When Samantha Gross visited UNLV in 2017, President Donald Trump had just announced that he planned to rescind the Clean Power Plan.

Fast-forward a year, and Gross was back in Las Vegas on the day when António Guterres, the United Nations secretary-general, told global leaders that the world had less than two years to avoid “runaway climate change.”

For Gross, a Brookings Institution expert on energy and climate change, the timing of her trips to UNLV have been interesting to say the least. Hours after Guterres’ announcement, she sat down with the Sun to discuss that statement and a number of related issues. Edited excerpts of the conversation follow:

How did the Guterres statement strike you?

You make those kinds of statements to get people’s attention, and I don’t think that’s a bad thing. But I don’t think there’s any particular science that supports the suggestion that it’s two years or else.

That said, there’s no question that it becomes more urgent all the time.

We’re continuing to pump CO2 into the atmosphere with our energy activities, land-use change and all that, and at some point we have to turn the corner.

Whether it absolutely has to happen in the next two years ... it clearly needs to happen soon.

And where my optimism starts to fall apart a little is when you look at the pledges that different countries made in Paris, a lot of the countries that were more ambitious are not on track to meet those pledges.

A lot of the big developing countries are — China and India are on track. But those pledges were frankly a little less ambitious.

But Europe and the U.S., we were quite ambitious in our pledges and we’re having a difficult time — for obvious reasons here in the U.S.

A year ago, you said you were optimistic about progress toward emissions reductions and renewable energy development because the states were working toward improvements despite the Trump administration. Is that still the case?

Things have changed tremendously since we last talked, but one of the interesting things that has just happened was the California Climate Summit.

I couldn’t go myself; I was in the Middle East that week. But people I know who did go found it really interesting. There were more substantive pledges, more substance over pomp and circumstance than they expected.

Have we seen a slowdown by the Trump administration in its attacks on regulations?

The rush to walk back regulations continues. We saw the Clean Power Plan withdrawn, and the Trump administration has put out a very weak “replacement” that really requires next to nothing.

In fact, acting administrator Andrew Wheeler of the Environmental Protection Agency may be somewhat less extreme than Scott Pruitt was, but is also a bit better in his job. Pruitt was in such a rush that in some cases, he didn’t dot his i’s and cross his t’s in the things he was trying to do, where Wheeler is a little more detail-oriented.

However, the federal regulations set a floor for those states where the politics isn’t that supportive of climate action, but still there are significant strides on clean energy, even in states where you wouldn’t expect it. Red states — Texas, Oklahoma, North Carolina — have significant clean energy.

Texas has more than twice as much wind capacity as any other state. But people are making money there.

And that’s not a red state issue — everybody likes to make money.

Is that largely because the cost of renewables keeps going down?

Exactly. And really the only new power plants you’re seeing built in the U.S. are gas plants and renewables.

There’s one nuclear plant that’s run into some pretty serious financial difficulties, so we’ll set that aside for a minute.

But apart from that, it’s all gas and renewables — nobody’s building anything else.

There may be some environmental thought in it, but frankly it’s an economic decision. And those are the things that make me more optimistic, to see gas driving change and see the cost of renewables coming down.

When people can make money fixing a problem, that’s when the problem gets fixed.

But on the other hand, there’s the environmental damage from fracking. Where does that fit into the equation?

Hydraulic fracturing can be done safely. It needs to be well regulated. You need to think about a lot of nuts-and-bolts things, like well integrity. Building a solid, tight, safe well and thinking about how you dispose of water. But it can be done safely.

Another thing that’s important is methane emissions. Methane is a very strong greenhouse gas, close to 100 times as potent as CO2. It doesn’t stick around in the atmosphere very long, but it’s very potent in the time it’s here.

So it’s very important when you’re producing natural gas to not have leaks and emissions from that process.

That’s something that, sadly, the Trump administration has been backing off. I’m beside myself over that. It’s completely ridiculous.

Because not only is methane a really strong greenhouse gas, you’re also basically wasting your product. You can burn that stuff. It’s worth money! And it’s far better to use it as a fuel than to have leaks and fugitive emissions.

Why don’t producers capture it, then? Is it just too expensive?

You know, many do, and you’re actually seeing a number of large operators coming together with the American Petroleum Institute with a voluntary initiative to reduce their greenhouse gas emissions.

The challenge is with some of the smaller operators who have a little tighter profit margins. It may be harder for them to make the investments, and that’s where the regulation is really important.

On the brighter side, we keep seeing new advancements in energy storage technology — for instance, pumping water upstream during daytime hours when solar power generation is happening and then letting it flow back downstream and running generators off of it when the sun goes down. How are you feeling about the progress on storage?

Pump storage works. It’s an existing, proven technology. The key is there are only so many places where it’s good to do it. There are only so many large dam sites where it works, because you have to pump a lot of water and you also have to think about the other uses of the reservoir and river system. So recreation, fish, irrigation, those sorts of things.

There’s also battery technology — utility-scale batteries. When you think about putting a battery in a car, you have to think a lot about how big it is and how much it weighs, whereas if a battery is just going to sit still, you don’t have to care about that so much. It just needs to be cheap.

But the technology is still expensive. If we can crack the nut of a battery chemistry that makes that cheap, though, that will help a lot.

Then, particularly with solar, if you can store and shift some of the energy into the evening when we’re running our dishwashers and watching our TVs, that would make a huge difference.

Particularly as the renewable generation technologies get significantly cheaper, this is the next frontier in making this really economical for lots of applications. And so there are a lot of engineers in a lot of places working on it, which tends to be a good thing.

There’s a lot of money and a serious benefit for society if they can figure this out, and that makes me optimistic.

You wrote recently about energy policy in Mexico, and how it may change under the new president, Andrés Manuel López Obrador. Can you encapsulate your message from that piece?

Obrador during his campaign was very strongly against the energy reforms of the previous administration, which did a lot of liberalization of the Mexican energy market. He opened up oil and gas production to companies other than Pemex (Mexican Petroleum), which required a constitutional change in Mexico. That was a huge deal. The oil and gas patrimony there is serious; people feel strongly about it.

And also the current administration opened up the electricity market to more competition, allowing generators other than CFE, which is the Mexican federal utility.

I think this was terrific for Mexico. There were a lot of things Pemex didn’t have the expertise or funding to do, so oil production in Mexico was declining. But they have resources. They just need additional investments and technology to develop them, which is what these reforms were designed to do.

Same thing with electricity. Electricity is really expensive in Mexico in some places, so allowing competition and encouraging more building out of renewables is good.

Obrador came out very strongly against these reforms. He’s backed off a little since his election, which makes me wonder if he’s come to understand that they are good for Mexico. He originally said he was going to cancel the new contracts, but he’s since said the contracts would be reviewed to ensure there was no corruption.

So he’s moving in a good direction. Hopefully he reviews them and finds the process was clean and transparent.

If he would dial back the reforms, what effect would that have on the U.S.?

Mexico imports a lot from the U.S. We still import Mexican crude oil, but we export refined fuels and significant natural gas. So if he decided he didn’t want those products, that could be a challenge for the U.S. energy industry because they’re very good customers of ours.

And frankly, the relationship is good for Mexico. We have really efficient refining capacity on the Gulf Coast that’s well set up to run Mexican crude. So that’s useful for Mexico, and we have serious natural gas resources that go to Mexico at a pretty reasonable cost.