In Section 7.2.1, we focused on the major consequences of global warming that we are already experiencing, and in Section 7.2.2 we saw what models predict for future global warming, depending on what we do with future greenhouse gas emissions. We are now ready to put these ideas together, and consider how future climate changes will affect you personally and affect others around the world. We’ll focus on three key ideas about these effects.
Regional Differences in the Temperature Rise
The first of our key ideas is to remember that the effects won’t be the same everywhere. As you already know, different regions have been warming differently (as you saw in Video 7-1). You also know that global warming tends to warm nighttime more than daytime , and that changes are magnified during temperature extremes. Figure 7.2.3-1 shows predicted regional changes in daytime and nighttime temperatures for global average temperature increases of 1.5°C and 2°C. Study the figure carefully, then try the questions that follow.
Figure 7.2.3-1 – These figures show what models predict for regional temperature changes for daytime (top) and nighttime
(bottom) . The left side shows the predictions if the global average temperature increases by 1.5°C (compared to the
20th century average) and the right side shows the predictions for a 2°C increase. Credit: IPCC.
Before you continue, discuss the following questions about Figure 7.2.3–1 with a classmate, then click to open the answers and see if they agree with what you came up with.
1. Based on the maps shown, are there any regions that are expected to become cooler (rather than warmer) in the future? Explain how you know.
No. The key shows that the white and blue colors correspond to warmings of less than 1.5°C, but there are no colors to represent cooling on these maps.
2. Overall, which is expected to warm more in the future: temperatures over land or temperatures over the oceans? Why do you think that is?
Temperatures warm more over the land than over the oceans. This should make sense based on what you learned in Chapter 6: The oceans tend to moderate temperatures, so they will warm less than the global average while the land will warm more than the global average.
3. Overall, which is predicted to warm more in the future: daytime or nighttime temperatures?
The darker/redder colors on the nighttime maps represent greater warming than shown on the daytime maps. That is, nights are predicted to warm more, just as we should expect with warming due to the greenhouse effect.
4. Consider the regions of the world that are expected to warm the most. About how much warmer will average days be in these regions if the global average temperature increase is 1.5°C compared to how much warmer they will be if the global average increase is 2°C?
On the daytime map for a 1.5°C increase in average temperature (left), the darkest regions are in the color representing an increase of 2–3°C (or 3.6–5.4°F). On the map for a 2°C increase (right), many these same regions have a color representing an increase of 3–4°C (or 5.4°–7.2°F). In other words, the daytime warming will be significantly greater (up to double) with just a 0.5°C additional change in the global average temperature.
5. How much will nighttime warm up in the regions of the world expected to warm the most, and how does the amount depend on whether the increase in global average temperature is 1.5°C or 2°C?
The darkest color on the key corresponds to warming of 8–10°C (about 14–18°F), which is a lot! The maps show that some regions will warm this much at night even under the 1.5°C global average warming, and much of North America, Europe, and Asia would warm this much at night with a 2°C global average warming.
6. Do these maps show the worst-case scenarios for warming by the year 2100? Explain.
These are not the worst-case scenarios. In fact, if you look back at the models in Figure 7.2.2-4, you’ll see that the “high” pathways predict an increase in the global average temperature of 3–5°C, which means the regional temperature changes would be much larger than those shown on the map for a 2°C increase.
Discussion
The Future of Winter Sports
Consider a winter sports city such as Aspen, Colorado (USA). In the recent past, its average daily high temperature in February was about 4°C (about 39°F) and its average nighttime low was about –10°C (14°F). The maps in Figure 7.2.3–1 show that under a 2°C global average temperature increase, Aspen could expect its February daytime high to rise by roughly 2.5°C (or 4.5°F) and the nighttime low to rise by roughly 6°C (or 11°F).
- Approximately what would be the new February daytime high and nighttime low average temperatures for Aspen?
- You can get a rough sense of the average temperature for an entire day simply by adding the daytime and nighttime values and dividing by 2. Find the old and new full-day average temperatures for Aspen in February.
- Based on your answers above, how would you expect a global average temperature rise of 2°C to affect the prospects for February skiing (and other winter sports) in Aspen?
This question should help students understand why winter sports face a grave threat from global warming. Notes:
- (1) Simply add to calculate the new daytime and nighttime averages under this scenario: for daytime, the new average high would be about 4°C + 2.5°C = 6.5°C (which is almost 44°F); for nighttime, the new average low would be about –10°C + 6°C = –4°C (about 25°F).
- (2) The recent full-day average is (4°C + –10°C)/2 = –3°C (about 27°F). The new average would be (6.5°C + –4°C)/2 = 1.25°C (about 34°F).
- (3) Notice that the new full-day average would be above freezing, which means that, on average, snow will melt rather than accumulate in February. This means that, at minimum, the winter sports season will end much earlier than it does at present.
Amplification of the Major Consequences
The second of our key ideas is to remember that a larger amount of global warming will amplify all of the major consequences of global warming. For example, larger carbon emissions and a greater overall warming will mean even more extreme weather events, more melting of Arctic sea ice, larger sea level rise, and increased ocean acidification. And again, these consequences will differ in different parts of the world.
