Download past climates – ice ages signs of global warming

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Global Warming and Climate Change
Fitting the Pieces Together
• What changes climate?
• Is it real? How do we know?
• Climates of the past  Ice Ages
• Signs of global warming  Melting glaciers,
increased and erratic patterns of temperature and
• Why should we care?
• How sure are scientists?
• What next — what can we do?
What causes climate change?
Natural Causes:
 Earth’s orbital changes
 eccentricity, obliquity,
Volcanic eruptions
Drifting continents
Oceanic circulation
Impact Events  meteorites  asteroids 
Human Causes:
 Adding Greenhouse Gases, CFC
Scientists have a good understanding of what has changed earth’s climate in
the past:
• Incoming solar radiation is the main climate driver. Its energy output increased
about 0.1% from 1750 to 1950, increasing temperatures by 0.2°F (0.1°C) in the
first part of the 20th century.
•But since 1979, when we began taking measurements from space, the data
show no long-term change in total solar energy, even though Earth has been
• Repetitive cycles in Earth’s orbit that occur over tens of thousands of years
can influence the angle and timing of sunlight.
•In the distant past, drifting continents make a big difference in climate over
millions of years by changing ice caps at the poles and by altering ocean
currents, which transport heat and cold throughout the ocean depths.
•Huge volcanic eruptions can cool Earth by injecting ash and tiny particles into
the stratosphere.
•Changes in the concentration of greenhouse gases, which occur both naturally
and as a result of human activities, also influence Earth’s climate.
Increasing greenhouse
gases trap more
Greenhouse gases
Nitrous oxide
Carbon dioxide
Sulfur hexafluoride
Is It Real?
How do we know?
Effects on precipitation
Effects on ecosystems
Aspen, CO Forecast:
Partly cloudy today
High : 28°F
Low: 13°F
Increasing clouds
over night. Colder
Why should we care?
Sea-level rise projections : a few inches to a few feet
•2 ft: U.S. would lose 10,000 square miles
•3 ft: Would inundate Miami
•Affects erosion, loss of wetlands, freshwater supplies
•Half of the world’s population lives along coasts
•Big question: Ice sheets
How sure are scientists?
What don’t we know?
• Is there some critical piece of the puzzle about climate process we don’t
• How and when will our fossil fuel use change?
• Will future , yet-to-be-discovered technologies mitigate the problem?
• How will changing economics, global population, and political processes
affect our ability to tackle the problem?
2007 Conclusions
• Warming of the climate system is unequivocal
• Very high confidence that global average net effect of
human activities since 1750 one of warming
• Human-caused warming over last 30 years has likely had
a visible influence on many physical and biological
• Continued GHG emissions at or above current rates
would cause further warming and induce many changes
in the global climate system during the 21st century that
would very likely be larger than those observed during
the 20th century.”
What do climate scientists really think?
What next—what can we do?
What next—what can we do?
Produce more fuel-efficient vehicles
Reduce vehicle use
Improve energy-efficiency in buildings
Develop carbon capture and storage processes
Triple nuclear power
Increase solar power
Decrease deforestation/plant forests
Improve soil carbon management strategies
Individual actions
Use mass
transit, bike,
walk, roller
Buy water-saving
appliances and
toilets; installing
low-flow shower
Tune up
insulate, and
replace old
appliances or
plug into a
power strip and
switch it off
Buy products
with a U.S. EPA
Energy Star