Global Climate Change:Evidence and Causes

Maureen Knabb1, Tim Lutz2, and Win Fairchild1

Department of Biology1 and Department of Geology2 West Chester University

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CQ#1: Based on your current knowledge, which statement is closest to your thoughts about the scientific evidence for global climate change?

A. There is no evidence; it’s a scare tactic promoted by environmentalists and some politicians.

B. There is evidence for climate change, but no evidence that human activities are involved.

C. There is some evidence that humans are having an effect on climate.

D. The evidence is clear that humans are significantly affecting climate.

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CQ#2: Based on your current knowledge, which statement is closest to your thoughts about the consequences for humans of global climate change?

A. The effects of climate change, if any, will be small compared to natural changes that have occurred before.

B. The effects of climate change will be minor except in poor, less developed countries.

C. Climate change will significantly affect many countries.D. The effects of climate change will be catastrophic around

the world.

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You are an intern working with a U.S. Senator who is required to make important decisions about legislation designed to limit the impacts of global climate change.

Imagine that…

Your job is to help the Senator…

Understand the science behind climate change.

Appreciate the impact of global climate change.

Assess the effects of human activities on global climate change.

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Climate refers to time and space patterns of precipitation, temperature, and wind. For example, temperature and precipitation differ across the United States.

What is climate?

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Climate change occurs when the patterns change in time (e.g., winter months get warmer) and space (e.g., monsoon rains occur further south).

Suppose winter in Pennsylvania began to look like winter in Florida?

What is climate change?

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• Climate changes naturally on a range of timescales, from decadal (10’s of years), centennial (100’s of years), millennial (1000’s of years), and longer (glacial cycles, e.g. Ice Ages).

• Climate changes naturally on a range of spatial scales, from local and regional to global.

Why is studying climate change a scientific challenge?

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• Climate determines the type and location of human-managed ecosystems, such as agricultural farmlands.• Climate affects the weathering of rock, the type of soil that forms, and the rate of soil formation.

Why should we be interested in climate change?

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• Climate helps to determine the quantity and quality of water available for human use.• Climate determines the severity of droughts, storms, and floods.

Why should we be interested in climate change?

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Climate largely determines the nature and locations of biomes (major terrestrial ecosystems, defined based on their plant communities).

Why should we be interested in climate change?

Example: A prediction of climate change for eastern PA. By the end of this century Philadelphia, PA, could have the climate that Savanna, GA, has now.

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CQ#3. If Pennsylvania’s current climate (9 °C, 105 cm) becomes more typical of southern Georgia or northern Florida (19.5 °C, 133 cm), the prevailing forest may be most similar to:

A. Temperate deciduous forest.

B. Woodland shrubland.C. Tropical seasonal

forest.D. Temperate rain forest.E. Taiga.

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CO2 measured continuously at Mauna Loa Observatory since 1958 has provided strong evidence for atmospheric change.

Air bubbles in ice cores retain atmospheric gases present when the ice was formed.

Annual tree rings not only indicate tree age, the ring width indicates growth spurts due to warmer temperature.

How do we study climate?

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At what rate have global surface temperatures changed over the last 30 years?

A→B: 0.6 °C/30 years= 0.02 °C/yr

A

B

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At what rate did global temperatures change during the warming period following major ice ages?

A

B

A→B: 12 °C/9700 years = 0.0013 °C/yr

Ice Ages

Interglacials

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Why do times of glaciation occur episodically on Earth?

Systematic changes in the distance and orientation of Earth relative to the Sun are thought to account for glacial cycles.

Climate results from a balance between the rate at which energy arrives at and leaves Earth

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A. There is no evidence for a systematic temperature change.

B. Earth is moving in the direction of a major glaciation.C. The change is small compared to a glacial cycle, but

temperature is increasing at a high rate.D. The change is already larger than any to have

occurred in Earth’s past.

CQ#4: What should the Senator know about changes in Earth’s temperature in recent decades?

