Module 12 Lab: Options for the Future of Climate, Energy, and Economics, Including Geoengineering
Module 12 Lab: Options for the Future of Climate, Energy, and Economics, Including Geoengineering ksc17The goal of this exercise is to explore a range of scenarios for our future in such a way that our energy needs are met, our economy is strong, and our climate is controlled to some extent. The underlying premise is that if do nothing and continue down our current path, the climate will warm to truly dangerous levels, which will have serious consequences for our economy and thus our quality of life. The options we will explore include shifting to renewable energy sources, conserving energy (being more efficient so that we do the same things with less energy consumption) — both of these limit the carbon we emit to the atmosphere. We will also explore two other options that sometimes are called “geoengineering” — one involves injecting sulfate aerosols into the stratosphere to block a little of the sunlight and another involves the direct removal of carbon from the atmosphere, sometimes called negative carbon emissions.
All of these choices involve costs, and the model calculates these costs. Another kind of cost comes in the form of climate damages, and the model calculates these too. From an economic standpoint, the best scenario is one that minimizes the costs because these costs represent a drain on the global economy; the global economy will be better able to meet all of the needs of humanity if we can keep the costs down. The figure below, modified from the one you’ve seen before in Module 5 on the carbon cycle, shows the general scheme the model uses to calculate all of the costs.
The flowchart diagram illustrates a process with colored rectangular boxes and directional arrows. The boxes are arranged in a vertical and slightly overlapping sequence, with the following color coding: blue, green, yellow, and red. The flow begins with a blue box at the top, followed by a green box with a downward green arrow leading to another green box. A yellow box appears next, followed by a red box. Another red box is connected by a curved green arrow looping back to a lower red box, indicating a feedback or iterative process. Additional blue boxes are scattered throughout, suggesting parallel or alternative steps in the process.
- Diagram Overview
- Type: Flowchart
- Background: Black
- Boxes and Colors
- Blue Boxes: Scattered throughout, likely initial or parallel steps
- Green Boxes: Middle section, with downward flow
- Yellow Box: Single instance, following green
- Red Boxes: Lower section, with feedback loop
- Flow Direction
- Green Arrows: Indicate progression (downward and looping)
- Description: Starts at a blue box, moves through green and yellow, ends with red boxes including a feedback loop
It might help to look at this backward from the total costs, which sums the climate damage costs, the costs of fossil fuel energy, the costs of renewable energy, the costs related to energy conservation, and the costs related to geoengineering. The climate damage costs are related to the temperature change, and these costs go up as the square of the temperature increases, so that the costs related from going from 5°C to 6°C are considerably more than going from 1°C to 2°C. The fossil fuel costs, renewable costs, and conservation costs are related to how much energy is provided by those sources. The ideal thing from an economic standpoint is to have the smallest Total Costs because that means there is more money to pour back into the economy and to provide a higher quality of life.
At the core of this model is the global carbon cycle model coupled with the simple climate model — you’ve seen these before. The model also calculates the energy demands and carbon emissions that reflect the population size and choices we make about how much to pursue conservation and renewable energy sources. The model you will work with here has some additions that represent two geoengineering solutions — the addition of sulfate aerosols into the stratosphere to block some of the sunlight (SAG for sulfate aerosol geoengineering) and the direct removal of carbon dioxide from the atmosphere (DRC).
