# Planetary Dieticians

The toughest part of predicting the future is predicting choices people make.
What choices are you making?

### A plan for a healthy body

Donut consumption provides punctuated delights in Bob’s daily, humdrum routine. Aware, however, that donuts drive weight gain, and that excessive weight gain is linked to health disorders, Bob commits to reigning in his high-energy-consumption lifestyle. Aware of the multitude of “down-donut-diets” circulating on social media, but unable to choose or commit to a plan on his own, Bob schedules an appointment with Cindy, a professional dietician. Cindy will help Bob chart a course to lower donut consumption.

The session with Cindy goes well. She impresses him with her knowledge and experience, and inspires in him hope for a better Bob. Cindy predicts that Bob can achieve his goal of 200 lbs in one year’s time. Bob pictures his slimmed-down self, laying in the sun, on a beach. Life will be good with his new plan!

One year later Bob returns, upset. Cindy’s predictions were wrong. Instead of decreasing to 200 lbs, as she “predicted”, Bob’s weight increased from 240 to 260 lbs! In addition, Bob is starting to feel winded when he goes grocery shopping. Bob is desperate, because he is beginning to feel the early effects of his donut binging. If the relationship between excess calories and weight and health is so well understood, why was Cindy’s prediction so far off? Perhaps dieticians don’t know as much as they claim or perhaps she is just scamming her clients! Obviously, dieticians like Cindy can’t be trusted.

Predicting Bob’s weight and health depends not just on understanding the relationship between diet and health, but also on Bob’s choices. Because Cindy cannot control Bob’s choices, she made predictions based on the following, three down-donut scenarios:

• Plan A: Net-0 donut consumption,1 leading to weight reduction to 200 lbs.
• Plan B: Net-3 donuts/day, with Bob’s weight stabilizing at 240 lbs.
• Plan C: Net-6 donuts/day, causing Bob’s weight to increase to 280 lbs.

Bob only remembered Cindy’s prediction of 200 lbs, but not the conditions that led to it. Bob therefore incorrectly concluded that Cindy’s model was inaccurate. However, for the down-donut scenario that Bob followed (about 4.5 donuts/day), he gained the amount of weight Cindy predicted.

Cindy’s only failing was not correctly predicting Bob’s choices.

Cindy also apparently failed to predict the onset of Bob starting to feel winded. However, although there is broad understanding of the relationship between diet and health effects, the severity and onset of diet-related health effects is difficult to predict.

Predicting the effect of diet on one’s health requires that we know ...

• The relationship between a person’s diet and weight.
• This is relatively easy to predict.
• The relationship between a person’s diet and health effects.
• This is difficult to quantify, but qualitative relationships exist.
• What choices a person will make.
• This is impossible. Dieticians can only make recommendations.

Even though Cindy cannot predict the exact relationship between Bob’s diet and his overall health, by monitoring Bob’s cholesterol, vital signs, and testing Bob periodically, Cindy can track changes in Bob’s health, making recommendations to help Bob feel better.

The combination of imperfect modeling combined with accurate monitoring leads to effective dietary guidance.

### A plan for a healthy planet

Just as the health community has imperfect, but useful knowledge about the relationship between dietary choices and health effects, the climate-science community has useful information about the relationship between various levels of warming and expected increases in extreme precipitation events (both floods and droughts), stronger storms, more frequent wild fires, and higher sea level. We do not know with any certainty the timing and severity of such effects. But we are getting better at taking the pulse of the planet and combining monitoring data with imperfect models to improve our predictions of likely consequences of various levels of warming.

What we do not know with any certainty, however, are the choices that mankind will make in the face of the current climate crisis. Cindy can give us multiple dietary plans to follow, but she cannot predict which one we will choose. Climate scientists and policy makers can give us a roadmap to net zero emissions, but they cannot make it happen.

Whatever we do or don’t do as a planet to lessen the severity of GW/CC, you can mitigate the negative impacts, somewhat, on your life by paying attention to the professional climate science community. Like weather models we use to plan our lives, although they frequently fail to predict exactly how much rain will fall on a particular day, just knowing when rain is likely to occur helps us plan: they don’t have to be perfect to be useful. Although we don’t know with certainty how much, and when, sea level will rise, just knowing that sea level will rise significantly over the coming decades and centuries can help you plan.

Climate models are not perfect, but they are useful for informing our choices.

### Footnotes

1. Bob can eat donuts, but must exercise an equal amount to remove the excess calories.

Posted by Evan on Tuesday, 24 May, 2022