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Long-term variation of temperature and of CO2 in air bubbles preserved in the Vostok ice core

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CQ#5: The ice core shows that temperature and CO2 were correlated in the past. The graph suggests that:

A. The correlation is too rough to be meaningful.

B. CO2 caused temperature to change.

C. Temperature caused CO2 to change.

D. A mechanism needs to be found to explain the correlation.

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CO2 and energy in the atmosphere

• The Earth’s surface absorbs solar radiation, and reradiates it as heat.• CO2 and other greenhouse gases (GHG) reduce the rate at which this heat can escape into space.• The more GHG, the higher the global temperature.• This role of CO2 and other GHG has been understood for over a century.

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A. In the past, changes in CO2 have been associated with large swings in Earth’s climate.

B. Increased levels of CO2 in the atmosphere are correlated with increased temperature.

C. The greenhouse effect explains why climate can be affected by CO2.

D. All of the above.

CQ#6: What should the Senator know about the effect of CO2 in the atmosphere on climate?

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CO2 in the Vostok core (blue), other ice cores (yellow, green), and measurements since 1958 (red).

Glacial cycles were very large naturally-occurring changes in global climate that occurred over hundreds of thousands of years. Why are we worried about rapid climate change now?

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CO2 , CH4, and N2O changed slowly after the end of the last Ice Age, but began to increase rapidly about 200 years ago.

When did CO2 and other GHG begin to increase? Detailed analysis of ice cores and measurements shows:

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• Energy retention in the atmosphere depends on the abundance and effectiveness of the GHG.

• The diagram shows how much each gas contributed to warming from 1750 to 2005 (termed radiative forcing).

CO2

CH4

N2O

How much does each GHG contribute to climate change?

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A. Although CO2 has been increasing, other GHG have not.B. Levels of CO2 and other GHG have been increasing

steadily over thousands of years.C. All GHG began to increase in the last 200 years but don’t

yet exceed normal interglacial levels.D. Levels of CO2 and other GHG began to increase more

rapidly about 200 years ago and are now higher than they have been in hundreds of thousands of years.

CQ#7: What should the Senator know about the role of CO2 as a cause of recent warming?

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CO2 and other GHG vary naturally. Why are humans thought to affect GHG, and thus climate?

Human activities including land use change (agriculture, deforestation), fossil fuel use (coal, oil, natural gas), and cement production are known to release CO2 and other GHG.

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Why do we think that CO2 released by human activities is causing the increase in the atmosphere?

• Seasonal cycles in CO2 result from photosynthesis and respiration.

• Such short-term flows of carbon cannot explain the upward trend

• The trend has to result from carbon that has been stored for long periods of time, such as in fossil fuels and soils.

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Is all of the human-caused CO2 in the atmosphere?

• Only about 50% of the increased CO2 stays in the atmosphere.

• The rest is absorbed by the oceans and other sinks.

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Is all of the human-caused CO2 in the atmosphere?

CO2 dissolved in the oceans is forming extra carbonic acid which is causing a decline in pH and other ecosystem problems.

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CQ#8: The Senator should know that scientists conclude that:

A. Fossil fuel burning is the only source of human-caused CO2 emissions.

B. CO2 emissions from a range of human activities are causing the increase in the atmosphere as well as acidifying the oceans.

C. The increase of CO2 in the atmosphere results from natural processes in the biosphere.

D. Scientists don’t know how much CO2 is emitted or where it goes.

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Could factors other than human-caused GHG emissions be changing earth’s

climate?

Other factors that can influence climate include:

• Variations in the Sun’s output of energy.• Dust and gases from volcanic eruptions.

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How can scientists decide which factors are actually responsible for climate change?

• Scientists model both human and natural factors to determine which best explain the observed climate changes.

• Both natural and human factors are needed to explain the climate change that has already happened.• Human factors are particularly important in explaining the rapid temperature increase in the last three decades.

