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The palaeoclimatic fluctuations described in part 1 were due to factors beyond our control. Increased or decreased solar output, subtle variations in Earth's orbit, changing patterns of oceanic currents and products of volcanic activity have all played their part. To this equation we must now add the changes to the composition of Earth's atmosphere as a direct consequence of human industrial activity, on top of which all other factors will continue to play their part as they always have done.

So let's have a look at some present-day issues which, partly affected by our activities and partly natural, have a bearing on how our climate may change in the medium term.


Our planet is warmed by intense radiation from the sun. Without it, Earth would not be habitable. The radiation passes through the atmosphere (after certain wavelengths being filtered out by the ozone layer) and is absorbed or reflected by the surface. The ability of a surface to reflect sunlight (also known as albedo) is controlled by its composition. Snow and ice are much better reflectors than rock or water, for instance:

a heavy snowfall over Cadair Idris, February 2004. The snow's bright white appearance hints at the amount of solar radiation that simply reflects off it. The albedo value for fresh snow can be as high as 90%...

Plynlimon shimmers in a summer heatwave in July 2003. Land such as this reflects much less incoming solar radiation and absorbs most of it. The albedo value for moorlands such as these is well below 20%.

An easy way to demonstrate the effects of differing albedo values is to go out on a hot summer's day in a black T-shirt. You'll cook! White clothing is far more comfortable in heatwaves because it has a higher albedo value and reflects more incoming radiation than it absorbs.

Thus, in our current situation, we rely on the polar and mountain icecaps to assist in reflecting a proportion of the Sun's radiation back out into space. The less snow and ice there is, the less this reflectance can occur: instead more energy is absorbed. The more energy that's absorbed the warmer it gets and the more likely further melting is to occur. So that's one factor.


Greenhouse gases absorb heat energy which is trying to escape by radiation out into space. If you leave your car locked up on a sunny day then open it up after a few hours you'll have witnessed the greenhouse effect for yourself: while the car is very good at absorbing the incoming solar radiation, it's hopeless at getting rid of the consequent infra-red (heat) radiation that it generates, so that increasingly warmer air remains trapped inside until you open it and allow the airflow to bring the temperature back to an acceptable level.

To a certain extent we need greenhouse gases. It is estimated that they maintain the current avarage global temperature (about 15
oC) some 33oC above what it would otherwise be. In other words, without them we would have an average global temperature of -18oC. So to an extent greenhouse gases are beneficial. To an extent. Look at Venus, where CO2 forms over 95% of the atmosphere and the surface temperature is in excess of 460oC. That's an excellent example of the greenhouse effect taken to an extreme - the planetary equivalent of that car parked all afternoon in blazing sunshine. So we need that happy medium - not too much, not too little. Let's have a closer look:

an extremely simplistic representation of the heat-exchanges going on within Earth's atmosphere. Visible solar radiation (yellow) is partly absorbed and partly reflected by clouds and the Earth's surface. When such radiation is absorbed, the excitation of molecules in the absorbent (rocks, water, buildings etc) causes them to emit heat (infra-red) radiation (orange). Some of this escapes out to space via various complex routes. Greenhouse gases are able to absorb, rather than transmit, infra-red photons, and cause a "back-radiation" back towards the lower layers of the atmosphere. This in turn raises the temperature of those lower layers.

There are several greenhouse gases present in the atmosphere, of which carbon dioxide is the one in the news most of the time. It is established fact that levels of atmospheric CO
2 have increased during the last 100 years, from about 290 parts per million (ppm) in 1900 to around 375ppm now. The Intergovernmental Panel on Climate Change has extrapolated the rate of increase forward to 2100: the results indicate that, if unchecked, atmospheric CO2 will by then be somewhere between 650 to 970ppm. This in turn has been projected to cause an average global temperature increase of 1.4 to 5.8oC. Significant - or is it?

Advocates of a blissful continuity in the way we are doing things often cite palaeoclimatic figures at this point. There is evidence, for example, that CO
2 levels 500 million years ago were approximately 20 times greater than at the present day, and by 200 million years ago were still at 5 times the modern level. Therefore what's the problem? Our atmosphere is deficient in CO2!

All well and good, but remember, we are living in an unusual phase of Earth history in which we have experienced repeated, and in geological terms sudden, climatic oscillations from glacial to interglacial. These have been happening over quite predictable cycles, in the recent past. What we don't entirely know is how human interference with atmospheric composition effects these cycles. Yet there are some direct effects that we can consider:


The retreat of glaciers is well-documented from many areas of the world. Both direct melting and changes in precipitation (trends towards dryer conditions create a deficit in snowfall, inhibiting new ice formation) play their part. The result is that ablation of glacial ice by melting and sublimation is currently exceeding the rate of new ice generation with two results: firstly, glaciers are indeed retreating and secondly, and more importantly in the short-term, sea-levels are rising gradually.

a sketch-map of NW Europe about 10,000 years ago. Much more land is present than there is now because so much water was still trapped within the retreating ice. In Wales, all of Cardigan Bay was land: in fact, it has been estimated that the sea in this area rose by 90m as the last ice-age came to an end.

by 7,500 years ago the more familiar shape was emerging....

...while 6000 years ago it was pretty much as today.

