WednesdayMay 18, 2011

(Human Impact on Global Climate)(Period 5 Only)

The Launch PadWednesday, 5/18/11

No Launch Pad Today.

AnnouncementsPlease 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-Weeks Date Issued Date Due

Lab – Air Masses, the Mid-Latitude Cyclones, and Weather Maps 4/20 4/25

Lab Quiz - Air Masses, the Middle-Latitude Cyclone, and Weather Maps 5/3 5/3

Lab – Weather Maps 5/4 5/6

Lab - National Weather Service Southern Regional Headquarters Local Weather

Information5/6 5/6

Test 10 5/10 5/10

Lab – Climate Change 5/13 ??

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 WarmingWater 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

CO2 concentrations over the past 1 000 years

Fossil fuel CO2 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 2100.

Average global temperature variations 1860–2006

The left half of the graph shows global temperature

changes for the 20th 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 1980-

1999. 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

higher 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 LabClimate Change