Large Scale Human Impacts

• As the human population is rapidly increases, humans are creating larger environmental changes.

• Two major concerns are:– Ozone depletion– Global climate change

Ozone Layer• a layer of concentrated ozone gas made up of three

oxygen molecules (O3) between 20 and 50 kilometers above Earth’s surface absorbing harmful UV radiation

UV-c = most harmfulUV-b = main cause of most sun burnsUV-a = least harmful

Ozone Depletion

– Since the 1970’s scientists have been finding evidence that the ozone layer was thinning

• Holes in the ozone layer were eventually found above both poles

– Ozone holes caused by CFCs (chlorofluorocarbons) which break down ozone molecules

Ozone cont…• Destruction of the ozone

layer has increased the ultraviolet radiation reaching Earth’s surface.

• chlorofluorocarbons -chemicals used in refrigeration (Freon) and aerosol cans, and in certain manufacturing processes

Ozone Depletion

protects from UV rays

Loss of ozone above Arctic

Progression of atmospheric damage

Impacts• Ozone layer absorbs most of the harmful UV-B

radiation• more UV-B means:

– more melanoma and non-melanoma skin cancers– more eye cataracts– weakened immune systems– reduced plant yields– damage to ocean eco-ecosystems- kills producers-

phytoplankton– more damage to plastics

Effects of loss of Ozone

Wrinkles & SKIN CANCER

Ozone Success

• A phase out of cfc’s was enacted in 1987

• In 2000 the majority of governments banned the use of cfc’s

• Ozone depletion has now slowed, and recovery is expected over the next 50-100 years

Global Climate Change

• As human consumption of fossil fuel has increased, so has our emissions of green house gasses

• As these gasses have accumulated in our atmosphere, they have contributed to a change in the average temperature and climate on earth= global climate change

Climate Change

• A 0.5°C increase in the average temperature of the biosphere has occurred in the past 120 years (abiotic factor)– Natural variations do contribute to the variation

in climate– However, human activities are adding carbon

dioxide and other greenhouse gases into the atmosphere, making the atmosphere retain more heat

• More carbon dioxide from burning fossil fuels, cutting down trees and burning forests

How it works…• Greenhouse Gasses trap and redirect

infrared radiation back to the earth. This causes warming, like a car in the sun

• The greenhouse effect is actually beneficial- without it, earth would be too cold to support much life.

Different surfaces reflect different amount of light/radiation

• What happens when the glaciers melt??

Most Important Greenhouse Gases

Source: U.S. EPA 2005

GHGs:• Water: H2O• Carbon Dioxide: CO2

• Methane: CH4

Source Examples:Oceans, Rivers, Plants,

SoilCombustion, Respiration,

deforestation + burningWetlands, Oceans,

Combustion, Animals(thawing permafrost)

http://www.for.gov.bc.caPCC slide no. 034

Sources of anthropogenic greenhouse gases (2007)

Source: U.S. EPA 2009

by gas by sector

Methane By Source

U.S.

186.1

EuropeanUnion

127.8Russia

68.4Ukraine

21.7Poland

14.4

China

57.6Japan

31.2

Australia

7.6

India

15.5

Kazakhstan

10.1

South Africa

8.5

Canada

14.9

Mexico

7.8Trinidad and Tobago

United Arab Emirates

Kuwait

Total CO2 emissions

Between 1950-2001 in billions of tons

TIME magazine, 2001

US: 4% of world’s total population

25% of the world’s greenhouse gases

China:25% of the world’s population

8.5% of the world’s greenhouse gases (since 1950)

China emission

How cars generate CO2

Source: Murray 2005

CH2 + 1.5O2 CO2 + H2O

6.3 lb/gal

20 lb/gal

PCC slide no. 005

Climate Change v. Climate Variability

We see the sum of both

Climate variability (e.g. Natural swings)

Climate change (e.g. warming trend)

Time (years)

"clim

ate"

More Evidence: Ice Cores

• Ice layers preserve information about each yearSources: NOAA, GISP2 websitesPCC slide no.

036

Correlations

• Carbon dioxide (CO2) and other greenhouse gases warm the planet

• Human activities have increased the concentration of the major greenhouse gases since 1750.

• Average global temperature has increased 1.3°F since 1906. Warming since the 1950s very likely (>90% chance) due to human increases in GHG

Scientific Consensus on Scientific Consensus on Climate ChangeClimate Change

+35%

+142%

+18%

Figure source: IPCC

Future climate change

Source: IPCC 2007PCC slide no. 008

Effects

• It may result in rising sea level causing more frequent and more severe weather disturbances

• Environmental changes benefit some species, but greatly disturb others that may not survive

Effects1. Increase in the global temperature.2. Melting of polar ice caps and glaciers.

1. Sea level rise- displaces people and habitats

3. Changes in the climate of certain areas of the world.4. Increase in the number and severity of extreme weather

events– hurricanes and tornadoes.– Increased droughts in certain areas of the world– Increased flooding worldwide

5. Decreased biodiversity in the coral reefs and rainforests.6. May affect food production in key food producing

nations.

Sea Level Rise

• Melting of– Greenland Ice Sheet

– Antarctic Ice Sheet

– Glaciers and ice caps

• Expansion of heated (warm) sea water

2 - 4C warming by ~2100

0.18 - 0.59 meter rise in sea levelIPCC (2007)

Arctic Sea Ice (in September)

data from National Snow and Ice Data Center (Boulder, CO, USA)

2005

5.6million km2

2007

4.3million km2

sea ice edge (where normally found)

Loss of Sea Ice

PCC slide no. 038

Source: Arctic Council 2004

Could be a runaway process

Solar energy

Production of oxygen

Storage and recycling of nutrients

Regulation of climate

Purification of water and air

Storage and distribution offresh water

Food production

Nursery habits for wildlife

Detoxification of human andindustrial wasteNatural pest and disease controlManagement of soil erosionand runoff

Section 6-4

Ecosystem services are provided, but it’s your responsibility to help save the Earth!

Go to Section:

The Value of a Healthy Biosphere

• What we have to remember:– A healthy biosphere provides us with

many valuable goods and services (food, medicine, temperature control, water purification, soil formation, etc)

• Make wise choices about resources used, disposal, recycling, and energy conservation