What is the scientific basis for Anthropogenic Global Warming (AGW)?

The scientific basis for anthropogenic global warming (AGW) is formed based on three ideas that logically build off of each other. In the first step, there is data proving that fossil-fuel burning from humans has increased the carbon dioxide emissions. Second is the fact that carbon dioxide is a greenhouse gas. Lastly, the argument is that the increase of greenhouse gases in the atmosphere has caused an increase in temperature.


First off, it is important to show numerically how the concentration of carbon dioxide has changed over the past 1000 years, as shown in the figure below ^[3].

As can be seen on the figure, the level of carbon dioxide emissions was relatively constant until the year 1769, the start of the Industrial Revolution and the burning of fossil fuels. The year 1769 conveniently marks the year in which carbon dioxide emissions started rising and has not looked back, with the level of emissions still growing today. Thus, it can be concluded that there is sufficient proof from scientists that the human fossil-fuel burning has in fact increased carbon dioxide emissions.

The second step in the scientific bases for AGW is proving that carbon dioxide is indeed a greenhouse gas. According to David McKay, carbon dioxide is not the strongest GHG, but nonetheless it is a greenhouse gas and acts as any other normal greenhouse gas does. “It absorbs infrared radiation (heat) heading out from the Earth and reemits it in a random direction […] the fact is not based on complex historical records of global temperatures but on the simple physical properties of carbon dioxide molecules.” ^[3]

Finally, the third step in proving that increases in GHGs causes increases in temperatures is by far the most uncertain. However, many scientists do agree that the two subjects are directly related. David McKay proclaims in his book that the consensus of the best climate models predicts that “doubling the CO2 concentration would have roughly the same effect as increasing the intensity of the sun by 2%, and would bump up the global mean temperature by something like 3°C.” ^[3]


These three steps form the basis of AWG and are widely accepted by scientists.

What is Global Warming Potential (GWP)?

Since CO₂ is the most abundant harmful greenhouse gas we give it special attention over the other GHGs. For example, many charts or graphs in this blog are relating emission of CO₂ rather than, say CH₄. CO₂ has become the standard to compare other GHGs with.


The Global Warming Potential (GWP) of each GHG is shown below. ^[20]

The chart shows how dangerous the less-known gases are to our atmosphere. Each number means it is that many times a greater hazardous potential. It’s important that engineers and any industrialization process leaders take into account the impact of the work they are doing on the environment.

Is human activity, particularly the use of fossil fuels, causing irreversible changes in Earth's climate?

In general, human activity has potentially caused some major, irreversible climate changes. According to the Intergovernmental Panel on Climate Change, human activity has very likely contributed to the continuous rising of the sea level the past 50 years and has likely affected wind patterns, affecting tropical storms. It has also likely increased the temperature of extreme hot nights and extreme cold days, and has somewhat likely increased the risk of heat waves ^[7].


Specifically in terms of the effects of fossil fuel burning by humans, it is very likely that fossil fuel burning has increased the global average temperature. If this is the case, it is possible that ice sheets on polar land could start melting more and more if fossil fuel burning does not stop. Also, it is slightly possible that the irreversible process of extinction of 20-30 percent of species could become extinct if the global average warming exceeds 1.5°C to 2.5°C (relative to 1980-1999) ^[7].

Where are greenhouse gases coming from?

Greenhouse gases typically come from almost every human activity. ^[18] While electricity (including heating and air conditioning) is the largest contributor, land use change, transportation and agriculture are other major categories. Energy consumption is proven to be the main contribution to greenhouse gases increasing with 61 percent. ^[18] Most CO₂ is the result of burning fossil fuels while most CH₄ and N₂0 comes from agriculture and wastes. Cattle contribute largely to the methane in our atmosphere because of the large amounts of food they eat (some of the food gets converted to methane by the stomachs). The following figure shows how our energy consumption methods are directly related to C0₂ emissions. ^[19]

It is easy to see that most carbon dioxide emissions are from the uses of petroleum and coal. Residential and commercial sectors use most of their energy to make electricity ^[19] and the figure below shows their percentages. Coal is clearly the dominant energy source related to electricity generation.

What are the sources of greenhouse gases?

