Showing posts with label Global Climate Change. Show all posts
Showing posts with label Global Climate Change. Show all posts

Tuesday, 12 June 2012

Monsoons

Hello everyone!!! I suspect the nerves are starting to kick in so good luck to everyone doing the AQA A2 Unit 3 Geography exam! This is a rather late request from quite a few people so I thought I would quickly write it - last minute cramming always helps right.....

MONSOON = a large scale seasonal reversal in wind direction

This wind reversal is experienced in regions across the world but the most significant is the South East Asian Monsoon (this is our example of a climate in a tropical region) and is influenced by three main factors:-
1. Movement of the ITCZ - moves with regards to season as point of maximum insolation changes due to the 23.5 degree tilt of the Earth so ITCZ moves north of equator during northern hemisphere summer
2. Differential heating of land and sea which initiates pressure differences - land masses heat and cool quicker and to more extremes in relation to smaller heat changes over nearby seas; these differences are responsible for strength and direction of winds
3. Himalayas, which are high enough ot influence the general atmospheric circulation in the region

Summer: SW Monsoon = June - September
  • ITCZ dragged north
  • Low pressure over India
  • Land warmer than ocean
  • Coriolis deflects northerly winds to the east
  • Heavy rains move north along west and east coast
  • East rains deflected west due to Himalayas
  • Pattern of rainfall in summer monsoon is altered by topography. Western Ghats create rainshadow in central India, whilst Himalayas have same effect for central India
  • Some areas of SE India and Sri Lanka recieve rainfall in winter as winds pass over Bay of Bengal and gain moisture
Winter: NE Monsoon = October - May
  • ITCZ dragged south
  • High pressure over central Asia
  • Land cools rapidly
  • Coriolis deflects southerly winds to the west
  • Dry air dries further as it moves over Tibetan Plateau
  • Air warms as ut descends to the Indian Plains
- Monsoon in both retreat and arrival is stepped so Sri Lanka gets rainfall in early May whereas Pakistan in July. Retreat begins in September but does not reach Southern India until late November

Couple of facts.....
- 40C in May - average temperature is 30-35C year round
- 13000mm rain per year in Cherrapunji (well its spelt something like that!)
- 80% rain falls between June and September

Positives : )
- Very predictable!
- Relief from hot season as monsoon cools areas that reach 45C so cities have powershortages
- Reservoirs topped up
- Crop growth = stable diet is rice and Indian agriculture built around monsoons
- Monsoon clears out dust and pollution and rejunventates vegetation

Negatives : (
- Temperature restricts tourist season
- Droughts and issues with water supplies
- Flooding increases spread of water bourne diseases
- Restricts agricultural productivity
- 500 died in 1994 flash flood in Bangladesh

Monsoons and Global Climate Change
  • Half of global population rely on annual monsoon to bring water for agriculture
  • Variations of timing and intensity will affect billions of people
  • Frequency has increased 10% since 1950s and severe rains have doubled
  • Impacts of heavy rains i.e flash floods/landslides which then impact agriculture
  • Temperature increase of 3C means some areas get more rain, others droughts
  • Increase in malaria and cholera
Well I think that is about it for monsoons, well atleast I hope so as I don't think I really know anymore and the exam is tomorrow afternoon.

Good luck everyone!

P.S after unit 3 is out the way I will try and write some stuff for 4B at the weekend but remember all the skills stuff is already on here from January!

Wednesday, 25 April 2012

Climate Modelling - [based on video notes from Earth: The Climate Wars]

Hello everyone! I hope the revision is going well; only like 8 more weeks of hard work and then it will all be over!!!

Climate modelling is a really, really complicated mathematical area and I got the pleasure of spending some time with many of the worlds best climate modellers whilst at the Met Office. During my time there, understanding modelling was an area that I really struggled to understand and my inquistive nature lead to much confusion on my part (sometimes I really need to just accept things!). Fortunately it seems that we dont really need much knowledge on the modelling but I thought I would summarise what we should have learnt from the documentary we watch - if anyone fanices learning more, this could be a good topic to look into over your long summer holidays (it is on my list for looking at!) and there is some stuff on the blog about it; word of warning though, the maths get very confusing very fast!!!

Here is the links to the three episodes, in order - we only watched the third one in class....
- The worlds first climate models were far from computer based! Instead small scale models were used and these helped to formulate the basics of atmospheric circulation, allowing scientists to generate the basic laws that the atmosphere abides by. However they failed to represent the complex oceanic/atmospheric intergration or predict weather patterns
- Computer modelling was first used to predict the weather on a 24 hour timescale. However, at first it was taking 24 hours to produce a forecast and was not until the 1970s that this became efficient enough and worked reasonably well
- Early on, the models were not deemed that reliable and consequently many climate skeptics used this as a point of attack, saying that as results were not reliable, it could not be said that climate change was happening in reality
- It was not until the 1991 Pinatubo eruption that the models could be tested to see if predictions were accurate. Hansen, a world leader in climate modelling used the eruption to see if the models predictions of the extent of cooling caused was accurate. This event was ideal due to timing of eruption and duration of impacts. The 1980 eruption of Mount St Helens unfortunately came to early to be used to test modelling accurracy due to level of computer technology at that time
- Subsequently, by the late 1990s climate models were deemed, worldwide, as reliable and so their projections viewed with confidence. At this time the models were suggesting that a doubling of CO2 would increase global temperatures by 3C. However, this will never be 100% accurate as resolution of the models still needs improving and modellers still struggle to ensure computers consider influential factors in affecting climate on a smaller, more local scale - this is quite a good explanation of why climate modelling has improved over the years, produced by the Met Office -  Climate Modelling


- There is also the complication of field observations, which are crucial in producing the models, and the increasing level of understanding we are gaining over time. This is an inherent problem with climate modelling and will continue to be as we discover new feedbacks operating in the climate system. The example in the video was based around glacial movements as a once believed 'dead' glacier became 'alive' again and started moving at a faster rate, as the planet has warmed, this has then increased the rate of sea level rise etc. Feedbacks control the extent of change with negative considered stable and positive feedbacks often detrimental due to their amplyfing effect. These feedbacks are very hard to model  so uncertainities will always exisr with modelling; meaning tht changes in sea level, for example, could happen a lot quicker than models predict
- 1961: Lorentz's discovered 'chaos' in the climate sytem by changing degree of rounding used in models and this went on to explain variations in modelling projections. Thousand of runs and run and the general trend is then taken and countries all use different models. The UK uses the Met Offices HadCM3 which was influential in both IPCC AR3 and AR4. Ensemble forecasting is being used to an increasing degree. Ensemble forecasting basically means that all the different runs are started at slightly differing conditions and then by comparing the results it produces a much better idea of what weather events will occur at a given time.
- The discovery of the 'Chaos Theory' made climate scientists realise that there were factors with an influence on climate that they had yet to discover and incorporate in models or to quantify their signigicance
- Proxy data such as Greenland ice cores and pollen and beetles help us formulate the temperature record going back to the Younger Dryas. Understanding how past climates have changed and incorporating this knowledge into modelling helps to make long term prediction more accurate than say the 5 day forecast. The proxy record also indicates that abrupt climate change is possible
- So, far Antartica seems to have experienced the most rapid climate change, especially in terms of sea ice coverage. In 2007 sea ice shrunk by an area 10 times the size of the UK, leading to some scientists predicting that in a decade no sea ice will remain during summertime in this area
- Models say that warming may be slow and steady but history indicates it can be rapid and so we are now experiencing changes happening at a faster rate than model predictions and faster than we originally thought
- Technology has allowed us to deal with some climate condition e.g Las Vegas is built in a desert yet is full of water, thanks to the Hoover Dam which created the 100 mile long Lake Mead. An 8 year drought has been experienced in this region though and models suggest that the drought will continue and, as population expands, water will become scarce and Lake Mead will become ineffective by the late 2020s

So, these are all the notes I managed to take! The basic knowledge we need to have for climate modelling I think is a bit about when they were developed, how they started off etc and then why there are uncertainities and why they are still considered unreliable. Within in this, you need to be able to link in the use of Mount Pinatubo and proxy data to reduce modelling unceratinity but meanwhile realise that they will arguably never be 100% certain. Hopefully I have covered all of this!

