HONR 229L: Climate Change: Science, Economics, and Governance

1. HONR 229L: Climate Change: Science, Economics, and Governance Introduction to Climate Change Your name here 27 September 2018

2. You might consider starting with the first admission ticket question, which is: The reading states "Climate is the average of weather" and includes a sentence that likely seems preposterous to many: Projecting changes in climate due to changes in greenhouse gases 50 years from now is a very different and much more easily solved problem than forecasting weather patterns just weeks from now. The field of actuarial science can be viewed as being analogous to the field of climate prediction: an actuary studies the life expectancy of large groups of people, allowing insurance companies to thrive financially even though they will likely pay out a benefit of some sort upon the passing of everyone they insure. Some contend that "actuarial science is to trying to predict when a specific person will pass away" as "climate science is to trying to predict the weather next month at a specific location such as College Park". State whether you agree or disagree with this contention, and support your answer with a few sentences. Consider asking the class to weigh in on this matter, then of course give your view. I’ll be happy to give you my two cents, if you’d like 

3. If you stick with the Admission Ticket questions to start the discussion, can then move to the next question, which reads: This question is focused on greenhouse gases, or GHGs. State: a) the most important and abundant GHG in the atmosphere followed by: b) the most important anthropogenic GHG c) the second most important anthropogenic GHG d) the third most important anthropogenic GHG The answers to b), c), and d) should be based on the magnitude of increase in the radiative forcing of climate, between 1750 and 2005. NEXT, for one of the three anthropogenic GHGs (pick one but be clear which one you are writing about), explain how it is known that the increase in the abundance of this gas, since the start of the industrial revolution, is caused by human activity. Note: while answers to a), b), and c) should be clear, once could make a plausible argument as to whether the correct answer to d) is either O3, N2O, or halocarbons. Should you use this AT question, you will need to explain why the answer to a) involves a gas that humans do not directly control, then review b) & c) along with some material (can ask for discussion, of course) on why we know the rise in abundance is due to humans, then perhaps follow this discussion with a brief overview of O3, N2O, and halocarbons based on material from FAQ 7.1. The charts on the following three pages may be of use.

4. Radiative Forcing of Climate, 1750 to 2005 Question 2.1, IPCC, 2007

5. Radiative Forcing of Climate, 1750 to 2011 Figure 1.4 Salawitch et al., Paris Climate Agreement: Beacon of Hope, 2017. Our update to the IPCC figure that you are welcome to use, should you so desire.

7. You’re welcome to use this 2 slide sequence, as well CO2, CH4 & N2O time series IPCC 2007 FAQ What do these time series resemble ?

8. You’re welcome to use this 2 slide sequence, as well CO2, CH4 & N2O time series IPCC 2007 FAQ

9. Should you want to use the figures on the rise of either sea level or global mean temperature, I have placed on the following pages:

10. Discuss how sea level and Earth’s mean temperature have changed

11. Discuss how sea level and Earth’s mean temperature have changed

12. Discuss how sea level and Earth’s mean temperature have changed

13. We have spent considerable time in class talking about the importance of drought, which begs the question “is precipitation changing?” Consider preparing a slide or two, based on the material in FAQ 3.2, focused on historical changes in precipitation. You could relate the changes in the Palmer Drought severity index to the instances where drought was implicated in the past “Collapse” of particular societies in Diamond’s book. I do not mean this in a literal fashion, as most of the collapses we had studied occurred before 1900. Rather, I mean in a hand-waving fashion, to illustrate that “stuff happens” wrt to precip on a multi-decadal time scale.

15. Next, consider leading a discussion about the importance of atmospheric feedbacks. Can base this off the admission ticket, which reads: a) As the concentration of GHGs in Earth's atmosphere rises, the surface temperature will rise, causing snow and ice to melt. State whether this melting of snow and ice acts as either a negative feedback, no feedback (null), or positive feedback, in response to the initial perturbation and justify your reply with an explanatory sentence b) As the concentration of GHGs in Earth's atmosphere rises, the surface temperature will rise, resulting in larger amounts of water vapor to be present in the global atmosphere. State whether this rise in atmospheric water vapor acts as either a negative, null, or positive feedback and also give the best estimate of the magnitude of this feedback, relative to the greenhouse effect caused by rising CO2. Should you want to go down this path, you could lead a discussion of clouds. Here, if rising GHGs lead to more of a “blanketing effect”, the feedback is positive. If rising GHGs lead to more of a “reflective effect, the feedback is negative. Perhaps the image on the next slide will be of use for helping to talk through clouds. Fine to supplement with other images. In my opinion and that of many colleagues, a key weakness in predicting future climate is our present inability to properly simulate cloud feedback

17. Finally, should you so desire, consider leading a discussion on: why scientists are confident the observed warming of the 20th century is primarily caused by human release of GHGs and is not due to the natural variability of climate the strength and weaknesses of climate models This can constitute a few slides. If you go this route, be sure to engage the class in a discussion about whether or not they feel comfortable with so much (i.e., future habitability of our planet Earth) relying essentially on computer simulations conducted using archaic programming languages such as FORTRAN.

18. Feel free to alter, ad lib, change in any way you’d like provided the topic is about Earth’s climate system and bears some relation to the reading. You have 45 mins to use as you see fit! For this discussion in particular, I do not expect the classroom presentation to cover every page (or each question) of the reading. There simply is not enough time. Rather, I hope you can touch on the high points, address some of the AT questions, and lead of a discussion of the ESSENTIAL ELEMENTS of Earth’s climate system as described in this reading. This reading is long, will be confusing to some (hence my asking for questions in the last segment of the ATs), but is comprehensive and is the best material I can find explaining the climate system to non-experts, written by IPCC. If you need more figures from the reading and are having trouble pulling into PowerPoint, please let me or Laura know. Good luck!