Ch 14.1 & 14.3 Causes of Climate (Review) Latitude – differential heating Topographic effects – Proximity to water Altitude Mountain range Air Masses

Chapter 14.3 Climatic Influences/Changes 1. Seasons due to Earth’s tilt on its axis 2. Volcanism 3. El Nino 4. Solar activity (sunspots) 5. Milankovitch Cycle Part 1: Earth’s wobble (every 26,000 yrs) Part 2: Earth’s orbit (changes every 100,000 yrs) Part 3: Earth’s tilt (every 41,000 yrs) 6. Atmospheric composition

1. Seasons What causes them? The tilt of the earth on its axis. Seasons are NOT caused by distance from the sun. The hemisphere tilted toward the sun receives more direct radiation. How does this affect intensity?

2. Volcanic activity Big eruptions send a massive amount of dust in the atmosphere. It can remain suspended for years blocking solar radiation. IR from Earth is able to pass through clouds, dust and gas Cause cooler climate periods Short term climate change

3. El Nino Climate changes due to reversing of an ocean current in the Pacific Ocean. Basically, El Nino can flip climate conditions in many areas.

4. Solar activity Relationship between low sunspot activity and colder climates on earth. Maunder Minimum – low sunspot activity period More sunspots deliver more E to Earth’s atm so global temps rise Even though sunspots are cooler than normal According to current theory, sunspots occur in pairs as magnetic disturbances in the convective plasma near the Sun's surface. Magnetic field lines emerge from one sunspot and re-enter at the other spot. Also, there are more sunspots during periods of increased magnetic activity. At that time more highly charged particles are emitted from the solar surface, and the Sun emits more UV and visible radiation.

5. Milankovitch Cycle Part 1: Earth’s wobble The axis of the earth points to a different point every 26000 years. Switches cause summer and winter to be more drastic, because the earth will be closer to the Sun during summer and farther away during winter.

5. Milankovitch Cycle Part 2: Earth’s orbit Earth’s orbit cycles between circular and elliptical every 100,000 years. A more elliptical orbit = warmer climate because earth is closer to the sun.

5. Milankovitch Cycle Part 3: Earth’s tilt Currently the earth has a 23.5 degree tilt on its axis. Seasons are caused by the tilt changing throughout the year. The angle varies from 22.1º to 24.5º every 41,000 years. Less angle = seasons not as drastic (milder winter, cooler summer)

6. Atmospheric Composition Concentration of greenhouse gases, particularly CO2, is important in global climate regulation These gases trap heat inside earth’s atmosphere --> Greenhouse Effect Greenhouse effect – natural heating of earth’s surface caused by certain atmospheric gases (water vapor, carbon dioxide, methane, etc.). What does the amount of carbon dioxide have to do with climate?

Greenhouse effect video clip The gases trap heat that is radiated by the earth. It is NOT a human invention. It may be possible to increase or decrease the greenhouse effect by changing the amount of greenhouse gases (CO2) This is the current controversy To see how the Earth reacts to different forms of radiation, click here.

The “Greenhouse Effect” The Earth’s surface thus receives energy from two sources: the sun & the atmosphere As a result the Earth’s surface is ~33C warmer than it would be without an atmosphere Greenhouse gases are transparent to shortwave but absorb longwave radiation Thus the atmosphere stores energy http://www.windows2universe.org/earth/Atmosphere/earth_atmosph_radiation_budget.html

Other planets also have Greenhouse Effects, but these are unsuitable for life Venus Atmosphere: mass 90x earth’s GH Gases: >90% CO2 Sfc. Temp.: 477C GH Effect: 523C FAR TOO HOT! Sun Earth GH Gases: ~0.04% CO2 ~ 1% H2O Sfc. Temp.: 15C GH Effect: 33C NOT BAD! Although the high surface temperatures on Venus are partly attributable to its closer proximity to the sun, a primary reason is the strong greenhouse effect induced by a dense atmosphere almost entirely made up of carbon dioxide. In contrast, Mars is cold because it is farther from the sun than earth and has a very thin atmosphere. Despite the high CO2 concentration, the net greenhouse effect is much weaker than for earth. Reference: IPCC 1990. Climate Change: The IPCC Scientific Assessment [Houghton,J.T. et al. (eds.)]. Cambridge University Press, Cambridge, UK. pg. Xxxvii Images: NASA Mars Atmosphere: mass <1% earth’s GH Gases: >80% CO2 Sfc. Temp.: -47C GH Effect: 10C FAR TOO COLD!

Climatic Changes & Atmospheric Evidence

Objective 7: Evidence of atmospheric changes

Atmospheric CO2 Data Direct Measurements, Hawaii Evidence

Ice Core CO2 Data

Global Warming Temps have warmed over the last 200 yrs (scientists agree) Could eventually cause ice caps to melt, coastal flooding, deserts to spread, and more severe storms More… EPA…

Global Warming, pg 376!!! Scientists agree that temps are climbing Do not all agree about why Natural vs artificial (human) influences increasing CO2 in the atmosphere

The CO2 Cycle Natural process Sources: volcanism, metamorphism, respiration, fossil fuel burning, deforestation Sinks: photosynthesis, rock weathering, carbonate depsoition, ocean adsorption

The CO2 Cycle as Earth’s Thermostat Increased volcanism inputs huge quantities of CO2 into the atmosphere = T° increases T° increase causes increased chemical weathering and marine carbonate deposition which lowers atmospheric CO2

The CO2 Cycle as Earth’s Thermostat Feedback is not instantaneous! Perturbations in CO2 cycle take on the order of 500,000 years to restore.

Increase of carbon dioxide Burning of fossil fuels Deforestation How can we help?!?! Artificial

Renewable vs. Nonrenewable Renewable energy sources – energy from resources that are continually replenished Examples? Nonrenewable energy sources – take thousands of years to form. Cannot be replaced as quickly as they are used Compare and contrast benefits?

Renewable Energy Nonrenewable Energy