About Lesson 12

In the last lesson, we discussed one means of attempting to mitigate climate change — geoengineering. We saw that geoengineering is not without its perils and potential unintended consequences. If we take geoengineering off the table, that leaves only one approach to mitigation: decreasing our greenhouse gas emissions. How can we reduce greenhouse gas emissions while meeting growing global energy demands? That is the topic of our final lesson.

What will we learn in Lesson 12?

By the end of Lesson 12, you should be able to:

• summarize the contributions of various sectors to current fossil fuel emissions and the potential for mitigation of carbon emissions in the various sectors;
• discuss both the economic and ethical considerations of climate change mitigation; and
• evaluate the efficacy of specific climate change mitigation strategies (i.e., various proposed policies for limiting fossil fuel emissions).

What will be due for Lesson 12?

Please refer to the Syllabus.

The following is an overview of the required activities for Lesson 12. Detailed directions and submission instructions are located within this lesson.

• Continue Project #3 (due next week).
• Read:
  • IPCC Fifth Assessment Report, Working Group 3 [1]
    • Summary for Policy Makers [2], p. 1-30
  • Dire Predictions, p. 164-213
• Participate in Lesson 12 discussion forum: Project #3 Videos (begins next week).

Questions?

If you have any questions, please post them to our Questions? discussion forum (not e-mail), located under the Home tab in Canvas. The instructor will check that discussion forum daily to respond. Also, please feel free to post your own responses if you can help with any of the posted questions.

We saw the family of past and possible future trajectories of greenhouse gas emissions and concentrations [3] earlier in the course. But what are the specific greenhouse gases involved, other than the obvious culprit - CO₂, and where are these emissions actually coming from? What are the sectors of society and economy responsible for these emissions, the potential for reducing emissions in these various sectors, and the larger economic, political, and ethical considerations surrounding these issues?

First, let us tackle the first question. What are the anthropogenic greenhouse gas emissions in the first place? Indeed, the main culprit is, as we might have expected, CO₂. In terms of the net increase in the greenhouse effect due to human-produced greenhouse gases, CO₂ is responsible for the lion's share. CO₂ from fossil fuel burning alone is more than half the net force. If you add CO₂ from fossil fuel burning, deforestation, and other minor sources, this comes to a little more than three-fourths of the net greenhouse radiative forcing by human-caused emissions. That means, however, that a non-trivial fraction of the effect is coming from other gases. What are they?

Well, roughly 14% is methane, mostly from agriculture, livestock raising, and damming projects (which create an artificial breeding ground for methanogenic bacteria), though some also escapes during natural gas recovery attempts. Another 8% is nitrous oxide—also a byproduct of agriculture, and the remaining 1.1% is chlorofluorocarbons (CFCs). It is tempting to simply lump the contribution of these greenhouse gases together with that of CO₂, representing the net impact in terms of an effective CO₂ concentration called "CO₂ equivalent" [4] as we saw briefly earlier in the course. There is a catch, however! Some of these gases (like methane) are considerably more short-lived in the atmosphere than CO₂, persisting for decades rather than centuries. Such complications are often dealt with through the concept of global warming potential (GWP), which takes into account both the radiative properties of a particular greenhouse gas molecule and the lifetime that such a molecule typically has in the atmosphere, once emitted. In any case, such details represent a complication for greenhouse emissions mitigation policies. If we need to avoid a dangerous near-term climate tipping point, we might focus more effort on reducing methane because it is a particularly potent, if short-lived, greenhouse gas. On the other hand, if our goal is to stabilize long-term greenhouse gas concentrations, we would be better served by focusing purely on CO₂ emissions.

Figure 12.1: Greenhouse Gas Emissions By Gas, 2010.

Click for a text description of Greenhouse Gas Emissions by Gas 2010.

• Carbon dioxide/CO₂ fossil-fuel use: 65%
• Carbon dioxide/CO₂ (deforestation, decay of biomass, etc.): 11%
• Methane/CH₄: 16%
• Nitrous Oxide/N₂O: 6%
• CFCs/F-gases: 2%

Credit: IPCC, 2014

So, where are these greenhouse gas emissions coming from? They come from literally every sector of our economy. The largest single source is energy supply—primarily coal-fired power plants, and natural gas—used by consumers for electricity and heating. The next largest contribution comes from industry, which includes electricity and heating used by the industrial sector and greenhouse gases released as a byproduct of cement production, chemical processing, and other industrial processes. Energy supply and industry combine for nearly half of the greenhouse gas emissions. Next, accounting for about 17% of emissions, is forestry—mostly the carbon released from forest clearing and forest burning, followed by agriculture and transport, each of which accounts for around 13% of emissions. Agricultural emissions are mostly in the form of methane released by ruminants such as cows used as livestock, and by cultivation of rice paddies, which provide breeding grounds for methanogenic bacteria. Transport-related emissions are mostly in the form of petroleum-based fuels used for personal (i.e., cars and motorcycles, minivans, SUVs, small trucks, buses, airplanes) and commercial (large trucks, ships, airplanes) transportation. Finally, residential buildings (including both construction and maintenance, electricity requirements, etc.) and waste management are responsible for about 8% and 3% of emissions respectively.

Figure 12.2: Greenhouse Gas Emissions By Sector 2010.

Click for a text description of Greenhouse Gas Emissions by Sector 2010.

• Agriculture, Forestry, and Other Land Use: 24%
• Transport: 14%
• Residential and commercial buildings: 6%
• Electricity and Heat Production: 25%
• Other Energy: 10%
• Industry: 21%

Credit: IPCC, 2014

While it is useful to know what the historical contributions to our emissions have been from the various sectors, looking forward towards the future it is also important to know which sectors are growing most rapidly in their contribution to anthropogenic greenhouse emissions. By comparing emissions rates during the middle of the past decade with those at the beginning of the 1990s, we see that the largest absolute increase (an increase of nearly 3 gigatons/year of CO₂ released) has been in the energy sector, though other sectors such as transport and forestry have shown similar (35-40%) increases in emissions over this time frame. It is logical to conclude that these sectors might demand special attention in considering possible emissions mitigation approaches.

Figure 12.3: Greenhouse Gas Emissions By Sector in 1994 and 2004.

