Global warming: too much energy.

• Author: Robertson, Henry
• Position: 80% Less Energy - Report

The concentration of greenhouse gases in the atmosphere is increasing and the temperature is rising along with it. This phenomenon is usually called either global warming or climate change. Neither name is adequate to convey the danger and the challenge. Global warming, says Bill McKibben, "is better thought of as excess energy trapped in the atmosphere, which will express itself in every possible way." [1]

Climate change is caused by forcings and feedbacks. A forcing is a process or event that alters the energy in the system. [2] Human activities like deforestation and burning fossil fuels are anthropogenic climate forcings. We have it in our power to reduce them. But sometimes global warming triggers other events that reinforce it. These are positive feedback loops, and it may not be possible for us to stop them or even foresee them. Is there a tipping point beyond which global warming will be out of our control?

Greenhouse Earth

Water vapor is a greenhouse gas (GHG). It lets sunlight reach the Earth but prevents some of the long wavelength, infrared radiation that rebounds from the planet's surface from escaping to space, trapping its heat energy in the atmosphere. We need GHGs. They act like the panes of a greenhouse to warm the Earth, which would otherwise have a surface temperature of 0[degrees]C or below instead of 57[degrees] [3]

Clouds play a dual role. High, thin clouds warm the planet while low, thick ones cool it. Next in importance as a GHG, and less ambivalent in its effect, is carbon dioxide, which only heats the atmosphere. Methane, the main component of natural gas, is 21 times more potent than C[O.sub.2] in warming the Earth, but it is less abundant and only stays aloft for 12 years, not a century like C[O.sub.2]. [4]

Human activity is increasing the amount of C[O.sub.2], methane and other trace GHGs. Scientists have reconstructed the history of C[O.sub.2] in the atmosphere from air bubbles trapped in ice cores drilled deep into the Antarctic ice cap. For 650,000 years the concentration of C[O.sub.2] in the air stayed in a band of 180-290 parts per million (ppm) by volume. [5]

Then, 200 years ago, the Industrial Revolution began, achieving unprecedented levels of production by burning fossil fuels, first coal, then oil, then natural gas. Industrialized economies are free from the constraints of direct solar radiation. They mine the solar energy of the past in the form of buried organic matter subjected to heat and pressure over a period of 300 million years. Burning combines the fossil carbon with oxygen to make C[O.sub.2]. Economic growth accelerated this mining; half of all fossil fuel consumed since the Industrial Revolution was burned in the last 20 years. [6]

In 1958, when measurements began on Mauna Loa, Hawai'i...