Fair Isle's uncertain future

What impact will climate change have on Fair Isle? Truth is, no-one really knows

I have just begun reading George Monbiot’s book, Heat: How to Stop the Planet Burning and am feeling rather miserable.

The optimistic, inspirational stuff will, I’m sure, come later in the book, but at the moment I’m still on Chapter One, and it’s just depressing. The world is getting hotter, the ice caps are melting, the water is rising, ecosystems are collapsing, crops will fail, people are going to starve, and frankly it’s all going to get much worse. Soon.

Up here in the North Atlantic we are extremely vulnerable to climatic changes, and global warming has already begun to have a serious effect on our weather, as well as on the environment around us. Unlike in many other parts of the world, however, where the effects of warming can be easily foreseen – drought, melting ice, etc. – here in Shetland the changes are worryingly unpredictable.

Ours is a relatively mild and stable climate. At 60° north, we are on the same latitude as Alaska and southern Greenland, but are considerably warmer through most of the year. This is, in large part, due to the effect of the Gulf Stream, which brings warm water from the Gulf of Mexico up to the most northerly parts of Europe. It helps keep the icebergs away from Lerwick harbour, let’s put it like that.

No-one is quite sure what the effect of global warming will be on the Gulf Stream. Some scientists predict a decrease in the circulation of water in the Atlantic, which could actually bring a dramatic cooling effect in the north. Most, however, are just not sure. It is, at the moment at least, a case of wait and see.

Here in Fair Isle we have our very own weatherman, Dave Wheeler, who has been providing the Met Office with hourly observations from the weather station on the island since 1974. In that time, Dave has witnessed a fairly steady increase in temperatures.

"In the last 30-plus years, the number of days with snow lying at 0900 hours between December and February has fallen by over 40 per cent. At the same time, the number of days on which snow or sleet was observed to have fallen (at any time during the day or night) has dropped by 25 per cent.

"Sea temperatures also continue to rise, most notably during the summer months, with a one to two degree Celsius rise over 30 years."

This upward trend in temperatures has been accompanied, in winter, by an increase in storm frequency and wind strength. In summer, it has meant more fog.

These changes, Dave says, have also brought a greater level of variability in the weather. Prolonged periods of cold weather are far less common than three decades ago, and summers too are increasingly unpredictable.

"An analysis of the daily mean temperatures appears to show that, during recent years, temperatures fluctuate (on a time scale of days to a week or so) far more widely than they did 20 to 30 years ago. I believe our climate is becoming even more variable than it was."

Small changes, particularly in sea temperatures, can have a huge impact on the ecosystem in the North Atlantic. Already certain types of plankton are moving north in order to escape the warming water. Some fish species are also doing the same. This, in turn, is affecting the success of breeding seabird species.

The long term future for the climate here at 60° north may be uncertain, but the short term future is not: in a few minutes I am going to pick up George Monbiot’s book again. I really need to get beyond chapter one.

Photos by Dave Wheeler

Malachy Tallack is 26 and lives in Fair Isle. He is a singer-songwriter, journalist, and editor of the magazine Shetland Life.
Getty
Show Hide image

Inside Big Ben: why the world’s most famous clock will soon lose its bong

Every now and then, even the most famous of clocks need a bit of care.

London is soon going to lose one of its most familiar sounds when the world-famous Big Ben falls silent for repairs. The “bonging” chimes that have marked the passing of time for Londoners since 1859 will fall silent for months beginning in 2017 as part of a three-year £29m conservation project.

Of course, “Big Ben” is the nickname of the Great Bell and the bell itself is not in bad shape – even though it does have a huge crack in it.

The bell weighs nearly 14 tonnes and it cracked in 1859 when it was first bonged with a hammer that was way too heavy.

The crack was never repaired. Instead the bell was rotated one eighth of a turn and a lighter (200kg) hammer was installed. The cracked bell has a characteristic sound which we have all grown to love.

Big Ben strikes. UK Parliament.