Credit: Dire Predictions by Mann & Kump

We have alluded to some of the economic considerations in climate change mitigation elsewhere in this course; now we are going to jump into it with both feet. To some extent, the economics of climate change is a matter of cost-benefit analysis. Alternatively, we can view this as balancing dueling costs. There is, of course, the cost of action. Some mitigation schemes actually cost nothing, and, in fact, they might even save us money—these are called no regrets strategies. They are the things we ought to do anyway: recycle, reuse, reduce our use of energy, etc., whether or not they make a difference for climate change—we will have more to say about these later in the lesson when we discuss reducing individual carbon footprints [5]. However, other mitigation schemes, like carbon sequestration or use of energy sources that are more expensive than relatively cheap fossil fuels, cost money. On the other hand, there is the cost of inaction. We have seen those costs — we know that there is potential harm that could be done across all sectors of society by climate change impacts.

One complication is taking into account so-called externalities — hidden costs that are not, by default, taken into account in the economic decision-making process. What is the value of a coral reef? What is the value of a functioning ecosystem? What is the value of a species? What is the value of human life and does this differ among nations, between rich and poor? Quickly, as you may gather, discussing the economics leads us into a discussion of matters that are no longer simply economic in nature, but, indeed, raise fundamental ethical questions as well. We will discuss these ethical considerations [6] later in the lesson.

But, for the time being, let us return to the economic framing of the problem. To do so, we need to introduce a quantity known as the social cost of carbon (SCC). This is the cost to society of emitting a (metric) ton of carbon. As noted above, precisely evaluating the true cost to society becomes very difficult. Economists typically resolve this difficulty by simply ignoring those costs that are not easily quantified (i.e., ignoring the externalities), and focusing purely on the more straightforward economic costs.

There is quite a bit of debate among economists regarding the true value of the SCC. In part, the divergence of opinion relates to different assumptions regarding the appropriate level of what is known as discounting. Discounting, in economics, relates to the fact that a dollar a year from now is worth less to you than a dollar today, because of the lost opportunity of not having the dollar today. In typical financial markets, this discount rate is somewhere in the range of 6%. One can argue that there is a similar discounting phenomenon that applies to climate change mitigation. The argument is that money that might be spent on climate change mitigation today could be spent on other investments, and perhaps because of improvements in, e.g., energy or in emissions mitigation technology that will arise in the future, it will actually be cheaper to decrease our emissions by the same amount a year from now.

What is unclear, however, is whether or not it is appropriate to apply similar discount rates to those used in financial markets to climate change mitigation. For one thing, the costs and benefits are not borne by the same individuals. The carbon we are emitting today will most likely incur the greatest costs for our children, or even our grandchildren's generation. Is it appropriate to place less value on their quality of life than we place on our own? Once again, we see that deep ethical considerations are easily hidden in the sorts of assumptions that might superficially seem to be objective economic considerations. While some economists like William Nordhaus of Yale University have argued for discount rates as high as 6% (though in recent years he has lowered his estimate of the appropriate discount rate to 3%), others such as Sir Nicholas Stern of the UK, in his well known review [7] of the economics of climate change, argues, for ethical reasons, that the appropriate discount rate should be far lower (Stern favors a 1.4% discount rate). There is a direct relationship between the discount rate and SCC. A 6% discount rate amounts to an SCC of roughly $20/ton, while a 3% discount rate translates to $60/ton, and a 1.4% discount rate translates to an SCC of roughly $160/ton.  The U.S. under the Obama administration used a value of $36/ton despite the uncertainties [8].  The Trump administration wanted to reduce this to $1 to $6/ton [9], even though there are indications that even the Obama-era number could be a substantial underestimate (at nature.com [10] and scientificamerican.com [11]).  As of March 2021, the Biden administration has the SCC set at $51/ton.  More on the SCC and how we arrive at these numbers can be found in the article: "The Social Cost of Carbon" [12].

Another complication is the possibility of tipping points. Most economic cost-benefit analyses assume that climate changes smoothly with increasing greenhouse gas concentrations. However, if there is a possibility of abrupt, large, and dangerous changes in the climate—e.g., the sudden collapse of ecosystems, melting of the major ice sheets, etc.—and the threshold for their occurrence is not precisely known, then any amount of future climate change could be perilous, with costs that cannot be anticipated in advance. This is one potentially crucial flaw in standard cost-benefit analysis approaches and part of the reason for the so-called precautionary principle, which advises erring on the side of caution (i.e., on the side of dramatic emissions reductions) when the potential threat—great harm to civilization and our environment in this case—is unacceptably costly.

Mitigation efforts, nonetheless, will only proceed if they pass the cost-benefit analysis, and to do so, the estimated SCC must be greater than the cost of emissions reductions. One way to make emissions reductions cost less is to make the emissions themselves cost more, i.e., to put incentives on the reductions. Any serious effort to mitigate carbon emissions must internalize the cost of the damage to our environment that they cause. There have been fierce arguments among economists and policy experts about how best to accomplish this.

The two widely considered approaches are the so-called carbon tax — a surcharge on carbon emissions at the point of origin, e.g., automobiles and trucks, coal-fired power plants, etc., and the so-called cap and trade — a system of tradable emissions permits aimed instead at end use, e.g., the automobile or airline industries, the energy industry, etc. In such a system, a limit is placed on the total allowable emissions; this is the cap for a particular industry, and the emissions rights can be traded in an open market.

Advocates of a carbon tax often see it as a market-based mechanism that is relatively free of bureaucracy, can be used to raise revenue, or can be made revenue-neutral though offsetting reductions in other taxes. Proponents of cap and trade, by contrast, might point out that it is a more effective approach for insuring that emissions remain below some specified level—something that could be particularly important when dangerous tipping points loom. The cap and trade approach, moreover, has been tested and shown viable in other contexts, such as the mandated reduction of sulfate aerosols with the clean air acts of the 1970s to combat the acid rain problem. A limited tradable system for carbon emissions has shown success in the European Union.

We have already seen that, depending on discount rates and other assumptions, one can come up with vastly different estimates of the SCC. But there seems to be some consensus that a reasonable estimate lies somewhere within the range of $20 to $100. As a point of reference, a 9 cents per gallon gasoline tax would amount to roughly 30$/year for the average American who drives roughly 10,000 miles a year, thus emitting a metric ton of carbon.

So, what sorts of emissions reductions might be expected at varying levels of assumed SCC? This is shown in Figure 12.4 below.

Figure 12.4: Reduction Potential at 3 Different Carbon Costs (U.S. $ Per Metric Mon)

Credit: Mann & Kump, Dire Predictions: Understanding Climate Change, 2^nd Edition
© 2015 Pearson Education, Inc.

