Response to a passage in "Climate Casino"

                   I'll be talking about a certain passage I read from the book "The Climate Casino: Risks, Uncertainty, and Economics for a Warming World" by William Nordhaus, that I found interesting.  In that particular passage he talk about externalities and how it works.  He uses an example of lettuce and the cost of lettuce is determined by the cost of it's production.  For anyone that isn't familiar with externality, it simply means that the by product of an activity that we partake in has its affects on those who did not.  He brought the example of lettuce production back up explaining that in that price of lettuce they are not factoring in the emissions that came from the machine that had to irrigate the lettuce, or the truck that had to transport the lettuce to be sold.  These situations would be considered externalities.  I found this particularly interesting because a lot of the time as humans there are many activities that we participate in without thinking of the externalities it may have.  It can range from anything as simple as going to school and the gas we may have used to get there, or ironically something as complex as building a piece of medical equipment in order to save lives, where its by product will ultimately just shorten all of ours.  It was just something I found to be quite interesting and made me a little more aware of what I do in my life.  Hope you found it just as interesting!