Climate change (Class of 2019): follow-up lecture

This page was written to be shown during the follow-up lecture on 8 Aug. 2019. So, the text is not (yet) finished as a written text.

Section 1 of the term report assignment

This is a very crude example of "projections" of climate in the future. Please do not consider this as projections to be used in real policy-making. I wanted you to be accustomed to our (climate scientists') way-of-thinking.

There are a lot of uncertainties, but it does not mean that we know nothing. The human society must make decisions under this kind of situations.

Concentration scenarios: A (crude) measure of how climate can be different according to choice of policies regards to CO2 emission.

Others: Some measures of uncertainties of scientific knowledge about the climate system.

Notes about computer software [added 2019-Aug-12]

This kind of simulation can be done with spreadsheet software, as some of you tried successfully. I do not recommend spreadsheets for serious use of this kind, however, because it will be difficult to avoid mistakes and to make the processes of analysis traceable.

In this class, I showed an example program in R. R is a special-purpose programming language for statistical data analysis.

It seems to be better to use general-purpose programming languages. One candidate, contemporary popular, is "Python".

I used R, partly because I wanted to use graphics capabilities of R. I am sorry I showed just an example of very crude numerical ourput of the result. I should show examples of graphical output, and also numerical output in good formats for re-use, but I could not create them in time. Parhaps I add some examples later somewhere linked from the index page of the class.

Specific notes about experiments in R [added 2019-Aug-12]

Some of the students who tried calculation in R successfuly changed "2" of "kscenario <- 2" to "1", "3", or "4". You can also try to change "500" of "depth <- 500" to "4000" or "100" etc., and "3" of "tssrdouble <- 3" to "1.5" or "4.5" etc., and re-run.

Section 2 of the term report assignment

"One paragraph" was not a good way of assignment. (The typical length of a paragraph depends on the cultures of schools.) I should say "approx. 5 lines, or 80 words" for each item.

I wanted you to discuss major causes that can change total energy of the climate system. I regret that I mentioned "global mean temperature" as something that is likely to be proportional to the total energy. Some processes have strong influence to temperature though they do not change total energy significantly. (I included temperature because discussions of feedbacks usually start from temperature.)

Section 3 of the term report assignment

I wanted to exclude (such actions that people categorize as) "mitigation" from the report assignment. But apparently my intention did not reach all of you. There are some answers saying that "our environmental policy should not be just CO2 emission reduction", which I count as relevant answers.

Countermeasures to (impacts of) climate change

Notes on water [added on 2019-Aug-09]

Shortage of water is one kind of important possible impacts of climate change on the human society. But, we should distinguish the two items:

The amount of drinking water is much less than the amount of irrigation water. So, scarcity of one may happen in different place and time from scarcity of the other. Even in changing climate, availability of safe drinking water can be kept high, if the goal is given high priority in international policy-making. But, it is very hard to move irrigation water from one region of the world to another. Sustainability of food production with irrigation is much uncertain. As a way to adapt to climate change, maybe we need to have technology to grow crops with less irrigation water.

Other environmental issues (not directly related to CO2 emission)

Another interesting cause-and-effect chain (rather than "climate change -> impact")

land use change -> change of biogeochemical cycles -> change of greenhouse gases in the atmosphere -> contribution to climate change

Updated: 2019-Aug-08, 2019-Aug-09, 2019-Aug-12
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