It is evident that if we adopt a very low (e.g., $20/ton) value for the SCC, then emissions reductions will be quite modest, while at $100/ton the reductions are considerably more substantial. We saw earlier in the course [13] that carbon emissions, at least approximately a decade ago, were roughly 8.5 gigatons of carbon per year; in the most recent years they are near 10 gigatons per year. In terms of CO₂ equivalent that amounts to 37 gigatons/year. [To convert from carbon to CO₂ equivalents, we need to consider the following: 1 mole of CO₂ contains one mole of carbon; molar weight of carbon is 12 g/mole; molar weight of oxygen is 16 g/mole; molar weight of CO₂ is 12+2*16 = 44 g/mol. Therefore, to convert from units of carbon to CO2 equivalents, units of carbon must be multiplied by 44/12 conversion factor.] To bring emissions to zero, we would need to reduce these emissions by 37 gigatons per year. At a $20/ton cost, we see that the reductions over all 7 sectors (energy supply, transport, buildings, industry, agriculture, forestry, and waste removal) add up to about 13 gigatons/year, a small portion of that 31 gigatons/year. On the other hand, at $100/ton, the reductions add up to almost 24 gigatons/year, making a quite serious dent in the 37/year that constitutes current emissions, reducing carbon emissions to 13 gigatons CO₂ equivalent/year.

Let us try to place this discussion in the context of what strategies might need to be implemented to avoid dangerous anthropogenic interference (DAI) with the climate system. We saw earlier (in Lesson #6) that to stabilize below 450 ppm, CO₂ levels must be brought to a peak within the next decade, and ramped down to 80% below 1990 levels by mid-century. Emissions in 1990 were about 6.5 gigatons carbon per year.

So, doing the calculations, 80% below 1990 levels yields about 5 gigatons CO₂ equivalent per year, about 40% of the 13 gigatons we estimated would result from an SCC of $100/ton. So, let us estimate that reducing emissions to 5 gigatons CO₂ equivalent would require a SCC on the order of $180/ton.

We can use the Kaya Identity approach to interpret what improvements in carbon efficiency such an SCC would translate too. Since the Kaya identity evaluates emissions in terms of gigatons carbon, let us convert the 5 gigatons CO₂ equivalent back to carbon emissions: just under 1.5 gigatons carbon/year, as it turns out.

So, the bottom line is that if you place a large enough cost on emitting carbon, it is possible to achieve the necessary reductions to stabilize CO₂ concentrations at non-dangerous levels. Stabilizing CO₂ concentrations at 450 ppm would appear to require an SCC roughly in the range of $180/ton carbon emitted, which, in turn, would amount to a roughly 4% per year improvement in carbon efficiency. How that improvement will come about, necessarily, will be dictated by governmental policies. Only by internalizing the true costs of carbon-based energy and fundamentally revising government incentives for developing non-carbon (or carbon neutral) based energy sources, such as wind, solar, hydro-power, bio-fuels, and potentially—albeit with certain important caveats—nuclear, will market mechanisms operate under rules that will increase the SCC to the necessary levels.

Now, let us take a more detailed look at the opportunities for reductions in the various sectors of our economy and society.

Energy supply is the single largest source of carbon emissions. As such, it demands special attention in efforts to reduce emissions. The primary fossil fuel energy sources are from the burning of coal and the burning of natural gas (methane), both of which release CO₂ into the atmosphere. Petroleum is primarily used for transport—a sector we will discuss in more detail later. Renewable sources of energy, including nuclear energy, biomass burning, hydroelectric, wind, solar, and hydrothermal combine for less than a fraction of either coal or natural gas.

Figure 12.5: World Primary Energy Consumption by Fuel Type in Megatons of Oil Equivalent (Mt Oil Equivalent).

Credit: Mann & Kump, Dire Predictions: Understanding Climate Change, 2^nd Edition
© 2015 Pearson Education, Inc.

Here at Penn State, we have historically gotten much of our power on campus from campus-based coal-fired power plants, but there was a recent move to switch over to natural gas as a primary energy source on campus [15], a move that was completed in March 2016 (see "Switch to Natural Gas" Article [16] and "One Year Later" Article [17]). Penn State is also making an investment in renewables, like this solar project [18].

Burning of natural gas emits less carbon than does a similar amount of energy derived from burning of coal, and has thus been favored by some policy advocates as a preferable energy source. On the other hand, coal-burning represents large point source carbon emissions, and thus has the advantage that CCS technology [19], when it progresses beyond the experimental stage, can be used. Both coal and natural gas extraction are associated with potentially serious environmental externalities. Controversial mountain top removal practices are increasingly being used to get at hard-to-reach coal deposits, but this process can cause extreme environmental degradation over very large areas. Natural gas has its own problems, in particular, damage done to the environment by the controversial practice of hydraulic fracturing or "fracking", which may release harmful chemicals into groundwater and the greater environment. This, and other potentially harmful practices associated with natural gas extraction, has generated quite a bit of debate regarding the development of Pennsylvania's Marcellus Shale. Penn State is now home to the Marcellus Center [20] for Outreach and Research, which focuses on both the potential benefits and potential harm associated with developing Pennsylvania's Marcellus shale.

Figure 12.6: Penn State Students Protesting in front of Campus' Coal-Fired Power Plant, (left), and Natural Gas Extraction, (right).

Credit: Sierra Club Allegheny Group [21] and Treehugger.com [22]

When we look at the regions of the world where per capita energy consumption is greatest, we find, not surprisingly, that much of the current energy consumption is by the developed world, especially the U.S. and Canada, and to a lesser extent Australia, the former Soviet Union, and Japan. However, from the point of view of controlling future emissions, it is important to note that certain developing nations like China and India, are making an increasingly large dent in world energy consumption, and given their very large populations, they are projected to make an even bigger dent in the future. Up until the last few years, China, was now building a new coal-fired power plant every few days! Even today, China continues to subsidize coal-fired power in developing economies [23] despite a push toward lower emissions in their own country.  Any efforts aimed at controlling future energy-related emissions clearly need to take into account the developing world, including China, India, and South America.

Figure 12.7: World Energy Consumption by Region.

Credit: Mann & Kump, Dire Predictions: Understanding Climate Change, 2^nd Edition
© 2015 Pearson Education, Inc.

Transportation, as we have seen, accounts for 13% of fossil fuel emissions. Historically, the vast majority of these emissions have come from the road (cars, trucks, SUVs, motorbikes, etc.), and much of the recent growth is related to freight trucks, but emissions from air and sea transport are increasing (much of it is also related to freight transport), and emissions from airlines are projected to become increasingly significant in the decades ahead.

Figure 12.8: Historical and Projected Transport Emissions by Mode 1970-2050.

Credit: Dire Predictions by Mann & Kump

As with the energy sector, transport-related emissions from the developing world, especially China, but also South America and the former Soviet Union, are projected to become increasingly important as these nations develop their transportation infrastructure and adopt driving patterns similar to the developed world.

