought it would be a good source of inspiration for a blog post. Luckily for me, there was an interesting paper about contrails by Burkhardt and Kärcher in the first issue, AND there was a piece in the news and views section by Boucher about the paper. So I thought I’d do a kind of a ‘digested read, digested’ for this paper about contrails.

For the uninitiated, contrails are the line-shaped clouds that you sometimes see in the wake of aircraft in the sky. Contrails form when hot, moist exhaust from aircraft at cruising altitudes is emitted into the cold, dry air, and the water condenses (hence the name, which is a contraction of condensation trail). Contrails can spread out from their original line shape to cover much larger areas with cirrus (thin, wispy) cloud. This cirrus reflects some sunlight back to space (which cools the atmosphere), but it also absorbs infrared radiation coming from the Earth’s surface (warming the atmosphere), so the net effect is thought to be a warming. The interesting thing is that aircraft have the potential to punch above their weight (compared to other modes of transport) because of these contrails. Burkhardt and Kärcher developed a model of the formation, spreading and dissipation of contrails, so that they could see what effect the contrails had on the radiative forcing (a measure of the radiative imbalance of the atmosphere caused by a particular forcing agent; a positive value means a warming to the atmosphere, and a negative value means a cooling). What they found from their model might come as quite a surprise: that one of the biggest effects on climate from aircraft comes from the spreading out of contrails into cirrus clouds.

They found that the radiative forcing from the contrail cirrus as a whole was 9 times larger (37.5 mW m-2) than for line-shaped contrails alone (4 mW m-2). This is in comparison to a radiative forcing from aircraft emissions of carbon dioxide of 28 mW m-2. They also found that the contrail-induced cirrus reduced the amount of natural cirrus (-7 mW m-2), so the net effect was a 31 mW m-2 radiative forcing from contrail-induced cirrus. Put another way by Boucher: “Overall, and despite their short lifetime, contrails may have more radiative impact at any one time than all of the aviation-emitted carbon dioxide that has accumulated in the atmosphere since the beginning of commercial aviation. It is important to note, however, that the emitted carbon dioxide would continue to exert a warming influence for much longer than contrails, should all aircraft be grounded indefinitely.” This work gives an interesting starting point for further investigation into both the climate effects of contrails, and potential climate change mitigation strategies. The Boucher article gives ideas on possible ways of reducing the radiative forcing caused by aircraft. I rather like the idea of reducing the water vapour in aircraft exhaust emissions (maybe releasing the water as ice instead), so the condensation trails don’t condense in the first place.