what Harris and Trump said about science

Science issues took a back seat to the economy, immigration and national security during the first — and perhaps only — debate between US presidential candidates Kamala Harris and Donald Trump on 10 September. But US vice-president Harris and former US president Trump did make passing references to subjects such as climate change and scientific competitiveness.

Neither candidate revealed much about the specific policies they plan to implement if they become president in the upcoming election in November. But that, researchers say, was not necessarily the point.

“We rarely learn anything of substance in a debate, but we do form impressions of who the candidates are as people,” says Matt Carlson, a media researcher at the University of Minnesota in Minneapolis. “And this debate offered a particularly stark contrast between Trump’s angry gut reactions and Harris’s optimistic outlook.”

Here Nature analyses what the candidates did and did not say about science, and what researchers think of the candidates’ stances.

Abortion and women’s health

This was one of the big topics of the debate. Harris said she supports reinstating the protections of Roe v. Wade — the US Supreme Court ruling that once ensured the right to an abortion until the point when a fetus can live outside the womb — typically around 23 weeks of pregnancy. It was overturned in 2022 by a majority-conservative panel of justices, three of whom Trump appointed during his presidency. Trump said the decision about whether to ban abortion should be left up to each US state, and did not directly answer whether he would veto a national abortion ban if it came to his desk.

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Harris also discussed how abortion bans in various states are affecting health care, saying that women suffering from miscarriages are being denied crucial care in emergency rooms. This is true, says obstetrician and gynecologist Daniel Grossman, director of Advancing New Standards in Reproductive Health, a research programme at the University of California, San Francisco. His team released a report earlier this week detailing, among other things, how people with pregnancy complications have been put at risk because of delayed access to abortion care.

Trump said that abortion should be allowed in cases of rape, incest and when the life of the pregnant person is at risk. Grossman notes that, in practice, implementing those exceptions is very difficult. “Medicine is not black and white,” he says. “How threatened does the life of the pregnant person need to be before someone is eligible for legal abortion?” Physicians worried about criminal prosecution are struggling with how to make that type of decision, he says.

China and scientific competitiveness

When asked about the economy, the candidates argued over tariffs. Trump touted tariffs that his administration put on goods from China, which he claims brought money into the economy. Harris clapped back that during his presidency, Trump was “selling American chips to China to help them improve and modernize their military.” The United States should focus on domestic innovation, she said, and that means “investing in American-based technology so that we win the race on AI and quantum computing”.

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Although it’s true that during the early part of the Trump administration US companies such as Nvidia in Santa Clara, California, were selling advanced semiconductor chips and high-performance GPUs to China, later on, such technology exports were subject to increasing restrictions, says Denis Simon, a non-resident fellow at the Quincy Institute for Responsible Statecraft, a foreign policy think-tank in Washington DC. The administration of Harris and current US President Joe Biden followed up with further restrictions, as well as the Chips and Science Act, which authorized more money for US research agencies to foster innovation and boosted domestic semiconductor manufacturing.

It was a missed opportunity that Harris didn’t talk about that, Simon says, though he still thinks she came out on top in the debate. Regarding China, though, he would have liked to hear either candidate detail a clear policy. “It is the second largest economy in the world,” Simon says. “What China does or doesn’t do is an important part of shaping the international landscape.”

The United States can’t cut itself off from China, says Caroline Wagner, a specialist in science, technology and international affairs at The Ohio State University in Columbus. “We’ve gained a lot by having China in the knowledge system. You can’t close the door without getting your fingers stuck in it.” The world also can’t make any meaningful progress on global-challenge issues such as climate change and food security if the United States does not have a collaborative relationship with China, Simon agrees.

Climate and energy

The two candidates were asked a direct question about climate at the end of the debate. Harris pointed to climate-related disasters and then touted the Biden administration’s historic investments in clean energy and advanced manufacturing. “We know that we can actually deal with this issue,” she said. Throughout the debate, however, Harris found herself on the defensive regarding oil and gas production and, in particular, the controversial ‘fracking’ technologies that have enabled companies to expand US oil and gas development. Although she once said that she was against it, she repeatedly emphasized her support for fracking while also indicating that she supports using a diversity of energy sources.

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Trump didn’t answer the question and instead talked about imports from China, ending with personal attacks on Biden. Earlier in the debate, however, he emphasized the need to boost fossil-fuel production and warned that a Harris administration would push the United States to depend on ‘windmills’ and solar-energy farms, which he claims occupy too much land and “are not good for the environment”. (It’s true that renewable energy facilities can have a significant environmental footprint¹, but researchers have argued that the damage wrought by the production and burning of fossil fuels, which cause millions of premature deaths annually owing to air pollution and are altering the climate², are far worse.)

Michael Mann, a climate scientist at the University of Pennsylvania in Philadelphia, says that there is room for growth in Harris’s approach to tackling climate change. In line with the Biden administration, she takes a ‘demand-side approach’ to reducing emissions by incentivizing renewable energy, which is “not enough,” he says. But she at least embraces the scientific consensus and acknowledges the “catastrophic impacts on human health”, while a second term for Trump, who once called climate change a hoax, “would be game over for climate action as we know it”, he says.

In terms of the energy and climate issues actually discussed during the debate, the biggest factor might well be the issue of tariffs and “the veritable arms race between the two parties to show who will be tougher on China,” says David Victor, a political scientist at the University of California, San Diego. This could drive up the cost of technology imports to the United States and disrupt clean-energy supply chains, he adds.

In the end, however, neither the candidates nor the debate moderators spent much time on the issue. “If this debate is a barometer of what will determine the election, it’s not climate and energy,” Victor says.