Understanding climate change isn't complicated, but it requires some energy bookkeeping.
We get our energy from two sources: the sun, which is monitored carefully and changes little, and the Earth's interior, which, except for the occasional and relatively short-lived volcanic eruption, also does not change.
About 90 percent of the incoming energy gets stored initially in our planet's water, keeping it warm. The excess is radiated back into space. To achieve the sweet spot conditions of present-day life, greenhouse gases in our lower atmosphere reflect energy back to the earth like a protective blanket. Some of these are gases that we humans can cause to vary.
The major greenhouse gas is water vapor. At 70 degrees and 50 percent humidity it makes up about 2 percent of our air. If we had no water in our atmosphere, temperatures would vary widely over a day, the average temperature would be about 0 degrees Fahrenheit, the oceans would freeze over, and we would not be here. Fortunately, Earth has a lot of water in the atmosphere. You can see this when clouds form and carry water around to dump it as rain or snow. If the atmosphere needs to dump more water, severe storms and hurricanes result, as in the Aug. 12-14 Louisiana floods.
The upper part of the Earth's oceans initially store 90 percent of the energy from the sun. This increases ocean temperatures and expands the oceans (contributing about 30 percent of the measured ocean rise). As temperature increases, so does evaporation, putting more water into the atmosphere.
For example, for every 1 degree temperature rise due to increased carbon dioxide - or any other greenhouse gas - there is an additional 1 degree temperature rise due to increased water vapor. This positive feedback effect with water is true for all greenhouse gases. They are long lived in the atmosphere and control both surface temperature and the amount of water vapor in the atmosphere.
Although CO2 makes up only 0.04 percent (400 parts per million) of our atmosphere, it is the next most important greenhouse gas and plays a large role in climate change. Methane, the next concern, is 25 times more efficient than CO2 in reflecting energy back to the Earth. Its present concentration of 2 ppm is equivalent to 50 ppm CO2. The major contributors to the present sharp rise in methane are fossil fuel industries, including fracking.
Overall, these and other gases contribute to global temperature rise. Climate scientists construct mathematical models that aim to predict future conditions by studying fish migration as oceans warm, severe storms, global air and water circulation patterns and many other things. It's not just putting out a lot of temperature stations to get an average temperature.
To test their predictions, since there is no data on the future, they instead put their models through "back-casting" trials. We have a wealth of data from previous times. Models must be spot-on in "predicting" the past before they can be used for forecasting. Models have become very robust in their predictions.
The question now is what, if anything, should be done about increasing temperatures. It is not easily answered and must be discussed in a nonpolitical manner.
We need to ask all our elected representatives about their plans for addressing climate change. The time has passed to be satisfied with the sound-bite response "the temperature goes up and down; no need to be worried." It is quite possible the next election cycle may be too late for this discussion. Everyone needs to be concerned about the future. It is where you will spend the rest of your life.
Bob Kearney, amateur photographer, writer and retired University of Idaho professor of physics, lives with his wife, Kathy, in Moscow.
