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Climate Change

Climate change has been among the most hotly debated topics over the last few decades. Are temperatures and sea levels rising? Are weather patterns becoming more extreme? Are such changes due to human activity? Can or should we try to reverse these trends? Is doing so worth the enormous cost and change in the way we live? Answers to these questions have profound implications for how we and our descendants will live their everyday lives.  

This write-up is intended to provide a summary of climate related topics that are more fully explained in a set of policy briefs that dive deeper into specific scientific knowledge, industry data and real-world implications surrounding climate change. We focus on exploring various policy options, from reducing the use of fossil fuels (oil, coal, and natural gas) to developing infrastructure to support electric and hybrid vehicles, as well as general pros and cons to it all. Links to these other briefs and supporting documents are in the Further Reading section.

Our central argument is that climate, and more specifically, climate change, is a complex issue. Global temperatures are the result of many poorly-understood processes, from nuclear fusion inside our Sun, to patterns in cloud cover around the globe, to changes in urban sprawl. Scientists are uncertain how temperature changes will affect sea levels, severe weather events, and many other factors. It is also unclear as to the nature and extent of changes that will occur in the next 100 years, or the next 1000, and how or if some of these changes naturally reverse themselves as in the past with little to no modern human impact or intervention.  

In these various briefs we take a look at the costs, benefits, limitations and negative implications of measures to address climate change. Many technologies, such as carbon capture, are experimental. Reforms that reduce the use of fossil fuels will be enormously expensive and may require large changes in American society. Someone can reasonably believe that climate change is a problem, yet not endorse the direction, timing, and speed of proposed policy changes.

Our goal is to present arguments about the magnitude, causes, and potential consequences of climate change from a 360-degree perspective. We report scientific data and commercial data and insights, highlighting findings and supporting evidence. We also identify the limitations of these analyses and dissenting views. 

Regardless of what you think about climate change, it is a certainty that this policy issue will be on governmental agendas for years to come. Our policy briefs give you a basic understanding of climate change so you can form your own conclusions about what role the government and society should play.

What evidence is there that the climate is changing?

The Intergovernmental Panel on Climate Change (IPCC) reports that the Earth’s average temperature has risen by 1.1 C (1.9 F) over the last 100 years. The figure below shows average temperatures in North America over this time. The clear trend is toward warmer temperatures.

Other indicators of climate change include melting glaciers and polar ice caps and a resulting rise in sea levels. Changes in precipitation and increased frequency and intensity of extreme weather events, such as hurricanes and heat waves, are also cited as evidence of climate change. 

All these claims are the subject of intense analysis and debate. It is not easy to track temperature changes over time. For example, a portion of the network of scientific temperature recorders are in rural areas. Over time, these rural areas develop into cities, suburbs, or industrial areas. As a result, the data may reflect increased temperatures simply because developed areas are warmer than rural areas due to heat released by structures.  

Similarly, some studies have documented increased extreme weather events in recent years. However, it is impossible to determine whether a particular hurricane, flood, or forest fire was caused by climate change. In addition, when data is tracked regarding the severity of such storms, much of this data is based on threats to life and property. As areas across the globe become more developed, populations increase as does the cost of such storms due to an increase in physical improvements (buildings, bridges, etc.) in these areas. Furthermore, we do not know what would have happened in a hypothetical world where temperatures had remained stable over the last century. 

Moreover, serious storms are relatively rare. One recent study predicted that over the next 100 years, there will be an increased likelihood of two severe hurricanes hitting the same spot on the east coast of the US during the same season. However, the probability of this outcome is still low, about 1 percent.  

Is climate change the result of human action?

The most-cited evidence for human action being the cause of climate change is the observed correlation between atmospheric carbon dioxide (CO2) and temperature increases. CO2 is a greenhouse gas – it limits the amount of heat that can escape from the surface of the Earth. As we discuss in our policy brief on decarbonization, CO2 is produced by industrial processes, electrical power generation, transportation, and other human activities. Studies show that an increase in CO2 levels began during the Industrial Revolution. Levels have increased with higher population and development worldwide.

