Paul Alexander
Univeristy College Dublin.

"Climate Change and Dublin" - Adapted from Talks at local Schools / Residency meetings, Dublin 15.
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Global Climate Change is undoubtedly one of the most (if not the most) talked about, contested, and most challenging issue of our time.

It encroaches on every facet of live as we know

• It is in our politics - Our most recent example being the COP-15 meetings
• It is in our media - Rarely a day goes by without news of a weather event deemed to be "out-of-the-ordinary" by news reports
• It is in our popular culture - I can wager that 1 in 2 of you reading this will have at some point seen the movie "The Day After Tomorrow" and/or "An inconvenient Truth"

The term "Climate Change" almost instantly sparks questions, and simultaneously, debates on the answers, when really there is nothing wrong with the term itself, nor is there anything wrong with the even less popular term "Global Warming".

The Climate does change: it changes all the time: every second, every minute, every hour, every day, every month, every year, century and millennium the climate is constantly in flux: it is ever changing, it is simply a matter of "what scale?" over (/) "what time?".
From microscale / short time (minor precipitation increases/decreases over a day) to macroscale / long time (Global changes in temperature increase/decrease over thousands of millenium)

What Causes natural Change

Our planet is intimately linked with the Sun, life has thrived and diminished based on the amount of solar radiation we receive from it. This is the first thing to note in relation to this issue: that our planet goes through cycles of warm and cool periods controlled primarily by access to solar radiation, but has little to do with the amount of solar radiation emitted by the sun - rather it has to do with the Earth's tilt and the Earth's orbit.

Everyone is aware of this: In Ireland we have distinct climatic seasons, four of them in fact.

Summer, winter, spring and autumn represent orbitially related climatic changes induced by a change in our access to solar radiation -only marginal in scale and marginal in time. Seasons are far less distinct around the equalatorial zones.

Changing Climate

Changes in our orbit were identified by an Astronomer Milutin Milankovitch. He developed mathematical formulas upon which orbital variations are based, thus they became known as "Milankovitch-Cycles" or "M-Cycles" for short.

Picture a perfect circle, at the dead centre sits a large dot representing the sun, on the line of the circle itself, a smaller dot, representing earth - the line itself, represents our orbit around the sun. In this configuration, every side of earth gets some access to solar radiation depending on its location in orbit throughout our orbital cycle (one year).

Now we re-draw the configuration: All the initial elements are there, the sun, the earth and the orbit, but instead of placing the sun in the centre of the circle, we move it to the left-centre. So, for 1 season, one side of earth is going to get scorched, for 2 seasons, the status quo is maintained, and for the last season, things are going to get colder. A lot colder.

Now we re-draw the configuration again: Again all the initial elements are there, but this time we don't draw a perfect circle, we draw say, an elliptical shape (just imagine getting a squishy ball and pressing it flat down onto a table) - now everything is pretty messy, but for simplicity let’s say this orbital pattern means we get winter like conditions for 3/4 of the year, and about 1/4 of the year relief.

This underpins everything on earth as we know, Ice Age to Inter-Ice Age and back again, i.e. from 'cold spells', to 'warm spells', and back again.

Ireland's Changing Climate

The last 'cold spell' began in and around 30,000 years before present (BP) in Ireland's neighbourhood, this climatic shift caused the Arctic ice to descend from the North Pole Southwards, towards what is now Europe. By 20,000 BP Ireland was almost totally covered by a thick ice sheet stretching south-west from Scotland, changing the green colour that covered much of Ireland into a sheet of white.

This is significant, returning to the present for a moment: In the rare days we get sunny spells, (or more likely when you travel abroad to areas closer to the equator for a sunny holiday), you might notice a change in your clothing choice. Perhaps its now larger instinct but in sunny days, we tend not to opt for darker colours such as black, grey or brown, but rather lighter ones such as blue, pink and white. There is a reason for this (besides the Irish need to be fashion kill abroad) - Darker colours absorb more solar radiation, you literally feel warmer in a black top than a white top on a sunny day: this property of a material is known as albedo or simply "the reflectivity of a body". Its measured in percentages but if scientist talk about it, they usually use numbers from .01 (Very low reflectivity) to 1.0 (Highest reflectivity), but for our sakes 50% (.5 to the scientists) means about half of sunlight is reflected.

Fresh snow sits around at 90% albedo, meaning sunlight is largely reflected off its surface (ski-goers reading should be able to verify this; most will wear glasses to counteract the glare experienced while on the snow). If the sunlight is reflected like this, then it is unable to heat the surface - like passing your hand quickly through a naked flame.