Figure 12.9: Projection of Transport Energy Consumption by Region 2000-2050.

Credit: Mann & Kump, Dire Predictions: Understanding Climate Change, 2^nd Edition
© 2015 Pearson Education, Inc.

There has been quite a bit of discussion about the prospects for so-called Peak Oil [24] taking hold in the decades ahead, as conventional oil reserves begin to run dry. Such predictions are based on the idea of Hubbert's Peak, which uses a simple theoretically-derived expression for the time evolution of production from individual wells, combined with estimates of the declining rate at which new wells/reserves are discovered over time, to project global petroleum production over time. One often encounters the argument that the peak oil phenomenon will serve as a solution to the carbon emissions problem. This argument is flawed, however. While it is true that conventional petroleum reserves could begin to run dry in the years ahead, there are other unconventional reserves in the form of tar sand and oil shale, which could provide a century or more of additional petroleum supplies—of course, such reserves may be considerably more costly to recover. Thus, it is ultimately going to be a matter of economics—as discussed earlier in this lesson—as to whether or not petroleum-based energy will be able to compete with alternative technologies (hydrogen cells, electric vehicles, bio-fuels) for transportation.

Figure 12.10: A traffic jam is seen during the rush hour in Beijing.

Credit: China Daily [25]

As we have seen earlier, emissions arising from industrial processes, e.g., steel, cement, oil refineries, and paper productions, constitute the 2nd greatest among all sectors, accounting for nearly 20% of all anthropogenic carbon emissions.

As with emissions from coal burning for power, industrial carbon emissions are often from large point sources (i.e., factories), and CCS technology is potentially available as a mitigation option. This means that market-based decisions on emissions reductions are able to consider both the cost of CCS implementation and the cost of paying for emitted carbon (i.e., carbon tax or costs of emissions permits, depending on what scheme for pricing carbon is in place). Estimates of the mitigation potential in the various industrial sub-sectors therefore involve both options.

Figure 12.11: Reducing Industrial CO2 Emissions Through Taxation and Carbon Sequestration.

Click for a text description of Reducing Industrial CO2 Emissions Through Taxation and Carbon Sequestration.

There are four pie charts to the left of an image of a coal power plant. They are split into three colors: red, blue and yellow. 

• Red = EFFECT OF CARBON TAX ON CO₂ EMISSIONS: If government agencies were to impose a tax of the amount listed (US $ per metric ton of emissions) on an industry, then it is estimated that the taxed industry would potentially reduce its annual emissions by the amount shown in red. 
• Blue = PROJECTED ANNUAL CO₂ EMISSIONS BY 2030: These values include emissions resulting from energy supplied to industry from the energy sector.
• Yellow = COST OF CARBON SEQUESTRATION: Some industries also have the potential to remove and store CO₂ from industrial emissions before it is released to the atmosphere. Different industries can sequester different amounts per year. If CCS procedures cost the amounts listed about (per metric ton of emissions), then it is estimated that each industry would potentially reduce its emissions by the amounts shown in yellow. 

The four pie charts are as follows:

1. STEEL: Total amount of projected CO₂ emissions by 2030: 1.2 billion metric tons (Gt)
   • red (a little over 50%) - Tax: $20-50 per metric ton; Emission reduction: 0.43-1.5 Gt CO₂/yr
   • yellow (about 5%) - CCS Cost: $20-30 per metric ton; Emission reduction: 0.07-0.18 Gt CO₂/yr
   • blue (about 45%)
2. CEMENT: Total amount of projected CO₂ emissions by 2030: 6.5 billion metric tons (Gt)
   • red (about 17%) - Tax: up to $50 per metric ton; Emission reduction: 0.72-2.1 Gt CO₂/yr
   • yellow (about 33%) - CCS Cost: $50-250 per metric ton; Emission reduction: 0.25-4.5 Gt CO₂/yr
   • blue (about 50%)
3. PETROLEUM REFINING: Total amount of projected CO₂ emissions by 2030: 4.7 billion metric tons (Gt)
   • red (about 3%) - Tax: up to $20 per metric ton; Emission reduction: 0.15-0.30 Gt CO₂/yr
   • yellow (about 2%) - CCS Cost: $17-31 per metric ton; Emission reduction: 0.08-0.15 Gt CO₂/yr
   • blue (about 95%)
4. PULP & PAPER: Total amount of projected CO₂ emissions by 2030: 1.3 billion metric tons (Gt)
   • red (a little over 23%) - Tax: up to $20 per metric ton; Emission reduction: 0.05-0.42 Gt CO₂/yr
   • yellow (0%) - Carbon Capture does not apply to this industry
   • blue (about 77%)

Credit: Dire Predictions by Mann & Kump

The potential for mitigation in the agricultural sector is often given less attention than that in, e.g., the transport sector, even though the two sectors are responsible for nearly equal contributions to global carbon emissions (in fact, agricultural emissions are roughly 0.5% greater!). While agricultural emissions are largely due to methane production from, e.g., rice cultivation and methane-producing livestock, such as beef cattle and dairy cows, interestingly enough, the primary opportunities for greenhouse gas emissions reductions in the agricultural sector actually involve CO₂. This is because of the large amount of land globally used for agriculture or livestock pastures. This land has typically been degraded by these uses (i.e., vegetation has been destroyed and soil has been depleted of key nutrients) so that it cannot absorb and sequester atmospheric CO₂ efficiently, in contrast with natural vegetated land. Because of this, the primary opportunities for mitigation of carbon emissions in the agricultural sector involve restoring degraded pasture and farm lands. There are other mitigation opportunities, however. One scheme that is being seriously considered involves changing the diet fed to ruminants to decrease their methane emissions. More efficient use of fertilizers can also potentially reduce agricultural emissions of nitrous oxide (not carbon dioxide, but a greenhouse gas, nonetheless).  Another scheme involves improving the methods for rice cultivation [26], which could lead to both fewer emissions and more productive yields.

Figure 12.12: Global Mitigation Potential of Various Agricultural Management Practices by 2030.

Credit: Mann & Kump, Dire Predictions: Understanding Climate Change, 2^nd Edition
© 2015 Pearson Education, Inc.

All of the major continents of the world contribute to agricultural carbon emissions today. As nations of South America, Asia, and Indonesia struggle, however, to feed increasingly large populations in the decades ahead, opportunities for carbon emissions mitigation will be greatest in these regions.

Figure 12.13: Estimated Mitigation Potential in the Agricultural Sector by 2030.

Credit: Mann & Kump, Dire Predictions: Understanding Climate Change, 2^nd Edition
© 2015 Pearson Education, Inc.