The five principal greenhouse gases are water vapor, carbon dioxide, methane, nitrous oxide, and chlorofluorocarbons (CFCs). Sources for producing these GHGs can be broken down into two distinct groups: natural processes and anthropogenic sources (human-induced).


Natural greenhouse gas sources are those that generate any of the five principal gases, are continuously being recycled through the atmosphere, and have been present for millions of years. Among many natural GHG sources, the most popular are photosynthesis, respiration, and volcanoism ^[8].


On the other hand, anthropogenic GHG sources arise mainly from producing energy. Below is the breakdown of U.S anthropogenic greenhouse gas emissions by gas as of 2001.

It is shown that as of 2001, 82 percent of human-made GHG emissions can be attributed to the burning of fossil fuels for energy. Other notable GHG sources that are human-induced are landfills, coal mines, oil and gas operations, agriculture, industrial processes, and some fertilizers^[9].

What are greenhouse gases?

Most people have probably heard of their “Carbon Footprint” and can even tell you that it has to do with how much Carbon Dioxide they are responsible for producing. Most people do not realize that water vapor is the most abundant greenhouse gas mostly because the water vapor isn’t considered to be a big deal in terms of contributions to "the problem." Water vapor actually helps to absorb radiation to keep the Earth warm. CO₂ is the gas that contributes the most by volume of the greenhouse gases, but it is not the strongest component. Methane (CH₄) and Nitrous Oxide(N₂0) are two other main gases that compose the greenhouse gases. Man-made industrial gases also are contributors such as Hydrofluorocarbons (HFCs), Perfluorocarbons (PFCs), and Sulfur hexafluoride (SF6). There are hundreds of gases that exist in very small portions but will not be discussed at this time.

When sunlight enters Earth’s atmosphere it is dispersed and much of the sunlight strikes the surface. Some of this radiation is absorbed and some is reflected back towards space. The greenhouse gases trap this radiation, which would have otherwise escaped, and scatter the energy. This phenomenon is actually what makes the Earth a suitable place for humans to live since the sun’s heat is trapped in the atmosphere and keeps us warm. ^[16] However, too much of these greenhouse gases can become a bad thing. With the amount of these gases increasing each year, our atmosphere is warming up and the surface temperature is steadily increasing. The following charts show the three major gases and their emissions by sector. ^[17]

We can conclude that most of the N₂O and CH₄ comes from agricultural byproducts while agriculture only makes up 12.5 percent of all GHG emissions. CO₂, which composes 72 percent of the GHGs, comes mostly from power stations, industrial processes, and then transportation fuels.

What is the greenhouse effect?

The greenhouse effect is a natural process that is integral for life on Earth to function. In fact, without the greenhouse effect, the Earth’s average surface temperature would likely be around -18°C or -19°C. How the greenhouse effect works and maintains the Earth’s surface at a reasonable temperature is shown on the figure below. ^[6]

In Layman’s terms, sunlight (solar radiation) first passes through the atmosphere and a portion of the solar radiation reaches Earth’s surface, warming the Earth. The solar radiation not absorbed by Earth’s surface gets reflected in the direction of space. A portion of this reflected energy escapes through the atmosphere and into space; the remainder is absorbed by greenhouse gases and gets trapped in the atmosphere. This absorption of energy by the atmosphere causes an increase in temperature of the atmosphere and also Earth’s surface, making it livable. Equilibrium occurs when the amount of greenhouse gases in the atmosphere remains the same and the amount of solar radiation coming from the sun is constant. Thus, there would be no outlying problem.

Before the Industrial Revolution, it is probable that no problems existed with the natural greenhouse effect. However, since the beginning of this era the level of GHGs in the atmosphere has increased substantially, creating what many call the “enhanced greenhouse effect.” It is very likely that the increase in GHGs that results in an enhanced absorption of radiated energy from the Earth’s surface is warming the Earth at a rate that is undesirable. This rate of warming has the potential for great dangers and disasters.

If the current energy profile of the world is sustained, what impact will it have on the environment?

If the current energy profile of the world is sustained, there is much debate about what will happen. One thing that experts can agree on is that within approximately 100 years we will run out of coal. Oil is predicted to last approximately the same amount of time.