This triggers what is known as a "positive feedback":

Less solar radiation means colder climate > colder climate leads to snowfall > snow leads to even less sunlight > which means less heating > which means more snow etc.

So we can see how ice ages endured long after the orbit returned to a similar regime that is in motion today. Back to Ireland 20,000 BP: Over the next 2000 years (18,000 BP) snow accumulation and expansion peaked, the expansion of the ice slowed, reached equilibrium and then eventually began to retreat.

By 15,000 BP only Ulster was still buried under the retreating ice sheet. Although the rising sea levels had begun to flood the lower lands, a land bridge still connected the south-eastern tip of Ireland to south-western England. Trapped between this land bridge (and the ice sheet still lingering in the north) the Irish Sea began to fill forming a vast freshwater lake. It was at this time that the first plant life returned to reclaim the rocky wilderness that Britain and Ireland had been reduced to under the harsh colder climate.

First rugged grasses coated the land and, around 13,000 years ago, the first trees (hardy Junipers) began to grow.
Many animals, including the Giant Deer, crossed into Ireland across the land bridge and since then, homo-sapiens have flourished and grown.

So whats the fuss about?

Hopefully the above has imparted that really there is nothing about the term "Climate Change" that should immediately cause contestation, nor "Global warming" (if there's global cooling, there has to be global warming) but where there is conflict is on Recent Climate Change and Recent Global warming.

I'm not writing to try sway readers; how you reach a decision is your own business and none of mine. What I will say here as a researcher, as a scientist and as a climatologist, there have been observed changes. The why of this is where people differ.

The Intergovernmental Panel on Climate Change (IPCC) is an organisation of over 1,500 scientists from around the world. They come from every walk of life; climatologists, economists, political analysis’s, planners, policy makers, engineers to name a few, and under the direction of their governing bodies, they study the big why question.

Now, its no secret that many scientists working together is a volatile collaboration even if they are all in the same discipline - so imagine this many and all from different disciplines - all with different training, different theories and different methods, different governments and different languages.

What changed people's minds?

Every 5 or so years they release progress reports, we know them as "assessment reports" and they are freely available for any of you to view (http://www.ipcc.ch/) be warned, they go into meticulous detail (some are a 7000 page read). Heads of house-holds reading might agree that co-ordinating even a small family unit into picking a movie at the cinema can be a chore, so in 2007 when the IPCC, the family unit times 300 or 400, announced that they had reached a scientific consensus, even those of us in the academic world not involved felt the sharp peak of our curiosity. What did we find?

In 2007 The IPCC released its 4th assessment report which stated that there was a 'scientific consensus' that much of the recent observed changes in our climate can be attributed to global warming and that humans are responsible.

Like anyone, else those of us not involved (after getting over this jaw dropping assertion) carried on with our own research - its a bit paradoxical, but when you want to make it big in academics, you try disprove a big theory to be forever immortalised as the one who took on 1500 scientists and came out on top.

Research to that end has been, on the whole, fruitless.

If the fact that so many scientists agreed on this wasn't enough, every research endeavour to the contrary found
"it all was, as is" (if you would like to discuss this further I'm always happy to meet up.)

This leads us to explaining the whole concept of how a global increase in temperatures can change climate, and rest assured its very complex (if the world is heating globally why is it winters have on average been getting colder in Ireland for example?) but thankfully - not an issue here. Here as is suggested, we are discussing Climate Change and Dublin.

So what is Climate Change then?

Well we've touched on it already, its simply a shift from one gear to the next and back, from one regime of climatic conditions (Such as Temperature, Precipitation, Wind and Storm patterns) to a different one.

Much of my own career so far has tried to at every opportunity avoid the why argument when it comes to talking or writing in non-academic literature; again whether or not you believe in human activities driving global warming is pretty irrellevant from my corner: For this moment all that needs to be stated is that I along with many other fine academics in Ireland look at whats happening.

Whats happening is an observed, documented and often violent, change in our climate.

So why Dublin?

If you study population statistics for Ireland, you'll note that much of our population lives in and around our cities. Dublin is the capitol city of Ireland. Its houses our population, our politics, our culture and a lot of tax payer investment.

Not only this, but Dublin is sitting right on the coast line, meaning that everything in Dublin is potentially very vulnerable to Climatatic Changes.

(Last update: 02/02/10)