As planet warms, scientists explore ‘far out’ ways to reduce atmospheric CO2

JUDY WOODRUFF: As we heard, there’s been some
debate on Capitol Hill about how to tackle climate change, but the expectation is that
very little legislation is going to pass in the foreseeable future. And yet climate change’s impact is growing
around the world. The federal government’s own assessment found
climate change is already costing the U.S. hundreds of billions of dollars and having
a major effect in parts of the country. Some researchers argue the problem is getting
so serious that it’s time to start exploring ideas that have long been seen as far out
and potentially loaded with other problems and consequences. But these scientists say the times demand
new approaches to lower the Earth’s temperature. Miles O’Brien is back with this story. It’s part of our Breakthroughs, reports for
our regular series on the Leading Edge of science. MILES O’BRIEN: Engineer David Keith has run
the numbers on climate change, and for him the bottom line presents a stark reality. DAVID KEITH, Harvard University: Even if we
eliminate emissions, we simply stop the climate problem getting worse. We don’t make it any better. MILES O’BRIEN: The planet is already in trouble
. There is too much carbon dioxide in the atmosphere, and human civilization is doing
precious little about it. As you can see, these trend lines have a lot
of inertia. So even if we stopped using all fossil fuels
tomorrow, there’s still so much carbon dioxide in the atmosphere that the problem will persist
for decades. DAVID KEITH: We do need to drive emissions
to zero, but we also need to reduce the risk from the CO2 that’s in the air. MILES O’BRIEN: So Keith is asking some big
questions, like, what if we could suck carbon dioxide out of the air? It may sound like an impractical idea, but
he has some proof of concept. It’s a prototype plant in Canada built by
Carbon Engineering, a company Keith founded. It extracts carbon dioxide out of thin air. The pure CO2 is then combined with hydrogen
to synthesize fuels, gasoline diesel or aviation kerosene. Choose your grade. DAVID KEITH: That fuel didn’t come from the
ground. All the carbon that you released burning it,
you took from the atmosphere when you made it. So, in the net, there’s no carbon emissions. And that’s a way to help decarbonize. MILES O’BRIEN: So what if we don’t decarbonize
and reduce greenhouse gas emissions fast enough to avoid dire consequences? David Keith is leading research into a drastic
measure to turn down the global thermostat. It’s called solar geoengineering. The idea? Inject large quantities of sulfur dioxide,
or maybe another aerosol, into the stratosphere using high-altitude aircraft. This should lower global temperatures by reflecting
sunlight away from our planet. It sounds like an idea hatched by a James
Bond villain, and David Keith is keenly aware of that. DAVID KEITH: Geoengineering seemed like a
bit of a crazy idea. But there was a taboo. And I think taboos are unhealthy. And my view is, we should understand it better
to see just how crazy it really is. MILES O’BRIEN: Indeed, he’s been exploring
this idea since 1989, and, over the years, it’s made him a bit of a scientific pariah. DAVID KEITH: Senior colleagues would tell
me this would ruin my career or people would kind of like want to move away from me in
the elevator. This topic was just toxic, and the mainstream
climate science community just didn’t want to talk about it. MILES O’BRIEN: He may not have had scientists
on his side, but nature has been running solar geoengineering experiments for millions of
years, in the form of volcanic eruptions. When the really big ones blow, they launch
sulfur dioxide into the stratosphere, six to 30 miles above us. DAVID KEITH: It gradually turns into aerosols. It turns into small droplets, liquid droplets
of sulfuric acid, and those droplets reflect away sunlight. And that reflection of sunlight cools the
climate, and we see that after big volcanic eruptions. MILES O’BRIEN: When Mount Pinatubo blew its
top in 1991, global temperatures cooled one degree Fahrenheit over the subsequent 15 months. David Keith thinks humans can do the same. DAVID KEITH: If we decide to maintain the
taboo and not have a serious research program, then what we give to our kids is ignorance,
and they will still make decisions, but they will make decisions without knowing. MILES O’BRIEN: Maybe that’s why the snicker
factor is starting to fade. PETER FRUMHOFF, Union of Concerned Scientists:
We’re not going to limit the risks of climate change to even reasonably safe levels by reducing
emissions from burning fossil fuels alone. MILES O’BRIEN: Climate scientist Peter Frumhoff
is director of science and policy at the Union of Concerned Scientists. PETER FRUMHOFF: And so, therefore, we’re looking
at a whole range of hard choices about how to pull carbon dioxide potentially out of
the atmosphere at scale, and maybe, just maybe, to begin to think about mimicking volcanoes
by injecting reflecting particles into the stratosphere. That’s a terrible idea, but people are beginning
to give it some attention. DAVID KEITH: Yes, it’s really changing. Suddenly, many more of the kind of the environmental
leadership and sort of science policy thought leadership take this seriously. It really feels very different even from a
year ago. MILES O’BRIEN: But the devil, as always, lurks
in the details. One of the big questions, could it make the
climate worse in some places, better in others? PETER FRUMHOFF: It has all kinds of unclear
ramifications. We don’t know what the regional changes in
rainfall patterns might look like. MILES O’BRIEN: That’s just one of the possible
unintended consequences of solar geoengineering. Other questions: How would it affect agriculture? How would any aerosol interact with the gases
already present in the stratosphere? And could there be some unwelcome byproducts? That’s what David Keith and his colleague
Frank Keutsch are trying to determine. In the lab, they are testing various aerosols
to see how they might behave in the stratosphere. Sulfur dioxide may be a good reflector, but
it also reacts with and reduces the ozone layer and causes acid rain. So they are considering alternatives. The leading contender? Calcium carbonate. FRANK KEUTSCH, Harvard University: These calcium
carbonate particles certainly will not have the same chemistry as these concentrated sulfuric
acid particles. What we don’t know is, how do they actually
react? Because it could be that they react even worse. MILES O’BRIEN: To find out, they are planning
an atmospheric experiment called SCoPEx. No launch date is set, but whenever it flies,
they hope it will answer some important questions. This is an artist rendering of the SCoPEx
experiment. And next to me, it’s pretty impressive, kind
of big. But, of course, relative to the size of the
atmosphere, it’s minuscule. Above me is a high-altitude balloon, and right
now it’s lifting SCoPEx to the upper reaches of the atmosphere. It will rise into the stratosphere, about
twice the height of where airliners fly. Once SCoPEx is here in the stratosphere, it
will release a small amount of calcium carbonate. The onboard propellers mix the experiment
into a plume less than a mile in length. DAVID KEITH: This is a tiny-scale thing. We’re talking about injecting less than a
kilogram of aerosols. This in no way alters the climate. It’s simply a scientific experiment to improve
our knowledge of how some future aerosol injection scheme might alter the climate and impact
the chemistry of the stratosphere. MILES O’BRIEN: But just to be sure, an independent
panel of scientists will review everything before launch. They will evaluate the potential risks, along
with the reward. The data, as well as the lessons learned,
could be huge. Now the particles are interacting with sunlight
and the atmosphere. As the experiment plays out, SCoPEx isn’t
far away. When the time is right, the gondola is lowered
right into the mix. Here, a suite of sensors will determine chemical
composition and reflective properties of the plume. The experiment’s done — there goes the parachute
— and this valuable data is on the way home. SCoPEx is a small-scale experiment designed
to test some of the unintended consequences of a really big idea. But perhaps the greatest unintended consequence
of geoengineering might be in the realm of psychology. If we know we can do it, will we use it as
an excuse not to reduce our fossil emissions? For the “PBS NewsHour,” I’m Miles O’Brien.