The figure above shows how the world uses energy on a regular basis. The figure was constructed using statistics by the International Energy Agency and was created via Wikipedia. The depiction of the real critical situation is imperative. If we run out of oil and coal, our number one and two resources used for producing energy, what will we do? That’s what experts around the world are asking each other right now trying to figure out a way to “save” civilization.

Unfortunately, civilization isn’t the only thing at risk and dependent on our energy crisis. The prolonged use of burning fossil fuels to supply energy has already increased the surface temperature, increased harmful atmospheric gas concentrations, contributed to the rising sea level, and polluted parts of the world past the point of possible recovery. A hundred years from now it’s impossible to judge exactly what will happen but we know it will not be good unless people drastically change their habits and the way they consume energy. We as consumers are responsible not only for ourselves but for our children, our children’s children, and even their children, assuming the Earth is still able to support civilization.


The two figures below were taken from the Ventana Systems website and show the current and projected energy consumption, GDP, and population for the United Sates and for the rest of the world.

It is evident from the figures that the United Sates has taken the initiative at least to consume less energy in the last 50 or so years. Americans do consume more energy per capita than any other nationalities and along the way we have realized this and attempted to alter the trend. The exponential growth (red line) for the rest of the world in the total energy consumption graph shows how severe the issue is becoming. While it’s nearly impossible to stop consuming energy all together, there are little things that we can do. Things that may seem insignificant such as walking to work instead of driving, or canceling that flight across the sea to do something closer to home will eventually add up.

 With the projected energy consumption per capita so large for Americans, it’s really up to Americans to lead the front in the energy issue. For ourselves and for our environment, change is essential.

Can the current energy consumption profile last?

Since the United States is one of the world’s largest energy consumers and affects many other countries’ energy supplies, the U.S will be under observation. It is assumed that if the U.S current energy consumption profile can last, then the world’s current energy consumption profile will also be able to last.

In the middle of 2009, there was an investigation done on current and future United States energy consumption by the Energy Information Administration. In their study, they predict that if federal policy remains constant from 2009 to the year 2035, fossil fuels will provide 78 percent of the total energy supply domestically in the year 2035. This statistic is shown in the figure below, which provides the data acquired in the EIA study.^[4]

Based on the EIA projections, the fossil fuels coal, natural gas, and oil will produce 21 percent, 24 percent, and 33 percent, respectively, of total energy consumption for the U.S in the year 2035. Meanwhile, renewable energy is projected to increase only subtly, from 7 percent in the base year of 2009 to 10 percent in the year 2035.

By combining the current energy consumption portfolio for the U.S, the projected energy consumption portfolio in 2035 for the U.S, and the fact that global energy demand is expected to rise by 52% from the years 2002 to 2030 ^[5], it is likely that the current energy consumption profile can last in the short-term, but great environmental and economic dangers may ensue. In the long run, however it is very likely that the current energy consumption profile will not last.

The profile is very likely not to last long-term because of the implications that coal, natural gas, and oil have. Three significant problems are associated with the current energy status of large-scale burning of fossil fuels: emissions of Greenhouse Gases (GHGs), energy dependence on foreign countries, and a finite supply of these fuels.

The first main problem dealing with fossil fuels is the emission of Greenhouse Gases (GHGs), which can create significant climate changes in the future. The GHGs that are most prevalent in the atmosphere generated by the burning of fossil fuels are Carbon Dioxide, Sulfur Dioxide, and Nitrogen Oxides. Together, these three chemicals work together in the atmosphere, leading to environmental problems like local pollution and acidification. Also, the emission of large levels of Carbon Dioxide likely leads to the Earth’s temperature heating up. If no actions are down now to reduce the GHG emissions, the Intergovernmental Panel on Climate Change (IPCC) predicts the average global temperature will likely rise 1.4 to 5.8 degrees Celsius by the year 2100. This increase in global average temperature has a chance to raise the sea level by one meter by the year 2100, meaning 40% of Bangladesh would be underwater.

Another problem is the dependence on foreign oil and natural gas and their health effects on United States citizens. Since the United States demand for natural gas and oil is extremely high, their volatile prices affect the whole macroeconomy. The long-term economic growth of the U.S has to be stable.

