A Companion to the Philosophy of Technology

The Science of Global Warming

By absorbing infra-red or “heat” radiation from the earth’s surface, “greenhouse gases” present in the atmosphere, such as water vapor and carbon dioxide, act as blankets over the earth’s surface, keeping it warmer than it would otherwise be. The existence of this natural “greenhouse effect” has been known for nearly two hundred years; it is essential to the provision of our current climate, to which ecosystems and we humans have adapted.

Since the beginning of the industrial revolution around 1750, one of these greenhouse gases, carbon dioxide, has increased by over 35 percent and is now over 380 parts per million (ppm) – a higher concentration in the atmosphere than for many hundreds of thousands of years. Chemical analysis demonstrates that this increase is due largely to the burning of fossil fuels – coal, oil and gas. If no action is taken to curb these emissions, the carbon dioxide concentration will rise during the twenty-first century to two or three times its pre-industrial level.

The climate record over past centuries shows a lot of natural variability arising from external factors (such as changes in the sun’s energy or the influence of volcanoes) or from internal variations within the climate system. However, the rise in global average temperature (and its rate of rise) during the twentieth century is well outside this range of known natural variability. The twelve warmest years in the instrumental record that goes back to 1860 have occurred ...