The rate of sea-level rise following the end of the last glaciation has slowed as the phenomenon of isostatic adjustment has caught up with the rising waters. Isostatic adjustment in this context is the uplift of land that has formerly been under the pressure of a heavy ice-cap for thousands of years. It is a slow process that continues today and is responsible for some of the earthquakes that the UK experiences as movements take place along geological faults to adjust to the stresses set up by uplift. More pronounced in the northern UK (because this is where the greatest ice thicknesses were), its effects are less important further south: in fact, instead of rising, far southern areas are very gradually sinking

Although the rate of sea-level rise is currently slow, the rate of melting of glacial ice is according to many climatologists on the increase. The projected 2100 CO2 and temperature levels are a cause for concern as they will only encourage further melting: should the trend continue, the results could be serious. Why?

Because, for the first time EVER in geological history, we have a warming climate plus continued melting plus large centres of human civilisation established in low-lying coastal areas. It didn't matter to us whether or not the polar ice-caps were present during the Cretaceous Period. We weren't around to get worried. This time it's different.

high tide at Borth, on the Cardigan Bay coast, during the infamous Burns' Day Storm of 1990. It is not hard to imagine what would have happened, had the high-tide level been just a metre higher. Coastal population centres are especially vulnerable to sea-level rises.


Another issue that merits concern is the triggering of a cooling episode which may lead to prolonged dry and windy conditions. Ideal for desert generation, very unfortunate with a large population to feed.

Cooling episodes that lead to such conditions, such as the Younger Dryas and the early Holocene events are thought to have been triggered by large releases of cool, fresh water, derived by ice-melt, entering the sea in northern latitudes. Such occurrences can affect the thermohaline circulation of an ocean. Our currently mild, temperate climate is influenced by one such circulation - the North Atlantic Drift. Warm, salty water of relatively low density flows at the surface northwards, is cooled in wintertime and sinks in Arctic regions to the ocean floor. This deeper, cooled water then makes its way back south. Simplistically it's like a large conveyor-belt: trouble can occur if someone drops a wrench into one of the pulleys driving it. Large ejections of meltwater can do just this.

highly simplified diagram of a functional North Atlantic. The supply of the near-surface warm water drives our climate in NW Europe, which is far milder than it would otherwise be for the latitude.

If the thermohaline circulation is interrupted, the warm water cannot make it so far northwards and colder conditions extend further to the south. The lack of warm water interferes with the humidity of the troposphere (the bottom ~10km of the atmosphere where most of our weather goes on) - the lack of moisture means dryer weather patterns.

A prolonged disruption of the thermohaline circulation coupled with natural factors such as reduced solar input could see a progressively colder climate becoming established. The data from ice-cores suggest that this happens steadily (as opposed to "The Day After Tomorrow"), but inexorably. In the previous Holocene cooling events, renewed warming occurred and the climate recovered. The worst possible scenario is a steady deterioration into another full-blown glacial episode. Never mind that: it would take many centuries. Shorter-term cooling events like that which occurred 6000 years BP are potentially serious in the extreme. Why?

Because, for the first time EVER in geological history, we have a huge global population entirely dependant on successful global agriculture and the ability to distribute its products from the areas where production occurs to the areas where most of the products are consumed. Most of us in the West rely totally on this system to be successful. If it even half-fails due to a change to cool, dry conditions, we are in deep trouble. We don't even need a full-blown new Ice-age to create chaos.


So: will this happen? What will we see - further warming and deglaciation, accompanied by rising sea-levels, or a cooling event causing drought or even triggering a glacial advance? The truth is that, currently, we do not know - as ever we need more data - but given that there is now a large population in the way of any advancing climatic adversity, we need to do our best to find out and adjust the way in which our societies are organised accordingly.

We are organised in such a way that we are incredibly vulnerable to even localised severe weather events. A good example is thus: for centuries, we avoided building houses on the flood-plains of major rivers. But in recent years society has begun to regard the natural world as something that gets in the way of "progress" and the climate and its effects have been ignored. Housing estates have thus been appearing on flood-plains all over the place. And guess what? They have ended up being flooded. That's what happens on flood-plains, for heavens' sake! If the prevailing mindset is the one that ignores such irritations because they interfere with "progress" then we are already in deep trouble! And that's just one example.

It is surely better to understand any potential problems caused by our activities and attempt to deal with them, rather than to ignore the whole issue and possibly get a nasty surprise. For all the wealth and confidence of Western society, we are still entirely controlled by the natural world about us. We have to accept this absolute. Currently it supports us and our pleasantly indulgent lifestyles. One day it may be less capable of doing so, for all of our inventiveness and sophistication.

Put it another way. Here's a question. You have driven up a mountain pass, only to find at the top that your car's brakes do not appear to be working properly. The pedal feels a bit soft, and there's something that looks suspiciously like brake fluid dripping onto the tarmac underneath. Do you:

Phone a breakdown service on your mobile and get it trailered off to a garage mechanic in order to check them out and, if necessary, fix them. Better safe than sorry.


Pretend that there's nothing wrong, jump back into the drivers seat, and drive at high speed down the other side of the pass, where you know there are lots of hairpin bends and nasty drops?

Most of us don't know enough about braking systems to be confident enough to continue, and those who knew what was wrong wouldn't continue full stop. What will it take for us to develop a greater awareness of our changeable, sometimes friendly, but sometimes hostile, climate?

Remember again:

Climate change (impact definition): Change of the climate system that is faster than the adaptation time of social and/or ecosystems.


New! Fine Art Prints & digital images for sale-
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