Let us finally talk about emissions in the forestry sector. Deforestation, as we know, is a major source of carbon emissions, larger than either transportation or agricultural, and the 3rd largest among all sectors, with only energy and industry responsible for greater emissions. So, clearly, the forestry sector has to be on the table if we are looking to mitigate global greenhouse emissions.

Reforestation would seem like an obvious strategy for mitigation in this sector. Unfortunately, reforestation faces some uphill challenges. The process of deforestation actually renders the land greatly degraded and largely stripped of key nutrients (these nutrients, after all, were taken up by the trees which have since been harvested). This makes it more difficult to grow trees on those lands. Since tree root systems and forest canopies are the main features that allow forests to retain water, deforested land has also lost much of its potential to store water and tends to dry out. Combined with a tendency for drying continents as a result of climate change, reforestation faces a serious battle. Indeed, forests are projected by climate models to transition from a net sink of carbon (which they are today) to a net source of carbon, constituting yet another potential positive carbon cycle feedback [27].

Figure 12.14: Rate of Change in Forested Area.

Credit: Mann & Kump, Dire Predictions: Understanding Climate Change, 2^nd Edition
© 2015 Pearson Education, Inc.

Figure 12.15: Historical Trends in Forest Carbon Emissions.

Credit: Mann & Kump, Dire Predictions: Understanding Climate Change, 2^nd Edition
© 2015 Pearson Education, Inc.

We have already seen in this lesson that reducing carbon emissions will ultimately require policies to ensure that market-based economic decisions internalize the cost to society and the environment of emitting additional carbon. Clearly, there is, therefore, not only a role, but a need, for enacting governmental policies to incentivize moving away from practices that emit carbon, including fossil fuel burning.

This does not mean, however, that there is not also a role for the individual. Clearly, making more responsible individual choices can help in the process of reducing carbon emissions. As we saw earlier, the typical American adds 1 metric ton a year to the atmosphere via the use of a personal vehicle. Of course, they would have furthered additional transport-related emissions through air travel, and even through the food and various projects they purchase, many of which are transported large distances. Then, there is the energy we use to power our homes, etc. By the time all is said and done, the average American, through all of their collective activities and actions, will have effectively emitted roughly 20 metric tons of CO₂ equivalent in a given year. Call this your carbon footprint.  Calculate your personal carbon footprint using the US EPA's calculator here [28].

Figure 12.16: What's your carbon footprint?

Click for a text description of What's your carbon footprint?

What's Your Carbon Footprint?

Before you go on a diet, you might weigh yourself to establish a starting point and also, perhaps, to further motivate yourself to cut back on calories. In a similar way, you can calculate your "carbon footprint"—your personal contribution to the problem of global warming—as a first step in reducing the emissions your lifestyle generates.

There are numerous carbon footprint calculators on the Internet; you may wish to try a couple to compare results. We give the U.S. EPA's URL below right. All of these calculators help you to evalutate your lifestyle and determine your personal contribution or "footprint". Carbon footprints are usually measured in metric tons of CO₂ equivalent (eq) per year. 

To asses your footprint, you will be asked to answer questions about your lifestyle.

Footprint questions

• Where do you live? There are regional differences in the energy sources used to generate electrical power, and these affect emissions. 
• How many people live in your home? Your carbon footprint is smaller ID the energy you use is shared.
• What type of vehicle and how many miles per year do you drive? Your car's gas mileage affects emission.
• How often do you fly, and are your trips short or long? Airline travel is a big emissions contributor. Short trips use more energy per mile because takeoffs are particularly fuel-intensive.
• Do you heat your home with natural gas, heating oil, or propane? How much is your typical monthly heating bill? What is your typical monthly electric bill?
• Do you eat red meat, just chicken and fish, or are you a vegetarian? The various activities that put these foods on your table have differing carbon emission profiles.
• Do you eat mostly local foods and buy mostly local products, or do you prefer imported goods? Long-haul freight consumes fossil fuel aggressively.
• What types of recreation do you prefer? A bicycling trip that begins at your front door contrasts quite markedly with snowmobiling or motor boating at distant recreation sites.

Now take off your shoes and compare your print to two famous footprints!

Sasquatch

Carbon footprint: 30 metric tons CO₂ EQ per year

• At home: Lives in a poorly insulated, air-conditioned apartment in the American Midwest with electric heat, loves to soak in a hot bathtub several times a week; does not recycle
• On the go: Drives an SUV 24,000 km (15,000 miles) per year, takes 5-10 business trips by plane each year, both short haul and long haul; and takes one exotic personal vacation each year by plane. 

Cinderella

Carbon footprint: 4 metric tons CO₂ EQ per year

• At home: Lives with two roommates in France in an energy-efficient, well-insulated apartment with electric heat; prefers taking showers; recycles a significant fraction of household waste
• One the go: Drives a hybrid car 16,000 km (10,000 miles) per year; journeys by train 1,600 km (1,000 miles) per year, uses videoconferencing rather than traveling for business; and takes one exotic personal vacation each year by plane. 

Does your footprint look more like Cinderella's dainty glass slipper or Sasquatch's big paw? Get online, find a carbon footprint calculator, and let the site suggest ways in which you can become more carbon stingy and environmentally friendly. 

Credit: Mann & Kump, Dire Predictions: Understanding Climate Change, 2^nd Edition
© 2015 Pearson Education, Inc.

Just like real footprints, carbon footprints vary greatly in size. An especially gluttonous individual might emit as much as 30 metric tons a year through his actions—call him a "Sasquatch" (otherwise known as "big foot").  On the other hand, an individual with a more ascetic lifestyle might emit as little as 4 metric tons of CO₂ equivalent per year—call her a "Cinderella".

Individuals, one might argue, must do their part in achieving the reductions necessary for achieving stabilization below dangerous levels. Recall that 80% below 1990 global emissions by mid-century, as required for 450 ppm stabilization,  is about 5 gigatons CO₂ equivalent per year, whereas current emissions are about 31 gigatons.

So, if you are a Sasquatch, or even just a typical emitter, what can you do to try to fit into Cinderella's shoes? Well, a picture is indeed worth a thousand words—see below. 

Figure 12.17: Ways to reduce one's own greenhouse gas emissions.

Click for a text description of Ways to reduce one's own greenhouse gas emissions.

1. Appliances that are not in use can be unplugged, reducing electricity leakage.
2. Clotheslines make an excellent substitute for dryers
3. Drive alone less or drive a fuel-efficient or electric vehicle
4. Remember to recycle
5. Replace incandescent bulbs with fluorescent bulbs
6. Commute to work by bicycle or on foot.

