Explaining the Evidence

Activity 2: Clearing the Air

• 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.

How Many of You Have Heard That…

• 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

Beliefs and Assumptions

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.

Sample Beliefs and Assumptions about Climate

ChangeAssumption: 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.

• Science is a way of knowing about the natural and material world.–Hypothesis–Data–Evidence–Conclusions

Science

• 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

Weather vs. Climate

• 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

Evidence of Climate Change

1. Temperature (1880-2010)

1. Temperature (1000-2000)

Variations of the Earth’s surface temperature for the past 1,000 years

Observed Precipitation Changes: 1901-2007

2. Precipitation

3. Sea Ice

4. Sea Level

5. Catastrophes, Including Extreme Weather Events

Historical Climate Change• Solar radiation• Ocean composition• Greenhouse effect• Albedo effect• Continental land arrangement• Volcanic eruptions

Recent Climate Change• Solar radiation• Ocean composition• Greenhouse effect• Albedo effect• Continental land arrangement• Volcanic eruptions• Fossil fuel combustion• Land-use change from human

activities

Climate is Affected by Several Factors

Solar Radiation

Radiative Forcing

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.

Land-Use Change

Greenhouse GasPre-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(different for each CFC)

NA

Ozone (O3) 25 ppb 34 ppb 36%

We Have Also Altered the Atmosphere

ppm = parts per millionppb = parts per billion

Atmospheric Greenhouse Gases

a

Focus on CO2

800,000 Year Record of CO2 Concentration

Carbon is Everywhere

Natural forces alone do not explain the changes in temperature.

Global and Continental Temperature Change

• 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.

What Does All This Mean?

Agreement Among Climate Scientists

What Will Happen in the Future?

Current Modeled ForestFuture Model – Low EmissionsFuture Model – High Emissions

Forest Habitat Changing

LegendWhite/Red/Jack PineSpruce/FireLongleaf/Slash PineLoblolly/Shortleaf PineOak/PineOak/HickoryOak/Gum/CypressElm/Ash/CottonwoodMaple/Beech/BirchAspen/BirchNo Data

A Movable Carbon Map

www.carbonmap.org

• 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

What Could Happen in the Southeast?

• A very complex system• Regional variation• Changes are hard to see• No firm predictions; models have limitations • Not just about the science

- Political, Economic

It’s a Challenge

The U.S. Public Has Many Beliefs about Climate Change

• 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

But Why disagreement?

• 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!

Solutions to Climate Change