Climate and Climate Change

Chapter 21

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

• 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

Climate controls

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

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

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

Think, Pair, Share

1. What things can effect Earth’s heat budget?

2. What can cause climate controls to change?

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)

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

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

Think, Pair, Share

Based on what you have learned so far in meteorology and oceanography how do scientists know about past climate changes?

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

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