Wednesday, 19 October 2011

What should be the top environmental priority for the next 40 years?

Last week, in London, some of the world's experts in environmental change and challenges gathered, as part of Earthwatch, to discuss what aspect of environmental change should be our priority for the next 40 years. So, what factors came up during the discussion...........

Education and Population:

Since the beginning of the industrial revolution some 250 years ago, we have changed the character of the Earth;  hence the increasing use among geologists of the term Anthropocene to follow the Holocene epoch. Although a complex mix of factors are responsible for such changes, population growth is without a doubt the most dominant - and continues to be. The human population rose from around one million 12,000 years ago to around one billion 250 years ago. Since then there has been an extraordinary acceleration from 2 billion in 1930 to 6 billion at the end of the century and now approaching 7 billion this month, with projections suggesting a further rise (albeit at a slower rate) to 9 billion by 2045 - scary thought if ask me!!! As hopefully you have gathered from the AS Population module and our current Development A2 module, education is critical if we hope to solve the issue of population growth and thereby dilute the effect of the appending impacts - especially education of women ( = the Girl Effect) as where emancipation of women is achieved, CBR drastically drops, as seen in most industralised countries where the fertility rate is below replacement level fertility. However, in reflection, this does causes problems in its own right - think ageing populations - but, with regards to the environment, is no where near as detrimentally damaging. There are also many other issues such as increasing population density and rapid urbanisation, especially in the developing world, which are all causing global societal problems with secondary economic, political and environmental impacts.  To think that global education could attenuated many of these demographic issues is incredibe - if education is the answer, something which is perhaps possible to start to globally implement on the mentioned timescale, should it be our priority for the next 40 years?

Oceans:

I will try and keep this one short and simple as in truth I could probably write a few essays for you on this one! Approximately 70% of the globe is ocean and we are incredibly connected and consequently reliant on it in a multitude of ways. The oceans (although specifically the ocean circulation)  are a critical mechanizism in the Earth's heat transfer system, feeds over 25% of our population and, as a result of its close coupling with the atmosphere, absorbs the heat generated by our unhealthy addiction to burning fossil fuels. Although the oceans may look very stable and unchanged over recent decades, they are not, and are increasingly vulnerable to anthropogenic forcing. With more photosynthesis occuring on the sea surface than anywhere else, many consider that the oceans breathe for the planet, with the oceans also being the largest carbon sink. This is all set to change, if our unsustainable environmental usage and consequentially accentuated global climate change continues to happen and once a significant change happens within the oceans (as is already happening with depletion of the oceans fisheries, toxic contamination of the sea by industrial runoff and plastic pollution and acidification etc.) it will pose a great threat to the health of the world's population.

Water:

Water is a resource that many take for granted but it is a resource that we simply cannot survive without. Whilst we cannot live without it, when we are forced to drink that which is not clean it becomes lethal with diarrhoea the biggest killer of children in sub-Saharan Africa - preventable diarrhoea associated with dirty water and poor sanitation kills more children than Aids, malaria and TB combined.Water provokes other societal issues, especially for women and girls who bear the burden in developing countries of walking for miles in search of water whilst dirty water, poor sanitation and hygiene undermines maternal and child health and nutrition. This has knock on impacts on education, with 443 million schools lost due to water-related diseases, as girls, especially, are needed to find water thus cannot attend school. The World Health Organisation estimates that every $1 invested in water generates $8 in wider economic benefits. All of the above, are linked to water as a drinking resource, but it has wider uses to, in industry and agriculture. Agriculture is reliant on water supplies, with 70% of the globally available freshwater used for agriculture, making livelihoods even more reliant on water what with droughts and famines going hand in hand. It is a critical ingredient for industry - almost every manufacturing process needs water - whilst,  it's intertwined with energy and not just through hydropower but thermal power stations need water for cooling and for the steam needed to turn turbines.

Energy:

I am guessing that this one is quite obvious - we humans are different to other species on Earth as not only do we gain energy from the things we eat but also from things that we don't eat. Our energy usage throughout our history has changed, as both a consequence of our development and as a factor allowing for our development. Currently, the issue of generating energy sustainably is a huge issue for the global community, with climate change accelerated by our insatiable hunger for burning fossil fuels, a desire that is only likely to increase as the global population continues to grow and countries continue to reach higher levels of development.

Food security:

With water security and supplies under threat, whilst the population continues to expand, the challenge of feeding the world is a huge! This challenge is not going to be easy with our oil-reliant food system, our environment under stress from global climate change, distruption to water supplies and soil degradation/loss, weakening overturning in oceans, biodiversity loss, land use competition with people and animals needing space to live, space needed to grow food and people starting to utilise fertile land for energy production. Perhaps one of the greatest challenges is changing our attiutde towards food and waste as if every country fed its population to the extent that we do in the UK or the USA, we would need several planets just to grow food, with estimates that 40% of what is fit to eat we waste. If we have to feed 9 billion people by 2045 we cannot continue in the way that we are - especially if you factor in the likely future changes to agriculture patterns and productivity as a result of global climate change.


What do I think? Well, I think that just the above mentioned are cause for concern and there are other factors that I am shocked did not get on the list. We place a lot of focus on how oil fuels fighting and whilst it cannot be argued that it doesn't, I think greater focus should be placed on possible/likely future fighting over resources that are essential to our survival - primarily water and food. If we are prepared to start wars over oil what would countries be prepared to do when the resource we are all after is one intrinsic our survival. This is worthy of a few blog posts on its own but I am reading a really interesting, if not slightly worrying, book at the moment called Climate Wars which covers this - a book review will be on its ways shortly, once I have finished reading it, but it is definetly worth a read for any Geographer! Anyway, back to the question,  to be honest, I feel that all these factors (and many many more) are so closely interlinked that we cannot hope to untangle them and thus it is crucial that instead of trying to prioritise them we spend the time discussing how to prevent worse case scenairo's from occuring by developing mitigation techniques whilst also ways in which society can adapt to the inevitable consequences of the damage already caused by humankind. So, I suppose what I am trying to say is that I believe we need a more holistic approach to environmental change rather than trying to prioritise different aspects.

Anyway, the afore mentioned are the factors covered during Earthwatch, followed by my view for the need for a holistic approach but what do you think should be the top environmental priority for the next 40 years? Would you choose one of the above or do you think something is missing from the list? Let me know what you think!

I am a bit reluctant to tell you which of the above factors was voted to be the greatest environmental challenge and thus should be our priority over the next 40 years but I am guessing I probably should tell you and anyway, hopefully, by now you will have formed your own opinion. The chosen factor was Population and Education with the agruement for the desperate requirement to address expotential population growth and providing education for all, viewed as the most compelling. The speech given by Sir Crispin Tickell, on this topic, can be replayed here - do you agree with the factor chosen?

Friday, 23 September 2011

Geography Picture of the Week - Highest resolution global map of ocean surface salinity

First up, the most observant of you will notice that I have changed my 'Geography Picture of the Day' to 'Geography Picture of the Week' as, in reflection, it was always high unlikely that I would post a picture everyday! Instead, hopefully, I will be more likely to post one weekly and although I am guessing that most will be linked to physical geography, I will try and find some relevant to our current human module........

So, what is my Geography Picture of the Week this week???


