Lecture 6: Human-environment relationships

Climate is a function of the interaction of what 5 spheres?

1. Atmosphere → gases

2. Hydrosphere → oceans, large bodies of water

3. Lithosphere → plate tectonics

4. Cryosphere → glaciers, ice sheets, snow cover

5. Biosphere → vegetation, animals, humans

If the climate has always been changing, what’s the concern about climate change today?

RATE of the temperature change  

When was the last glacial period? Was Canada covered?

• 18,000 years ago

• all of canada except northern yukon was covered

Why has there been a rapid rise in global temps since the 1900s?

Human industry —> increase in GHG’s

What are the 4 causes of climate change?

1. Variations in solar radiation → natural

2. Changes in compositions (gases) → human impact

3. Changes in earth’s surface → natural

4. Variations in earth’s orbit → natural

What is a sunspot?

a cool region of high magnetism on the sun

• cool areas on the sun that are surrounded by faculae (bright areas that emit high amounts of energy)

• they occur in cycles and reach a max every 11 years

When does the sun emit more energy?

During periods of high sunspot activity

more sunspots = more solar energy

What was Maunder Minimum (1645-1715)?

A period with no sunspots

• corresponds to a time known as the Little Ice Age 

How do changes in composition of the atmosphere affect climate change?

The addition of greenhouse gases (carbon dioxide, water vapour, methane) increases global temperature

• CO2 has a long residence time in the atmosphere (100 years) 

• Therefore, even though we are reducing carbon dioxide today, the effects will not be felt for decades

What are the 2 ways we can determine past climates?

1. The width of an ice layer

2. Dendrochronology (tree rings)

How do ice layers help us determine past climates?

• provides insight on the temperature and snowfall of that year.  

• Each year, a new layer of ice forms. 

• Bubbles of air are trapped in the ice (can show us gases composition) 

• Ice cores provide climate data for up to 600,000 years in the past  

How do tree rings (dendrochronology) help us determine past climates?

• Wide ring = warmer/wetter

• Narrow ring = cooler/drought  

• Tree rings provide climate data for up to 1000 years in the past  

 

How do changes in Earth’s surface affect the climate?

The collision of converging plates results in uplift and the creation of mountains

• This affects wind, temperature, and precipitation patterns on the surrounding landscape 

What is the Milankovitch Theory?

Proposes that 3 separate phenomena relating to earth’s orbit contribute to climate change

What are the 3 Milankovitch cycles?

1. Eccentricity

2. Precession

3. Obliquity

What is eccentricity?

Changes in the shape of earth’s orbit (from circular to elliptical)  

• 100,000-year cycle

• This cycle accounts for ice ages 

• most impactful cycle

What is precession?

The wobble of earth’s axis

• 23,000-year cycle

What is obliquity?

Changes in tilt of earth’s axis  

• 41,000 year cycle

• Changes in seasons 

Why does the greenhouse effect exist?

• greenhouse gases allow solar radiation to pass through, but they absorb infrared radiation from earth 

• Gases don’t allow heat to leave

How are humans enhancing the greenhouse effect?

By adding greenhouse gases, especially CO2

• Because more infrared radiation from the earth is absorbed by the atmosphere 

• Carbon dioxide emissions are rapidly increasing in China and India as the economies in these countries continue to industrialize 

What is ozone?

• It is a gas composed of oxygen with a pungent smell 

• Forms naturally in the stratosphere 

  • ozone in stratosphere = good

• It forms in the troposphere by chemical reactions with other gases  

  • ozone in troposphere = bad

• protects us from suns harmful UV rays  

No ozone = damage to skin

What is the major cause of the destruction of the ozone layer?

Chlorofluorocarbons (CFCs)

• CFCs were found in inefficient appliances, spray cans, and industrial processes

• Non essential uses of CFC were banned in North America in the 1970s 

  • Called the Montreal Protocol (1987) **ban CFCs 

  • Example of a worldwide agreement that has been successful (everyone signed!!)  

