Meteorology – Page 2

Time for Plan B – Geoengineering

There has been a huge amount of coverage of the need to cut Greenhouse Gas emissions as the primary route to slow down, halt and eventually reverse the current global warming trend and rightly so. However, in the background there have been a number of suggestions for actions that mankind could take to directly counter-act global warming. Such measures are collectively known as geoengineering and include such things as the direct removal of carbon dioxide from the atmosphere (e.g. by planting trees or fertilising the oceans) and reflecting incoming solar radiation away from the Earth (e.g. by using mirrors in space or changing the land surface to make it more reflective). These measures have not recevied much public attention, partly because they are all really, really expensive, partly because no-one knows how effective they would be and partly because by discussing the ideas in public we might distract attention from the goal of reducing Greenhouse Gas emissions.

Now, the tide has turned a little. A recent report produced by the Royal Society has highlighted the need to urgently begin considering geoengineering as a Plan B to reducing emissions. The report works through various geoengineering ideas examining their affordability and effectiveness and suggests that there should be a major shift of funding into geoengineering research. The report was widely publicised in the media at the beginning of September and the geoengineering debate is nicely summarised in New Scientist, Issue 2724 [05 September 2009].

Clouds and solar heating feedback

Clouds play an important role in determining the Earth’s climate. They can have a number of different effects but perhaps the most basic one of all is that clouds generally reflect solar energy back out into space thus lowering the amount of solar heating that strikes the Earth and is absorbed. This reflection contributes to something called the planetary albedo, which is essentially the overall reflectivity of the planet. The Earth’s albedo is generally taken as having a value of a little more than 0.3 which means that just over 30%, or a third, of all the solar energy that arrives at the Earth is reflected back out to space and clouds contribute a lot of this reflection. If the Earth had a higher albedo, it would absorb less solar energy and would potentially be cooler; if it had a lower albedo it would absorb more solar energy and be warmer.

So far so good, but it is actually really difficult to determine what will happen to clouds when the Earth’s atmosphere warms up (as it is). More heat in the atmosphere could mean less clouds as the air temperature rises and the water droplets in the clouds evaporate (becoming water vapour). On the other hand a warmer world will mean a greater tendency for water to evaporate from the land or ocean surface, increasing the humidity of the overlying air and increasing the potential for clouds to form when air cools (e.g. at high altitude).

Some new research has suggested that, in the north-east Pacific at least, a warming ocean is leading to less cloud which in turn leads to more solar energy reaching the surface (lower local albedo), which in turn leads to a warmer ocean, which in turn leads to less clouds, which in turn… This is an example of “positive feedback” and is a potentially important finding which may help to determine which of the current climate models is doing the best job of predicting future global climate scenarios. But nothing is simple – it’s nigh on impossible to know whether the clouds studied are typical and/or whether the findings can be applied more widely. The work is described briefly in a news item on the BBC Website [24 July 2009].

Raindrops are falling…

As I write this it is pouring with rain and has been for several hours. It is what seems to have become a typical summer’s day… But what do raindrops actually look like as they fall? A recent news item on the BBC Website (20 July 2009) reports on new research that has used high-speed cameras to film falling drops of water and the result is some fascinating footage of complex deformation and break-up (there is a viewable clip that accompanies the news item). It is thought that the research might improve rainfall models although apparently the drops used are on the large size for typical UK rain.

Noctilucent clouds

Noctilucent clouds are a rare type of cloud that comprise ice crystals so high up in the atmosphere that they reflect sunlight to the surface of the Earth long after sunset. It seems that noctilucent-like clouds are sometimes observed a few days after space shuttle launches – the shuttle launch creates eddies that carry water into the thermosphere (90-500km altitude). Similar clouds were also recorded as being observed in the days following the Tunguska blast (in Siberia) in 1908. The similarity between the two sets of observations has led to a suggestion that the Tunguska blast was caused by a wet, icy comet crashing to Earth rather than a dry, stone asteroid as had previously been thought. The story is described in New Scientist, Issue 2715 [04 July 2009]