I apologise to any of you who are getting fed up with oceanography-related posts (my EPQ will be over very soon so hopefully I won't be so tempted to write about oceanography stuff all the time when I should really be writing about Development and Globalisation!) but I really couldn't resist posting this one!!!

The above image was released by NASA and represents the one of the first and high resolution global map of ocean surface salinity made, using data acquired by the Aquarius/SAC-D satellite, launched in June this year with the map itself only incorporating the first 2 and 1/2 weeks of data since Aquarius became operational on the 25th August. Scientists have been able to measure ocean salinity for decades by lowering instruments from ships or by deploying robotic floats, but the technology to gather data from orbit is a recent innovation.

The generation of this map has been long anticpated by oceanographers and meterologists so I am guessing there are a few very happy scientists around the world at the moment! If you have followed any of my highly unorganised posts on oceanography you might be able to appreciate why........

Well, our ability to map and thus determine salinity (basically the 'saltiness') will improve our understanding of ocean circulation, the risks of future alterations to it and also an understanding of a few key climatic processes (note that the oceans and atmospheres are incredibly closely coupled with, in simple terms, the oceans provided the memory for the climatic signals generated in the atmosphere).

So, what excatly does this map show? Well, the red and yellow colours represent areas of high salinity with blues and purples denoting those with low salinity and black showing areas with no data(note no data retrival on land). The maps clearly shows well-established, large scale features, significantly the major salinity differences between the Atlantic, Pacific and Indian oceans. With the Pacific ocean by far the 'freshest', supporting the absence of deep-water formation sites, and the Atlantic by far the most saline. The salinity of ocean water is intrinsic to ocean circulation, although most precisely thermohalince circulation, which is soley driven by density differences (salty water is denser than less saline waters and so is forced to sink, thereby helping to drive the circulation). Also apparent is the corespondance between areas of lower salinity and rain belts and the areas of high evaporation found in the subtropics (regions of evaporative enrichment). Smaller-scale features are also possible to identify like the freshwater outflow from the Amazon River which acts to dilute immediate Atlantic surface waters.
The goal of the Aquarius mission is to retrieve salinity with a resolution of 0.2 parts per thousand (a concentration change equivalent to about one millilitre of salt in six litres of water). Aquarius carries three high-precision radio receivers that will record the natural microwave emissions coming up off the water's surface; emssions varying with the electrical conductivity of the water - a property directly related to how much dissolved salt it is carrying.
Smos global salinity map
The Nasa-Conae spacecraft is not the first ocean salinity mission in orbit as Europe already have a satellite in operation (Smos) which was launched in 2009, producing the first ever global salinity maps generated from space. The intention is to inter-calibrate and combine the Aquarius and Smos measurements as, together,these spacecraft are now acquiring volumes of salinity data that dwarf all the information ever gathered in this field of study.

Thursday, 4 August 2011

Met Office Work Experience - Day 3 (for Wednesday)

I spent my third day at the Met Office talking to various researchers about the work they are doing, how it relates to my EPQ topic and asking them lots and lots of questions (I did have to apologise to one person as I literally spent an hour quizzing them about the thermohaline circulation!). I am unsure as to how much knowledge some of you will have surrounding ocean circulation so some of this may not make a lot of sense - if you hunt around on the blog though you will find various posts on the basics of ocean circulation.

So, first up I had a very long discussion with someone about the thermohaline circulation. For those of you who don't know much about the thermohaline circulation  it is the driving force behind the deep currents of the ocean that are collectively referred to as the Global Conveyor Belt. This deep circulation is caused by density changes in oceanic water resulting from changes in temperature and salinity, hence its name ‘thermohaline circulation’, which are caused by cold winds cooling surface waters, the input of freshwater from either precipitation or melting ice, the cooling and freezing of seawater into sea ice or the evaporation of sea water. The basic thermohaline circulation is initiated when denser water (predominately the cooler, saltier water) sinks below the more buoyant water (warm, with a low salt content). Convection penetrates to a level where the density of the sinking water matches that of the surrounding water. When this maximum penetration level has been reached, it will gradually spread into the rest of the ocean. Once the dense water masses have spread into the full extent of the ocean, they will slowly upwell to supply the slow return flow to the sinking regions and replace the surface waters lost - thus driving and sustaining this circulatory movement. Anyway, the discussion I had was focused on the likelihood of it weakening or shutting down and the resulting impacts such an event would have on us. In terms of the UK, if the MOC (Meridional Overturning Circulation) was to significantly weaken or shutdown then the UK would get a lot colder as a slower circulation means a slower heat transfer from the Equator to the Poles and thus a warmer tropics but colder high latitudes. Changes in wind patterns and precipitation would also occur although, in terms of precipitation, the biggest changes would be experienced by those who currently have monsoon climates as a change in the ocean circulation would impact on the movement of the ITCZ. Due to the colder poles, more sea ice is likely to form and this is something that would impact the path taken by the Gulf Stream. The warm moist air brought to us by the North Atlantic Current ( a branch of the Gulf Stream) is what allows us to have a temperate climate, one far milder than countries of the same latitude. However, if the MOC stopped then the path of the Gulf Stream would be altered and it would split at a much lower latitude in the North Atlantic and so we would not get the warm water and moist air that dictates the climate we currently experience. Therefore this would amplify  the effects of an MOC shutdown and further cool our climate. When you then factor in the predicted changes due to global climate change, it becomes slightly more complicated. To some extent it is believed that global climate change could, to a certain extent, offset the effects of an MOC shutdown and so they could act to cancel each other out in most of the world. In the Northern Hemisphere though, due to the reduction in speed of the meridional heat transfer, the UK and areas above it would stay cold or perhaps even get colder! So, what would be needed to cause a shutdown or weakening? Well, something that will upset the delicate density differences and so the most likely thing to do this would be an input of freshwater. They are a few possible sources of freshwater that could do this. First is the collapse of ice sheets/shelves in Greenland due to rising sea and air temperatures as not only would you get the obvious freshwater input from that but after ice shelf collapse glacial flow is also increased. Another possibility is the melt of pack ice in the Arctic and the finally possibility is an increase in precipitation as a result of global warming. It is debatable which poses the greatest threat to the MOC as little is known about the stability of ice sheets and shelves in Greenland etc (lots of research is being done at present) and so many think that the most likely threat could come from an increase in precipitation - something that I realised would have an impact but was surprised to know was believed to have the biggest impact in the near future. A question I was quite interested to know the answer to was how much freshwater would be needed to shutdown the MOC and on what time scale would a shutdown be likely to occur. However, no one really knows and research into this is currently being conducted around the world. One thing that was said for certain was that a shutdown is unlikely in the near future and that one would not occur on the time scale portrayed in The Day After Tomorrow (film review on its way soon!)!!! To try and answer these questions lots of models are being used to try and calculate what state the MOC is currently in.
This graph is rather simple but does help when trying to explain some of the theory behind the response of the MOC to freshwater and how it may recover from an input - another area that really intrigues me. So basically along the x-axis is the volume of freshwater and along the y-axis the strength of the MOC/THC. The idea that many have is that the MOC, despite an input of freshwater, will maintain a constant strength until a certain point is reached. At this point, a rapid decline in its strength will be witnessed and then the MOC will fall off its 'track' (kind of onto the bottom line). Therefore, for it to re-initiate, a decline in freshwater would need to occur, which I suppose is like a reversal of the current pattern, for it to get back on 'track'. The idea of this graph originates from some of the thinking behind how the oceans would respond to an input of freshwater and the contrasting ideas produced by models.
The first comes from  more complex models which seem to suggest a more gradually weakening in response to a freshwater input. The simple models, upon which the first graph I showed you is based on, suggest something different.
The rapid decline in strength after a certain point has been reached is something that many believe would have in reality.

The same graph as the first one, but based on the response results produced by the complex models, is slightly different.