The third and last central problem to fossil fuel consumption is the finite supply of the materials. Simply put, it is an estimated 100 years until all fossil fuels will have run out.

As of now, the current energy consumption profile of the United States is dominated by fossil fuels. If there is no new federal legislature after 2009, the EPA predicts fossil fuels will still dominate the energy economy in the U.S in 2035. The three undermining problems that are at the heart of fossil fuels for energy production not only apply to the U.S, but the world as well. Therefore, it is strongly unlikely that the energy consumption profile for the world will last.

What is the carrying capacity of the Earth?

One question that arises frequently in discussion of energy and the Earth is “to what extent are humans responsible?” Basically, the research is there to indicate that since the first coal mine was opened up, levels of greenhouse gasses have increased and the climate has shifted in a negative manner. Dictionary.com defines the Earth’s carrying capacity as the maximum, equilibrium number of organisms of a particular species that can be supported indefinitely. ^[12] For a typical population, if the level of inhabitants exceeds the carrying capacity the population will decrease due to competition for resources. Once the population level is back near the carrying capacity, the competition will stabilize and numbers may again begin to increase. ^[13] For humans it’s difficult to simply explain this because we have so many technological advancements on a regular basis. However, is it possible that over the past couple hundred years we have done so much harm to our planet that it will never be the same again?


The Earth is currently 30 percent past the point where it would retain regenerative capabilities. This means that the regenerative capacity is lost, and most certainly is lost at least in part due to human activities. The following graph shows how the surface air temperature has risen over the years. ^[14]

What is sustainability?

The term “sustainability” can encompass several different subjects, but the underlying idea is that “systems need to be regenerative and balanced in order to last.”^[1] Specifically in terms of the energy industry, a very common definition of sustainability is given by the United Nations as “meeting our needs without compromising the ability of future generations to meet their own needs.”^[2] How the preceding quote came into play was the concern by the UN in 1987 of the effects of the current energy portfolio, for both the environment and economics. The need to be “sustainable” arose due to three main factors: fossil fuels (the most predominately used fuels) are of finite supply and will eventually run out, energy security became an important issue, and the current usage of fossil fuels has likely tarnished the environment because of the high emissions of carbon dioxide.


Transforming the current energy industry crisis to one that is sustainable and solves the three preceding issues takes into account how the energy is supplied and the way energy is used. By combining the implementation of renewable energy sources such as wind, solar, and geothermal, along with making energy conversion processes more efficient, will likely lead to sustainability. Thus, the quantity and quality of energy for future generations will not be compromised while also maintaining the amount of energy necessary for society to function.

Why should we think about energy?

The topic of energy production and consumption is becoming a more important issue each year. We need to think about energy more now than ever so that we can preserve our planet for as long as possible. 

Before coal was discovered as a valuable energy source, there were still other fuels burned to produce energy. The most plentiful and most commonly used resource was wood because it can be found easily and can be used easily to cook food. Problems with wood arose because the energy extraction process is very difficult and inefficient. A large abundance of wood is needed to keep a fire going for a long time. Also, a hot fire also needs adequate space to burn. For example, a present-day kerosene lamp with a wood fire in place of the kerosene fire seems very impractical. To solve this issue, whale oil taken from the blubber of a whale was a common resource. It was used in lamps most commonly and when coal production really got going whale oil became obsolete.

Since the discovery of coal in 1742, America's energy production along with the rest of the world's production has grown exponentially. ^[10] Ever since the discovery, America has been the front runner in coal.West Virginia alone currently boasts four percent of coal reserves in the world. ^[10]. Each day, there are more and more people living on this planet. With nearly 7 billion already here, focusing attention on the Earth and its energy usage is a very important goal.

The following table is taken from the World Coal Association Website and shows each the geographic region on the x-axis and the billions of tons of estimated coal reserves on the y-axis. ^[11]

Each country trades with other countries, and when a region is abundant in a resource it makes for a valuable “bartering” source. The increased levels of overseas manufacturing have led to a world-wide problem concerning energy, its abundance, and its impact on our planet.