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Do the models prove that humans are causing climate change?

• Models cannot prove that humans are involved; however, they show that the changes observed so far are consistent with human causes.

• Models do not account for some complexities of climate, such as the feedback effects of water vapor and cloud formation.

• Scientists consider the models sufficient to say that it is very likely (>90% probability) that the climate change observed in the last 50 years is not a result of natural effects alone.

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CQ#9: What should the Senator know about human involvement with climate change?

A. Humans are definitely causing climate change.B. Human involvement in climate change, particularly

recent warming, is probable.C. Models of climate are so incomplete that no

conclusions can be drawn.

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CQ#10: Based on your NEW knowledge, which statement is closest to your thoughts about the scientific evidence for global climate change?

A. There is no evidence; it’s a scare tactic promoted by environmentalists and some politicians.

B. There is evidence for climate change, but no evidence that human activities are involved.

C. There is some evidence that humans are having an effect on climate.

D. The evidence is clear that humans are significantly affecting climate.

Slide CreditsSlide 4 Description: The United States Capitol Building in Washington DC, framed with the Supreme Court columns. Author: ©Michael Shake Source: Dreamstime.com, ID: 11882582 Clearance: Licensed royalty free.

Slide 6 Description: Climate map for the U.S. Source: Natural Resources Conservation Service (NRCS), United States Department of Agriculture. Link: http://www.nrcs.usda.gov/news/thisweek/2006/071906/techtip07-19-06.html Clearance: As a work of the U.S. federal government, the image is in the public domain (17 U.S.C. § 101 and § 105).

Slide 7—Left Description: Pennsylvania in winter. Author: User:Ruhrfisch Source: Modified from Wikimedia Commons, http://commons.wikimedia.org/wiki/File:Plunketts_Creek_Winter_Panorama.JPG Clearance: Licensed in accordance with Creative Commons Attribution-Share Alike 3.0 Unported.

Slide 7—Right Description: Florida in winter. Author: WV-Mike www.EpicRoadTrips.us Source: Modified from Wikimedia Commons,

http://commons.wikimedia.org/wiki/File:Saw_palmetto_Serenoa_repens_and_Oak_Forest_at_Edward_Ball_Wakulla_Springs_State_Park_in_Florida.jpg

Clearance: Licensed in accordance with Creative Commons Attribution 3.0 Unported.

Slide 9—Left Description: Farmland in Niger river delta region. Author: ازرق, Radosław Botev Source: Modified from Wikimedia Commons, http://commons.wikimedia.org/wiki/File:Macina.jpg Clearance: Licensed in accordance with Creative Commons Attribution-Share Alike 2.0 Generic.

Slide 9—Right Description: Terraced rice paddy in Vietnam. Author: AJ Oswald Source: Modified from Wikimedia Commons, http://commons.wikimedia.org/wiki/File:Sapa,_terraced_rice_paddy.jpg Clearance: Licensed in accordance with Creative Commons Attribution-Share Alike 2.0 Generic.

Slide 10—Left Description: Drought scene in Australia. Author: Peripitus Source: Modified from Wikimedia Commons, http://commons.wikimedia.org/wiki/File:Drought_Swimming_Hole.JPG Clearance: Licensed in accordance with Creative Commons Attribution-Share Alike 3.0 Unported.

Slide 10—Right Description: Flood on the Stillaguamish River, Washington, U.S. Author: Walter Siegmund Source: Modified from Wikimedia Commons, http://commons.wikimedia.org/wiki/File:Granite_Falls_26455.JPG Clearance: Licensed in accordance with Creative Commons Attribution-Share Alike 3.0 Unported.

Slide 11 Description: Climate change for Eastern PA Source: Right panel (Eastern Pennsylvania) of Figure 2 (Migrating Climates) in “Climate Change Impacts and Solutions for Pennsylvania:

How Today’s Actions Shape the State’s Future,” Union of Concerned Scientists, 2008, available at http://www.climatechoices.org/assets/documents/climatechoices/exec-summary_climate-change-in-pennsylvania.pdf.

