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Climate Change

Grace came home last weekend for her fall break, and we had some great discussions about the state of the world. On the drive to our favorite place to eat the girls started talking about the recent IPCC report on keeping the world at or below a 1.5°C rise in temperature from pre-industrial levels.

So what’s the problem?

For the benefit of the people in the back of the class checking their phones instead of paying attention, I’ll summarize what the SR15 report is all about. To quote the IPCC press release summary page, “Limiting global warming to 1.5°C would require rapid, far-reaching and unprecedented changes in all aspects of society.” Why 1.5°C? Because scientists who used to advocate for keeping the ceiling at 2.0°C realized they were mistaken.1 Further research since the last report revealed that the extra half degree will be likely be catastrophically bad. Remember these reports are written by international committee, and no country wants to promote bad news, so it is likely that the science would err on the side of even less warming, but the politicians know that cutting CO₂ emissions even faster would be unpalatable to their constituents.

So back to the story. There we were, driving to dinner in our Honda SUV, talking about what we can do versus what we will do to reduce carbon emissions. I asked rhetorically “Why are we driving to dinner?” Grace said that she was going to start biking everywhere. Emma (never one to advocate for extra exercise) pointed out that solving global warming will require new technologies to be invented to clean the air of carbon retroactively, so maybe one trip by car to dinner isn’t so bad.

The micro-example of that trip is a fairly common representation of why we can’t rely on good intentions. We have a Fiat 500e that is very efficient and really does fit all four of us for short trips. But it was low on charge, it is a little cramped for the girls in the back seat, and Grace was only home for the weekend so we didn’t want to make her suffer unnecessarily. The trip is also bike-able (less than 3 miles, no hills), but even if Grace hadn’t taken her bike to college, there are just too many cars driving way too fast and no safe bike routes for anybody but hardcore bicyclers. (I do that trip all the time, but I’ve been bicycling everywhere for decades.)

We could have skipped the trip entirely, of course. The cost of not driving and not going out to eat would be that we wouldn’t be able to take Grace to get her spring rolls fix. On the other hand, our perceived cost of driving is the gas used, micro wear and tear on the car, and the guilt of knowing we contributed a micro additional amount of CO₂ to the atmosphere. Balancing the benefits (East Borough) versus the costs (gas is cheap), we drove to dinner in the SUV.

Note that I said that our CO₂ emissions are only being internalized as guilt. We don’t yet have a carbon fee on gasoline, nor can we trade carbon credits if we had ridden bicycles. The gasoline taxes in California are pretty low, and make no effort to include passenger travel in the cap and trade carbon emissions market. So our emissions are perceived as essentially free to us, aside from some nebulous long term cost to the planet. Without imposing a serious, direct financial cost to cut CO₂ emissions and/or direct incentives to use electric cars or non-motorized modes like biking, even left-wing liberals like us are likely to do the immediately expedient thing and drive.

The problem with this current state of affairs is that the SR15 report presumes that starting in 2020 the net carbon emissions will drop off a cliff. Below is figure 1 from the summary for policymakers.

Net CO₂ emissions need to drop to zero by 2040 or so

SR15 Figure 1

IPCC SR15 report page

Notice plot panel (b) in that figure. The trend since the 1960s has been a steady increase of about 400 million tons of CO₂ per year, to our current output of about 40 billion tons per year. Then in 2020, the IPCC expects that trend to reverse, so that by 2040 (at the earliest) we are emitting a net zero additional tons of CO₂ per year. That lets us level off at about 2.5 to 3.0 trillion tons of “extra” CO₂ in the atmosphere2.

Granted, the whole point of the report is to game out realistic scenarios in which the planet’s global warming bill comes due under 1.5°C. Even so, the plot showing the required drop in carbon emissions looks ridiculously unobtainable. So either we have no hope of keeping the planet cool, or we have to get cracking right away.

Changing behavior through education isn’t going to get society on that sharp downward slope fast enough. If you take as given that people are generally in equilibrium with their situation in life, effecting a severe change in behavior will takes an equally severe change to the circumstances that engender that behavior. Again, taking our drive to dinner as an example, if we were in Manhattan or London, we would have walked or taken public transit to dinner. Driving in Orange County is convenient only because everything has been designed around driving.

I’m not a quitter, and humans throughout history have demonstrated the ability to sacrifice and survive when necessary. While there will continue to be cheap political rhetoric from the right that we are “entitled to consume”, the world really is heating up and the consequences are becoming undeniable. I’m going to assume that we really will make every effort to fall off that carbon emissions cliff. But what does it mean for transportation? What does it mean for our behavior as travelers? What tools can we use to change suburbia in two years such that internal combustion engine use declines to zero? Those are the questions I’m going to explore in the coming weeks.


  1. That’s the way science works. Guesses turn into hypotheses turn into theories, with changes along the way as facts and tests are accumulated.

  2. I did 10 minutes of internet reearch to see what all those tons of CO₂ means. I found a page at tallgrass ontario with a few numbers for how much CO₂ is sequestered by growing switchgrass and other prairie grasses. Taking the middle of the numbers on the page of 0.3 to 1.7 tons of CO₂ per acre per year (convenient sums!), zeroing out our current 40+ billion tons annual CO₂ emissions will take 40+ billion acres of mature prairie grasses. That’s 162 million square kilometers according to the handy dandy Google website. According to Wikipedia, in 2012 the world had 13.9 million square kilometers of farmland. You can do the math. And please don’t suggest that grazing cows on the world’s deserts will solve our problems. Cleaning up the extra trillions of tons emitted since the industrial revolution will likely be the province of science fiction tech like nanobot carbon scrubbers. We can’t plant our way out of this mess even if we wanted to, and humans are not well known for planting rainforests and jungles and then walking away.