During Saturday’s speech on New York City’s Roosevelt Island that marked the thematic beginning of her second campaign for the presidency, Hillary Clinton largely stuck to broader economic topics. Yet climate change merited two significant mentions, as well as a promise to make America “the clean energy superpower of the 21st century.”

First, Clinton turned to the climate science denial running rampant through the Republican presidential field early in the speech.

“Ask many of these candidates about climate change, one of the defining threats of our time, and they’ll say, ‘I’m… not a scientist.’”

“Well then why don’t they start listening to those who are?”

The punchline merited one of her larger applause lines, which could mean that it makes it into her stump speech and that climate science receives more focus in this campaign than past races. Over the last year, many Republicans have sought the refuge of the “I’m not a scientist” phrasing to avoid directly denying mainstream climate science or acknowledging the problem.

President Obama mocked the dodge during his last State of the Union address, saying, “Well, I’m not a scientist, either. But you know what  — I know a lot of really good scientists at NASA, and NOAA, and at our major universities.” He then described how they know human activity is causing climate change.

Indeed, the impacts of climate change are becoming more and more difficult to ignore, as last year became the hottest year on record, last month was the wettest month on record, and states around the country deal with extreme flooding, drought, sea level rise, and heat.

Clinton later moved on to how to address the problem: cutting carbon pollution.

She listed solar, wind, advanced biofuels, smarter electric grids, cleaner power plants, greener buildings, and using fossil fuel extraction fees “to protect the environment and ease the transition for distressed communities to a more diverse and sustainable economic future.”

Those communities, Clinton said, include inner cities, coal country, “Indian country,” and the Mississippi Delta.

“Now, this will create millions of jobs, and countless of new businesses, and enable America to lead the global fight against climate change.”

Bill McKibben, the founder of 350.org, wrote an open letter to Clinton on Friday, explaining the reasons “why many serious environmentalists currently distrust you.”

“In the end, if you’re the Democratic candidate in the general election, environmentalists may vote for you no matter what, on the general theory of: Republicans don’t believe in physics,” he wrote. “But that’s different from building the kind of enthusiasm that makes elections easier to win, an enthusiasm that would be essential if you actually planned to change things once taking office.”

What can Clinton do to earn that enthusiasm back, in McKibben’s view?

• First, make climate change her “issue.” A speech like this is a start but advocates will be looking for far more. With campaign chair John Podesta pushing publicly for a focus on climate, they might get it.
• Address her past support and current silence on Keystone XL. Many environmentalists will be waiting for her to answer that question during the campaign, as the proposed pipeline has become an organizing tool and signpost on one’s seriousness about climate and keeping fossil fuels in the ground.
• Come clean about her advocacy of fracking at the State Department. With water quality concerns mounting and local fights over fracking bans taking place across the country, Clinton will have a hard time avoiding this topic.
• He blames her in part for the failed Copenhagen climate conference in 2009. Clinton obviously has a different view, though with the Paris talks coming up this December, many will be asking what she would do this time.
• “Stop talking about an ‘all-of-the-above’ energy policy.” She avoided it in this speech, but as this is a common phrasing used by many Republicans and Democrats, it may not be going away.
• “Signal your support for divestment from fossil fuels.” It’s a long campaign, and she’s bound to be asked in a youth forum about divestment.
• He notes that the money in the form of speaking fees and foundation donations also came from fossil fuel interests, which can potentially buy influence. One way to address this, he says, is to use the ties formed by the Clinton Foundation to help honor the global $100 billion Copenhagen pledge to move developing countries to renewables.

It’s going to be a long campaign, and with her primary rivals either making climate big parts of their campaigns or boasting strong records of their own, primary voters will likely have much more to hear from Clinton on these topics before the the Iowa caucuses.

*Disclosure: John Podesta founded the Center For American Progress Action Fund, which is the parent organization of ThinkProgress.