The Home of American Intellectual Conservatism — First Principles

December 16, 2017

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On Climate Change
P. E. Hodgson - 02/13/09

The Evidence for Climate Change

By climate we mean the sum of the many variables describing the condition of the atmosphere: the temperature and humidity of the air, the rainfall, the strength of the winds, and the clouds. All these are constantly changing, and we can take averages for a local region or for the whole earth. Climate is determined by many natural causes, and in addition there is evidence that it is affected by human actions. We cannot do anything about the natural causes, but if there is a causal link between human actions and climate change we may have reason to expect the present changes to continue, and furthermore, we will have a strong incentive to take action to mitigate their harmful effects.

Such a causal link has been proposed. Extensive measurements have shown that the concentrations of carbon dioxide, methane, and some other gases in the atmosphere are steadily increasing. In the 1780s the level of atmospheric carbon dioxide was about 280 parts per million (ppm), as it had been for the last six thousand years. Industrialisation increased the level to 315 ppm by the 1930s, 330 ppm by the mid-1970s, and 360 ppm by the mid-1990s. In the last ten years the level has risen by a further 20 ppm. By the middle of the present century it could rise to 500 ppm. The annual increase of carbon dioxide is now 0.4 percent, that of methane 1.2 percent, of nitrous oxide 0.3 percent, of the chlorofluorocarbons 6 percent, and of ozone about 0.25 percent. In the European Union, fossil fuels are the main source: oil 50 percent, natural gas 20 percent and coal 28 percent. Of this, electricity generation accounts for 37 percent, transport 28 percent, industry 16 percent, households 14 percent, and the service sector for 5 percent. These are established facts, and in addition there is a strong correlation between carbon dioxide concentrations and temperature changes. It is then suggested that these increased concentrations are responsible for global warming and that global warming is responsible for other climate changes and predicted effects such as a worldwide rise in the sea level. The evidence for anthropogenic climate change has increased in recent years, and its reality is now generally accepted.

The connection between the increase in carbon dioxide and global warming is known as the greenhouse effect. The carbon dioxide in the atmosphere acts like the glass in the greenhouse; it lets the heat of the sun reach the earth, and some of this heat is emitted with a different wavelength that is stopped by the carbon dioxide. The heat that is trapped in this way warms the earth so that the average temperature is 14 C. Without the greenhouse gases it would be –18 C (or –64 F).

There is impressive evidence for the reality of climate change during the last few decades. Some of this has been described in a book by Sir Ghillean Prance, former Director of the Royal Botanic Gardens in Kew, London. [1] He recalls that there were devastating floods in Mozambique and Venezuela and quite serious ones in England. In other countries there has been drought that in the Midwest of the United States in 1988–9 caused losses estimated at $39 billion. Hurricane Mitch killed ten thousand people in Central America. The average temperatures are rising in many countries: of the five warmest years ever recorded in the United Kingdom, four have been in the last decade. The heatwave in 2003 killed about 20,000 people in Italy and 15,000 in France as the temperatures topped 40 degrees celsius during the day and 30 degrees celsius at night. Crops failed, forests burned, and rivers reached an all-time low. It was almost certainly the direct result of global warming. On a longer timescale, one result of these increasing temperatures is that in some regions the growing season for plants is increasing, with earlier development in spring, and autumn events being delayed. Birds and animals are also affected, and some species, unable to cope with the climate change, have become extinct.

There are however many examples of climate change occurring long before large amounts of carbon dioxide were emitted into the atmosphere by human beings. Some communities that have flourished for centuries have been destroyed by climate change. One example is the Anasazi who lived in Colorado and were finally forced by major droughts in 1130–1180 and 1275–1299 to abandon their cities and to move away to areas with a climate that allowed them to continue their way of life. Greenland, as its name implies, was at one time a fertile land and supported a colony of Vikings until colder weather forced them to move elsewhere.

Other changes have not been quite so catastrophic. The same cold spell around the fourteenth century caused parts of the Baltic Sea to freeze, and also the river Thames. In the 1930s the reduction in rainfall on the Great Plains in the USA, followed by winds that removed the topsoil and created a dustbowl, forced farmers to pack up and move away. In other parts of the world weather patterns are subject to violent changes. The normally regular monsoons in India, for example, can sometimes fail, causing catastrophic famines. The warm ocean current called El Niño can have disastrous effects on the eastern Pacific shores. It is now known to be part of a vast global water circulation, and satellite observations and computer modeling now enable some predictions of its effects to be made. [2] Thus for example severe floods and storms were predicted to occur in California in 1997–1998. During autumn and over Christmas the weather was fine, but in January and February hurricane-force winds battered San Francisco, floods rose, and mudslides swept houses away. Floodwaters submerged the freeway to Los Angeles and swept away the Southern Pacific railroad bridge. Fourteen years earlier another El Niño caused floods and landslides that caused a billion dollars worth of damage. In other tropical regions, the 1997–1998 El Niño caused over $10 billion in damage. There were severe droughts in Australia and Southeast Asia, vast forest fires in Indonesia and Mexico, and famine in Brazil.

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