Sulfate Aerosol Geoengineering
The idea behind sulfate aerosol geoengineering has its origins in the studies of how volcanic eruptions affect the climate. When volcanoes erupt, they a combination of ash (tiny fragments of volcanic rock and glass) and gases, including water vapor, carbon dioxide, sulfur dioxide, and others. The sulfuric gases condense into little droplets called sulfate aerosols that can reflect sunlight, cutting down on the solar energy that drives our climate system — this causes a cooling effect that can last for a couple of years, ending when the aerosols finally fall back to the surface. The key to this is that if the force of the eruption is great enough, the sulfate aerosols end up in the stratosphere (higher than 15 km in altitude); gravity is weak there and there is essentially no water to wash the aerosols out, so they can stick around for a few years. The idea that we humans could add sulfate aerosols into the stratosphere to cool the climate (or prevent further warming) was first suggested by the Nobel Prize-winning atmospheric chemist Paul Crutzen in 2006. Crutzen admitted that a much smarter way of dealing with the problem of global warming was to drastically reduce our carbon emissions, but he pointed out that humanity has not yet shown the resolve needed to tackle this problem; so he proposed this as a potentially easier way to avoid the dangerous consequences of further warming.
This is kind of a thorny issue for a number of reasons. Some people worry that pursuing this kind of solution is dangerous because it just treats the symptoms of the problem without tackling the underlying cause, which is the excess CO2 we keep adding to the atmosphere. Many people see this as dangerous in the sense that tampering with natural systems almost always has hidden unintended consequences. In fact, sophisticated 3D climate model simulations with the addition of sulfate aerosols suggest that the cooling effects would not be uniform and it would change patterns of precipitation as well, which means that some areas of the globe might suffer, while others would see benefits. But, if you are in a car going down a hill and your brakes are not working, you may need to consider doing something other than stepping on the brake pedal — and time is of the essence!
How would this work? Crutzen and others since him have worked out a variety of scenarios for getting the sulfate into the stratosphere, including sending loads of it up in balloons and dumping it out of huge military airplanes that can fly high enough. The general idea is illustrated in the figure below, where the red plus and minus signs indicate changes to the solar energy caused by the sulfate aerosols.
The image is showing the global distribution of deserts. The map highlights desert regions in a distinct color (likely yellow or beige) against a standard world map background. Key desert locations include the Sahara Desert in North Africa, the Arabian Desert in the Middle East, the Gobi Desert in East Asia, the Kalahari Desert in Southern Africa, the Great Victoria Desert in Australia, and the Sonoran and Chihuahuan Deserts in North America. Major continents—Africa, Asia, Australia, and North America—are visible, with deserts spanning arid regions across these areas.
- Map Overview
- Title: Major Deserts of the World
- Type: World map
- Desert Locations
- Sahara Desert: North Africa
- Arabian Desert: Middle East
- Gobi Desert: East Asia
- Kalahari Desert: Southern Africa
- Great Victoria Desert: Australia
- Sonoran and Chihuahuan Deserts: North America
- Visual Elements
- Deserts: Highlighted in a distinct color (likely yellow or beige)
- Continents: Africa, Asia, Australia, North America
- Background: Standard world map layout
Although this is difficult to price out, some of the estimates (Robock et al., 2009) are that it would cost between 1 and 30 billion dollars per year to add one teragram of (1 Tg = 1012 g) of sulfate into the stratosphere per year. 1 Tg of sulfate, evenly distributed in the stratosphere is estimated to block about 1.3 W/m2 of solar energy, which is about 0.4% of the total. In our simple climate model, changing the solar input by 1 W/m2 changes the temperature by about 0.35°C. One of the challenges is that the sulfate aerosols fall out of the atmosphere, so we would have to constantly add it to maintain the desired level of solar reduction to combat the warming. In the model, if you activate this geoengineering scheme, you set a desired limit to the global temperature change and sulfate is added in the necessary amount to keep the temperature change close to this limit. This then generates a cost that affects the global economy.
Direct Carbon Removal
The idea of carbon sequestration has been around for a relatively long time — emissions from a fossil fuel-burning power plant can be captured at the source and processed to remove the CO2. The extracted CO2 is then pumped deep underground where it can reside in the pore spaces of sedimentary rocks. In some cases, it is pumped back into the rocks from which oil or gas have previously been removed. Carbon sequestration is expensive, but it can virtually eliminate the carbon emissions from some power plants. However, carbon sequestration does not actually remove CO2 from the atmosphere, and if we were to continue to burn fossil fuels in cars and in homes, then the concentration of CO2 in the atmosphere would continue to rise. Carbon sequestration has not really taken off because the extra expense means that it is far cheaper for a power company to produce new electricity using solar or wind systems.