Activity
Future Effects of Global Warming
The difference between 1.5°C and 2°C of warming may not sound like much, but as you’ve already seen, it can have dramatic regional effects. The same is true for other consequences of global warming. Do the following to learn more about what these changes will mean to you and to others around the world.
- Based on the model predictions show in Figure 7.2.3-1, how much daytime and nighttime warming will there be where you live under global average temperature increases of 1.5°C and 2°C? What would each of these cases mean to you for a typical hot summer day and night? What would happen if the global average temperature rises by more than 2°C?
- Spend a view minutes exploring this interactive (from Carbon Brief) that summarizes many other consequences expected in different regions under different increases in the global average temperature. Click the icon for your continent, then read about and discuss the many different expected effects. Based on your discussion, prepare and record a 2-3-minute presentation in which you summarize how future warming is likely to affect your region, and how much better or worse the effects will be depending on how much warming occurs.
- Now choose another region of the world that differs from yours economically (either richer or poorer) and explore the interactive for this region. Make a similar presentation to summarize how future warming will affect this region in contrast to yours.
This activity will work best in small groups, though it could in principle be done individually as well (aside from discussions). Notes:
- (1) Answers to this question will depend on your location, but students should be able to read approximate values from the maps. They should then be able to apply their answers to a typical hot summer day in your area, and should notice that the temperature changes will be quite significant under either scenario, but quite a bit larger under the 2°C scenario. They should then recognize that it will be even worse if the warming is larger.
- (2) The linked interactive has an excellent summary of recent model predictions for different regions and different amounts of warming. The goal for this question is for students to sort through these in a way that allows them to come up with a simple summary, recorded as either an audio or video, of the most important local consequences. Note: If any students create a particularly good recording, you might consider sharing it with your whole school or even sending it to local leaders.
- (3) The point of this question is for students to recognize that different regions will have different effects. In general, the effects will be worse in poorer regions.
Activity
Debate on Future Global Warming
Prepare for this debate by exploring this interactive (the same one used in the prior activity). Then divide into two teams and hold a debate as follows:
- Team 1 will argue that we should spend whatever it takes to limit future global warming to no more than 1.5°C.
- Team 2 will argue that while 1.5°C warming would be better than 2°C (or more), it won’t be worth the economic cost of limiting the warming that much, so we should allow the warming to be 2°C.
You can hold this debate regardless of whether you’ve done the prior activity, since it again gives the same interactive to explore. Specific notes:
- It should be possible for both debate positions to be strongly defended, so be careful not to favor one or the other team as the “winner.”
- Most students will probably be in favor of the first option, so you should plan to assign students to the two teams randomly, and be sure that they engage fully in debating the position their team is taking.
- The debate hinges largely on the difference in the presumed costs. Most students won’t have enough background in economics to make definitive statements, so allow them to make assumptions about how much each scenario would cost, as long as they give at least some defense of their assumptions.
- Note: The general assumption in real debates like this one is that it will cost more to limit the warming more. However, as we’ll discuss in Section 7.3 on solutions, this may not actually be the case, as many economists argue that a more rapid transition away from fossil fuels could actually save money and thereby strengthen the global economy.
Effects on Economics and Social Justice
If you’ve done either or both of the above activities, then you’ll already understand our third key idea about future global warming: The effects will vary dramatically depending not only on location but on local economics. In particular, poorer communities are likely to have a much harder time dealing with the consequences than richer communities. In other words, while we’ve discussed global warming primarily as a scientific issue in this chapter, it also has a social justice component, because it will tend to hit hardest at the people who can least afford it.
Discussion
Global Warming as a Social Justice Issue
In small groups or as a class, discuss the following questions.
- In what sense is global warming a social justice issue as well as a scientific issue?
- What are the social justice implications of global warming for your community? For example, do you think your community is one that is well-prepared to deal with future consequences of global warming, or do you think your community will suffer more than the average?
- Historically, the vast majority of the greenhouse gas that has been released into the atmosphere has been released by wealthier countries, but the effects of warming tend to be greater on poorer countries. Do you think that gives wealthier countries an obligation to help poorer countries adapt to global warming? Defend your opinions.
- Within your own state or country, what do you think can or should be done to address the social justice aspects of global warming?
If at all possible, we suggest you ask a social studies teacher to help with this discussion, or to have it conducted during a social studies class. This will ensure that students can bring what they are learning in social studies to bear on the social justice issues of global warming.
- For your own background, you might explore these two articles from Time magazine and National Geographic that discuss social justice impacts of climate change that are already visible around the world. For scholarly research on the topic, try this study from Stanford University or this research article from the Proceedings of the National Academy of Sciences for a statistical study of economic impacts.
Journal Entry
The Importance of a Solution of Global Warming
Consider all the various consequences of global warming, and what is likely to happen in your own lifetime if the world continues on its current path. Based on all this, write at least a paragraph or two about how serious you believe the problem of global warming to be, and how much importance you think we should place on finding a way to slow or stop global warming.
This journal entry is designed to set the stage for the discussion of solutions in the next section. It is open ended, so students can express themselves in terms of how they now feel about the problem of global warming and the importance of a solution. As usual for journal entries, be sure to grade on the thought involved, not on the particular response. For example, you may still have some students who are unconvinced of the seriousness of the problem; don’t penalize them for their opinion, but be sure they are able to discuss the scientific evidence correctly even as they voice this opinion.