This graph suggests that a gradually response would occur to an input and that, therefore, a gradual return to normal would occur as freshwater was removed and the density differences restored. Excatly which model is correct has yet to be decided but validating one of thiese models is crucial if we are to understand how the THC/MOC will respond and how it is likely to be re-started. Understanding this is also likely to help with calculating just how much freshwater the MOC can 'cope' with before weakening/shutting down.

Another area that is being researched is what feedback system the oceans are currently in. All of these ideas tie in together and understanding the mechanisms is vital if we are to gain a better understanding of how the ocean responds to different factors.
The negative feedback loop represented, rather simply, above is the state that the models used suggest that the oceans are in; which is the idea that freshwater goes in to the North Atlantic, sinks, and then salt water emerges in the South. However, scientists actually believe that the oceans are in a state of positive feedback instead......
Work into which one the oceans is in is currently being done as by understanding this, it is hoped that more reliable predictions for the future will be able to be produced. Just as kind of a side note, scientists think that the oceans may be able to switch between the two feedbacks  mechanisms with this switch being provoked by changes caused to the basic circulation pattern of the oceans, in repsonse to freshwater input.

I realise that this is a bit all over the place but I hope by now you have got the idea that a freshwater input could cause a shutdown or weakening of the MOC and this would have a large impact on the climate of the UK, amongst other countries. Hopefully you we also be able to understand how the alterations of our climate would effect other factors that affect us and other aspects of our lives like, for example, agriculture and food production. Something else though that needs to be taken into account when talking about a possible shutdown is the location of the freshater input. An exact location which would have the largest impact is yet known, but in general, it is believed that any input into the North Atlantic could have a major impact, especially in comparison to the Pacific or Indian Ocean. Again, understanding some of the things above will help aid the discovery of where is the key point in terms of the MOC and this just demonstrates how interlinked all of these things are. During this discussion we covered loads more, hopefully some of which will appear in my EPQ, but I have probably talked about this all a bit too much already! There is some other really interesting stuff that I might right about in a couple days that we also covered - in reflection I do feel a bit sorry for the woman who kindly gave up a lot of her time to talk to me about all of this stuff as I literally bombared her with hundreds of questions!!!

Once last thing I need to mention, which is related to the above, may be of general interest. I don't know if any of you have ever read anything about the thermohaline circulation or meridional overturning circulation but whilst doing research for my EPQ it has confused me how some people switch frequently between THC and MOC and was excatly the difference is. So, I thought who better to ask then the very intelligent scientists at the Met Office! Well, here is the answer............. the MOC is used as to represent the integral across an ocean basin of the meridional flow (south to north movement hence why it is often used to describe the THC in the Atlantic). Given a flow field, the MOC can be precisely defined as a function of depth, or potential density, and latitude. On the other hand, the THC is a less precise concept and is used to describe the whole Global Conveyor Belt circulation. The THC is generally, broadly, taken to mean the part of the circulation that is directly and solely driven by density differences rather than wind stress. However, it is important to note that there are thereotical difficulties in disentangling which forcings are responsbile for a specific part of the circulation and in many cases the MOC is not purely a result of the THC. In many cases, though, the conceptual difficulties may be less severe when considering the changes to the circulation rather than determining the causes of the circulation. Therefore, the reason for some papers alternating between the two is that whilst there are some differences, in some circumstances, both terms are appropriate for use - I hope that explains the small difference!

Then, to finish off what has been an amazing three days, I had a chat with two scientists who are researching the impact of climate change on the ocean ecosystem. These guys were in the Biogeochemistry working group meeting I talked about earlier in the week and so they do a lot of work into CO2 uptake etc. and the idea that phytoplankton can control temperature. Our discussion included many things such as the way in which they model ocean ecosystems and how the models have developed over the years, some of the basics of the cycles involved in the ocean ecosystems and how excatly climate change is likely to alter the delicate ecosystems. This meant that the discussion moved on to the issue of ocean acidification and how studies are being conducted into the impacts this has on ecosystems, especially fish and corals. This is a rather large topic and so, again, I think I will write a seperate post on this over the next few days. At some point in conversation (can't really remember when!) we moved on to a discussion about Daisyworld and the Gaia hypothesis/books. Daisyworld is one of the ways in which James Lovelock tried to represent the ability of the Earth to self-regulate and for a quick idea of what Daisyworld is all about follow the link - Daisyworld animation - its a bit simple but portrays the general idea. I have read the first one and have nearly finished the second one (thanks Millie for getting me to read them as it enabled be to fully participate in the discussion!) and it was quite interesting to get the view of two scientists on the book which is written for the non-scientists about some of the work they are researching.

Anyway, so thats what I got up to during my 3 days at the Met Office (sorry that the posts have been all over the place and written a bit late). I had an incredible time and met some really lovely and highly intelligent people who were more than willing to answer my questions, talk about the work they are doing and offer lots of general advice. There are so many people I need to thank for helping me get into the Met Office, preparing me for the priviledge, allowing me in in the first place, organising many things for me to participate in, for giving up their time to talk to me, allowing me to bombard them with questions and for just being so welcoming whilst I was their. I learnt so much from the experience and its given me a lot to think about in terms of what I want/need to do in the future - I have a lot of thinking to do! It has also reinforced the fact that I know so little about the world of Geography and so I have a lot of reading to do to try and cover as many of the things I didn't quite understand as possible and just expand me knowledge (I will say sorry in advance as a lot of writing is likely to appear on here over the next few weeks!) - I relish the challenge!!! So, all that is left for me to say, apart from another thanks to everyone who has helped make this possible, is that I can't wait to hopefully go back at the end of August!


Wednesday, 3 August 2011

Met Office Work Experience - Day 2 (for Tuesday)

My second day at the Met Office and I think I am starting to get used to being here - well what I really mean to say is that didn't get lost!

So, what did I learn today? As to be expected an awful lot - although again much of it went over my head and so I need to go away and do some more reading on some of the areas. First thing this morning I had a really interesting chat to a researcher who is currently running and then analysising the results of various models linked to the changes he estimates will happen to the contiental shelf, temperature and salinity of the oceans, risk of storm surges and sea level in the future. They have been running loads of these simulations in the hope that they will be able to provide a better and more reliable picture of future conditions to several organisations so that they can take the appropriate steps so that they can effectively adapt to the predicted changes. The majority of this session was spent going over the idea of Ensemble modelling anf forecasting (or atleast I think that is what it is called). Over the next few days I will try and explain the basics but first I need to either locate or draw some diagrams etc to help aid the explanation as it will be tricky enough without them. It is actually really interesting as by understanding the basics (and I refer to the real basics as all this modelling stuff soon gets really complex - just trust me on that one!) of the modelling system, you can see how various factors are linked to or provoke a certain reaction and start to understand why there is often much variablility and uncertainity over future projections. Listening to how and why he was doing the research he is doing at present (and I mean like right now - the plots etc he showed be had literally on that morning been completed!) was really interesting and some of the stuff he was looking into really fascinated me. This talk really demonstrated how the some of the work completed help to guide government policy on various topics. I was given a copy of the last MCCIP Annual Report Card which has some interesting regional snapshots of Marine Climate Change Impacts and various impacts, accompained by the risk of them occuring. Here is the link to the summary report which you can read online http://www.mccip.org.uk/media/7562/mccip-report-2010-2011.pdf ; it is quite interesting to read and not that hard to understand as it was written for people and politicians who may not have a great deal of previous knowledge of the topic. We also discussed UKCP90 and went over loads of graphs, plots and data linked to various changes that are likely to occur due to climate change. Again here is the link to their webpage http://ukclimateprojections.defra.gov.uk/content/view/12/689/ and if you click on 'Quick Downloads' you can download the pdf files of the report they produced which I worked through quite a bit of with this researcher. If anyone is doing an EPQ related to climate change they might find the stats, plots, graphs and diagrams included useful to use in their write up or presentation - I may try and sneak a few in!