Clearance: Used with permission from Union of Concerned Scientists.

Slide 12 and Slide 13 Description: Temperature, precipitation and terrestrial biomes. Source: Originally from R.H. Whitaker Communities and Ecosystems, 1975; redrawn and modified after R.E. Ricklefs The Economy of

Nature, 2000. Clearance: NCCSTS

Slide 14—Left top Description: Deep ice core sheathed in protective netting at WAIS (West Antarctic Ice sheet) Divide field camp. Author: Chad Naughton (National Science Foundation) Source: http://www.usap.gov/; exact source Clearance: This image is a work of a National Science Foundation employee, taken or made during the course of the person’s official duties.

As a work of the U.S. federal government, the image is in the public domain.Clearance: Used in accordance with terms of use on http://www.ipcc.ch/home_copyright.htm.

Slide 14—Right Description: The Scripps Institution of Oceanography (Keeling) carbon dioxide analyzer at NOAA’s Mauna Loa Observatory. Source: NOAA Celebrates 200 Years of Science, Service, and Stewardship; http://www.usap.gov/; exact source Clearance: This image is a work of the National Oceanic and Atmospheric Administration (NOAA). As a work of the U.S. federal government, the

image is in the public domain.

Slide 14—Left bottom Description: Tree rings seen in a cross section of a trunk of a tree. Author: Arnoldius Source: http://www.usap.gov/; exact source Clearance: Licensed in accordance with Creative Commons Attribution-Share Alike 2.5 Generic.

Slide 15 Description: Graph of annual temperature change. Author: Graph prepared by case author, Timothy Lutz. Source: Data from Jones, P.D., D.E. Parker, T.J. Osborn, and K.R. Briffa. 2008. Global and hemispheric temperature anomalies—land and marine

instrumental records. In Trends: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A.

Link: http://cdiac.ornl.gov/trends/temp/jonescru/data.html Clearance: Graph used with permission.

Slide 16 Description: Long-term changes in temperature derived from isotopes in the Vostok ice core. Author: Graph prepared by case author, Timothy Lutz. Source: Temperature data from: Petit, J.R., D. Raynaud, C. Lorius, J. Jouzel, G. Delaygue, N.I. Barkov, and V.M. Kotlyakov. 2000. Historical isotopic

temperature record from the Vostok ice core. In Trends: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A.

Clearance: Graph used with permission.

Slide 17 Description: Milankovitch cycles, the pace makers of ice ages. Author: Hannes Grobe, Alfred Wegener Institute for Polar and Marine Research. Source: Wikimedia Commons, http://commons.wikimedia.org/wiki/File:Milankovitch-cycles_hg.png Clearance: Licensed in accordance with Creative Commons Attribution-Share Alike 2.5 Generic.

Slide 19 Description: Long-term variation of temperature and of CO2 in air bubbles preserved in the Vostok ice core. Author: Graph prepared by case author, Timothy Lutz. Source: CO2 data from Barnola, J.-M., D. Raynaud, C. Lorius, and N.I. Barkov. 2003. Historical CO2 record from the Vostok ice core. In Trends: A

Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A. Concentrations are in parts per million by volume (ppmv).

Clearance: Graph used with permission.

Slide 20 Description: Temperature and CO2 correlation in the ice core. Author: Graph prepared by case author, Timothy Lutz. Source: CO2 data from Barnola, J.-M., D. Raynaud, C. Lorius, and N.I. Barkov. 2003. Historical CO2 record from the Vostok ice core. In

Trends: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A.

Clearance: Graph used with permission.

Slide 21 Description: Greenhouse gas effects. Author: Figure created by Robert A. Rohde from published data and is part of the Global Warming Art project. Source: Wikimedia Commons, http://commons.wikimedia.org/wiki/File:Greenhouse_Effect.png Clearance: Licensed in accordance with Creative Commons Attribution-Noncommercial-Share Alike 2.5 Generic.

