Wednesday May 18, 2011 (Human Impact on Global Climate) (Period 5 Only)

The Launch Pad Wednesday, 5/18/11 No Launch Pad Today.

Announcements Please check your yearly average in this class. If you are below 70 for the year, please come and see me ASAP! There are only two more grades remaining!

Assignments For This Six-WeeksDate IssuedDate Due Lab – Air Masses, the Mid-Latitude Cyclones, and Weather Maps 4/204/25 Lab Quiz - Air Masses, the Middle-Latitude Cyclone, and Weather Maps 5/3 Lab – Weather Maps5/45/6 Lab - National Weather Service Southern Regional Headquarters Local Weather Information 5/6 Test 105/10 Lab – Climate Change5/13??

Human Impact on Global Climate Humans have been modifying the Earth’s environment over extensive areas for thousands of years. The use of fire changes the environment. Overgrazing of marginal lands can cause changes as well. Most hypotheses of climatic change are to some degree controversial.

Global Warming Water vapor and carbon dioxide absorb heat and are largely responsible for the “greenhouse effect” of the atmosphere. Burning fossil fuels has added great quantities of carbon dioxide to the atmosphere.

Energy Consumption in the United States, 2004 Figure 20.17

CO 2 concentrations over the past years Fossil fuel CO 2 emissions

Americans are responsible for about 25% of the world’s greenhouse gas emissions.

The Atmospheric Response It is a fact that global temperatures have increased. The balance of evidence suggests a human influence on global climate change. Our globally-averaged surface temperature is projected to increase by 34 to 42ºF by the year Average global temperature variations 1860–2006

The left half of the graph shows global temperature changes for the 20 th Century. The right half shows projected global warming in different emissions scenarios. The shaded zone adjacent to each colored line shows the uncertainty range for each scenario. The basis for comparison (0.0 on the vertical axis) is the global average for the period The orange line represents the scenario in which CO2 concentrations were held constant at the values for the year 2000.

The Atmospheric Response Atmospheric trace gases like methane, nitrous oxide, and certain chlorofluorocarbons, absorb wavelengths of outgoing Earth radiation. Taken together, their warming effects may be nearly as great as carbon dioxide.

Climate-Feedback Mechanisms Climate is a very complex interactive physical system. Thus, when any component of the climate system is altered, scientists must consider many possible outcomes. These possible outcomes are called climate feedback mechanisms.

Climate-Feedback Mechanisms So far the climate-feedback mechanisms we discussed have magnified the temperature rise caused by the buildup of carbon dioxide. Because these effects reinforce the initial change, they are called positive-feedback mechanisms. However, other effects must be classified as negative-feedback mechanisms because they produce results that are just the opposite of the initial change and tend to offset it.

Springtime breakup of ice near Antarctica. The inset shows a likely feedback loop.

Human-generated aerosols are concentrated near the areas that produce them. Because aerosols reduce the amount of solar energy available to the climate system, thay have a net cooling effect. Here we see a dense blanket of pollution moving away from the coast of China. the plume is about 120 miles wide and 360 mile long.

Table 20.2

Some Possible Consequences of Global Warming Global warming can alter the distribution of the world’s water resources and can effect the productivity of agricultural regions. It can cause a rise in global mean sea level. By changing weather patterns, global warming could cause a h igher frequency and intensity of hurricanes. It can cause shifts in the paths of large-scale cyclonic storms. Global warming could also cause changes in frequency and intensity of heat waves and droughts.

Global Sea-Level Rise

The Effects of Sea-Level Changes on Gently- Sloping Shorelines

The Effects of Sea-Level Changes on Steeply- Sloping Shorelines

Sea Ice Melt

Figure 20.26B Sea Ice Melt

Shrinking and Disappearing Lakes

Video - An Inconvenient Truth

Continue Lab Climate Change