The direct removal of CO2 from the atmosphere sometimes called negative emissions is a relatively new idea — the first facility was put into action in the fall of 2017 in Iceland. A Swiss company called ClimeWorks developed a partnership with a geothermal power plant to essentially test the technology. There are several other companies in Canada and the US at earlier stages in development. The general idea is to pump huge volumes of air through a chamber in which there are numerous small beads coated with a substance that effectively grabs onto CO2 molecules. When the beads have absorbed as much as possible, the chamber is sealed off and the CO2 is released by changing the humidity in the chamber. The resulting air in the chamber has a very high concentration of CO2; it is mixed with water and then pumped deep underground. The CO2-rich solution reacts with the basaltic bedrock and new minerals are formed, locking up the CO2. This process essentially takes the CO2 out of the air and turns it into rock — pretty clever! The general scheme is shown in the diagram below.
A schematic illustration of the Direct Carbon Removal (DCR) process, also known as "negative emissions," as implemented by Climeworks at their facility in Iceland. The diagram depicts the process of capturing CO2 from the atmosphere and sequestering it as new minerals. It begins with air containing CO2 being drawn into a capture unit (likely shown as a structure or fan system). The CO2 is extracted and combined with water to form carbonated water. This mixture is then injected into basaltic bedrock, illustrated as a layered underground formation. The interaction between the carbonated water and the basalt leads to the formation of new minerals, effectively sequestering the CO2. Arrows indicate the flow from air intake to CO2 capture, mixing with water, and final injection into the bedrock.
- Diagram Overview
- Title: Implied as Direct Carbon Removal (DCR) Process by Climeworks
- Type: Schematic illustration
- Process Steps
- Air Intake
- Description: Air with CO2 enters the system
- Visual: Likely a fan or structure on the left
- CO2 Capture
- Description: CO2 extracted from the air
- Visual: A capture unit or filter system
- Mixing with Water
- Description: CO2 combined with water to form carbonated water
- Visual: A mixing chamber or pipe
- Injection into Basaltic Bedrock
- Description: Carbonated water injected into basalt
- Visual: Layered underground formation
- Mineral Formation
- Description: CO2 sequestered as new minerals
- Visual: Indicated within the bedrock layer
- Air Intake
- Visual Elements
- Arrows: Show the flow of air, CO2, and carbonated water
- Colors: Likely blue for air/water, gray/green for bedrock
- Context
- Location: Climeworks facility in Iceland
- Purpose: Negative emissions through CO2 sequestration
This process is in the early stages of development, so it is difficult to know how much it will cost. The companies doing this believe that they can probably get the cost down to $366 billion per Gt C removed. There would have to be thousands of these units set up around the world in order to scale this up. In our model, we are going to assume that if we were to begin this process, we would initially be limited to 5 Gt C removed from the atmosphere per year, but that as time goes on, our capabilities would increase and we could draw more and more out of the atmosphere.
This process of direct removal of carbon from the atmosphere has some consequences for other parts of the carbon cycle. As we remove CO2 from the atmosphere, the concentration decreases, which means that CO2 stored in the oceans will begin to flow into the atmosphere. This means that we will need to remove much more carbon from the atmosphere than you might think if we are aiming for a given concentration of CO2.
Experiments
Experiments ksc17Click here to go to the model. Please Note: The model in the videos below may look slightly different than the model linked here. Both models, however, function the same.
When you open the model, you will see that there are a lot of controls, reflecting the full range of choices we can make about our future energy consumption and geoengineering. There are also 15 pages of graphs that show the results of the model. Be sure to watch the video below that introduces you to the model before proceeding.