Credit: Dire Predictions by Mann & Kump

In many cases, as alluded to earlier in the lesson, there are simple no regrets strategies that can be taken to reducing one's own personal greenhouse gas emissions. Bicycling to work or to run errands is better for your health, as well as less expensive, than driving a car. Conserving energy by turning off appliances when they are not being used, buying energy-efficient appliances, compact fluorescent light bulbs, etc., lowers your energy bills. Many supermarkets give you a discount for using your own reusable canvas shopping bags, and many coffee shops give you a discount for using your own reusable container in place of a disposable paper cup. Other helpful practices such as the "Three Rs"—reducing, reusing, and recycling materials—are simply a matter of good stewardship, and make us feel better and help keep our environment clean. Of course, it is overly optimistic to imagine that civilization will make the major adjustments in lifestyle necessary to stabilize greenhouse gas concentrations based simply on no regrets strategies and an intrinsic commitment to better stewardship.

Policies that provide incentives for these types of behavior will have to play a key role.

We just completed a discussion of how individuals can make a difference in our collective carbon emissions through more responsible choices and decisions in their daily lives. But personal responsibility is hardly enough to effect major changes in carbon emissions. In a market-based economy such as prevails over North America, Europe, and the developed world, and increasingly the developing world as well, only proper market incentives can insure major changes in collective behavior. Ultimately, to solve the climate change problem, we need to fundamentally reshape our incentive structure, which currently provides very little investment for renewable sources of energy, while subsidizing development of fossil fuel sources. Putting a price on the emission of carbon is the only way to do that. And whether it is a carbon tax or emissions permits, only governmental policies coordinated among the nations of the world can implement such a system.

Kyoto Accord

Given the global nature of our carbon emissions, negotiated international treaties are essential if we are to stabilize greenhouse gas concentrations. Awareness of the need for such treaties was recognized by the early 1990s, in the form of the the United Nations Framework Convention on Climate Change (UNFCCC), which was first put forward at the 1992 Earth Summit in Rio de Janeiro. The framework convention was updated at an international summit held in Kyoto, Japan in 1997 to constitute the now-famous Kyoto Protocol, which had as its stated goal, holding greenhouse gas concentrations below a level that would constitute dangerous anthropogenic interference (DAI) with the climate system. This was, indeed, the first reference to the now-familiar concept of DAI. The Kyoto Protocol went into effect 8 years later, in 2005.

While putting a price on carbon emissions is the only way that free market forces will insure stabilization of greenhouse gas concentrations, the Kyoto accord did not mandate a particular approach (i.e., carbon tax, or tradable emissions), nor did it define DAI in terms of a particular CO₂ equivalent stabilization level or amount of warming. However, by 2007, the European Union had taken such initiative, defining DAI as 2°C warming relative to pre-industrial time, and implementing its own pilot program in emissions trading.

By the end of 2008, all industrial nations had ratified the treaty except the U.S. (though Canada withdrew from the treaty in 2012 under a new administration). Many developing nations also ratified the protocol, but were not held to mandated reductions due to the financial hardships the reductions might have imposed upon their fragile economies. While ultimately 192 nations signed on to the Kyoto Accord before it expired in 2012 (and many were willing to sign on to even stricter controls on carbon emissions), the two largest emitters of all ”the United States and China” remained holdouts. This is, perhaps, unsurprising. Both countries, as we have seen, rely upon a fossil fuel energy economy and—in the case of the U.S., politicians are lobbied heavily by fossil fuel industry groups not to pass legislation that might put a price on carbon emissions. Progress in mitigation of global carbon emissions is unlikely to occur without the participation of these two nations, placing much of the global political pressure on the U.S. and China to agree to an emissions reductions treaty.

Some nations, for example low-lying island regions and tropical nations most likely to be impacted in the near-term by climate change, argued that Kyoto did not go nearly far enough, and that for them DAI is already around the corner, and they do not have the resources to implement a program of wide-scale adaptation that richer nations have. Other supporters of Kyoto pointed out that it was just a first step in a process that will hopefully lead to more stringent reductions in the future. Critics on the other side argued that the impacts of climate change are overstated, and that passing the Kyoto accord would cost the economy. However, as we saw earlier in this lesson, sober cost-benefit analyses indicate that the costs of inaction are likely to greatly exceed the cost of action, so the credibility of this particular argument might be called into question.

Other complications arose due to the politics of differing interests of the two major holdouts, China and the U.S. China's net greenhouse emissions are now greater than those of the U.S., but their per capita emissions (due in large part to their extremely large population) are lower. Not surprisingly, the U.S. argued that the required emissions reductions be based on total emissions, while China argued it should be based on per capita emissions. Another complication is that western nations, like the U.S. and Europe, have enjoyed the benefits of more than a century of access to cheap fossil energy, while emerging industrial nations like China and India are only now exploiting fossil fuel energy reserves. These nations argue that the developed world already had its turn, and that they deserve their fair share. There are consequently substantial political tensions that make progress in achieving a negotiated emissions treaty slow and difficult.

Paris Agreement and Future Policy

Little progress was made in achieving a binding international climate treaty in the years following Kyoto. No such agreements were reached during either the 2007 Bali summit, or the 2009 Copenhagen summit. The primary obstacles seemed to be those cited above, namely the differing interests of various major players such as the U.S. and China, and more generally between the developed, developing, and undeveloped world. The reticence of the U.S. in committing to mandatory carbon reductions is, too, in part a product of political pressures. Those favoring U.S. participation have had to fight a coordinated, massively funded publicity campaign by the fossil fuel industry and trade groups representing it, which has successfully prevented passage of energy legislation dealing with climate change by attacking its scientific underpinnings, and by opposing politicians who support such legislation by funding their opponents in political campaigns, among other tactics.

This lack of progress and the apparent lack of will to confront the climate change threat has caused many to become discouraged over prospects for a meaningful carbon emissions policy.  However, there is some cause for cautious optimism as well. While China is the single largest net emitter of carbon on the planet now, this country has shown signs of commitment to developing renewable and clean energy, investing far more money in this area in recent years that other countries, such as the U.S. In November 2014, General Secretary Xi Jinping, along with President Obama, created a plan to limit greenhouse gas emissions.  Meanwhile, the Obama administration pursued executive actions via the EPA to reduce U.S. carbon emissions, including calling for higher automobile fuel-efficiency standards and regulations on coal-fired power plants such as the Clean Power Plan, with a target of reducing U.S. electrical power generation emissions by 32% by 2030.  While the U.S. Congress failed to pass a comprehensive climate bill, many states and localities have implemented their own greenhouse gas reduction schemes.

