Explaining the Evidence
Activity 2:
Clearing the Air
How Many of You Have Heard That…
• Climate change is due to human activities.
or…
Climate change is due to human and natural causes.
• Nearly all climate scientists agree on causes of
climate change.
or…
Most scientists do not agree on causes of climate
change.
Beliefs and Assumptions
• People have beliefs about many things.
– Ideas that we think are true
– Based on a number of sources such as past experiences,
faith, or what someone said
– Can change as people learn and have new experiences
• Assumptions are underlying ideas behind beliefs.
– Connect evidence to conclusions
– May or may not be based on fact
– Important to distinguish assumptions from beliefs
Sample Beliefs and
Assumptions about Climate Change
Assumption: Carbon dioxide is one of many atmospheric
gases, and it makes up a small percent of the total gases in
our atmosphere. Therefore, it is logical to believe…
Belief: The small amount of carbon dioxide added to the
atmosphere by humans cannot cause climate change.
Assumption: Carbon dioxide occurs naturally in small
amounts, but is very efficient at absorbing heat energy.
Therefore, it is logical to believe…
Belief: Any amount of carbon dioxide added to the
atmosphere by humans can cause climate change.
Science
• Science is a way of knowing about the natural and
material world.
–Hypothesis
–Data
–Evidence
–Conclusions
Weather vs. Climate
• Weather describes the atmospheric conditions at a
specific place at a specific point in time.
• Climate is determined by long term trends in weather.
http://www.youtube.com/watch?v=e0vj-0imOLw
Evidence of Climate Change
• Will not be the same everywhere
– Some places will be wetter, others will be drier
– Polar regions will see greater increases in temperature
than tropical regions
• Includes changes in
– Earth’s average temperature
– Patterns and amounts of precipitation
– Ice and snow cover
– Sea level
– Extreme weather events
1. Temperature (1880-2010)
1. Temperature (1000-2000)
Variations of the Earth’s surface temperature for the past 1,000 years
2. Precipitation
Observed Precipitation Changes: 1901-2007
Statistically Significant Trends in
Precipitation Anomaly (inches/decade):
1895-2011
Southeast
Winter
Spring
Summer
Fall
Annual
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-0.10
+0.27
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3. Sea Ice
4. Sea Level
5. Catastrophes, Including
Extreme Weather Events
Climate is Affected by Several Factors
Historical Climate Change
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•
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Solar radiation
Ocean composition
Greenhouse effect
Albedo effect
Continental land arrangement
Volcanic eruptions
Recent Climate Change
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Solar radiation
Ocean composition
Greenhouse effect
Albedo effect
Continental land arrangement
Volcanic eruptions
Fossil fuel combustion
Land-use change from human
activities
Solar Radiation
Radiative Forcing
Land-Use Change
In the Southeast U.S., land use changes from bare soil in cotton and other row
crops to forests (currently 70 percent of the region) may have contributed to the
negative trend in temperature over the past 100 years.
We Have Also
Altered the Atmosphere
Greenhouse Gas
Pre-1750
Tropospheric
Concentration
Recent Tropospheric
Concentration
Change in
Tropospheric
Concentration
Carbon dioxide (CO2)
280 ppm
393 ppm
40%
Methane (CH4)
700 ppb
1874 ppb
168%
Nitrous oxide (N2O)
270 ppb
324 ppb
20%
Chlorofluorocarbons
(CFCs)
0
21-529 ppb
NA
Ozone (O3)
ppm = parts per million
ppb = parts per billion
(different for each CFC)
25 ppb
34 ppb
36%
Atmospheric Greenhouse Gases
a
Focus on CO2
• CO2 has changed the most.
• CO2 stays in the atmosphere a long
time.
• The US emits more CO2 than other
greenhouse gases.
• We can do something about it.
800,000 Year Record
of CO2 Concentration
Carbon is Everywhere
Global and Continental
Temperature Change
Natural forces alone do not explain the changes in temperature.
What Does All This Mean?
• 97% of climate scientists combine this and other
evidence to draw these conclusions:
– Earth’s climate is currently changing due to global
warming.
– Changes are not the same at all locations on Earth.
– Future changes may be more rapid than historical
changes.
– Human activities are responsible for most of the climate
change being observed.
Agreement Among Climate Scientists
What Will Happen in the Future?
Forest Habitat Changing
Future Model – High Emissions
Current
Modeled
Forest
Future
Model
– Low Emissions
Legend
White/Red/Jack Pine
Spruce/Fire
Longleaf/Slash Pine
Loblolly/Shortleaf Pine
Oak/Pine
Oak/Hickory
Oak/Gum/Cypress
Elm/Ash/Cottonwood
Maple/Beech/Birch
Aspen/Birch
No Data
A Movable Carbon Map
www.carbonmap.org
What Could Happen
in the Southeast?
• Southeast’s climate is largely influenced
by El Niño and La Niña
• Sea level rise
– Coastal erosion
• Warmer temperatures
– More invasive exotic organisms
– Greater risk of wildfire
• Increased yield in some crops if water is plentiful
• Less rain in the growing season in some places
– Harm to crops, or changes in planting times
It’s a Challenge
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A very complex system
Regional variation
Changes are hard to see
No firm predictions; models have limitations
Not just about the science
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Political, Economic
The U.S. Public Has Many
Beliefs about Climate Change
But Why disagreement?
• People see and remember information that
matches what they know
– So it is hard to change someone’s mind
• People have partial information and leap to
conclusions
– And then when presented with complete information, it
doesn’t match
• People listen to influential leaders
– Rather than figuring it out for themselves
Solutions to Climate Change
• Lots of options; no single solution
– Adaptation
– Mitigation
• Policies and actions implemented by
– Governments: international, national, state,
local
– Industry and business
– Individuals – all of us!