Video: Module 12 Intro to Model (7:09) (note the Model we use looks different from that in the videos but it works exactly the same and the results should be identical)
Module 12 Intro to Model
NARRATOR: This is the model that we're going to be working with in this lab, and it's similar to one you've seen before, that combines a global carbon cycle with a global climate model. And it includes components that calculate our energy needs and our sources of energy, which then relate to the carbon emissions that affect the climate. It also monitors the economics of all these changes to our climate and energy. This one also includes some geoengineering options that I'll explain in a little bit.
So, over here there are a lot of controls. They're kind of color-coded according to the different things that they represent. So, green here represents conservation of energy. The purple or blue represents renewable energy. The red down here relates to one of the geoengineering schemes, which is the direct carbon removal from the atmosphere. And the orange down here deals with the other geoengineering scheme, which is the injection of sulfate aerosols into the stratosphere to block sunlight.
So, let me just show you a couple things about this. So, you open the model and you run it and it calculates this all out over a couple of hundred years. And this shows the global temperature change that results, and here we haven't really done anything to increase conservation or renewables, and the geoengineering switches are off, so this is kind of a do-nothing scenario. We have a very high temperature rise by the end of this time here, six and a half degrees warmer. So now, we could say, of course, well what if we conserve energy? So, this number here is the percent of our energy that we reduce by conservation methods. And this is the growth rate of that.
So, this is five percent increase per year, which is pretty good. So, if we run this and see what happens and compare it with the do nothing scenario, you see it lowers the temperature, but it's still unacceptably high. And so, you could say, well what if we increase our reliance on renewable energy? Let's bring this up to say seventy-five percent and we run that, and we see that this does a little bit better. But still, by the end of this, look, we're up at three point six degrees of global temperature rise, which is really quite alarming and by the year 2000 we're, 2100 rather, we're above that 2 degree limit that we sort of agreed upon as the upper limit in the Paris Climate Accords.
So now, we've added here some geoengineering options and these are kind of like, if we just can't manage our carbon emissions for conservation and switch to renewables, we might want to investigate some of these to help us prevent this climate disaster. And so, I'm gonna restore the renewables to where it was before. I'll just turn this on, so now, this is going to activate the direct removal of carbon from the atmosphere and then the burial and sequestration of that carbon underground. So, here's the time at which it starts, 2030, and in here you pick a target atmospheric CO2 concentration. So, here, I've got 400. Let's raise that to 450 here. And this is the rate of cost decline of that process, which is initially fairly expensive. And this represents how quickly our capability to do this grows. And this gives us the initial amount of carbon that we can withdraw from the atmosphere in one year, at the very start.
So, this is pretty generous because it can't really come close to doing one gigaton at the present time, but things are changing rapidly in this field. So, let's see what happens here. And we run this, and we see here's our result. Look, this brings us down, keeps us below two degrees for a fairly long time. So that is a fairly effective means of keeping our climate under control. If I switch on some of these other pages, you'll see that this, the blue is the CO2 concentration in the atmosphere, rises and then we start to get it in control and then we've brought it under control here, it's close to 450, it's a little bit above. Until this point in time, in which it drops down dramatically there just because we've run out of fossil fuels, and so we're no longer able to emit any to the atmosphere at this point in time. So 2197 or 98, something like that. So, that's the direct removal of carbon.
Another option is sulfate aerosol geoengineering, and we turn that on. This is where we inject sulfate aerosols, these little tiny particles into the stratosphere. They block some sunlight and so here's the starting time for this process, and here's the targeted temperature change that we're going to try to control to. So, this will try to keep the temperature change to two degrees or less and this is the cost decline rate. I've got this at zero right now, kind of assuming that this is not such a technologically tricky process, and probably we're not going to see huge advances in the sort of ability to do this per dollar. So, I've got that at zero initially.