Slide 23 Description: CO2 levels from 450,000 year ago to the present. Author: Graph prepared by case author, Timothy Lutz. Source: Measurements (1958 through 2008) are from Mauna Loa as reported by Pieter Tans of NOAA

(http://www.esrl.noaa.gov/gmd/ccgg/trends/). Other ice core data from: (1) Neftel, A., H. Friedli, E. Moor, H. Lötscher, H. Oeschger, U. Siegenthaler, and B. Stauffer. 1994. Historical CO2 record from the Siple Station ice core. In Trends: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A. (2) D.M. Etheridge, L.P. Steele, R.L. Langenfelds, R.J. Francey, J.-M. Barnola and V.I. Morgan. 1998. Historical CO2 records from the Law Dome DE08, DE08-2, and DSS ice cores. In Trends: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A.

Clearance: Graph used with permission.

Slide 24 Description: Increase in CO2 and other GHG over the last 2000 years. Source: FAQ 2.1, Figure 1 in: Forster, P., V. Ramaswamy, P. Artaxo, T. Berntsen, R. Betts, D.W. Fahey, J. Haywood, J. Lean, D.C. Lowe, G.

Myhre, J. Nganga, R. Prinn, G. Raga, M. Schulz and R. Van Dorland, 2007: Changes in Atmospheric Constituents and in Radiative Forcing. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

Link: http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter2.pdf Clearance: Used in accordance with terms of use on http://www.ipcc.ch/home_copyright.htm.

Slide 25 Description: Contribution of GHG to climate change. Author: Graph prepared by case author, Timothy Lutz. Source: Diagram constructed from data in: Forster, P., V. Ramaswamy, P. Artaxo, T. Berntsen, R. Betts, D.W. Fahey, J. Haywood, J. Lean,

D.C. Lowe, G. Myhre, J. Nganga, R. Prinn, G. Raga, M. Schulz and R. Van Dorland, 2007: Changes in Atmospheric Constituents and in Radiative Forcing. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment

Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

Link: http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter2.pdf Clearance: Graph used with permission.

Slide 27 Description: Human activities and carbon emissions worldwide. Author: Graph prepared by case author, Timothy Lutz. Source: Fossil fuel-related emissions + cement production from: (1) Marland, G., T.A. Boden, and R.J. Andres. 2008. Global, Regional, and

National Fossil-Fuel CO2 Emissions. In Trends: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A. (2) Land use-related emissions from: Houghton, R.A. 2008. Carbon Flux to the Atmosphere from Land-Use Changes: 1850-2005. In Trends: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A.

Links: (1) http://cdiac.ornl.gov/trends/emis/overview.html; (2) http://cdiac.ornl.gov/trends/landuse/houghton/houghton.html Clearance: Graph used with permission.

Slide 28 Description: Yearly fluctuations in CO2 over the last 10 years. Author: Graph prepared by case author, Timothy Lutz. Source: Measurements are from Mauna Loa as reported by Pieter Tans of NOAA. Link: http://www.esrl.noaa.gov/gmd/ccgg/trends/ Clearance: Graph used with permission.

Slide 29 Description: Carbon sources and sinks Source: NOAA Earth System Research Laboratory Link: http://www.esrl.noaa.gov/research/themes/carbon/

Slide 30 Description: Carbon sources and sinks Source: Modified from a figure at NOAA/PMEL Ocean Acidification Home Page, http://www.pmel.noaa.gov/co2/OA/background.html Clearance: A figure of DOC / NOAA / OAR / PMEL

Slide 33 Description: Graphs from IPCC report. Source: Bottom panels of Figure SPM.4, p. 11. IPCC, 2007: Summary for Policymakers. In: Climate Change 2007: The Physical Science

Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

Link: http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-spm.pdf