Review Outline for Exam 3

Difference between weather and climate

n Give some examples of important climate information that cannot be determined from knowing the “average” temperature and precipitation for a location.

n Why is the magnitude and frequency of extreme weather events so important in characterizing the climate of a given region?

n What is the definition of climate change?

Natural emission of radiation

n All objects emit radiation. How do the amount radiation energy emitted and the type of radiation emitted by an object depend on its temperature?

n Compare radiation emitted from the surface of the Sun with that emitted by the surface of the Earth.

What do the terms transmission, scattering, and absorption mean with regard to radiation?

n How do atmospheric gases and clouds interact with ultraviolet, visible, and infrared radiation? Generally understand the energy budget of the Earth with respect to solar radiation. (Most absorption occurs where? Reflection?)

n Be able to explain blue skies, white clouds, red sunsets, and haze

Energy balance for a planet

n Relationship between energy in, energy out, and temperature changes

n Radiative equilibrium temperature

Describe the basics of the atmospheric greenhouse effect (I do not expect you to be able to give a detailed explanation)

n Which two gases are the most important greenhouse gases in Earth's atmosphere?

n How strong is the greenhouse effect on Earth? Compare with Venus.

n What is the difference between the terms “greenhouse effect” and “global warming”?

n How do clouds influence the surface temperature of the Earth? Describe how clouds can act to cool the surface. Describe how clouds can act to warm the surface.

Energy balance for the Earth’s surface and atmosphere individually

n Know the material at the bottom of the lecture web page “Earth’s Energy Budget II”.

n Significance of radiation imbalances for surface and atmosphere. This drives the vertical or overturning atmospheric circulations (latent heat transfer), and establishes overall energy balance at surface and in the atmosphere.

n Significance of radiation imbalances at different latitudes. This drives much of the horizontal atmospheric and oceanic circulations, and establishes overall energy balance at different latitudes.

Recent increases in greenhouse gases (CO₂, N₂O, CH₄, CFCs and CFC substitutes)

n measured trends (do not memorize numbers) for each

n anthropogenic sources for each

Carbon cycle

n Understand the fluxes between the land reservoir and the atmospheric reservoir: photosynthesis and respiration, decay

n How have humans altered the natural balances in the carbon cycle? Describe the two human activities that are responsible for increasing the concentration of CO₂ in the atmosphere.

n Be able to explain the “missing sink” issue for atmospheric CO₂.

Climate feedbacks

n Be able to identify/distinguish positive and negative feedbacks

n Understand the specific examples given in class

Climate modeling and Impact Studies

n Examples of how climate models are tested

n Uncertainties in climate model projections

n Why do different climate models give us different predictions of future climate? What is the approximate range of predicted change in global average temperature by the year 2100?

n Difficult to model all the complexities of climate, including feedbacks

n Relative uncertainties in model predictions Global average changes vs. Regional changes in climates

n Uncertainties in the results of impact studies

n Possible consequences of global warming

Historical temperature record

n Examples of proxy records

n Climate has never been constant

n Climate before the Pleistocene Epoch compared with today

n Climate of Pleistocene Epoch

n Ice age cycles. How long ago was the peak glaciation of the last ice age? Based on the recent pattern of ice age cycles, when is the next peak glaciation expected?

n Climate of Holocene Epoch

n Time and Significance of the Younger Dryas event

n Time and Significance of the Holocene optimum

n Time and Significance of Medieval Warm Period and the Little Ice Age.

Recent (measured) temperature record

n What do temperature measurements taken in boreholes tell us about the global temperature changes over the last 500 years?

n General description of temperature variations since 1860

n Which two periods are inconsistent with global warming predictions (see handout)? Can any of these periods be explained by those who believe that recent global warming is primarily caused by greenhouse gas increases?

n Which periods are consistent with global warming predictions? How might this be explained by those who think the recent warming is not caused by greenhouse gas increases?

Be familiar with the items listed on the “Global Warming Summary Sheet.”

Read the Scientific American article and Is the Earth's Climate Fragile or Robust excerpt.