After this, I attended another seminar but this time on "Climate sensitivity and ocean heat uptake" by Geoff Vallis of Princeton University, USA. I struggled to follow this seminar as, again, it involved lots of models, lots of acronyms I had never come across before, some horribly complicated looking equations and it kind of jumped around a bit. However I got some of the basics of what he was trying to show with his models and equations so I will go for explaining that - like I did with the other seminar. Essentially the overall sensitivity of the climate was discussed, with particular reference to surface temperature, to an increase in greenhouse gas emissions. You probably got this from the title but it focused on the role of the ocean in all of this - remember that the atmosphere and oceans are coupled and they talk to each other (this is what all the scientists at the Met Office refered to the relationship as) and also that the oceans are both a source and sink of gases like carbon dioxide. The main basis of the seminar was on the speed of responses and so say if carbon dioxide instantaneously doubled then an aspect of the climate system would respond rapidly, with a thermal inertia (describes the ability of a given volume of a substance to store internal energy while undergoing a given temperature change, but without undergoing a phase change, so is said to be resistant to temperature change) which is determined by the mixed layer in the oceans.When you then look at long timescales there is a slower element to global warming, one that many consider is effectively irreverisble even if emissions would cease. A fast response, which is commonly classed as the 'transient climate sensitivity' ( I have been picking up some new words and phrases over the last few days!), on the other hand, is only relevant to a response timescale of a decade to century. So basically the seminar was about responses to different factors by the climate and the oceans and the speed of the responses (something which when asked about seemed to divide the conference room in two!). It included links to not only anthropogenic greenhouse gas emissions but also links to volcanic eruptions and ENSO and various other things which he included in his models. The last aspect of this seminar was to look at the model which he referred to as being "embarrasingly simple" and used observational evidence of global warming over the past century to estimate the parameters(although it didn't really look that simple to me - but  the people I was with said that in terms of the equations used and parameters set it was quite simple) and compare it to the results from more complex models and show that the simple model had less uncertainity surrounding it and so is perhaps the better one to use. Over the last few days, one of the many things I have learnt, is that none of these models are perfect - something that was demonstrated in the 'Oceans and Iced Tea' meeting I attended in the afternoon - and that the scientists spend much of their time developing, refining, running and then criticising the models due to the uncertainities that they produce and the errors they sometimes generate. However, these models are crucial as they provide us a insight into the possible future conditions as the variables can be changed and things messed around with a bit to see how different factors provoke different responses. I have got so much I want to write about but I just have to find the time! Hopefully something on modelling (it will be the most simplistic explanation of the basics ever) and on climate sensitivity will appear over the next week.


The afternoon 'Oceans and Iced Tea' meeting was a bit easier to follow (perhaps as my knowledge of terminology on this topic is slightly better) and it was on the topic of erroneous eddies that were appearing on ocean models and why. The reasons discussed including the lack of bathymetry included in the models and the idea of the influence of continental shelves and the shelf currents. Work is always being down to improve the models that they use as they are used to generate data for some may things. Something that surprised me was that many of the models used across the different departments were quite similar and has only small adaptions to make the predictions generated more specific to certain areas.

I also had a rather long chat with some of the summer placement students who are doing like 12 weeks paid work experience at the Met Office where they get to do some proper research using on the models and stuff. These students were all at either the end of their degrees, doing masters or phd's but this scheme is something that I would strongly recommend you keep an eye out for if and when you get to that stage. They all said it was a really great and beneficial thing to do and, in reference to going into this line of work in the future, they all said excatly the same thing - you NEED to have evidence of have done some high level maths or physics from your degree and modelling work!

It was, again, another incredible day and I learnt loads and got a lot of good advice from various different people who definetly gave me a look to think about in terms my future!

Met Office Work Experience - Day 1 (for Monday)

I am an extremely lucky student as for a few days this week I will be at the Met Office in Exeter with the 'Oceans, Cryosphere and Dangerous Climate Change Gourp'; and today (Monday) was my first day! And, because this is such a privilege, I thought I would share with you some of the things I get up to and learn! You will have to bear with me on this thoughh as I can't even pretend to say that I understood everything that I heard about today - the vast majority of it went over my head - and I think my brain is still trying to take it all in!

One of the first things I did today was to sit in on a meeting of the Ocean Biochemistry Working Group whom, like the names suggests, do lots of research into the oceans - whether that be linked to ecocsystems or carbon dioxide uptake or DMS and lots more! Particular focus is placed on the factors affecing carbon dioxide uptake of the oceans and various negative feedback loops that they believe exist involing phytoplankton and temperature control (an idea I will come back to at a later date). This session was really interesting and gave me a really good insight into the work that some of the researchers at the Met Office do. Much of this research is based on calculating the amount of chlorophyll in the oceans and this can be linked to phytoplankton and plankton blooms. Due to its influence on global climate change, the study of such things is crucial in understanding likely future changes in climate. Phytoplankton take in carbon dioxide and is one of the ways in which the oceans take in carbon dioxide as it allows the carbon to sink deep into the oceans where it can be stored. This is an example of a biological carbon dioxide uptake process used by the oceans but there are also physical processes that are responsible for the ocean's uptake of carbon dioxide too. Carbon dioxide dissovles more easily in cold water that in warm water and it also dissolves more easily in sea water compared to pure water because sea water naturally contains carbonate ions (I will spare you from as much of the chemistry as possible at this stage!). The reaction of the carbon dioxide with carbonate produces hydrogen carbonate and because of this reaction, only 0.5% of the inorganic carbon in seawater occurs as carbon dioxide gas. Since levels of carbon dioxide are so low in seawater, more carbon dioxide can enter the oceans from the atmosphere. Something that I never knew before today was that carbon dioxide can be stored in 3 different 'forms' in the oceans and the oceans ability to do this enables it to store more carbon dioxide. Anyway, if the water stays at the surface and warms up as it moves around the globe, the carbon dioxide will relatively quickly escape back to the atmosphere but (this is where I can make a link to my EPQ!) if the water sinks to the deep ocean, the carbon can be stored for more than 1000 years before the general ocean circulation (via the upwelling of the THC after it has completed its circulation of the globe) returns it to the surface. This is one of the reasons that the current circulation pattern is so important as regions in which the sinking of deep water occurs are also, therefore, major physical carbon dioxide removal areas - especially the North Atlantic.

After a tour of the building (which is massive and very modern!) I attended a seminar on "The sensitivity of the energy and water cycles to different forcing agents" by Nathalie Schaller from the Institute for Atmospheric and Climate Science, ETH Zurich, Switzerland. I will try and talk about some of the background of this seminar as the majority of it discussed various models - something that went way over my head! It is now commonly accepted that, as a result of anthropogenic influences, primarily greenhouse gas emissions, that the hyrdological cycle, on a whole, will be intensified which, in turn, will have major impacts on human soieties and ecosystems. Therefore it is vital that more reliable statements about future changes to precipitation patterns can be found and this is where various global climate models come in. The variabilty produced by various models leads to some uncertainities which are then only amplified by the added complications of forcing agents such as solar forcing and carbon dioxide. So, basically, this seminar consisted of the results of running various simulations with different forcing factors, at varying levels and over varying temporal and spatial scales, to see what the likely impacts are. I think that one of the main messages was that the relationship between the energy and hydrological cycles with the forcing factors, especially CO2, was not linear and so say increasing the forcing agent by x2 wouldnt just lead to twice the impact on the hyrdological cycle and in many cases it is more. Despite the content being far to advanced for me to even start to really get an substantial understanding of it, it was really interesting to see some of the worrk happening in various research departments around the world and, if I manage to do a bit of reading over the next few days, I may write a post on the alterations that the discussed factors could make to the movement pattern of the ITCZ and the global impacts of this as this was something briefly touched upon.

