Climate change basics Ch. 19

Atmospheric changes lead to climate change Changes in the ozone layer Changes to the greenhouse effect

The ozone problem The ozone layer blocks UV radiation (high energy radiation from the sun). UV is dangerous because it causes skin cancer, cataracts, immune system problems and kills plants and animals. UV kills phytoplankton.

Why is there an ozone problem? A hole in the ozone layer has developed over the south pole. It was primarily caused by human use of CFCs, which were used as propellants in aerosols and in cooling systems such as air conditioning and refrigeration.

CFCs are banned The Montreal protocol banned the use of CFCs and our production is nearly zero now. CFCs are persistent and remain in the atmosphere to react with and break down ozone for a long period of time.

We are now shifting gears. Forget about the ozone problem for a minute We are now shifting gears. Forget about the ozone problem for a minute. Now we’re going to look at the greenhouse effect.

The greenhouse effect Heat is molecular motion. Earth’s atmosphere naturally absorbs some lower energy (infrared) radiation from the sun. This energy is absorbed by the molecules and causes them to vibrate faster. These vibrations transmit heat to the surface of the earth.

atmosphere Some naturally occurring molecules in the atmosphere absorb the IR heat better than some others. These are called the greenhouse gases.

Which gases? Water vapor Carbon dioxide Methane (CH4) Nitrous oxide (N2O) Ozone (O3)

Some are manmade CFCs and HCFCs are entirely manmade, but absorb/radiate heat in the same way. These are not natural parts of the atmosphere, nor are they produced much anymore, yet they are very persistent so must be considered.

Scientific consensus After many years of research by thousands of scientists, the verdict is in. Humans have increased the concentrations of greenhouse gases in the atmosphere and are causing the climates around the planet to change.

politics In the United States, the discussion of anthropogenic global warming has recently been politicized. It has become a popular position to be a “skeptic” and to suggest that AWG is not real or is a hoax. The evidence for a warming climate and the human cause of it is overwhelmingly strong. The scientific community is not divided on this issue.

How do we do science? Rachel Pike: The science behind a climate headline . James Balog explains why he is worried.