Critics of this approach note that global temperatures have moved up and down throughout history. At one time, the Earth was so warm that the polar ice caps melted, raising sea levels by several hundred feet. At another time in history, temperatures dropped enough that glaciers covered most of the planet. Given these changes happened without humans, why connect the much smaller changes in recent years to human activity?  

However, the argument for connecting human activity to climate change goes well beyond the fact that CO2 levels and temperatures have moved together. These conclusions are based on models of global weather that account for inputs like sunlight, biological processes, and the composition of the atmosphere. These models are incredibly detailed. For example, they account for the principle that higher CO2 levels stimulate tree growth, removing carbon dioxide from the atmosphere and reflecting heat away from the ground. Through satellite imagery, several universities and scientific groups have documented a ‘greening effect’ across the globe over the past 30 years.

At the same time, climate models have their limits. For example, while increased CO2 stimulates tree growth, the amount of CO2 captured by trees depends on what kinds are grown and whether they are cut down and burned. As a result, predictions made by these models have some uncertainty. They give a range of values for future temperatures rather than a precise number. 

Additionally, when shifting the conversation of the potential positive impacts of increased CO2 away from trees to man-made crops like rice, wheat, soy, peas and sorghum, all used in mass food production, it’s plausible an increase in concentration of CO2 could signal a reduction in vitamins and nutrients like iron, zinc and protein found in these crops. 

One of the central findings from climate models is that increased global temperatures result from greenhouse gas emissions. Most analyses also conclude that these changes are not the result of other sources of greenhouse gases, such as animal and plant life or natural processes like volcanoes. For example, one study analyzed the atomic structure of atmospheric CO2, concluding it results from human activity rather than biological or geological processes.  

Why do many scientists believe these findings? In part it is because the models incorporate known findings, such as how CO2 affects plant life. In addition, climate models generate other testable predictions. For example, one alternate hypothesis for increased global temperatures is that the Sun has become slightly hotter. If this change had occurred, it likely would cause larger temperature shifts at the Earth’s poles compared to the Equator. Data shows that the opposite is happening (temperature changes at the Equator are larger than at the poles), which is the expected result of increased global CO2 levels.

Why is climate change such a controversial topic?

Climate change is both a scientific matter and a values question. Scientists can test predictions drawn from climate models, identify limitations, and build and test better ones. Over the last generation, this process has produced an increasingly better understanding of how global temperatures are changing and how these changes might affect human life. As we have discussed, these analyses have their limits. However, it is difficult to justify ignoring this evidence entirely.  

At the same time, scientific research cannot tell us how to respond to climate change. People may have differing views on the nature of the problem or the viability of proposed solutions. For instance, transitioning to a low-carbon economy will produce job losses in some sectors, such as coal mining. It will require significant investment in new technologies, such as solar cells and wind turbines. This transition may seem worthwhile for people in coastal communities vulnerable to flooding and who are not concerned about potential implications to marine life. But people far away from coasts, or who live in a community sustained by fossil fuel production, may see this transition as undesirable. 

Another example are proposals to ban the sale of gasoline-powered automobiles. As we discuss in our brief on EV Infrastructure, this transition will require significant new infrastructure at home and on the road to charge these vehicles, and has other complications, including the environmental impact of mining for battery raw materials, disposal of key components that are not biodegradable and increased demand for electricity. And in fact, many recent studies are suggesting that hybrid vehicles may actually be a more viable path longer-term.

For many people, it is a real question of whether the costs and drawbacks outweigh the benefits of a reduction in CO2 levels. Even if changes are implemented, they may not have the intended outcome. Furthermore, efforts made by Americans will have little effect if other countries do not take similar measures. Nothing in the science of climate change tells us how to think about these issues. It is up to each of us to decide how we believe they should be addressed.

Here are links to our other climate change briefs.

Further Reading

Sirianni, C., Mills, J., and Ward, A. (2023). Climate Change as a Civic Challenge: Collaborative Models for American Policy and Practice. National Civic Review 112/ 6–16., accessed 11/30/23.

Hartmann, D. 2015. Global Physical Climatology.  Elsevier.  

University of Maryland Extension. (2023). Climate Change Basics and Evidence., accessed 11/30/23.



What evidence is there that the climate is changing?

IPCC. (2014). Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II, and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauri and L.A. Meyer (eds.)]. IPCC, Geneva, Switzerland, 151., accessed 11/30/23.