Then, to finish off a great day, I had a discussion with a researcher about ocean circulation. Lots was covered, which I won't go into too much now but I am hoping to be allowed to include some of it in my EPQ. Something I think I will briefly discuss is the idea of vorticity as it is important in explaining the differing characteristics of eastern and western boundary currents and the formations of gyres - I might elaborate on it at a later date (perhaps including some maths!). Energy and mass are not the only properties that must be conserved as momentum also has to be - both in terms of linear momentum (associated with motion in straight lines) and angular momentum ( associated with rotatory motion). Vorticity essentailly means the 'tendency to rotate' and it is referred to as 'tendency' rather than simply 'rotatory motion' as water can be aquiring both positive and negative vorticity at the same time. Therefore, instead of saying the conservation of angular momentum or tendency to rotate, it is referred to as the conservation of vorticity. Ocean water have rotating movements on all scales - from large basin wide subtropical and subpolar gyres to tiny eddies. For water to have vorticity, therefore the tendency to rotate, it doesn't have to been enclosed in a closed system as, as long as there is a current shear (a change in velocity at right angles to the direction of flow), rotatory motion will be possible. Mainly due to the fact that it apparently makes the maths easier, a tendency to rotate anti-clockiwise is referred to as positive and a tendency to rotate clockwise is referred to as negative. I mention a before about that fact that water could aquire both positive and negative vorticity and the first time I heard this I was a little confused but an example I was given helped me to understand it a little better. So, water could be aquiring positive vorticity as a result of current shear provoked by friction with an adjacent water body or coastal feature (say a spit), whilst also aquiring negative vorticity from a wind blowing clockwise. Therefore the actually motion will depend on the relative sizes of the two tendencies and so, in theory, no rotational motion could be the result as the tendencies could be equal. This rotatory motion is caused by wind stress and so is said to be relative vorticity but, as with anything linked to ocean cicrulation, the rotation of the Earth complicates things and so the vorticity possessed by a parcel of fluid on the rotating Earth actually has planetary vorticity - this is where the Coriolis force links in. When I have talked about Coriolis force before, I have explained it in terms of the poleward decrease in the eastward velocity of the surface of the Earth. However, although this is okay for the basics, there is something missing........... In addition to this linear eastward velocity, the surface of the earth also has an angular velocity which means that, in the Northern Hemisphere, it turns anticlockwise about a local vertical axis (southern hemipshere is opposite). This angular velocity os latitude dependent and so there would be a relative motion between the moving parcel regardless of the direction it was initially travelling in; with this relative motion increasing with increasing latitude (this applies to both winds and currents). This is where a lot of maths comes in but I will try and skip over most of it as I am struggling to get my head around all of it! Linear eastward velocity decreases with latitude whereas the angular velocity about a local vertical axis increases latitude. The bigger the angle between the Earth's axis of rotation and the local vertical axis, the smaller the angular velocity of the surface of the Earth about this local vertical axis and so, at the Equator, where a vertical axis is perpendicular to the axis of rotation, the angular velocity is zero. So, I guess what I am trying to say is that any parcel of fluid on the Earth shares the components of the Earth's angular rotation, appropriate to that latitude. I hope you kind of followed that - if you did it would be really good to know as then maybe I can include it in my EPQ! It is quite a tricky area and I am still trying to fully understand it and I haven't even got into much of the maths yet! I will come back to this idea soon though as when you combine it with a summary of Stommel's (he is this guy who has done loads of thereotical stuff on the basics of ocean circulation) calculations, it helps to explain the characteristics of different boundary currents - which is both relevant to my EPQ and I find it quite interesting!

Sorry for not going into much detail about these things but I still need to do a bit more further reading and perhaps some images to aid my explanation and my brain is rather tired and I need a good nights sleep! Honestly, I don't think I slept at all last night as I was like a little kid on Christmas Eve - but to be honest who can blame me as, being an aspiring Geographer, I really couldn't of asked for much more as a kind of early Christmas present really! Anyway, I will come back to these various topics at some poitn soon and write something that is more beneficial for you all to read...................

I have another extremely interesting day to look forward to tomorrow with another meeting, seminar and some more discussion groups and so, if I manage to contain my excitement, my blog post will hopefully make more sense and be a bit more logical!

Sorry that this is a bit late in arriving, I couldn't seem to get the post to publish over the last few days so its kind of all out of time but better late than never I suppose!

Wednesday, 8 June 2011

Geography Picture of the Day - Why has the USA experienced so many tornadoes this year?


An image shows the damage created by a tornado last week in the USA.
The community featured, to the right, is the community of Sturbridge and is
one of many that settlements that was damaged by the tornado.

The brown scar that runs down the middle of this image depicts the path taken, and the devastation left in its path, by a tornado that ripped through south-west and south-central Massachusetts last week. The tornado travelled over 63 kilometres and was 800 metres across at its widest point. Rated 3 out of a potential 5 on the enhanced Fujita, or EF, scale, it left four people dead, overturned cars and reduced buildings to rubble.  The EF scale, similar to the Fujita scale, has the same basic structure of 6 catergories (zero to five) and is used to represent the damage inflicited by tornadoes. The main difference between the Fujita scale and the revised EF is that the EF was designed to reflect better examinations of tornado damage surveys so that winds speeds could be better aligned with the damage caused.

This tornado is one of more than 875 tornadoes to have hit the US since the beginning of the year which, in total, have claimed the lives of more than 363 people, thereby,  making 2011 one of the deadliest years on record for US tornadoes (link to an interactive map that compares the number of deaths, caused by tornadoes, over the last decade)

So, just why have the USA experienced so many tornadoes? Well, for a tornado to form, cold air needs to sit upon warm, moist air whilst the winds need to go in different directions, at different heights.

(Slightly more detailed explanation of tornadoes formation)

 Over the last couple months, the jet stream, which has been stronger than usual, has dipped south over south-west America, therefore bringing them a string of storms. This change in path has been sustained which is why the south-west of the USA has frequently witnessed devastating tornadoes.

 Does it link to global climate change? It is impossible to unambiguously link this to climate change, due to a lack of older records, but many say that the frequency of such tornadoes has increased over the past decade. So, could this become a common occurence.............. It is hard to say as the effect of global climate change on tornadoes is unknown as, although rising global average temperatures will mean that their is more warm air around, it could also reduce the temperatre gradient between the poles and equator - the crucial factor that generates the jet streams in the first place. One thing is for sure though, after the destruction caused, so far, this year, the people of America will be hoping that this doesn't become an annual event.


Sunday, 5 June 2011

Existance of Climate refugees - fact or fiction?

Finding room for those displaced by climate change is an issue that is being viewed with greater and greater concern and India is one of the nations most worried about the possible influx of environmental migrants that they could experience, as rising sea levels threaten an increasing percentage of the densely populated, low-lying, coastal regions of Bangladesh (for more detail and statistics see  previous post on Buoyant Bangladesh with the link to a really good National Geographic article). The chair of the IPCC recently spoke to India's Military College of Telecommunications Engineering and said that "Our defence forces might find themselves........guarding our borders against climate refugees, as rising sea levels swamp low-lying areas [in Bangladesh], forcing millions of climate refugees across India's border". And so, perhaps, in direct reponse to this threat, India have started to construct a 6 ft high, 2500 mile long concrete and barbed wire barrier along the India, Bangladesh border. However, the question that so many are wanting to hear the answer to is, just how many climate refugees can we expect?

