The third Democratic primary debate in Houston had little discussion of climate change and energy, but still lent itself to some hot takes.The big picture: Climate is stitched into the fabric of 2020 now. Beyond the whopping 5 minutes or so of direct discussion, many candidates wove climate into their mini-stump speeches and answers on other topics.Pete Buttigieg hit President Trump for skipping the climate session at the recent G7 meeting as part of a broader foreign policy critique.Joe Biden, in his wide-ranging opening statement, said "I refuse to postpone any longer taking on climate change."Elizabeth Warren's answer caught my attention. The Massachusetts senator said "we've got to use all the tools" and then went on to say (emphasis added):"One of the tools we need to use are our regulatory tools. I have proposed following [Washington] Governor Inslee, that we, by 2028, cut all carbon emissions from new buildings. By 2030, carbon emissions from cars. And by 2035, all carbon emissions from the manufacture of electricity."But, but, but: All the candidates' plans are a mix of regulations and calls for major new legislation, and achieving those aggressive targets would almost certainly require the latter.Amy Klobuchar's answer also caught my attention. The Minnesota senator said her background is a plus for confronting the "existential crisis of our time" because ... "I think having someone leading the ticket from the Midwest will allow us to talk about this in a different way and get it done."On Cory Booker's veganism: The food system is super important to the climate, but come on! They were in Houston, the oil capital of the U.S. Yet there were no questions on fracking — which several candidates want to ban — or on energy more broadly.Why it matters: Energy production and use is by far the biggest carbon emissions source.And the moderators didn't even bother trying to draw out contrasts between the candidates, even though their plans have some real differences.Go deeper: The takeaways from 2020 Democrats' marathon CNN climate town hall