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Lecture 22

11:375:101 Lecture 22: Climate_Change


Department
Environmental Sciences
Course Code
11:375:101
Professor
Craig Phelps
Lecture
22

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Climate Change
Chapter 19: Climate Change
19-1: How Is the Earth’s Climate Changing?
Considerable scientific evidence indicates that the Earth’s atmosphere is warming
at a rapid rate that is likely to lead to significant climate disruption during this
century
Weather and Climate Are Not the Same
Weather is short-term changes
Temperature, air pressure, precipitation, wind
Climate is average conditions in a particular area over a long period of
time
Temperature and precipitation
Fluctuations are normal
Climate Change is Not New But Has Accelerated
Over the past 10,000 years
Interglacial period
Over the past 1,000 years
Temperature stable
Since 1975
Temperature changes
Accelerating
19-2: Why Is the Earth’s Climate Changing?
Scientific evidence strongly suggests that the Earth’s atmosphere has been
warming at a rapid rate since 1975 and that human activity has played a major
role in this warming
The Natural Greenhouse Effect Plays a Key Role in Climate
Greenhouse gases absorb heat radiated by the Earth
The gases then emit infrared radiation that warms the atmosphere
Without the natural greenhouse effect
We would have a cold, uninhabitable Earth
Human Activities Play a Key Role in Atmospheric Warming
Since the Industrial Revolution
CO2, CH4 and N2O emissions have increased
Main sources - agriculture, deforestation, and burning of fossil
fuels
There is a correlation of rising CO2 and CH4 with rising global
temperatures
Average atmospheric concentrations of CO2 rose from 280 ppm to 400
ppm since the beginning of the Industrial Revolution
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70% of CH4 emissions over the last 275 years results from human
activities
Human factors can amplify or dampen changes
What Roles Does the Sun Play?
The sun plays a key role in the Earth’s temperature
Researcher think that atmospheric warming in not due to an increase in
energy output from the sun
Since 1975
Troposphere has warmed
Stratosphere has cooled
Hotter sun would warm stratosphere
What Roles Do the Oceans Play in Projected Climate Disruption?
CO2 is soluble in ocean water
Warmer oceans
Last century - 0.32 to 0.67 C increase
Absorbed less CO2 and hasten atmospheric warming
CO2 levels increased acidity
Affect marine ecosystems
There Is Uncertainty about the Effects of Cloud Cover on Atmospheric Warming
Warmer temperatures create more clouds
Thick, Low altitude cumulus clouds - decrease surface temperature
Thin, cirrus clouds at high altitudes - increase surface temperature
Outdoor Air Pollution Can Temporarily Slow Atmospheric Warming
Aerosol and soot pollutants
Can enhance or counteract projected global warming
Sulfate particles reflect sunlight
Soot particles absorb sunlight
19-3: What Are the Likely Effects of a Warmer Atmosphere?
The projected rapid change in the atmosphere’s temperature could have severed
and long-lasting consequences, including increased drought and flooding, rising
sea levels, and shifts in the locations of croplands and wildlife habitats
Rapid Atmospheric Warming Could Have Serious Consequences
Temperatures rises rapidly
Harmful effects will be unevenly distributed
Climate change tipping points
Thresholds beyond which natural systems will not recover
More Ice and Snow Are Likely to Melt
Ice melting due to:
Warmer air above and warner water below
Positive feedback loop
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