Many of the greatest challenges the U.S. faces in coming years—from climate change to the spread of antibiotic-resistant bacteria—require scientific expertise to develop workable solutions. For the past eight years, nonprofit organization has spearheaded a grassroots effort to push presidential candidates to discuss these issues, which are every bit as important to America's future as international affairs or tax policy. This year the campaigns of the Democratic and Republican nominees have once again provided answers to 20 questions developed by leading scientific, engineering, health and other groups.

Four years ago Scientific American graded the answers given by Barack Obama and Mitt Romney on a 0-to-5 scale based on direct and complete answers; scientific accuracy; feasibility; sustainability; and potential benefits to health, education and the environment. We determined that the 2012 candidates were within striking distance of each other on most of their responses.

This year is a different story. Below are two questions, summaries of Hillary Clinton's and Donald Trump's answers, and our critiques.

Climate Change

Earth's climate is changing, and political discussion has become divided over both the science and the best response. What are your views on climate change, and how would your administration act on those views?

CLINTON acknowledges that “climate change is an urgent threat and a defining challenge of our time.” She then outlines a plan to “generate half of our electricity from clean sources,” to cut “energy waste” by a third and to “reduce American oil consumption by a third” over the next 10 years. To achieve these goals, she plans to “implement and build on” current “pollution and efficiency standards and clean energy tax incentives.” Clinton loses a point for not describing where she will find the money to pay for such initiatives.

TRUMP refers to “climate change” with quotations marks, supposedly to signal that he still believes—as he has asserted in the past—that human-caused global warming is a hoax. He has vowed to withdraw from the Paris climate accord and suggests that “our limited financial resources” are best spent on clean water and antimalaria efforts—without acknowledging that the success of both also depends on how climate change is addressed.

Public Health

Public health efforts such as smoking cessation, drunk driving laws, vaccination and water fluoridation have improved health and productivity and saved millions of lives. How would you improve federal research and our public health system to better protect Americans from emerging diseases and other public health threats, such as antibiotic-resistant superbugs?

CLINTON argues that “we are not investing in public health preparedness and emergency response the way we should” and backs up her claim with evidence showing that spending on public health has “fallen more than 9 percent since 2008.” She says she plans to tackle the problem in part by creating a “Public Health Rapid Response Fund” that offers “consistent, year-to-year budgets, to better enable” public health officials “to quickly and aggressively respond to major public health crises and pandemics.” Clinton loses a point for not detailing how much money she thinks the rapid response budget should contain or how it will be funded.

TRUMP suggests that “in a time of limited resources” public health spending may not provide “the greatest bang for the buck.” In fact, studies show that public health efforts typically offer returns on investment of between 125 and 3,900 percent, depending on the program. Trump offers no indication that he has grappled with the issue in any detail. He also states that he will work with Congress to make sure that “adequate resources are assigned to achieve our goals”—not noting that Congress has still declined, as of press time, to approve money to deal with the Zika threat that has emerged in the southern U.S.*

Full responses to all 20 questions—including those from Green Party candidate Jill Stein and Libertarian Party candidate Gary Johnson—as well as our evaluation of them are available at

*Editor's Note (10/17/16): Since publication, Congress has approved $1.1 billion in Zika funding (on September 28)—seven months after Pres. Obama requested the aid.