If you’ve been paying attention to the 2016 presidential debates, you may have noticed one topic that has been absent. While the GOP candidates have discussed everything from the price of tractors in China to killing baby Hitler to Carly Fiorina’s face, they have been almost silent on the gravest global threat of our age: climate change.

Now, this isn’t entirely the candidates’ fault (although not accepting climate change science certainly is), since the moderators in charge have barely mentioned the environment during the debates. But even though the presidential hopefuls — and debate moderators — are ignoring climate change, one man is not: Bill Nye, The Science Guy. In an op-ed published on CNN (the network that hosted Thursday’s Republican debate in Houston, Texas), Nye lays out the questions that should have been asked. He writes:

Here’s hoping someone can manage to ask the candidates a question like: “Mr. _______, you’ve stated repeatedly that you feel that climate change and global warming are not things we need to worry about in the short or even long term; why do you disagree with the world’s science community and the U.N.’s Intergovernmental Panel on Climate Change?”

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Then, I’m hoping that the same person or another citizen asks a follow-up: “Mr. _______, would you say that you believe your intuition and experience with weather are more scientifically correct than the research done by the world’s climate scientists, and do you believe that the world’s scientists are part of a conspiracy?”

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Of course, neither question made it into the debate in Houston.

The one brief mention of the environment on Thursday night was in the context of the budget: CNN moderator Wolf Blitzer followed up with Donald Trump about his plan to eliminate the EPA in order to save the country $8 billion, though it still only accounts for roughly 0.2 percent of the federal budget. (Trump, by the way, also says he’s going to eliminate the Department of Education, so if you have plan on having school-aged children during the Trump reign, you may want to consider Cape Breton.)

But even if Blitzer or the other moderators had brought up climate change, four out of the five candidates onstage deny its very existence. This isn’t just terrifying for those of us who care about the planet; it should also be terrifying for those who care more about the economy than the Earth. The fossil fuel industry is facing intense turmoil: Coal-fired power plants are closing, oil prices are at record lows, natural gas extraction has a huge PR — and earthquake — problem, and the decreasing cost and increasing availability of solar and wind power means the future just isn’t dirty energy anymore: It’s in renewables. Or, at least, it should be.

But even though Texas is the home to a big oil and gas industry and wind industry, none of this came up in Houston. And if past performance is any indication, it won’t in the debates still to come. Until moderators and network hosts force the candidates to explain themselves, they’ll talk about fruit salad and building walls across North America and who would defund Planned Parenthood the fastest — and they’ll certainly bicker over each other like divorcing parents — but as for climate change? On that, they won’t say a word.

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Unless, that is, Bill Nye gets to moderate.