During a tutorial for my General Chemistry class in the Fall of 2015 a student asked me if I believed in global warming. There were only two students in attendance and we were sitting together at a table working on problems from class. I was a little surprised: in my deeply conservative corner of Texas, the attitudes run toward the idea that global warming is a hoax designed to take your money and trample your rights. I told her that, yes, I did believe in global warming and so did most of the world’s scientists. At the time I did not have any handy websites to cite for further information. I put together this post so I could have a ready reference for my students.
What Is Climate Change?
First, let’s define climate. Climate is the average weather for a city, a region, or the whole earth. Weather is the conditions of temperature, precipitation, wind, and other properties that are present at any given time. For instance, because of our knowledge of the climate (the average weather) of Florida and Maine, we expect that the temperature in Florida on any given day (average temperature = 19.8 oC = 67.8 oF) will be higher than the temperature in Maine (average temperature = 7.6oC = 45.7 oF).
Climate change is a change in the average conditions that persist over a long period, usually decades or longer. The term “global warming” refers to the recent and continuing increase in the average temperature of the atmosphere surrounding the earth. Global warming is one aspect of climate change. Others are rain patterns, sea level, extent of polar ice caps, acidity of the oceans and many more. Sometimes the phrase “global warming” is used in conversation to mean the more general “climate change”. I suspect my student used “global warming” because that was the more familiar term.
What Causes Global Warming?
The current and ongoing global warming is being caused by a buildup of greenhouse gases, particularly carbon dioxide (CO2), in the atmosphere. How does this work? Energy from the sun falls on the earth and warms the surface and the atmosphere. The energy that hits the surface of the Earth is radiated back out. The atmosphere absorbs some of this energy thus causing the temperature to be higher than if there were no atmosphere at all. The expected temperature of the Earth without an atmosphere can be calculated. The calculated temperature is 255 K = -18 oC = -0.4 oF. Without an atmosphere, the big blue marble that is the Earth would be a big fat snowball. Since Earth does have an atmosphere, the average temperature is a comfortable 288 K = 15 oC = 59 oF.
In order to maintain a constant temperature, the amount of energy hitting the earth must eventually be radiated back into space. If one looks at the energy balance of the earth (some of the links below do this in detail so I won’t do it here) you find that more energy is coming into the Earth’s atmosphere than is leaving. This excess energy is heating the atmosphere and causing global warming.
More energy is being retained because of increasing concentrations of greenhouse gases in the atmosphere. Greenhouse gases are those that absorb the infrared radiation that is coming from the Earth’s surface and convert it into heat. Naturally occurring greenhouse gases such as water (H2O), carbon dioxide (CO2) and methane (CH4) help make Earth the blue marble rather then the frozen snowball. However, the more greenhouse gases, the more heat you produce, and the higher the temperature. Over the last one hundred and fifty years or so human activity has caused an increase in the concentrations of greenhouse gases in the atmosphere. These gases include methane, nitrous oxide (N2O), ozone (O3), halogenated compounds (those that contain chlorine (Cl) and fluorine (F)) and, of course, carbon dioxide.
Who Believes in Global Warming?
I made the claim to my student that many of the world’s scientists believe in global warming. To back up my claim, here are descriptions and links for four scientific societies and one international organization that have extensive information about climate change. These represent hundreds of thousands of scientists and in all cases support these conclusions: global warming is real and it is caused by human activity.
The American Chemical Society (ACS) is a scientific society that promotes inquiry in the field of chemistry. The ACS has 158,000 members worldwide. The ACS has a position statement that summarizes it’s stance on global climate change. The ACS supports the consensus position that the ongoing global climate change is caused largely by human activities. The ACS has a website, the ACS Climate Climate Science Toolkit, that discusses the evidence and ideas associated with climate change. I highly recommend this site. I am a member of the American Chemical Society.