There are past examples of success we can look to, where nations came to agreement on policies to mitigate other emerging global environmental threats, whether it be the passage of the Clean Air Acts in the 1970s to deal with the threat of acid rain, or passage of the Montreal Protocol in 1984 to ban the production of CFCs, which were known to be damaging the stratospheric ozone layer. These past examples show that nations can join together in binding agreements to confront emerging global environmental threats before these threats reach catastrophic magnitudes. Dealing with climate change is admittedly more difficult, as carbon emissions are at the very heart of our current global energy economy, and simple solutions (such as installing scrubbers in smokestacks in the case of acid rain), or ready substitutes (replacing CFCs with other non-ozone-destroying substitutes as propellants in spray cans) are far more challenging to come by. Clearly, confronting global climate change will require greater will and greater global cooperation than has ever been called for before. Nonetheless, we can look with guarded optimism at these past successes and use them as instructive road maps as we seek to deal with the problem of global climate change.

Figure 12:18: A spray can using CFC Propellant, (left). The United Nations Emblem, (right).

Credit: Wikimedia Commons, United Nations [29]

Finally, at the Paris summit in December 2015, the Paris Agreement was composed by consensus of the nearly 200 attending parties of the UNFCCC (countries plus the EU), and became legally binding in November 2016 after sufficient parties representing enough of the world's greenhouse gas emissions ratified the agreement - including, in particular, the United States and China.  Each participating party has been required to set an emission reduction target - a Nationally Determined Contribution (NDC) - but the chosen amount is voluntary, and no enforcement mechanism is in place. It was agreed that the goal would be to limit global warming to "well below 2 C above pre-industrial levels", but also "to pursue efforts to limit the temperature increase to 1.5 °C above pre-industrial levels".  Course author's Michael Mann's statement on the agreement can be found here. [30]

From a global perspective, there is evidence that mitigation policy is having a noticeable effect.  After steady growth in recent decades, global CO₂ fossil-fuel emissions nearly stabilized 2014 to 2016 [31] (less than 1% growth per year) despite substantial worldwide GDP growth, in large part due to the phasing out of coal power plants in China and the United States.  However, global emissions rose again in 2017 and 2018. [32]  The European Union and 174 world states have ratified the Paris Agreement, and after Syria in 2017 and the United States once again joining the agreement in 20201, every country in the world is now a party to the Paris agreement.  

Sustainable Development

Climate change is but just one of many global environmental threats we now face. Dealing with these threats in a way that allows us to continue to meet the basic needs of the people on this planet including food, water, shelter, and quality of life, while still maintaining the health of our environment, is the challenge of sustainable development. While the goals of economic growth and environmental sustainability may sometimes seem to be in competition in the short-term, we have seen that in the long-term the threat of environmental degradation and collapse potentially trumps all other considerations. Without a healthy and functioning planet, we cannot sustain the increasingly large global population projected by demographic forecasts. If we accept these assumptions, then the object of governmental policies must be to grow our economy while preserving our environment—the challenge, again, of sustainable development. As developed nations are currently on the most consumptive, unsustainable path, any hopes for environmental sustainability will require fundamental societal changes in developing nations, and a transfer of technology and assistance to developing and undeveloped nations to ensure that they grow their own economies in a manner that is more consistent with environmental sustainability than that of the industrial nations in the past.

Within each of the sectors contributing to global carbon emissions and climate change, we can indeed see opportunities for mitigation that more broadly serve the larger goal of sustainable development. Recycling, for example, saves costs, reduces carbon emissions, and preserves raw materials. Switching to a renewable energy economy will create new industries and economic opportunities, and new jobs. And so on.

While the economics of climate change get much attention, the ethical considerations of climate change often get short shrift by comparison.

One of the challenges of applying traditional economics and cost benefit analysis to the problem of climate change is that the costs and benefits are simply not borne by the same individuals. There is a disaggregation of the costs and benefits with respect to both generation and region. We have seen that those who live in the undeveloped and developing world, largely in the tropics, and have had little role in the carbon emissions that have led to climate changes thus far, are likely to see the most devastating impacts in key areas such as agriculture and freshwater availability and—in the case of low-lying island nations—loss of habitability. Because of their relative lack of wealth, the nations of the undeveloped and developing world are the least able to implement adaptations that might better allow them to cope with climate change. One possible solution is a system that would provide for a transfer of funds from industrial nations to poorer nations to allow them to implement adaptive measures.

Aside from the regional disparities, there is a fundamental generational disparity associated with climate change. The generation that is creating the problem—us—is unlikely to see the most severe impacts of climate change. Instead, it is future generations who will see the greatest impacts of the carbon we are emitting today, e.g., inundation due to sea level rise, stronger hurricanes, worsened drought. The economic discounting typically used in purely economic evaluations of the climate change problem, one might argue, does a grave injustice to future generations by placing lesser value on their world than ours.

There is, finally, the even more fundamental ethical question of whether it is ethical to be playing "Russian roulette" with the future of the planet. We have discussed the potential harm to the climate associated with ongoing carbon emissions. But there are other even more immediate and more visceral reminders of the hidden costs—the externalities—of our current reliance on fossil fuel sources that are increasingly more difficult, and more dangerous, to recover. Recent accidents over the past decade, like the Deepwater Horizons [33]oil disaster, which cost human lives and did potentially irreparable harm to the ecosystems of the Gulf of Mexico, or the Upper Big Ranch Coal Mine [34] explosion and collapse, which killed 25 miners (the company, Massey Energy, that runs the mine had been cited for over 500 violations in the past year; this is the same company responsible for the extremely controversial [35] practice of mountain top removal) are reminders of the true cost of our continuing reliance on fossil fuel energy.

Figure 12.19: Deepwater Horizon oil spill disaster (May 24, 2010), (left). Upper Big Ranch Coal Mine in West Virginia, site of disastrous explosion and collapse in April 2010, (right).

Credit: NASA [36] and ABC News [37]

The recent Japanese nuclear meltdowns, resulting from a major earthquake off the coast of Japan and devastating tsunami, serve as further warnings regarding the dangers of some other non-carbon energy sources that have been proposed as alternatives to fossil fuel energies. One can make a fairly compelling argument that there are no magic bullets. The only safe way of meeting our current and future energy requirements is to put far greater investment into clean, renewable energy sources—like wind, solar, hydropower, biofuels, etc.