UK weather in the 2080s – or maybe not

Last week, New Scientist, Issue 2714 [27 June 2009] ran a short news item highlighting a new set of climate projections from the UK Met Office for the 2080s (oddly defined as the years 2070-2099). These are presented as a series of maps showing changes in summer mean temperature and summer and winter mean precipitation across the UK based on a 5km grid. The Met Office website also introduces the material and provides a link to the dedicated UK Climate Projections 09 website where the maps can be found. The New Scientist piece points out that some climate scientists feel that the projections are useless, and or misleading, because such fine resolution projections are bound to be upset by processes occuring at the local scale. There is also doubt that the climate models used to make the projections can handle areas of blocking high pressure well enough to make them useful.

So, the projections may or may not be useful or useless depending on who you believe! Nevertheless, I thought I would take a look at the maps and see what they tell me about the likely conditions in Plymouth in the 2080s (I have only just done the mental arithmetic, but I’ll (probably not) be 115 years old in 2080 which has depressed me a little). Anyway, for what it is worth, it looks like it’s going to be 3-4 degrees Celsius warmer and about 40% less wet in the summer and about 10% wettter in the winter…

BBC Radio 4 – The Material World

As a child I grew up in a BBC Radio 4 household. People who know me well might say that this explains a lot, certainly it is probably responsible for the way I talk… Nowadays, with a busy life and a home life that seems to generally involve people rushing about here and there, I never seem to find the time to listen to Radio 4 and this is something that I often wish was not the case because Radio 4 is the home of a huge amount of interesting, funny and informative material. One particularly good programme is “The Material World”, a weekly half-hour offering on science. The format is generally the same – there are two items each getting roughly half of the air-time during which the presenter, usually Quentin Cooper, talks to one or more scientists, engineers or similar beings about a topical issue or piece of work.

Fortunately for people like me who never manage to listen to the radio at home, “The Material World” has its own web-page from which it is possible to listen online to past episodes. It is also possible to download episodes as podcasts (e.g. via iTunes). This is great because not only can you listen to past episodes that look interesting, but you can do so whenever you want! Now that I have set this web-site up I will write about episodes that I think are of particular relevance to oceanography and meteorology as and when they occur, but to start things off I thought I would provide a list of some of the past episodes that I might have included in this way if this site was already up and running. I don’ty pretend to have listened to all of these but they are all episodes that judging by the blurb should be of interest to anyone interested in marine and atmsopheric science. Please be aware that each time you click on one of the links the page for that episode will open in a new window. You can then listen to the episode by clicking on the Listen Again link provided. If any of the links are incorrect or broken please let me know so that I can correct or remove them.

From 2005: air pollution – trees and climate change – coastal wind jets

From 2006: ghost ship – Thames barrier – artifical gills – deep sea fish – gas hydrates – mega plumes – forecasting evolving coastlines(1) – Antarctic Science – solar energy – stratospheric broadband – a new look at the sun – sediment analysis and charting the ocean’s organisms – data logging animals

From 2007: the Thames whale – Scapa Flow – international polar year – El Nino – managing uncertainty in complex models – flood warning – seaside bouquet – Sumatran earthquakes – Arctic sea ice – fish stock extinction – algae(2)

From 2008: deep tropical ocean kelvin waves(3) – plate tectonics – Severn barrage – predicting natural disasters – seaweed and iodine – ocean acidification(4) – the secret seeds of clouds – subglacial lakes – seawater greenhouses – lobster hotels – the deep carbon cycle

(1) featuring my PhD supervisor Professor Alan Davies from Bangor University
(2) featuring Professor Peter Liss from the University of East Anglia, former President and current fellow-Council member of the Challenger Society for Marine Science
(3) featuring Professor Karen Heywood from the University of East Anglia, a postdoctoral researcher at Bangor University when I was taking my MSc and PhD there
(4) featuring Dr Jason Hall-Spencer from the University of Plymouth