Well, only one person has ever tried to calculate the number of climate refugees. In 1995 a British academic, named Myers, predicted that there were 25 million climate refugees (in 1995), due most in part to the drought-stricken African nations, and that this figuire would only continue to swell until it reached 50 million by 2010 and then 200 million by 2050. Since 1995, no one has tried to improve on these estimates or actually conduct a detailed review into excatly how many climate refugees exist and so Myers' figuires have continued to feature in reports by the IPCC, the UK's Stern review of economics of climate change and the UNHCR, despite the fact that many greatly question the accuracy of them. So, why is is so hard to calculate the number of climate refugees that exist? Firstly, the definition of a climate refugee is often under much debate. As explained in a previous post, Do developed countries have a moral obligation to help those displaced by climate change?, many believe that, technically, climate refugees should be classed as environmental migrants as they neither have the same rights as refugees or are fleeing from war or politcal instability; instead they are people who have been displaced by global climate change induced environmental disasters. Secondly, it is extremely hard, and many scientists are not prepared to stick their necks out and say so, to attribute events to climate change. For example the peak of the droughts in the Sahel, in 1973, lead to millions of people moving from the area and so did the Ethiopian drought of 1983-1984 which is estimated to have created 1.5 million refugees. Hurricane Katrina, of 2005, is believed to have created 300,000 permanent Amerian refugees and millions were displaced by the Pakistan floods last year. It is clear to see that these natural disasters have forced people to migrate but were these disasters induced by global climate change? This is slightly harder to prove but, as we gain a better understanding of the changes occuring it is becoming easier. Al Gore, famously, publically stated that human induced climate change was responsible for Hurricane Katrina and a few reports released this year, after the devasting flooding experienced across the globe which is attributed to an execptionally strong La Nina (which could be linked to the record high sea temperatures possibly provoked by global climate change) have started to publish links, with evidence, between disasters and global climate change [see Dealing with the aftermath of flooding for more detail on the reports published]. Finally, it is, often, difficult to discover the root cause of people's migration and although it cannot be denied that climate is frequently a contributing factor, whether or not climate alone causes people to migrate is different. Discovering whether or not climate is the root cause of migration is hard as this factor is normally shrouded by the clearly visible economic impacts that changes to the climate have. In Mongolia, for example, changes to climate led to the destruction of pasture land which had huge economic impacts on the local farmers and provoked them to move. Due to this they considered themselves as economic migrants when strickly speaking surely they are environmental migrants as the economic hardship experienced was provoked by changes to the climate. It can also work the other way around as, initially, the 1 million people in Mexico who were displaced, in the 1990's, by hurricanes and floods who first considered to be enviornmental migrants but after further analysis it was decided that they were in actual fact economic migrants as it was the economic crisis in Mexico that first provoked people to migrate and then this process was only accerlated by the hurricanes and floods. Myers intitally predicted large scale migration in India and China with 6 million environmental refugees in China, due to the expansion of the Gobi desert, but, a recent EU report concluded that it was, infact, the large scale development projects, like the Three Gorges Dam in China which has displaced 2 million, that has contributed the most to migration.

A recent review by the UNEP of several case studies concluded that, only, the 100 people from a coral atoll in Vanauta and 500 from an island in the Bering Strait, whose coastal villages were destroyed by waves, which had been intensified by the disapperance of sea ice, were actual climate refugees as they had to migrate inland for safety. Although this may prove that climate refugees are something more than a myth, it has fuelled further skeptism as 600 people compares rather badly with the 25 million Myers predicted and only strengths the arguement that climate refugees do not exist to the potentially catastrophic proportions predicted. Contributing to this belief is that fact that many don't think that climate changes necessarily lead to migration as migration is not the easiest thing to complete - especially when lacking the essential resources which are scarce during droughts and floods; two events that some view as being global climate change induced environmental disasters that provoke people to move. The Sahel area, over past decades, has been greatly affected by drought and so many have chosen to leave the area but latest figuires suggest that migration rates actually decreased during the worst droughts - this only supports the above belief held by some.  Many of those who hold this view fear that global climate change will actually have the opposite effect and instead of forcing millions to migrate, it will  remove the mobility of people and their ability to migrate to safer areas. Another agruement, against the existance of climate refugees, is the fact that perhaps people have always moved, and will continue to move as part of a stragegy to cope with the world's variable climate and take industry with them; thereby not moving becuase of a direct threat but because conditions are more ideal in another location. This starts to link in with something I started thinking about when I was revising the population module which is the impact that climate has on development and whether or not climate had a bigger impact on development when we started developing than it does to countries developing knowadays - but thats a topic for another post.

I can feel that I am starting to go slightly off track and if I continue this will probably go on for ever so I think will finish up pretty soon! From this, I think it is clear to see that it is extremely hard to calculate the actual number of climate refugees that exist, for the various reasons discussed, but perhaps even harder to prove that they don't exist. If this is true, is this a case of an environmental crisis provoking a population crisis or will the world  community be able to cope, as the global population continues to grow, with less habitable land? Will the global community respond by increasing the rate of urbanisation as cities are likely to be more greatly protected? Of course there is also the debate of where those, especially the estimated 30 million displaced, by rising sea-levels, from the Bangladesh coast line, are suppose to go? Is it right that India are building a physical barrier to prevent migration from Bangladesh? Who should take responsibilty for these people who, some, consider to be the victims of the developed worlds unsustainable lifestyles? The questions surrounding this topic are endless and the answers highly debatable (as with anything even remotely linked to global climate chage, it seems). Where do I stand on this topic........ Well, I am still a bit unsure on some of the things but I think I agree that climate refugees/enviromental migrants exist but to what scale I am unsure. I think part of the problem is that many are not aware about this issue and those that are displaced by climate change as it is not something that makes headline news all the time and I, myself, only found out about some of the case studies I mentioned above as I went looking for them. The other influential factor is that, climatic push factors are often shrouded by the more visible, resulitng, economic factors and so it is increasingly hard to determine the root cause. I do think though that global climate change, a likely environmental crisis, has the potential to provoke a population crisis and that, maybe, an increase in urbanisation would be an initial response - especially by those living in countries threaten by sea-level rise where the inland cities offer safety. If this was to occur then I believe it would be accompanied by detrimental social impacts such as issues with living conditions and sanitation, unemployment and food and water shortages. India building a barrier to prevent illegal migration and the movement of cows was always going to be a controversial move and although it will not help remedy the problems Bangladesh is and will continue to face, India itself cannot cope with an influx of migrants. When I was in India I spent most of  the time in Chennai, a city that is extremley densely populated, and if I am honest the thought of India's population exceeding that of China's before 2030 scares me as, already, only a tiny proportion have access to housing, sanitation, food, clean water, health care and education and shanty towns can be found in every direction you look and so at present, I feel that India cannot, without severly risking the already poor living standards of its population, help Bangladesh and its people on the scale needed. The idea of responsibilty is, with out a doubt, the one question that I am really struggling to make a decisive decision on and, after my last attempt at answering the question a few months ago, I am yet to make much progress on forming an opinion. Its tricky - especially when the effects that global climate change will have on all the different countries is still up for debate. Idealistically, I think that, if we view the world as being a global community then each country should do what it can to help out others which will mean that some countries will take more responsibilty than others  but with the present state of global affairs and politics I think that this is, perhaps, slightly to far from reality and won't occur unless necessity demands it too or politicians, especially in the most powerful nations, start to fully appreciate the significance of their nations interdependcy on some many others. I don't think I would, at present, be able to whole-heartedly agrue my opinions as I still have a few reservations and so I will probably come back to this at some point after further thought and a bit more reading around the subject but I am very intrigued to know what you think about it.........

Friday, 27 May 2011

The race for a million year old ice sample

Around every 100,000 years the Earth enters an Ice Age but it hasn't always been this way...... Up until about a million years ago the Earth swung between glacial and interglacial periods a lot faster, with this switch occuring every 40,000 years. However, no one knows why the time taken for Ice Age's to occur slowed and this is why scientists are so eager to find a million year old ice sample.