National Oceanic and Atmospheric Administration. (2023). Climate at a Glance: Global Time Series., accessed 2/6/2024. (Chart Data).

Bulkeley, H., and Newell, P. (2023). Governing climate change. Taylor & Francis. 

Xi, D., Lin, N., & Gori, A. (2023). Increasing sequential tropical cyclone hazards along the US East and Gulf coasts. Nature Climate Change, 13(3), 258-265.

U.S. Global Change Research Program. (2018). Impacts, Risks, and Adaptation in the United States: Fourth National Climate Assessment, Volume II: Report-in-Brief. Reidmiller, D.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, K.L.M. Lewis, T.K. Maycock, and B.C. Stewart (eds.)., accessed 11/30/23.

Is climate change the result of human action?

Manabe, S., & Broccoli, A. J. (2020). Beyond global warming: How numerical models revealed the secrets of climate change. Princeton University Press.  

Von Storch, H. (2022). From Decoding Turbulence to Unveiling the Fingerprint of Climate Change: Klaus Hasselmann—Nobel Prize Winner in Physics 2021. Springer.

Keeling, R. F., & Graven, H. D. (2021). Insights from time series of atmospheric carbon dioxide and related tracers. Annual Review of Environment and Resources, 46, 85-110.

What are the primary impacts of climate change on Americans?

U.S. Global Change Research Program. (2018). Impacts, Risks, and Adaptation in the United States: Fourth National Climate Assessment, Volume II: Report-in-Brief. Reidmiller, D.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, K.L.M. Lewis, T.K. Maycock, and B.C. Stewart (eds.)., accessed 11/30/23.

E360 Digest. (2020, October 13). Extreme Weather Events Have Increased Significantly in the Last 20 Years., accessed 07/10/2023.

UNDRR. (2020). Human Costs of Disasters 2000-2019., accessed 07/10/2023.

Di Gregorio, M., Fatorelli, L., Paavola, J., Locatelli, B., Pramova, E., Nurrochmat, D. R., May, P. H., Brockhaus, M., Sari, I. M., & Kusumadewi, S. D. (2019). Multi-level governance and power in climate change policy networks. Global Environmental Change, 54, 64-77.

Why is climate change such a controversial topic?

Markkanen, S. and Anger-Kraavi, A. (2019). Social impacts of climate change mitigation policies and their implications for inequality. Climate Policy, 19(7), 827-844, DOI: 10.1080/14693062.2019.1596873

Fisher, D. R., & Nasrin, S. (2021). Climate activism and its effects. Wiley Interdisciplinary Reviews: Climate Change, 12(1), e683.

University of Maryland Extension. (2023). Climate Change Basics and Evidence., accessed 11/30/23.



Dr. William Bianco (Research Director) received his PhD in Political Science from the University of Rochester. He is Professor of Political Science and Director of the Indiana Political Analytics Workshop at Indiana University. His current research is on representation, political identities, and the politics of scientific research.

Dr. Nick Clark (Content Lead) is Professor of Political Science at Susquehanna University, where he is also Department Head in Political Science and Director of the Public Policy Program and the Innovation Center. He received his Ph.D. from Indiana University and researches political institutions, European politics, and the politics of economic policy.

Dr. Robert Holahan (Subject Matter Expert) is Associate Professor of Political Science and Faculty-in-Residence of the Dickinson Research Team (DiRT) at Binghamton University (SUNY) where he advises undergraduate students conducting multi-year research projects on politics, ecology, and environmental assessments. His research focuses on property rights systems in natural resource settings like oil & gas drilling, wind power generation, fisheries, and forests. He holds a PhD in Political Science in 2013 from Indiana University-Bloomington, where his advisor was Elinor Ostrom.

Zul Norin (Intern) is a senior at Vanderbilt University majoring in Economics and is expected to graduate in May 2024.

Mary Stafford (Intern) is majoring in Public Policy Analysis and pursuing a certificate in Public and Civic Engagement at Indiana University. In addition to her role at Policy vs Politics, she serves on the board of directors for Monroe County Court-appointed Special Advocates and is in the process of applying to law school.


Publication Log

Published – 4/9/24

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