1. Climate and Climate Change Chapter 21

2. 21.1 What is Climate long-term weather patterns
based upon temperatures and precipitation
average temperature alone does not describe a climate
requires how weather varies through out the year
average precipitation does not necessarily describe the climate
precipitation numbers must be broken down by seasons

3. Climate description includes the following characteristics:
summer temperatures
winter temperatures
amount of precipitation by seasons
type of precipitation
sunlight
winds
direction
speed
steadiness
occurrence of severe weather

4. Climate controls

5. 21.2 Climate Zones
a location has a distinctive climate is base upon the climate controls
to help understand different climates around the world they have been classified by their similarities

6. 21.3 Climate Change Earth’s climate is constantly changing
minor heat budget changes can trigger climate change
global mean temperatures during the last ice age were only 5OC cooler than today
local temperatures show greater variation

7. Causes of Climate Change
Climate depends on the heat budget
changes can cause warming or cooling of the global and local climates
Changes in climate controls
can cause both global and local climate changes

8. Think, Pair, Share What things can effect Earth’s heat budget?
What can cause climate controls to change?

9. Causes of Climate Change
Earth’s motion effects intensity of the seasons
shape of Earth’s orbit varies with a period of 100,000 years
tilt of Earth’s axis varies between 22.1O and 24.5O with a period of 41,000 years
Earth’s axis of rotation precesses (wobbles) with a period of 23,000 years
Plate Tectonics – continents have not always been where the are today
changes in position affect
wind patterns
ocean currents
albedo
global temperatures (continents closer to the poles the temperature differences increase)

10. Causes of Climate Change
Sunspots
Earth’s temperature may change due to the number of sunspots
increase in sunspots, the sun energy given off increases
decrease in sunspots, the sun energy given off decreases
Volcanoes
dust and sulfur dioxide injected into the atmosphere can stay suspended for several years
suspended particles can reflect sunlight back to space resulting in a decrease of Earth’s temperatures

11. Human Effect on Climate
CO2 concentrations have increased since the 1800s due to
deforestation
burning and decomposing trees release CO2 into the atmosphere
reduces the number of trees available to remove CO2
burning of fossil fuels
Earth is currently experiencing a warming trend
Scientists are trying to determine the rate and if it will continue to warm through the use of climate models and the studying of past climate changes
Climate models are complex and must consider many factors, those described so far and
effects of oceans
changes in greenhouse gases
effects of different cloud types on sunlight at different elevations

12. Think, Pair, Share
Based on what you have learned so far in meteorology and oceanography how do scientists know about past climate changes?

13. Measuring Climate Change
past climate change evidence:
must use indirect evidence
sea-floor sediments
type and amount of microorganisms can give info on surface temperatures and changes over time
ratio of oxygen isotopes can indicate when there were periods of glaciation and no glaciation
glacier samples
Ratio of oxygen isotopes can indicate whether the snow fell during a warm period or cold period
tree rings
thickness of tree rings (growth rings) can indicate temperature and precipitation during the year it formed
tree rings indicate climate changes during a tree’s life

14. Measuring Climate Change
Other indirect evidence:
Soil layers
Fossils
Pollen
Corals
Fish bones
Stalactites
Historical documents
Various geological features such as hardened sand dunes and glacial sediments