The World’s Inconstant Climate

The world’s climate is not and never has been constant. Climate, the long-term behaviour of weather, is inherently changeable. Not only are there gross changes over geological time scales (ice ages and interglacial warm periods) but smaller changes on much shorter time scales occur, too. Temperatures in Europe during the medieval warm period were on average 0,5 ^{0 C warmer than they are now. But just two hundred years later it was a different story. The sixteenth, seventeenth and eighteenth centuries were up to 1 0} cooler than today’s average temperatures. This was the time of the so-called ‘Little Ice Age’.

Recent climatic changes have been less marked¹ than our changes in mental attitude, and our perception² of the weather. During the 1980s there has been increasing concern³ that the weather has become more extreme, that the climate is changing for the worse, and that it’s man’s fault. This may be true, but there is no evidence⁴ to show that freak⁵ events are likely to become⁶ more frequent. It’s unlikely, for example, that major floods are occurring with any greater frequency than they have in the past, but modern reporting ensures⁷ that greater numbers of people are rapidly informed about such disasters. While freak weather is nothing new, it is a good talking-point when it does occur.

The 1780s experienced a historically interesting pattern of climatic variations which in some ways echo the changes now in evidence.⁸ Several extremes in temperature and rainfall during that decade resulted in⁹ extreme variability of the weather from year to year and season to season. The unstable climate began to be a major cause for concern. Complaints about sunless summers, prolonged winters, droughts and unseasonal frosts were the order of the day. Europe was experiencing the tail-end¹⁰ of the Little ice Age, and beginning to warm out of this cold period. But increased volcanic activity in the late eighteenth and early nineteenth centuries produced dust veils¹¹ in the upper atmosphere which may have prolonged¹² the cold spell. The two conflicting influences were possibly the cause of the extreme variability.

Although the dust veils probably had an overall effect of keeping global temperatures down by partially blocking and scattering the sun’s rays, it is not believed that volcanic activity was responsible for the climatic change which caused the Little Ice Age in the first place. Some scientists believe that the Little Ice Age could have been the result of¹³ changing solar output rather than dust in the atmosphere. The sun’s output probably varies by about 0,1% during the eleven-year solar cycle, and this fact has recently been related to sunspot activity; the fewer the sunspots, the less the sun’s output. There were very few sunspots during the seventeenth century, so this is the most likely cause for the cool period.

The next Ice Age is still in the distant future, and our present concern is for the climate during the coming hundreds, rather than thousands, of years. But human concern is unavoidable. If the current global warming trend continues, and if it is due to man’s activities, we could be creating major problems for our children. Climatic change is a natural phenomenon, but Man’s excessive burning of fossil fuels may have begun to create climatic¹⁴ changes of a magnitude¹⁵ unprecedented in human history.