Well, let's just run this and see what happens. You run the model, and there you see, this does a very good job of keeping it right at two degrees through this whole time. While all of these changes have economic consequences, and some of those you can see, on some of the other graphs here, let's see this one. Here's the total cost per person, per capita, that is in terms of thousands of dollars per year. And those last two that we ran, they both end up costing something like about $9,000 per person per year by the end of it. And that's to pay for all of our energy supply and all the climate damages that are associated with the temperature change.
So, this is just a brief introduction to the model. You can restore everything to this sort of an initial by clicking those two buttons. And so, we're going to do a series of experiments with this model to make some sort of assessments about what is the best thing, from the standpoint of the climate and also the economy, in terms of getting us to a future that includes a tolerable level of global warming.
Practice Questions
Part A. Climate Control by Conservation and Renewable Energy
Be sure to watch the video below that shows how to do problems 1-3.
Video: Module 12 Questions 1 - 3 (2:01) (note the Model we use looks different from that in the videos but it works exactly the same and the results should be identical)
Module 12 Questions 1 - 3
NARRATOR: In this video, I'm going to show you how to manipulate the model to get the answers to the first three questions of the practice assessment. So, I'm going to follow the instructions and change the green colored sliders so that this is 30, and this is zero point one. Renewable upper limit, I'm going to change to 85, and the renewable growth rate to zero point one. I've done that. Now, I'm going to run the model. And I'll look at the ending temperature change. So, let's see, it's about two point one three, two point one four at the very end. And so, looking at the choices, the correct answer is two point one degrees C. So, that's answer C on the on the test.
Well, number two is, what is the lowest pH of the oceans in this case? I'm going to have to go to graph page number two. So, here in pink is the pH and it's dropping all the way down to eight point zero six, or eight point zero eight, somewhere in there. So, the closest value and the possible answers is eight point zero eight. So, we'll select that one. So, A is the correct one.
Then, what is the total cost per person? I'm here and it says to click through to page fourteen, so we're gonna skip through all these other plots that show all sorts of other parameters to page 14. This is the total cost per capita in thousands of dollars. And you can see that it rises to two point four thousand per person at the end of the time here. So, that's D. So 3D is answer for that one.
In this first experiment, we will use a combination of conservation of energy and greater reliance on renewable energy sources to limit climate change. Open the model and run it without making any changes — we'll call this the "do nothing" scenario. You will see that we end up with 6.55°C of warming by the end of the model run in 2210, and if you look through the other graphs, you will see that the ocean pH drops to 7.68 (graph page 2). Looking at some of the other graphs, we see that this scenario results in a bit over 19 thousand dollars per person (graph page 14) in terms of the total costs (energy, conservation, climate damages, geoengineering), and an ending net economic output of about $460 trillion.
Now, change the model as described below:
Green colored sliders
- Conserve upper limit: 30
- Conserve growth rate: 0.1
Blue colored sliders
- Renew upper limit: 85
- Renew growth rate: 0.1
Then, run the model and answer the following questions by finding the values from the resulting graphs.
- What is the ending global temperature change that results from these changes (page 1)?
- 4.2 °C
- 3.6 °C
- 2.1°C
- 1.6°C
- What is the lowest pH of the oceans in this case (page 2)?
- 8.06
- 7.6
- 8.20
- 7.85
- What is the Total Cost Per Person (page 14)
- 12.4
- 8.2
- 7.7
- 2.4
Part B. Climate Control by Geoengineering
Now, we will try geoengineering alternatives, beginning with the direct removal of carbon — DCR. Be sure to watch the video below that shows how to get the answers to problems 4-7.