The National Academies of Sciences, Engineering, and Medicine are non-profit societies of distinguished scholars. The National Academies sponsor an extensive website on Climate Change. Recently the National Academy of Sciences partnered with the Royal Society, the premier scientific society of the United Kingdom, to produce a booklet, Climate Change: Evidence and Causes. The booklet is organized around twenty questions such as “Is the climate warming?” and “Climate is always changing. Why is climate change of concern now?” There is also a section for further reading. Highly recommended.
The National Aeronautics and Space Administration (NASA) has a bunch of satellites. As you might expect, some of them are dedicated to watching the weather. So NASA is in the position to know something about climate change. NASA has a wonderful website about Climate Change. If you go to the site, be sure to scroll down to see all the goodies. There is a lot wiz-bang on this site, but there is a lot of solid information as well.
The American Association for the Advancement of Science (AAAS) is a nonprofit organization of greater than 120,000 members that promotes scientific freedom and the advancement of science. The AAAS has a website called What We Know that deals with climate change. They also have a fourteen-page booklet entitled What We Know: The Realities, Risks, and Response to Climate Change.” I am a member of the AAAS.
The Intergovernmental Panel on Climate Change (IPCC) is an international organization established in 1988 by the United Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO) and endorsed in the same year by the United Nations General Assembly. The mission of the IPCC is to provide assessments of the science concerning climate change and of the impacts on society and the environment. The IPCC has produced a series of report on the state of climate change. The most recent of these is the Fifth Assessment Report (AR5), which was released in four parts between September 2013 and November 2014. The four parts are: Climate Change 2013: The Physical Science Basis, Climate Change 2014: Impacts, Adaptation, and Vulnerability, Climate Change 2014: Mitigation of Climate Change, and Climate Change 2014: Synthesis Report. For light reading, I recommend the Synthesis Report Summary for Policy Makers.
Published Support of Anthropomorphic Climate Change
Two published studies (1,2) examined the consensus on climate change as determined from the abstracts of papers in the climate field. These are peer reviewed studies. For any non-scientists reading this post, this means that the studies were examined by other scientists in the field and were deemed worthy of publication. This is the highest standard scientists have in publishing their results. The two studies look for evidence in the scientific literature that scientists publishing in the climate field not only support the idea of climate change but that they also agree that human activity is causing it (anthropogenic global warming).
In the earlier study (1), Oreskes examined the abstracts of 928 papers published between 1993 and 2003 (this study was published in 2004). Of these, 75% explicitly supported the consensus position, namely that global warming is occurring and that most of the observed warming over the last fifty years is likely due to increasing concentrations of greenhouse gases caused by human activity. The other 25% of the papers concerned methods or early climate (paleoclimate) and took no position on current climate change. None of the papers disagreed with the consensus position.
The more recent paper by Cook et al. (2), examined 11,994 abstracts in the field of climate change from the period 1991-2011. The abstracts matched the search terms “global warming” or “global climate change”. 43.6% of the abstracts expressed a position on anthropomorphic global warming. Of these 97.3% concluded that human activity is the root cause of global warming.
In Conclusion
My student asked me if I believed in global warming. I do. The scientific evidence is clear and overwhelming. I also stated that most of the world’s scientists also believed in global warming. The websites I cite in this post show that hundreds of thousands of scientists support global warming and that the vast majority of the papers published by climate scientists do, too. Climate scientists are not making up their data. Climate change is a real problem and there will be real consequences.
References
- Oreskes N (2004) Beyond the ivory tower. The scientific consensus on climate change Science 306:1686 DOI: 10.1126/science.1103618 LINK
- Cook, J., Nuccitelli, D., Green, S. A., Richardson, M., Winkler, B., Painting, R., Way, R., Jacobs, P., and Skuce, A. (2013) Quantifying the consensus on anthropogenic global warming in the scientific literature. Environ. Res. Lett. 8, 024024 LINK
About the Graphic
The graphic at the beginning of this post is art; it is not meant to convey scientific information. I started with the graph from NASA. I traced over the NASA data line using the vector graphic program Inkscape then added the box and the text. I made box small so that the trace would pop out the top as if it were escaping. Use it if you want. Please give me an attribution.