Climate Change and Ozone Loss Chapter 20

The Greenhouse Effect We know that short wave radiation from the sun passes through the air to earth with little difficulty, excepting that clouds and certain pollutants reflect sunlight back into space. The radiation that reaches the ground/water warms it and then is reradiated as long wave radiation. This long wave radiation is slow to escape through the atmosphere and therefore keeps us considerably warmer. (Thankfully! We would be at -18ºC otherwise, bbhhuuurrrr!)

Do you know? 1.What are the four most important greenhouse gases? 2.Which gas is believed to be most directly responsible for global warming? 3.How much is the earth expected to warm in this century? 4.What are three things that make global warming effects hard to predict?

Greenhouse gases Water vapor is the most important, but is variable and hard to determine if we impact directly Carbon dioxide is the largest of the manufactured gases, mostly from burning fossil fuels Ozone is a greenhouse gas in the troposphere Methane from the anaerobic breakdown of organic matter Nitrous Oxide (N 2 O) – from smog and nylon production, burning coal and biomass CFC s in the troposphere act as a greenhouse gas

Global Warming Carbon dioxide has been steadily increasing over the last forty years and many scientists believe that global warming is occurring due to increased amounts of this gas Source- Canadian Climate Center, Hadley Center (UK), Intergovernmental Panel on Climate Change 1990 was the hottest decade on record (coincidence?)

How hot will we get? Scientists believe that we will increase between 1 – 3.5ºC or 1.8 – 6.3 ºF (now that’s hot) Realize that a 1ºC increase would make the planet hotter than it has been in 10,000 years

Why is global warming hard to predict? Solar output varies Oceans absorb unknown amounts of energy Clouds reflect light and will vary with changing moisture content in troposphere Ice reflects light and will change with temperature and precipitation Global weather/climate pattern are not fully understood

Global warming effects Warmer oceans will release stored up carbon dioxide further warming planet Melting ice will not reflect sunlight further warming planet Melting permafrost will release trapped methane further warming planet Positive Feedback Loops!!!

Global warming effects Warmer oceans may have different current patterns –Disrupts “normal” weather patterns causing increased weather related catastrophe –Can kill reef/fish ecosystems –Change wind patterns shift pollution to new areas

Global warming effects With increased carbon dioxide some plants may flourish reducing/removing carbon dioxide from the air, but as they decompose they release more methane into the air The world’s ecosystems are too complex for us to properly model on computers at this time