How do CFC’s destroy the ozone layer?

• Ultraviolet radiation breaks up CFC molecules causing the release of chlorine. 

• Chlorine rapidly destroys ozone  

• A CFC molecule can remain in the atmosphere for many decades  

  • have a high residence time

 

What is acid precipitation?

Precipitation that combines with pollutants that turn it acidic

• Main sources: sulfur oxides, nitrogen oxides

What are the effects of acid precipitation?

• slows tree growth

• reduces fish population in lakes

• erodes materials  

What is the pH scale range?

0-14

<7 = acidic

>7 basic

What is the natural pH of precipitation

5.5 → slightly acidic

Where is acid precipitation most common?

Most common in Eastern North America. 

When is the pH of lakes unliveable for aquatic life?

Aquatic life cannot survive when pH < 4.8 → too acidic

What was the Canada-U.S. Air Quality Agreement (1991)?

Treaty designed to reduce transboundary air pollution that harms human health and natural resources

• Specifically targeting acid rain and smog by setting limits on:

  • sulfur dioxide

  • nitrogen oxides

  • volatile organic compounds (VOCs)

What is a positive feedback loop?

A process in a system that encourages the continuation of the original process  

What is an example of a positive feedback loop specific to climate change?

• Less snow/ice decreases the reflectivity of solar radiation (because snow is highly reflective)

• Therefore, after snow/ice melts, more solar radiation is absorbed rather than reflected 

• This process leads to continually warmer conditions  

• It is the reason why the polar regions are warming the fastest (going from high albedo to low albedo)  

By 2050, where is the only remaining sea ice expected to be?

Ellesmere Island & Northern Greenland

How do we estimate how much the Earth will warm in the future?

Climate models

• work by solving a series of mathematical equations  

• What do the variables in the equations represent? 

  • greenhouse gases, solar radiation, other climatological components 

 

How much do climate models forecast that the earth will warm by in the next 100 years?

at least 1.5^o C

What does the IPCC stand for?

Intergovernmental Panel on Climate Change

What was the Kyoto Protocol (1997)?

A global agreement aiming to slow climate change  

• Objective was to reduce GHG emissions to 5 % below 1990 levels by 2010

• US and Australia did not sign  

• Canada pulled out once they realized they wouldn't reach the goal 

• unsuccessful

What are the 4 main impacts of climate change?

1. polar areas will warm most

2. boreal forests will expand northward → agriculture will shift northward

3. precipitation patterns will change

4. may be increased intensity of tropical storms & hurricanes

The issue of sea level rise:

• As sea level rises, erosion is affecting areas farther inland; some areas are eroding at 10 m annually

• Sea level is projected to rise as global climate changes and ice sheets continue to melt

• North America cities at greatest risk: Vancouver, Miami, New Orleans and New York 

Example of mitigating effects of sea level rise:

The Maldives

• ~80% of country <1m above sea level

• Seawalls have been built around many of its islands to protect from waves up to 2 m in height

What are the 4 main ways climate change affects humans?

1. Food production

2. Tourism

3. Human health

4. Biodiversity

What effects does climate change have on biodiversity?

• Warming temperatures will affect plant and animal habitats

• Coral bleaching (sensitive to warming ocean temps) 

• Loss of flora and fauna  

• Extinction risk for polar bears  

What is the most serious impact of climate change on humans?

The spread of malaria

• secondly is malnutrition

Two philosophies of human-environment relations:

1. Living in harmony with nature → sustainable development

2. Exploiting nature for economic gain → ignoring the costs of resource extraction

What are the realities of natural resources?

1. many natural resources are finite

2. using resources create waste products

Why is wind energy a good source of energy?

• Wind energy is a renewable and pollution-free  

• Winds farms are viable in areas with constant moderate winds

What are the 2 main issues preventing the growth of wind farms?

1. habitat disruption

2. appearance/aesthetics

Where are the best spots for wind turbines?

Along flat open land and coasts