We have talked previously about the so-called precautionary principle. There is only one Earth, and if we choose to perform an uncontrolled experiment with it, and that experiment goes awry--there is no going back. There is no restoring the Greenland and Antarctic Ice Sheets, which took millions of years to form, once they have collapsed. There is no restoring species, who evolved over many millions of years, once they go extinct because of human-caused environmental changes. Naive economic analyses of climate change damages can be surprisingly dismissive of the costs of such catastrophic outcomes. Critics have pointed out [38], for example, that one widely used economic model for performing carbon emissions cost-benefit analysis places a disturbingly low cost on ecosystem damages: the model favors the elimination of 99% of species going extinct within 40 years because it only values the net loss of those species at $250/capita! (the costs of lost species are valuated only in terms of the fact that humans like having them around, i.e., there is no intrinsic value ascribed to animal and plant species, functioning ecosystems, etc.—arguably a fundamental weakness in the way such damages are treated in these sorts of models in general).

Is this outcome defensible from a moral or ethical point of view? Could we rationalize leaving our children and our grandchildren not only a severely degraded environment, but a world lacking most of the wonder and beauty of our world —charismatic creatures like the polar bear and the now-extinct Golden Toad, and Hemingway's magnificent "Snows of Kilimanjaro"?

Figure 12.20: The Now-Extinct Golden Toad (left). The Endangered Polar Bear (center). The Disappearing Ice Cap of Mt. Kilimanjaro (right).

Credit: Public domain. Wikimedia commons [39]. and Mt. Kilimanjaro Trekking. [40]

Scientists are partnering with communities and evaluating the current best solutions for climate at Project Drawdown [41].  Many of the adaptation, mitigation, and reduction strategies discussed in this course are evaluated there to create a database of the best ideas for "drawing down" carbon in the atmosphere.  You can read more about the project here [41], and quiz your knowledge about the best solutions here [42]. 

And, with that thought, we have come to the end of the course.

In this lesson, we studied the details of greenhouse gas emissions, including the sectors of the economy responsible for emissions of various greenhouse gases, the potential for mitigation in these various sectors, and the economic and ethical considerations of climate change and climate change mitigation. We observed that:

• CO₂ from fossil fuel burning, deforestation, and other human practices, are the primary causes, responsible for roughly three fourths of net anthropogenic greenhouse gas emissions;
• there is a modest but non-negligible contribution (roughly 13%)  from methane, produced largely from agriculture/livestock and dam projects; other minor contributors include nitrous oxide, which also produced as bi-product of agricultural practices;
• the primary sector of our economy responsible for greenhouse emissions is energy production, amounting for more than 25% of emissions; other major contributors are industrial practices (nearly 20%), deforestation (roughly 17%), and transport and agriculture (each at 13%). Residential buildings and waste management make up the balance;
• the largest absolute increase over the past two decades (roughly 3 gigatons CO₂ equivalent per year) has been in the energy sector, while transport and forestry have shown similar  (roughly 35%) increases;
• economists use cost-benefit analysis to assess market-based solutions to stabilization of greenhouse gas emissions;
• a quantity known as the social cost of carbon (SCC) is used to estimate the cost to society of emission of one metric ton of CO₂ equivalent. Economists typically estimate the SCC as falling within the range of $20-$100/ton of CO₂ equivalent, but this value depends critically on what is known as the discounting rate, a quantity which assumes that costs and returns calculated for the future are less than those calculated for today. Carbon emissions reductions will only pass the cost/benefit analysis when the SCC exceeds the cost of mitigation, i.e.,  it costs more to emit carbon than not to;
• a simple way to encourage emissions reductions is to raise the cost of emitting carbon through some financial intervention in the form of either a carbon tax or tradable emissions permits  (e.g., cap and trade);
• there is a range of mitigation potential among the various sectors, with some of the most significant opportunities in the energy supply and industrial sectors owing to the availability of carbon sequestration for large point source emitters in addition to other mitigation opportunities. There are also substantial mitigation opportunities in the transportation sectors (e.g., use of alternative fuels) and agricultural sectors (e.g., the restoration of degraded agricultural lands);
• individuals have an important role in mitigation through reducing their personal carbon footprints; In many cases, no regrets strategies (i.e., things we ought to be doing anyway for health, financial, or ethical reasons) can greatly reduce greenhouse gas emissions. In the U.S., current emissions are roughly 20 metric tons of CO₂ equivalent per year per person; A reduction to under 4 metric tons per year by mid-century would be consistent with a scenario of 450 ppm CO₂ stabilization;
• only governmental policies and negotiated global treaties can ensure that proper economic and societal incentives are in place to limit carbon emissions below levels considered to constitute a dangerous anthropogenic interference (DAI) with our climate;
• ethical considerations arising from the disaggregation of costs and benefits of burning fossil fuels, with tropical/developing nations and future generations at great risk of suffering negative climate change impacts, complicate simple cost/benefit analysis approaches to climate change mitigation;
• ethical considerations related to the precautionary principle, i.e., that it is unwise and arguably unethical to be playing dice with the future of our planet, provide additional arguments for stabilizing greenhouse gas emissions beyond simple, and potentially flawed, economic cost/benefit analysis approaches.

Reminder - Complete all of the lesson tasks!

You have finished Lesson 12, the final lecture of the course. Double-check the list of requirements on the first page of this lesson to make sure you have completed all of the activities listed there. Good luck with the final exam!

Activity

Directions

Please participate in an online discussion of Project #3 Climate Change Videos.

This discussion will take place in a threaded discussion forum in Canvas (see the Canvas Guides [43] for the specific information on how to use this tool) over approximately a week-long period of time. Since the class participants will be posting to the discussion forum at various points in time during the week, you will need to check the forum frequently in order to fully participate.  You can also subscribe to the discussion and receive e-mail alerts each time there is a new post.

Please realize that a discussion is a group effort, and make sure to participate early in order to give your classmates enough time to respond to your posts. 

For this discussion:

1) Make an introductory post about your own video with a couple of sentences about the message you were trying to convey.  *Include a link or an attachment of your video, so other students can access it!!* 

(Note: if you have not created a Project 3 video but still want to participate in this discussion, for your introductory post state the detailed message you would have tried to convey had you made a video.)

2) Watch the other class videos (or as many as time will allow).

3) Comment thoughtfully on at least *2* of your classmates' posts/videos with a suggestion or critique.

Submitting your work

1. Go to Canvas.
2. Go to the Home tab.
3. Click on the Lesson 12 discussion: Project #3 Videos.
4. Post your comments and responses.

Grading criteria

You will be graded on the quality of your participation. See the online discussion grading rubric [44] for the specifics on how this assignment will be graded. Please note that you will not receive a passing grade on this assignment if you wait until the last day of the discussion to make your first post.