The Role of Natural and Anthropogenic Forces in Climate Change

Reader Contribution by Richard Hilderman and Ph.D.
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As this summer’s heat wave lingers on some people speculate that the current global warming trend is part of the natural cycle and there is nothing for us to worry about. Unfortunately the wealth of scientific data does not support this hypothesis. It is true that over geological time the planet has seen higher temperatures than we are witnessing today. However, there are two important differences between past natural cycles and the current global warming trend. The first difference is that previous global warming trends evolved over long periods of time (thousands of years) while the current trend is evolving at a much faster rate and takes only decades. Secondly, humans were not a contributing factor in earlier natural cycles.

In the natural cycle orbital variations of the Sun initiate global warming. This initial warming then triggers the release of the greenhouse gases carbon dioxide and methane and these gases amplify the orbital warming (my posting entitled Role of Milankovitch Cycles and Sunspots in Climate Change). In other words, the natural climate cycle is due to both orbital changes and greenhouse gases. These natural cycles have been occurring for millions of years long before humans entered the picture. The scientific consensus is that climate change is happening and that humans are responsible for the increased global temperature over the last century (my posting entitled Fossil Fuel and Atmospheric Levels of Carbon Dioxide). After a half century of scientific work it is clear that the human footprint on the planet is overwhelming the natural cycle. The natural cycle is being over whelmed by humans because of their use of fossil fuel which introduces are carbon overload into the atmosphere (my posting entitled Carbon Cycle).

The speed of human induced climate change is happening at a much faster rate than that of earlier periods. The temperature difference between the end of the last ice age and today is 5 degrees Celsius and this occurred over 10,000 years. This is a temperature difference of 0.05 degrees Celcius per 100 years. In contrast the observed rate for the past 50 years is 0.7 degreesCelsius (1.4 degrees per 100 years)! It is easy to comprehend that the ability of species to adapt to climate change over 10,000 years is less difficult than over 100 years. Most plant species can’t migrate faster than one kilometer per year. It is this fast change on the world’s ecosystem that could trigger major extinction of both plants and animals. A recent report in Science magazine demonstrates that global warming is already causing a migration of both plant and animal species poleward and to higher elevations. 

This rapid ascent of the global temperature along with rising sea levels will also necessitate humans to migrate away from the sea. Over 100 million people live less than 3 feet above sea level. What will happen when we these climate refugees start moving inland?

Some people also state that there is nothing we can do about global warming except adapt. They are correct that we must adapt. Hopefully one of the adapting measures will be to convert our energy infrastructure from a fossil fuel base to a non-carbon base renewable energy source. Converting to a non-carbon base renewable energy source will make our adaptation less stressful.

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