Transcript Global Warming and Climate Change Fitting the Pieces Together • The topic of global warming and climate change is like a puzzle.

Global Warming and Climate Change
Fitting the Pieces Together
• The topic of global warming and climate change
is like a puzzle with many different pieces
— Oceans, the atmosphere, ecosystems,
polar ice, natural and human influences
• Scientists have been working on this puzzle for
more than a century
• Most experts feel: the puzzle is now complete
enough to show that human activities are
having an adverse effect on our planet
• However, this is also a debate – there are
climate change/global warming “deniers”
Outline
 Is it real? How do we know?
• Climates of the past  Ice Ages
• What changes climate?
• Signs of global warming  Melting glaciers,
increased and erratic patterns of temperature and
precipitation
 Why should we care?
 How sure are scientists?
 What next — what can we do?
Is It Real?
How do we know?
PAST CLIMATES – ICE AGES
SIGNS OF GLOBAL WARMING
Evidence from the Past:
Ice Ages and Interglacial Periods
Pleistocene
Ice Ages
Nebraskan
Kansan
Illinoian
Wisconsinan
Little
Ice Ages
(More
Recent)
Climate Trends
Past 150,000 Years
Most Visible Evidence:
Melting of Polar and Glacial Ice
What causes climate change
and global warming?
Natural Causes:





Earth’s orbital changes
Volcanic eruptions
Drifting continents
Oceanic circulation
Impact Events  meteorites  asteroids  NEOs
Human Causes:
 Adding Greenhouse Gases
Earth’s orbital
changes 
 eccentricity
 obliquity
 precession
Volcanic
Eruptions
“Greenhouse effect”
CO2 comes from a variety of sources. The concern today is that
fossil fuel use is putting huge amounts of CO2 in the atmosphere
at a rate faster than the climate system can adapt to.
The warming resulting
from CO2 and other
greenhouse gases also
has the effect of
increasing evaporation.
This adds water vapor to
the atmosphere as well.
Water vapor is the most
important gas in the
natural greenhouse
effect, contributing 60%
of the effect to carbon
dioxide’s 26%.
Why should we care?
Global average temperatures are expected to increase by about 2-13°F by the
end of the century.
Even these small changes in global average temperature can lead to really large
changes in the environment.
Effects on precipitation
More water vapor due to warmer atmosphere leads to heavier rains and snowfall.
Effects on ecosystems
Increased warmth has also affected living things.
Tokyo cherry trees, for example, are blooming 5 days earlier on average.
Also, mosquitoes, birds, and insects are moving north in the Northern Hemisphere.
Effects on sea levels
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 unknown: How much will the ice sheets melt?
Impact of
Sea Level Changes
on Coastlines:
Eastern North America
Dark green shows the present coastline;
Light green shows the pre-Pleistocene
maximum rise of sea level;
Light blue depicts the Pleistocene
drop in sea level
Impact of
Sea Level Changes
on Coastlines:
Western North America
Dark green shows the present coastline;
Light green shows the pre-Pleistocene maximum
rise of sea level;
Light blue depicts the Pleistocene drop in sea level
How sure are scientists?
What don’t we know?
• Is there some critical piece of the puzzle about climate process we
don’t understand?
• 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?
The IPCC
2007 Conclusions
• Warming of the climate system is unequivocal
• Very high confidence that global average net effect of
human activities since 1750 is one of warming
• Human-caused warming over last 30 years has likely had
a visible influence on many physical and biological
systems
• 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?
Be an educated consumer
• IPCC Reports and Publications:
(http://www.ipcc.ch/publications_and_data/p
ublications_and_data_reports.shtml)
• Read this too: Michael E. Mann and Lee R. Kump, Dire Predictions:
Understanding Global Warming [the illustrated guide to the IPCC findings],
New York: D.K. Publishing, 2009
• Other organizations:
– NAS (http://dels.nas.edu/climatechange/)
– US CCSP (http://www.globalchange.gov/)
• Look for contrasting opinions
• Evaluate the source
What next—what can we do?
What next—what can we do?
Societal actions
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
skate
Buy water-saving
appliances and
toilets; installing
low-flow shower
heads.
Tune up
your
furnace
Caulk,
weatherstrip,
insulate, and
replace old
windows
Unplug
appliances or
plug into a
power strip and
switch it off
Buy products
with a U.S. EPA
Energy Star
label
Scientists are still working on the puzzle.
The IPCC’s 5th Assessment Report is planned for 2014.
However, the puzzle is already complete enough for us to know that
we need to take action now!