During a science budget hearing last month, we were surprised to hear certain congressmen bring up an issue we had never thought to worry about before. "I have been very concerned that we are not putting enough emphasis on trying to secure the world in case we would spot an asteroid heading toward the Earth," Representative Dana Rohrabacher (R-California) said. He wasn't alone in his anxiety: "I share the interest in planetary defense with Congressman Rohrabacher," Representative Bill Posey (R-Florida) later said.
That prompted quite a few questions on our end. Is the United States doing enough to protect the Earth from asteroids? Plus, Rohrabacher later said something that reminded us a lot of how environmentalists and climate change activists view their mission: "We have a bunch of young people here and we want you to have the world that we had." Yet both congressmen are known climate skeptics. Posey has called the idea that the planet's climate is now warming rapidly "speculative," while Rohrabacher maintains a webpage where he says "global warming is not man-made, if it is in fact even occuring [sic]." Both have voted to bar the Environmental Protection Agency from regulating greenhouse gases, and against legal limits to the U.S.'s emissions. Both sit on the House Committee on Science, Space, and Technology, where they oversee the budgets for NASA and the National Science Foundation.
These facts brought us to more questions: Why would men so clearly concerned about leaving a habitable Earth for future generations deny an important threat to it? What's the risk of Earth-destroying asteroids, anyway? How does it compare to climate change?
For answers, we consulted with some experts. "Climate change is going to happen," says Eric Wolff, an Earth scientist at the University of Cambridge who studies the planet's past climates by analyzing ice cores. On the other hand: "We can say there will not be any mass extinction event due to asteroid impact in the next several hundred years," says Michael Busch, a scientist who studies near-Earth asteroids at the SETI Institute. Busch referenced a NASA survey, completed in 2010, that identified 90 percent of space objects near the Earth that are greater than one kilometer in diameter—the size that's thought to be big enough to create worldwide effects. None are headed toward Earth any time soon. (A 1.1-kilometer object named 1950 DA does have a less than 1 percent chance of approaching the Earth in the year 2880.) The remaining few one-kilometer-or-bigger asteroids we have likely missed are currently on the other side of the Sun, which makes them difficult for telescopes to see. In the next few decades, they will make their way to Earth's side of the sun, at which time scientists will be able to observe and characterize them, Busch says.
Within each risk, there are specifics to consider. Scientists are sure the Earth will warm, but how bad will it be? If the world sticks to the Paris Agreement, from which the U.S. withdrew last year, the planet's average temperatures should rise less than two degrees Celsius. Since countries don't all yet have programs in place to achieve that level of warming, at least two degrees seems certain to happen. At those temperatures, people can expect to see changes in where crops can grow, hurting some farmers, and more frequent heat waves, which can kill thousands, if they hit big cities. Still, Wolff calls those effects "dangerous, risky, but they're not as catastrophic as if we get to four degrees" above the planet's averages from before the Industrial Revolution. At four degrees—the threshold the Earth will hit if humankind continues to emit greenhouse gases the way we are today—we'll see sea level rises that will make many coastal cities uninhabitable. Of course, either way, the world's poorest people will be hurt the most by these changes. "No matter how bad climate change is, in America and Europe, you can turn up the air conditioner," Wolff says. (Though vulnerable folks in the U.S. do still die of heat.)
With asteroids, there is a low possibility that objects less than one kilometer across, but still big enough to do serious local damage, will hit in the future. Smaller asteroid bits are much more common in space than big ones, but they're more difficult for scientists to detect ahead of time. In 2013, a 20-meter asteroid exploded in the sky above Chelyabinsk, Russia, releasing as much energy as more than 400,000 tons of TNT. The shock wave blew out windows over 200 square miles and injured more than 1,600 people, mostly from broken glass, according to NASA. NASA is funding a project designed to find Chelyabinsk-sized Earth impactors, and to give cities a day's notice, but mostly, the agency is focused on larger, more dangerous objects. In 2005, Congress directed NASA to identify at least 90 percent of near-Earth objects at least 140 meters in diameter by 2020. That survey is ongoing.
So it's possible that, some time before humans figure out how to predict and deflect it, a less-than-one-kilometer-wide, still-dangerous asteroid will hit the Earth in a populated area and cause injury or death—maybe a lot of deaths. It's just not likely, Busch says. A Chelyabinks-sized object reaches the Earth about once every 30 years, according to Busch, but they almost never enter the atmosphere in such a way that they threaten people. Compare that to the certainty that the planet will warm enough to cause deadly heat waves. In fact, scientists think that it's done so already.
So does the U.S. do enough to mitigate the risks of climate change and asteroids? As an asteroid, not a risk-benefit, scientist, Busch felt unsure about how to measure "enough," but, he says, "the U.S. is doing a lot" on asteroid risk. Meanwhile, the Trump administration is bent on doing nothing on the climate change risk and indeed, like Rohrabacher and Posey, is denying the danger is even real. Busch offered one way to think about it: Worldwide, nations spend about $100 million annually studying near-Earth objects and how to keep people safe from them. Given how many more people global warming is expected to hurt or kill in the near future, the world should be spending hundreds of billions on climate change mitigation every single year.
Why would lawmakers, who seem prepared to think about long-term dangers to Americans, nevertheless deny that climate change is an important risk? We cannot speak for the congressmen, but we quizzed everyone we talked to for this story. They came up with some interesting possibilities to explain a worldview that cares about asteroids, but is unconcerned about climate.
Wolff notes that asteroids could come for anyone—regardless of socioeconomic status. With climate change, however, the wealthy—particularly those living in developed nations—have far more resources to move or adapt to a warmed world. D.C. politicians might not be inclined to worry too much about it.
In addition, the actions people need to take to solve climate change are more uncomfortable than the fix for asteroid impacts, both Wolff and Busch say. Asteroid risk mitigation takes much less money. It also doesn't require people to make lifestyle changes, which Rohrabacher seemed disinclined to in a 2008 speech he gave about climate change. There, he talked about higher prices for airplane tickets, having to use public transportation, and having to eat less meat, all of which reduce individuals' contributions to climate change. "Heck, they won't even let us have a hamburger," his speech reads. "Of course, they don't want any of us to own automobiles; so what the heck."
Climate change, as a science topic, is politically polarized, while asteroid risk is not. That could lead people to prioritize taking climate change positions that fit in with their "tribe," says David Ropeik, a journalist and author of How Risky Is It, Really?: Why Our Fears Don't Always Match the Facts. "What researchers found is that the perception of risk has very little to do with the statistical odds or scientific facts say. It has to do with how we feel about those facts," he says. And when it comes to tribe loyalty, feelings run strong. Humans survived the vagaries of evolution by cooperating in groups, so fitting in with our people still helps us feel safe in a way nothing else can.
Busch brought up a possible reason for the politicization of climate change, but not Earth impactors. "There is notably no large industry invested in sowing misinformation about the asteroid impact hazard," he says. Journalists have documented how the oil companies Exxon and Shell knew for decades that fossil fuels lead to climate change—and then invested in making the science seem more uncertain than it was. But asteroids are not immune to politics or personal bias. Busch says he's heard stories from the 1990s, when scientists hadn't yet ruled out an Earth-ending asteroid, of "Cold War types" who argued against nuclear disarmament in case a big space object came around.
Figuring out real risk is hard for anybody. We've got our own evolution working against us, as well as larger interests that are difficult to navigate. Few congresspeople are scientists or statisticians and, arguably, they shouldn't all need to be. Then again, maybe we should expect more, at least from the leaders who help decide how Americans respond to science-based risks to our lives and others'.