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Unwittingly in the beginning and knowing at present, we are conducting a gigantic, uncontrolled experiment with the Earth. Although many outcomes of this experiment are uncertain, they will surely be very harmful, if not catastrophic, for humans and many other species. Even if we could stop the experiment now, the force we have already unleashed will haunt us for centuries. The experiment is global warming. It is due to the human abuse of the environment as a consequence of the Industrial Revolution and the unrestrained population growth during the last 250 years.

It is important to understand certain basic concepts about climate change before we delve into its cause and its consequences. These processes will be incorporated in the topics discussed throughout this bookk. They are fundamental to understanding the broader aspects of climate change and global warming issues.

All planets with atmosheres undergo weather changes of one kind or another. The could patterns and atmospheric conditions on the giant outer planets are constantly changing, and that is also true for the inner planter (Figure 3.1). These changes reflect short-term weather conditions, not climate changes. Before we examine the Earth’s changing climate it is useful to explore the climatic conditions on other planets similar to the Earth in order to appreciate the uniquences of Earth and its climate system.

There have been a number of significant climate changes in the geologic past. In order to appreciate what is happening to our climate now, it is important to understand past natural climate changes and their possible causes. We have just begun to delve into the realm of past climate changes in detail, but there is now a fairly good understanding of the major climatic conditions during the past 700 million years.

The Earth’s climate can be divided into two general conditions, Hot Houses and Ice Houses. These general conditions are also shown on the geological time scal in Figure 4.1 Figures 5.1 abd 5.2 are diagrammatic representations of the distribution of these general climates over geologic time.

There is now good evidence that our present interglacial period has experienced some climate shifts that have affected the course of history in different ways. New studies indicate that these climate shifts were mostly regional rather than global and less severe than previously thought. Aside from a sudden cooling 8,200 years ago and short-lived cooling events caused by very large volcanic eruptions, the current global warming represents the most radical global climate shift in probably the last 1,800 years and definitely in the past 400 years.

Global warming is a reality and its causes are now well known. Of the causes of climate change discussed in Chapter 4, only two can operate on time scales short enough to account for today’s rapid temperature rise: (1) increase of greenhouse gases and (2) increase in solar irradiance. Although large volcanic eruptions work on a very short time scale, they cool the climate, not warm it.

The emission of greenhouge gases is proportional to a country’s population and economy. A very populous country with a modest economy can produce more greenhouse gases than a very wealthy country with a small population. Therefore, the largest emitters of greenhouse gases are the wealthy industrialized nations and the countries with the largest populations.

Each one of us is responsible for the release of greenhouse gases into the atmosphere. Every time we drive a car, turn on a stove or a light, hear or cool a house, or contribute waste to a landfill, we are directly or indirectly emitting greenhouse gases (mainly CO).

Much of the Earth’s ice is melting at an unprecedented rate. If we had no other information than this, we would be forced to conclude that the Earth was warming. The Earth’s ice deposits can be divided into four broad groups: (1) mountain glaciers, (2) sea ice, (3) ice sheets, and (4) ground ice in permafrost. All four types are left over from the end of the last ice age. During the Hot House periods in Earth’s history there were no accumulations of ice.