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This paper was first written in 1990 - nearly 30 years ago - yet little has changed.

Except of course, that a lot of politicians and bureaucrats have put in a lot of air miles and stayed in some excellent hotels in interesting places around the world like Kyoto, Amsterdam and Cancun. 

In the interim technology has come to our aid.  Wind turbines, dismissed here, have become larger and much more economic as have PV solar panels.  Renewable energy options are discussed in more detail elsewhere on this website.

 


 

Climate Change

Issues Arising from the Greenhouse Hypothesis

 

Climate change has wide ranging implications for the World, ranging from its impacts on agriculture (through drought, floods, water availability, land degradation and carbon credits) mining (by limiting markets for coal and minerals processing) manufacturing and transport (through energy costs) to property damage resulting from storms.  The issues are complex, ranging from disputes about the impact of human activities on global warming, to arguments about what should be done and the consequences of the various actions proposed.  The following paper explores some of the issues and their potential impact.

 

 

The Causes of Climatic Change 

 

Climate changes all the time for many reasons.  Many of these effects are long term and plant and animal life has time to evolve to accommodate the changes.  Now, for perhaps the first time in history, climate may be changed very quickly by the impacts of human activity. 

Before the impact of human activity can be isolated the natural drivers of climate must be identified. The Sun is the main planetary climate engine. In the case of the Earth the Sun’s impact on our climate is mitigated by both geological and biological activity.

The Sun’s temperature is not constant year to year (with a peak every eleven years).  There is some evidence that the Sun is now hotter than it was a century ago.  Some scientists suggest that up to half observed global warming in the past 130 years is due to the sun getting hotter[1].

Regular changes in the Sun’s activity have a direct influence the climate. These changes in turn have an impact on biological activity that absorbs energy and converts carbon, oxygen and nitrogen (amongst others) into different compounds and changes the amount of water in the atmosphere and the amount of the Sun’s radiation absorber or reflected. 

Water amplifies or dampens these effects.  Snow and ice reflect the Sun’s energy many times more effectively than soil, plants or oceans.  If the planet warms to the extent that the polar and high-mountain snow and ice cover shrinks, then the planet will start to warm even more quickly. On the other hand higher precipitation rates may deposit more snow where temperatures remain below freezing year round (eg at the poles and on very high ranges).

We are observers of a tiny interval of time. Over geological time, the Earth’s climate and atmosphere has varied significantly.  Sea levels have risen and fallen a number of times in recent history.

The Earth is presently quite cool compared to its lifetime average but a lot warmer than more recently, during the last ice age.  Fossil and other evidence suggests that biological activity is higher when the planet is warmer.

Climate is changed by movements in the Earth’s crust (Australia was once under the South Pole) and temperature. These movements originally allowed liquid water to form. The distribution of the seas and continents changes over time changing the flow of ocean and air currents and limestone, created by biological activity, traps carbon dioxide in deep strata. Ocean currents have a strong effect on the amount of water vapour and heat take up by the oceans. At the present time there is a landmass under the Antarctic but not the Arctic.

The planetary orbit and present location of the continents has a lot to do with long term temperature change. The Earth’s orbit around the Sun is not circular and the earth’s axis is tilted so that one pole points more to the Sun than the other when the Earth is nearest to the Sun - this slowly cycles presenting first one pole to the Sun then the other. Thus it is presently colder in the Antarctic than the Arctic. In addition to cyclical changes there are factors such as the slowing of the Earth’s rotation and the Moon’s orbit.

Catastrophic events can also change the climate. Volcanic activity can change planetary temperature by increasing dust in the upper atmosphere (increasing reflection) and by emitting water and carbon dioxide.  It is estimated that there is more water and carbon dioxide trapped in the Earth’s crust than that in the atmosphere and the oceans combined. From time to time large objects in intersecting orbits (meteors, comets etc) hit the Earth. These cause temporary devastation and are thought to have resulted in past mass extinctions.

Although it is the main source of energy at the surface, the Sun is not the only source of the Earth’s energy.  The Earth’s central core is kept hot by the nuclear decay of elements under the massive pressure of the Earth’s gravity and by the effect of the Sun’s gravitational field.  Thus the Earth’s core is still molten after hundreds of millions of years and we find its decay products, such as uranium and radon gas, on the surface.  Heat energy is constantly leaking to the surface and deep mines must be cooled to allow miners to work in them.  In some places, such as mid ocean expansion zones, this heat is constantly emitted. It is assumed that this activity has been more or less constant for many millions of years but this may not be so.

It is difficult to be sure that changes in the climate are due to any one factor. But there are deep-seated cultural reasons for believing that it is mankind that is responsible for bad weather[2].

 

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