Tuesday, May 10, 2016

Climate Change: The Math

Many people deny humans are causing climate change, but few of them are climate scientists. 97% of climate scientists agree that anthropogenic climate change is really happening. There's tons of evidence.

I'm inclined to agree with the 97% of climate scientists who agree humans are causing global warming, but what if they're wrong? Nothing is certain in life but death. The climate change debate is not as settled as the Nickelback debate. They suck and no one is arguing the point—not even them:

Should we address climate change?

I won't refute all of climate deniers' arguments here. In fact, I don't have to. We can decide whether or not to do something about climate change without being 100% sure that it's happening. Sounds crazy, huh? It isn't. People make decisions with imperfect information about the future all the time. Parents save for toddlers' college education knowing full well that the rugrats might swallow a lego and kick the bucket. Frat boys buy roofies even though their jealous girlfriends might cut off their dicks at any moment.

It Is or It Isn't

Climate change is real or it isn't. The most ardent denier (skeptic) or proponent can agree on that. It sounds simple, but it's an important point. We can't CHOOSE whether or not climate change is real. Hopefully, the scientific consensus is wrong and climate change isn't real. Our temperature measurements are off. But it isn't our choice. It's physics. Humans are causing the Earth to heat up or they aren't.

What's in it for us?

Should we do something about climate change? Let's consider the four scenarios:

  1. Climate change is real and we address it
  2. Climate change is real and we ignore it
  3. Climate change is not real and we address it
  4. Climate change is not real and we ignore it

What would happen in each scenario?

Remember that we can't CHOOSE whether or not climate change is real, but we CAN choose whether to do something about it. Here the doing something about it means spending money to transform our energy infrastructure from a fossil fuels based infrastructure to a renewable energy based infrastructure. We get to choose the top row (do something about climate change) or the bottom row (do nothing).

We can use the model to avoid the worst outcome. That outcome happens if climate change is real and we do nothing. We don't need to put numeric values to the outcomes to know that.

Let's go ahead and put dollar values on the scenarios anyway. For penny pinchers, this is about to get grim. The model below uses some very conservative assumptions about the impacts of climate change. The numbers represent the economic costs to the U.S. this century. They don't take into account any human costs such as injury, loss of life, or extinction of species.

We can also calculate the average outcome (or expected value) of each action. Using gambling terminology, we consider the expected "payout" of various possible "wagers". We calculate the expected value of an action by multiplying the probability of a scenario occurring by the payout (how nice is the outcome). We then do that for each action. So how likely is it that climate change is real? I think 97% certain is a reasonable number, but we can examine multiple scenarios.

Note that it doesn't much matter how certain we are that climate change is real. Even if we are only 30% sure that climate change is real, it is still worthwhile to address the problem. The impacts are so incredibly bad that they far outweigh any costs we take to address the problem. Using this model, we have to be 90% certain that climate change ISN'T real for it to be worthwhile to NOT address it. Even then, we might want to hedge our bets in order to avoid

If climate change is real and we choose to do nothing, we are fucked. F-U-C-T. FUCT! Our way of life will cease to exist. Refugees will flee flooded and scorching hot areas. Tropical diseases will make their way into temperate areas. Wildfires will rage. It will basically be the apocalypse.

If climate change is not real and we choose to address it anyway, we will unnecessarily spend a few trillion dollars on some cool new technology.

TL;DR Summary

  1. Climate change is real and humans are causing it
  2. The worst impacts of climate change are apocalyptic
  3. Even if we aren't certain climate change is real, it is still in our economic interest to address it
  4. We can't risk doing nothing

The Denier's Rebuttal

Many deniers acknowledge that the Earth is getting warmer. It's pretty hard to deny given the temperature data. The 3% of climate scientists that refuse to acknowledge humans are causing climate change. Many of those still acknowledge the temperature data. The Earth is still heating up, they believe, but we can't be confident that humans are causing it yet.

This scenario is a red herring advanced by climate change deniers. Let's consider it anyway.

If we assume global warming is occurring but is not caused by humans, my analysis still holds! Any NATURAL warming that is disrupting human life and the broader ecology, we still need to address the issue!

So what would we do? Well, it isn't clear. If it isn't humans causing climate change, we don't know what is. In order to address, it we need to figure out what is going on and fast! In this case, we need to increase climate research funding. Of course, we need to do that anyway.

Model Assumptions

The estimated economic impact of climate change is estimated conservatively at $3.8 trillion per year by the end of this century if we do nothing. That number includes financial losses from flooded coastlines, higher energy costs, bigger hurricanes, and higher water and agriculture costs. It does NOT include the deaths from storms or heat. It does NOT include any of the costs of the wars that will ravage the earth. But let's roll with $3.8 trillion per year. Now the total cost this century would be $160 trillion.

This model assumes that the costs to convert the American economy to clean, renewable energy would be 1/2 2016 GDP or $8.5 trillion. That number is rather high. In fact, I believe that we can convert the economy for free or close to it. Crucially, if climate change is real, we will have to convert the economy to clean, renewable energy, anyway. We can do it now or later, so that cost has been added to $160 trillion cost of climate change for a total do-nothing-and-climate-change-is-real of $168.5 trillion.

This model assumes that we will only be able to avert half the cost of climate change if we start tomorrow. This is the most uncertain part of this model.

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