The climate change skeptic asks - 'Given that the climate changes over millenia due to powerful natural forces, how could humans possibly contribute any significant effect to climate change, given our brief existence in geological time?'

I shall try to answer that question with examples from engineering which show how short-term pulse events can significantly affect long-term cyclic events.

The Influence of Short-Term Events on Long-Term Events.

Many observed events can best be understood in terms of  cycles. The most obvious and visible cyclic events are the day/night cycle, the moon phase cycle and the season cycle. Cycles can be described mathematically in terms of time and space as amplitudes and durations. The radius of a planetary orbit is an amplitude, and its year is a duration. Real planetary orbits are nowhere near so simple, but remain cyclic nevertheless.

Tides, simply put, are a matter of amplitude (sea level variation) and duration (wavelength). Wavelength and amplitude are not sufficient to describe wave motions. As soon as we see two or more factors contributing to a wave pattern we must consider phase. Phase, simply put, is a measure of the degree to which any two waves are synchronised. We must also consider integration, the way in which waves contribute positively and negatively to a complex pattern.

There are some clear demonstration of wave patterns and interactions here, courtesy of Dr. Dan Russell, Kettering University.

This diagram shows a complex wave.

Here is another complex wave.

The first graph, from Illinois State Museum, is a plot of ice volume over thousands of years.  The second is a plot of speech sound over a few thousandths of a second.  Both graphs look chaotic.  Neither one is.  The speech graph is actually a plot of part of the English 'ou' sound in 'out'.

Stability and Instability in Wave Patterns.

An analogue television takes as input a complex wave, and shows a picture by plotting the waveform as scan lines of brightness and colour across a screen. The image has to be synchronised to the transmitted signal - we must know where in the waveform the start of each frame of the picture lies. Short pulses are injected into the transmitted signal to mark the start of each line, and each frame as a set of lines. Notoriously, older TVs were prone to interference from passing vehicles or aircraft. This would cause the picture to scroll vertically or to waver horizontally. Digital TVs are prone to a different kind of visual interference due to similar desynchronisation. A low energy brief pulse can destabilise a higher energy wave.

A wave pattern can be made stable by the injection of a brief wave or pulse at the appropriate frequency. This fact underlies much of the consumer electronics industry and is the subject of many patents. Conversly, a wave pattern can be made unstable by the injection of a desynchronising pulse. A passing vehicle with inadequate interference suppression, a drifting oscillator in a TV or monitor - examples are numerous. A regular wave pattern can be of exceedingly long duration, and a desynchronising pulse exceedingly brief. Nevertheless, the same dynamic principles apply. I must emphasise this simple fact: a low energy brief pulse can destabilise a longer duration and higher energy cyclic phenomenon.

Damping and Excitation.

If a periodic physical system has a force applied to it in such a way as to reduce the amplitude, it is said to be damped. Conversely, if the force tends to increase the amplitude, the system is said to be excited.

Excess damping can halt a cyclic system. Excess excitation can force a system into an overload or catastrophic failure mode. The common piston engine is a 'cyclic-event' machine. Water in tiny amounts can be injected into an internal combustion engine to improve its efficiency. This was done with the Merlin engine used in the WW2 Spitfire. Over-injection of water will cause over-cooling, leading to a drop in power and eventual stopping of the engine. Similar injection of nitrous oxide into a piston engine will also increase the power. Taken to excess, the engine will either overheat or over-rev, in either case the engine is severely damaged or destroyed.

Examples of Catastrophic Failure.

The Tacoma Narrows bridge and the Tay bridge collapses are widely known. Less widely known is the collapse of three cooling towers at Ferrybridge in the UK in 1965. These failures are briefly described in this report. I recall an official accident report citing venturi effects, but cannot find a link at this time. The venturi effect causes a lowering of pressure when air passes between two objects. That effect was overlooked when the towers were designed. Single models were used in a wind tunnel, not pairs or groups.

London's Millenium Bridge affords another good example of the pulse effect. Although the Romans, and probably the Greeks, knew about the need for soldiers to break step when crossing a bridge, it appears that the Millenium Bridge's designers never studied the history of engineering design.

Energy cycles and Climate Change.

Geological climate changes took place over vast amounts of time.
The span of the human race is but an eyeblink in comparison.

How very true! However. Over geological timescales the forces of nature laid down formations from which we extract coal, gas and oil. We are talking here about timescales measured in millions of years, with a relatively small deposit made in nature's energy banks every year. Taking CO2 out of the atmosphere through the use of solar energy had two effects. Firstly, the blanketing effect of CO2 as a greenhouse gas was kept within limits. Secondly, the effective extraction of the heat energy in sunlight and its storage in the energy banks undergound helped keep the planetary average temperature within limits.

The creation of organic molecules through photosynthesis absorbs energy. The conversion of biological remains into fossil fuels absorbs energy. Compare the energy rate and time period of geological deposition of fossil fuels as both carbon and heat energy with our current rates of heat energy and CO2 release.

Our exhaustion of fuel reserves implies the release as a geological scale short-term pulse of the carbon and the heat energy which was stored as part of a geological era.

Concluding Remarks.

In order to compare like with like, the total cooling effect of creating the fossil fuel stocks over millenia must be compared to the total warming effects of consuming them over decades. This effect of humans on the geological-scale rhythms of our planet needs to be investigated, rather than denied.

The thermal equilibrium system of our planet itself comprises multiple subsystems and factors. The single current most important, and most commonly overlooked perturbation factor is the heat released when fossil fuels are burned. The burning of fossil fuels at a geometrically increasing rate over a geologically brief period is, given our current knowledge of the physics, indisputably a significant factor in climate change. Not so much due to CO2 emissions, but due to the energy stored over millenia being released over decades. Only a fraction of this daily anthropogenic heat input is radiated into space.

Thermal Pollution causes global warming
Bo Nordell Division of Water Resources Engineering, Lulea University of Technology, Sweden - Dec 2001