Atmosphere and Climate Change Chapter 13 Ms. Cuthrell Ecology 2nd Period

Global Climate Change Over 100 years ago the scientist, Arrhenius conducted a thought experiment: If the amount of CO2 in the atmosphere doubled, then temperatures would increase by ~8 °F. He thought this would take about 3000 years. We now think it will take less than 100 years.

Current Observations Average Global Temperatures - Rising for 40 years. The 6 warmest years have been in the last decade. Warming has been seen the most at northern latitudes, over land, and at night. The U.S. is warming the most in the West and Alaska. No significant change in temperature has been observed for the Southern U.S.

Current Observations There is now less Arctic Sea Ice and less snow on the top of mountains. Some observation scientist have made are snow melts earlier, rivers have been reduced, earlier Spring weather, longer growing seasons and changes in animal habitats and behavior.

Glaciers Melting

What is the Cause? The Earth is experiencing the Greenhouse Effect: Sunlight shines on the Earth, the surface absorbs the light, the surface converts the light and radiates (gives off) heat, some heat goes off into space, and gases in the atmosphere absorb the heat and warm-up the air. These gases are known as Greenhouse Gases. Greenhouse Gases trap heat like a blanket! The 2 biggest problem gases are: Water Vapor and Carbon Dioxide. More of These Gases = Warmer Temperatures

What is the Cause? Carbon Dioxide (CO2) - Increasing from burning fossil fuels and clearing land. Plants take in CO2 during photosynthesis but because of deforestation and urbanization, ~50% of the extra CO2 is staying in the atmosphere and remains in the atmosphere for hundreds of years.

What is the Cause? Tiny Particles (Aerosols) suspended in the air - Put into the air from pollution, dust/dirt from construction, and volcanic eruptions. These reflect sunlight and cool the planet. They have shorter lifetimes in the atmosphere (decades). They are heavier so the Aerosol Effect is going down as a result of the Clean Air Act. Changes in Landscape - Surface Land and Water Changes, Heat Islands have a large impact on local/regional climates.

How can we predict the future climate? Computers! Start with standard Weather Forecasting software, add in all of the things that affect climate around the globe and the computer gives a projection for several decades to centuries. It does not give specific dates or events. There are variations based on how much CO2 we give off in the future. To test the accuracy we make the software predict the climate that we have observed during the 1900’s.

What’s going to happen in the future? Temperature will rise over the next several years. Most of the Earth is water; it takes a lot of energy to heat it up! Water also holds heat for a very long time, The Northern Latitudes, land, and winter seasons will have the greatest warming and there will be less snow and more rain. More extreme weather such as hurricanes because there will be more heat waves than cold snaps. Some areas will have extended rainy or drought periods.

What’s going to happen in the future? In the U.S.- more rain for the northern states, drought across most of the mid-west and especially the South! Southern Europe will go into drought. Air quality will go down and the oceans will become more acidic from dissolved CO2. The sea level will rise from polar ice melting and water expanding as it warms up. Plant life in drought areas will put more CO2 into the air.

What is being done in response? In 1997 several nations met to talk about greenhouse gases where they came up with The Kyoto Protocol which agreed to work to reduce emissions of carbon dioxide to 5% below the amount produced in 1990. The US decided NOT to ratify this treaty in 2001 In the past year the EPA officially concluded that carbon dioxide is harmful to humans and CO2 can now be regulated under the Clean Air Act. Congress has been given the option to regulate the gas themselves but the problem is that Congress doesn't want to hurt businesses in the process.

What is being done in response? In December 2009 countries around the world met in Copenhagen, Denmark to talk about CO2 emissions. They tried to decide limits that should be placed on CO2 emissions. The problem is that developed countries don't want to make cuts if developing countries don't and developing countries think they shouldn't have too, since they are try to raise the standard of living. This is the same thing we did 50 years ago.

What is being done in response? The warming is part of the Earth's natural cycle - It's true, the Earth does have natural hot and cold cycles. You may be asking yourself, “But, If this is a cycle what in nature is causing the warming?” You cannot propose an answer without an explanation. How are the increased greenhouse gases not affecting the temperature? We know that they will absorb and trap heat. So why aren’t they?

What is being done in response? More CO2 in the atmosphere means that plants will grow faster - Yes, plants need carbon dioxide to grow but they also need a lot of other things like water, minerals, and nutrients. More CO2 just means plants have the resources to grow more, not that they will grow more!