Instead, it is the Elizabeth Tower (1859) and the clock mechanism (1854), designed by Denison and Airy, that need attention.

Any building or machine needs regular maintenance – we paint our doors and windows when they need it and we repair or replace our cars quite routinely. It is convenient to choose a day when we’re out of the house to paint the doors, or when we don’t need the car to repair the brakes. But a clock just doesn’t stop – especially not a clock as iconic as the Great Clock at the Palace of Westminster.

Repairs to the tower are long overdue. There is corrosion damage to the cast iron roof and to the belfry structure which keeps the bells in place. There is water damage to the masonry and condensation problems will be addressed, too. There are plumbing and electrical works to be done for a lift to be installed in one of the ventilation shafts, toilet facilities and the fitting of low-energy lighting.

Marvel of engineering

The clock mechanism itself is remarkable. In its 162-year history it has only had one major breakdown. In 1976 the speed regulator for the chimes broke and the mechanism sped up to destruction. The resulting damage took months to repair.

The weights that drive the clock are, like the bells and hammers, unimaginably huge. The “drive train” that keeps the pendulum swinging and that turns the hands is driven by a weight of about 100kg. Two other weights that ring the bells are each over a tonne. If any of these weights falls out of control (as in the 1976 incident), they could do a lot of damage.

The pendulum suspension spring is especially critical because it holds up the huge pendulum bob which weighs 321kg. The swinging pendulum releases the “escapement” every two seconds which then turns the hands on the clock’s four faces. If you look very closely, you will see that the minute hand doesn’t move smoothly but it sits still most of the time, only moving on each tick by 1.5cm.

The pendulum swings back and forth 21,600 times a day. That’s nearly 8m times a year, bending the pendulum spring. Like any metal, it has the potential to suffer from fatigue. The pendulum needs to be lifted out of the clock so that the spring can be closely inspected.

The clock derives its remarkable accuracy in part from the temperature compensation which is built into the construction of the pendulum. This was yet another of John Harrison’s genius ideas (you probably know him from longitude fame). He came up with the solution of using metals of differing temperature expansion coefficient so that the pendulum doesn’t change in length as the temperature changes with the seasons.

In the Westminster clock, the pendulum shaft is made of concentric tubes of steel and zinc. A similar construction is described for the clock in Trinity College Cambridge and near perfect temperature compensation can be achieved. But zinc is a ductile metal and the tube deforms with time under the heavy load of the 321kg pendulum bob. This “creeping” will cause the temperature compensation to jam up and become less effective.

So stopping the clock will also be a good opportunity to dismantle the pendulum completely and to check that the zinc tube is sliding freely. This in itself is a few days' work.

What makes it tick

But the truly clever bit of this clock is the escapement. All clocks have one - it’s what makes the clock tick, quite literally. Denison developed his new gravity escapement especially for the Westminster clock. It decouples the driving force of the falling weight from the periodic force that maintains the motion of the pendulum. To this day, the best tower clocks in England use the gravity escapement leading to remarkable accuracy – better even than that of your quartz crystal wrist watch.

In Denison’s gravity escapement, the “tick” is the impact of the “legs” of the escapement colliding with hardened steel seats. Each collision causes microscopic damage which, accumulated over millions of collisions per year, causes wear and tear affecting the accuracy of the clock. It is impossible to inspect the escapement without stopping the clock. Part of the maintenance proposed during this stoppage is a thorough overhaul of the escapement and the other workings of the clock.

The Westminster clock is a remarkable icon for London and for England. For more than 150 years it has reminded us of each hour, tirelessly. That’s what I love about clocks – they seem to carry on without a fuss. But every now and then even the most famous of clocks need a bit of care. After this period of pampering, “Big Ben” ought to be set for another 100 or so years of trouble-free running.

The Conversation

Hugh Hunt is a Reader in Engineering Dynamics and Vibration at the University of Cambridge.

This article was originally published on The Conversation. Read the original article.