1. Climate Change: Should We Be Worried? Chapter 17: Climate

2. What is Climate? Climate is the average weather in a location over a long period of time, typically 30 years or more. The conditions that are averaged are temperature and precipitation.

3. Factors That Affect Climate Latitude – The latitude at which you are located will determine how much solar radiation you receive. Because the Earth is tilted, the poles get their solar radiation on an angle, and the equator gets it more directly.

4. More Factors… Bodies of Water & Ocean Currents – Because water heats up and cools down more slowly than land, coastal cities will have a different climate than those farther inland. The temperature of ocean currents will also change the air temperature as well. Cold currents keep the coast cool, and warm currents keep the coast warm.

5. More Factors… Mountains – Because of their high elevation, temperatures are much cooler. Cities – Buildings and pavement absorb lots of incoming solar radiation, along with car exhaust. They create a “heat island” affect.

6. Classification of Climates Vladimir Koppen created this alternative system in 1918 and then it was modified by Geiger and Pohl in 1953. 5 major climates: tropical (rainforest, savanna), dry (desert), temperate (forest, grassland, desert, chaparral), cold (taiga), and polar (tundra).

7. Global Warming vs. Greenhouse Effect Scientists have looked at the natural cycles and events that are known to influence climate. The only way to explain the pattern is to include the effect of greenhouse gases (GHGs) emitted by humans. There are several greenhouse gases responsible for warming, and humans emit them in a variety of ways. Most come from the combustion (burning) of fossil fuels in cars, factories and electricity production. The gas responsible for the most warming is carbon dioxide, also called CO 2. Other contributors include methane released from landfills and agriculture (especially from the digestive systems of grazing animals), nitrous oxide from fertilizers, gases used for refrigeration and industrial processes, and the loss of forests that would otherwise store CO 2.

8. More on Greenhouse Gases… A molecule of methane produces more than 20 times the warming of a molecule of CO 2. Nitrous oxide is 300 times more powerful than CO 2. Other gases, such as chlorofluorocarbons (CFC’s) (which have been banned because they degrade the ozone layer), have heat-trapping potential thousands of times greater than CO 2. But because their concentrations are much lower than CO 2, none of these gases adds as much warmth to the atmosphere as CO 2 does. The "greenhouse effect" is the warming that happens when certain gases in Earth's atmosphere trap heat. These gases let in light but keep heat from escaping, like the glass walls of a greenhouse. The average global temperature and concentrations of carbon dioxide have fluctuated on a cycle of hundreds of thousands of years as the Earth's position relative to the sun has varied. As a result, ice ages have come and gone. Now, humans have increased the amount of carbon dioxide in the atmosphere by more than a third since the industrial revolution. Changes this large have historically taken thousands of years, but are now happening over the course of decades.

9. Solutions? Even if we stopped emitting greenhouse gases (GHGs) today, the Earth would still warm by another degree Fahrenheit or so. But what we do from today forward makes a big difference. Depending on our choices, scientists predict that the Earth could eventually warm by as little as 2.5 degrees or as much as 10 degrees Fahrenheit. A commonly cited goal is to stabilize GHG concentrations around 450-550 parts per million (ppm), or about twice pre-industrial levels.

10. Solutions Cont’d… Researchers have suggested reducing GHG emissions from a variety of sources with technologies available in the next few decades, rather than relying on an enormous change in a single area. Ways to do this are to improve energy efficiency and vehicle fuel economy (so less energy has to be produced), and increases in wind and solar power, hydrogen produced from renewable sources, biofuels (produced from crops), natural gas, and nuclear power. In addition to reducing the gases we emit to the atmosphere, we can also increase the amount of gases we take out of the atmosphere. Plants and trees absorb CO 2 as they grow, using carbon naturally. Increasing forestlands and making changes to the way we farm could increase the amount of carbon we're storing.