Video: Module 12 Questions 4-7 (3:08) (note the Model we use looks different from that in the videos but it works exactly the same and the results should be identical)
Module 12 Questions 4-7
NARRATOR: Now we're going to move on and look at how to get the answers to problems 4 through 7, the next section of this assessment. So here I've got to make some new changes. I'm going to cut down the conservation of energy, turn that to 1, and the growth rate stays at .1. The blue sliders are going to change so that the renewable upper limit is 20, all the way down here, and the growth rate is .1. I'm going to turn the DCR, direct carbon removal, switch on. Set the start time to 2030. The target atmospheric concentration, I'm going to set this to 470. The cost decline rate I'm going to make .02, so 2 percent per year decline in the cost of this process. The growth rate in terms of capacity is going to be 2% per year and the initial amount that we can withdraw from the atmosphere is 5 gigatons of carbon. So that's all set according to the instructions. Now I'm going to run it and see what the ending temperature is in this case. And here by the end we see we're down to just below 2, 1.97. So that's answer C.
Then 5 is what is the lowest pH In this case? I'm going to flip to page number 2. Looks like the lowest pH is back in here, that's about 8.06, so that's answer, A.
Then the next one is, what is the total cost per person? So that's page 14 of the graph pad. I'm going to get there this way, there's 14. We see that's up considerably higher now it's 9.2 thousand dollars or 9.2 thousand dollars per person at the at the end of time. So that's answer B.
Now the last question, seven, is why do the human fossil fuel emissions drop to zero around the Year 2095? So if we went back to let's say graph pad number two, you can see the the human fossil fuel burning emissions. This is gigatons of carbons rising, flattening off and then it just crashes, boom, to zero here. And so why is that? Well it turns out that if we cycle through here to page eleven on the graph pad, we see the fossil fuels, so this is in gigatons of carbon. And by the time we get to about 2095 or so we've essentially gone to zero. So we've run out of fossil fuels and so that that's why the emissions dropped is because we've got nothing left to burn. So that's answer C on the assessment.
Make the following changes to the model:
Green colored sliders
- Conserve upper limit: 1
- Conserve growth rate: 0.1
Blue colored sliders
- Renew upper limit: 20
- Renew growth rate: 0.1
Red colored sliders
- DCR switch: On
- DCR start time: 2030
- Target atm pCO2: 470
- DCR cost decline rate: 0.02
- DCR growth rate: 0.02
- DCR init: 5
Once you've made these changes, run the model, and answer the following.
- What is the ending global temperature change that results from these changes (page 1)?
- 4.2 °C
- 2.6 °C
- 1.97°C
- 3.3°C
- What is the lowest pH of the oceans in this case (page 2)?
- 8.06
- 7.6
- 8.20
- 7.85
- What is the Total Cost Per Person (page 14)?
- 11.2
- 9.2
- 6.7
- 2.4
- Why do the human FFB emissions drop to 0 around the year 2195 (page 2)?
- Our energy needs drop to 0 at this time
- The economy has collapsed at this time
- We run out of fossil fuels at this time
- Must be a glitch in the model
Now we will try sulfate aerosol geoengineering — as before, the following video shows how to do this section.
Video: Module 12 Questions 8 - 9 (1:49) (note the Model we use looks different from that in the videos but it works exactly the same and the results should be identical)
Module 12 Questions 8 - 9
NARRATOR: In this video, I'm going to show you how to get the answers to Questions 8 & 9 on the assessment. And so, we look at the instructions, and we see that we set the conserve upper limit at 1, its growth rate at 0.1, the renew upper limit at 20, and its growth rate at .1. Make sure the DCR switch is off, and we turn the sulphate switch on, and start time 2030. The target key range is 2, and the sulfate cost decline rate is zero. So, you do those things, and we run it, and you'll see the temperature will flatten off at about two degrees. Once it gets done running here, there we see it, so it stays at just a hair above two degrees throughout the time.
Now Question 8 is, what is the lowest pH of the oceans in this case? So, we go to graph number two, look at the pH curve in pink here, and it drops down to 7.58 here at the low point. So, that's answer D. So, that's correct answer for 8.
Nine is, what is the total cost per person? That's page fourteen, that's the graph page. Go back to page 14 and see the total costs per capita at the end is about 9.3 thousand dollars per person at the very end. So, that's answer B on the assessment and that's the answer.
