Positive feedback to global warming keeps climate scientists up at night. Feedback can accelerate the rate of change in the climate. The worst-case scenario involves tipping points where the heating of the air and water make parts of the planet uninhabitable.
A frightening irony concerning global warming is the use of air conditioning to combat the heat. We obviously don’t think about cooling our homes and offices right now, but that is part of our problem. Using air conditioning requires power to generate the necessary electricity. The electricity comes to a large degree from burning fossil fuels which contribute to global warming. This short term reaction to a meteorologic phenomenon contributes to a long term climatological phenomenon.
Climate scientists call this positive feedback. Burning fossil fuels to run air conditioners contributes carbon dioxide to the atmosphere which traps heat and makes the planet warmer, which requires more air conditioning, which causes carbon dioxide release which causes more heating which… You get the picture.
In this case, the feedback has a human element. Other feedback loops are purely physical phenomena. These feedback loops add to the complexity of climate modeling. Predictions of future climate rely on computer calculations, the accuracy of which depends on how well the variables in a climate system are understood.
Water vapor in the atmosphere is without question the most important of the global warming feedback loops. Water vapor is a strong greenhouse gas itself; that is, its presence in the atmosphere traps heat and contributes to global warming. The positive feedback comes about because the amount of water vapor in the atmosphere is directly proportional to the temperature of the atmosphere. The hotter the atmosphere the more water vapor, the more water vapor in the atmosphere, the more heat trapped in the atmosphere, the more water vapor in the atmosphere, the more… you get the picture.
When natural gas (methane) is burned it produces carbon dioxide, a major greenhouse gas. Unburned methane released to the atmosphere is itself a potent greenhouse gas. There are vast stores of methane trapped in the permafrost of the tundra and the continental shelf under the oceans. As the planet warms, the permafrost thaws which releases methane. Methane release warms the planet thawing more permafrost which releases more methane which… you get the picture.
The amount of solar heating of the planet is a function of the albedo, the reflectivity of the planet. Sunlight is strongly reflected by snow-covered expanses near the north and south poles. As the climate warms due to global warming, the snow melts exposing soil which is much less reflective.
The less reflective soil traps more heat, warming the planet further, melting more snow, which traps more heat… you get the picture
The same is true of sea ice and the oceans. Ice is more reflective than water. As the ice cover melts, more heat is trapped, as more heat is trapped more ice melts… you get the picture.
A final irony is that as the area of the oceans covered with ice shrinks, it opens more area to exploration and untimely production of crude oil. Burning these fossil fuels adds more carbon to the atmosphere, which warms the planet… I hope you get the picture.
Dr. Bob Allen is Emeritus Professor of Chemistry, Arkansas Tech University.