Axial Precession

At present, the switch between glacial and interglacial periods is believed to be influenced by three cyclical changes to the Earth's motion known as the Milankovitch Cycles, which were named after the Serbian astronomer who is credited with discovering their magnitude. The first of these cycles is called Precession and relates to the wobble of the Earth as it spins on its axis provoked by the gravitional interaction between the Sun, Moon and Earth. Precession occurs on a 26,000 year cylce and there are two forms - axial and apsidal precession. Axial precession is linked with the tilt of the axis in relation to the fixed place of the stars Vega and the North Star as the Earth wobbles from pointing to the North Star to pointing at Vega. If the axis tilts towards Vega then then the winter solstice in the Northern Hemisphere will coincide with the aphelion (point at which the Earth is furthest away from the Sun) and the summer solstice with perihelion (the point at which the Earth is closest to the Sun) thereby creating the greatest seasonal differences. When this occurs, the Southern Hemisphere experiences warmer winters and cooler summers and so a smaller seasonal difference. However, when the tilt of the Earth allows for the aphelion and perihelion to, respectively, occur near the autumn and spring equinoxes, the seasonal contrasts experienced in the Northern and Southern Hemisphere become similar.  At present, the perihelion is closer to the Northern Hemisphere's winter solstice therefore meaning a small seasonal difference in the Northern Hemisphere. Apsidal precession occurs when the Earth's orbit, as a result of the influences of the Moon, Jupiter and Saturn, starts to precess in space. This movement is known as the precession of the equinoxes and it effects the intensity of the seasons. So, in summary, Precession does not effect the amount of solar energy recieved by the Earth but the way it is distributed between the two hemispheres, therefore altering the seasonal differences experienced.

Apsidal Precession
 
Obliquity
The second cycle is the tilt of the Earth's axis which, I think, is normally known as Obliquity or the Angle of Inclination. Currently, the axis lies at a 23.4 degree angle and over a 41,000 year period this varies between 22 degrees and 24.5 degrees, thereby altering the latitundinal distribution of solar energy. This fluctuation in the angle of incidence causes changes in the intensity of the seasons experienced. As the angle of incidence increases, during summer, areas at high latitudes experience more solar energy whilst in the winter they experience a decrease in insolation (insolation is a measure of solar radiation energy recieved on a given surface area in a given time). This allows for permanent snow fields to form in the Northern Hemisphere.  In relation to low latitudes, changes in Obliquity have little effect as the strength decreases the closer you get to the equator. Therefore, changes in Obliquity alter the strength of the latitudinal temperature gradient. When the axial tilt is lower the Sun's solar radiation is more evenly distributed between the seasons but the difference in radiation recieved between the equator and polar regions is greater. A smaller degree of axial tilt would provoke the formation of ice sheets because warmer winters would result in more warm air, which has the potential to hold more moisture and so produce more snowfall. Ontop of this, milder summers would mean that less of the ice formed over winter would melt.


Circular orbit
 

Ellipictal orbit 
 
The third, and final, cycle is known as Eccentricity which is the shape of the Earth's orbit around the Sun. The changes in Eccentricity occur due to the gravitional influences of Jupiter and Saturn and the shape of the Earth's orbit around the sun changes from being ellipictal (eccentricity of 0.0607) to less ellipictal/more circular (eccentricity of 0.0005) on a cycle of around 100,000 years. This is of great importance to climate and glaciation as it alters the distance between the Earth and the Sun, thereby changing the distance that the Sun's radiation has to travel before reaching the Earth. This subsequently reduces or increases the amount of radiation recieved on the Earth in different seasons as this variation has a direct impact on the amount of solar energy recieved at perihelion in constrast to aphelion. Currently the Earth's Eccentricity is 0.016 which results in a 6.4% increase in the level of insolation recieved in January in comparison to July. This increase has been provoked by the 3% difference in the distance between perihelion and aphelion. When the Eccentricity is higher (so a more ellipictal orbit) the difference between the solar energy recieved at perihelion can be anything between 20% to 30% greater than that recieved at aphelion. The variations in Eccentricity also impacts on the length of the seasons and, at present, in the Northern Hemisphere, summer is 4.66 days longer than winter and spring is 2.9 days longer than autumn. Overall, Eccentricity influences the amount of solar radiation that reaches the Earth and so the fluctuations in Eccentricity play a key role in determining climate and the occurance of glaciation. 

So, a short summary about Milankovitch cycles......  basically the changes in Procession, Obliquity and Eccentricity alter the intensity and distribution of solar radiation hitting the Earth which then affects the climate, with particular reference to the extent of glaciation. Milankovitch used these variations to develop a mathematical model which linked insolation to the corresponding surface temperatures and from this model he came to the conclusion that variations in insolation at high latitudes were responsible for the increase and decrease in the size of the ice caps at the poles. One crucial thing that I have yet to mention is the importance of landmass when talking about the Milankovitch cycles as it helps to explain why fluctuations in Precession, Obliquity and Eccentricity are harder to locate in older records. The Northern Hemisphere is known as a Milankovitch sensitive region and, as mentioned above, the effects of alterations in the three cycles decreases as you get closer to the equator and lower latitudes - which don't lie in Milankovitch sensitive latitudes. Therefore, when Pangea existed, which was centred around the equator, the cycles did not have such a prominent effect............. and so the question is, what did? 

This is perhaps the most puzzling question surrounding the shift to a slower pace, by the Earth, around a million years ago as records suggest that their was no obvious change to any of the three cycles and this is yet another reason as to why finding a million year old ice sample is so important. Understanding this shift would enable us to understand why we have the climate we do today and, perhaps, even help us make better predictions for the future climate. One of the most common possible explanations for this shift, at present, is the idea of the slow decline in concentration of the carbon dioxide in the atmosphere that is believed to have started to occur around 3 million years ago. This would have reduced the greenhouse effect and, possibly, cooled the Earth to the extent that the tilt of the Earth towards the Sun, every 41,000 years, was no longer able to provide sufficient heat to melt the glaciers that formed in between.  Confirmation of this is required though and is dependent on the finding of a direct record of the ancient atmosphere. This can only be uncovered from the analysis of the air that became trapped in tiny bubbles within ice as the snow it formed fell to Earth. In 2005, the European Consortium for Ice Coring in Antarctica discovered, to date, the oldest ice core which has stretched our records of the ancient atmosphere back 800,000 years - however, this is short of the crucial time period in which the key transition from a 40,000 year ice age pulse to an 100,000 year one occured.  And so, the race is on to find this crucial million year old ice core........

The EPICA have been joined in the race by an Australian Antarctic Division, an American contigent and a research team from the Chinese Arctic and Antarctic Administration. The Chinese have already secured a location in east Antarctica but have been set back by the discovery that the ice sheets in this chosen location are growing from the bottom up which means that the ancient ice has most likely melted or been replaced already. The Australians are close to securing a site in the Aurora basin, also in east Antarctica, which is believed to be home to the thickest ice in Antarctica, however research needs to be done to ensure that they too don't experience the same set back as the Chinese. Despite this, climatologists remain optmistic that a million year old ice core will be found eventually as it is one of those things that is going to take time. Current drilling methods, which are very similar to those used in the oil industry, mean that to reach this million year old ice core, which is hoped to lie at around 3000 metres deep, will take three summer seasons due to the remote locations of potential sites, but advances in technology mean that this process could be sped up.

This race for the million year old ice core is clearly no where near finishing and, despite the competition that exists between the four teams, the international collaboration that exists will hopefully allow for this increasingly important clue, that will be provided by this crucial ice core, to be uncovered and consequently provide information as to why the climate we presently experience exists and perhaps even how and why, due to physical influences, it could change in the future.