Make the following changes to the model:
Green colored sliders
- Conserve upper limit: 1
- Conserve growth rate: 0.1
Blue colored sliders
- Renew upper limit: 20
- Renew growth rate: 0.1
Red colored sliders
- DCR switch: Off
Orange colored sliders
- Sulfate switch: On
- Sulfate start time: 2030
- Target T change: 2.0
- Sulfate cost decline rate: 0.0
Once you've made these changes, run the model and answer the following.
- What is the lowest pH of the oceans in this case (page 2)?
- 8.06
- 7.6
- 8.20
- 7.58
- What is the Total Cost Per Person (page 14)?
- 11.2
- 9.3
- 6.7
- 2.4
Part C. Comparison
Now, let's step back and consider what we have found here. Clearly, the "do-nothing" scenario is the worst in terms of temperature change and costs. But how about the other scenarios, each of which gets us to a temperature change of close to 2°C by the end of the model run — which is the best? The following video shows how to answer questions 10-12.
Video: Module 12 Questions 10 - 12 (3:46) (note the Model we use looks different from that in the videos but it works exactly the same and the results should be identical)
Module 12 Questions 10 - 12
NARRATOR: Today, I'm going to show you how to get the answers to Questions 10 through 12 on the assessment. And this is where we kind of step back and consider all these different options, these three basic options together and compare them. And in the first one, we kept the temperature close to about a two degree warming by the end of the model run, by energy conservation and increased reliance on renewable energy. The next one, we achieved that same temperature level, approximately, through geoengineering and direct carbon removal. And the third case, shown in the blue here, was the sulfate aerosol geoengineering.
And so, the question is for 10, which of these three scenarios is the best from an economic standpoint?There are lots of different ways of looking at the economic performance of each of these three, but I think the one that sort of sums it all up best is this total costs per capita. So, these are costs per person that we're gonna have to pay for producing the energy and the consequences of producing that energy in the form of climate change, or moderating it in terms of geoengineering costs. Then, you can see the two geoengineering cases here are pretty close to the same 9.3, 9.2 thousand. The conservation scenario and renewable energy one is considerably less expensive, so 2.4 thousand per person compared to nine. So, that's the clear winner. So, that's answer A for ten.
Eleven asks which of the three scenarios is best from an ocean pH standpoint? And so, here, we have to look at graph page number two, and these are shown in different scales. This just shows the pH for the last one, the conservation one, and that was at 8.06. And if you remember from before, that's about the same, close to the same, that we got with the DCR geoengineering. So, those two were about the same. Sulfate geoengineering, the ph got down to 7.58 , which is really a pretty dramatic acidification of the ocean. So, that's the worst by far. Conservation and renewables are close to the same. There's not a clear winner. So, the best answer is D, which is A and B are about the same.
And the last question of the assessment, twelve, asks from an overall environmental and economic standpoint, which of the three scenarios is the best? Well, as we saw in terms of ph, the conservation renewables and the dcr geoengineering are about the same. In terms of temperature, they're all more or less the same by the time we get to the the end of time. Although, you know, you could say that the conservation and renewable approach here, kept us at a lower temperature for more of the time, so that might be preferable in that sense. But then, the other thing, the economic standpoint as we saw before, this conservation and renewable scenario, shown here in green, that's the clear winner. So, if you take all these things together the conservation and renewable scenario is the best, overall, from an environmental and economic standpoint. That's answer A on the assessment and that's the correct answer.
- Which of the three scenarios is the best from an economic standpoint?
- Conservation + Renewables
- DCR Geoengineering
- Sulfate Geoengineering
- Which of the three scenarios is the best from an ocean pH standpoint?
- Conservation + Renewables (by far)
- DCR Geoengineering (by far)
- Sulfate Geoengineering (by far)
- A and B are about the same
- From an overall environmental and economic standpoint, which of the three scenarios is the best?
- Conservation + Renewables
- DCR Geoengineering
- Sulfate Geoengineering
- There are no clear winners