The economic options for combatting climate change

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• GWEN IFILL:

  The federal government announced today that 2014 was the hottest year for the planet in the 135 years that records have been kept.

  Greenhouse gas concentration, land surface and sea temperatures all clocked in at historic levels.

  Economics correspondent Paul Solman explores a couple of climate change with the authors of a recent book on the subject. It's part of our weekly segment Making Sense, which airs every Thursday on the "NewsHour."

• MARTIN WEITZMAN, Harvard University:

  So, look, you can start to see erosion along here.

• PAUL SOLMAN:

  Economist Marty Weitzman thinks his property on a marsh in Gloucester, Massachusetts, is washing away due to climate change.

• MARTIN WEITZMAN:

  The water has risen a couple of inches in the time, in the 40 years I have been living here.

• PAUL SOLMAN:

  Right.

• MARTIN WEITZMAN:

  And what's happened is that it's caused erosion at the edge of the lawn.

• PAUL SOLMAN:

  Well, but a couple of inches doesn't seem like much.

• MARTIN WEITZMAN:

  Maybe that wouldn't be, but it's really a couple of feet that we're headed for.

• PAUL SOLMAN:

  A couple of feet, or conceivably, several dozen, says Gernot Wagner, a former student of Weitzman's who's now at the Environmental Defense Fund.

• GERNOT WAGNER, Environmental Defense Fund:

  Last time concentrations of CO2 were as high as they are today, we did in fact have sea levels up to 66 feet higher than today. Well, 66 feet and this house is gone.

• PAUL SOLMAN:

  Now, Weitzman and Wagner can't know for sure, of course, that manmade higher temperatures are rising the tides here or anywhere else, but a plausible probability of true catastrophe was enough to prompt "Climate Shock," about the dangers that lurk, dangers Weitzman wasn't worried about when he first went into environmental economics years ago.

• MARTIN WEITZMAN:

  I was wondering, how could it be possible that mere human beings could change the climate in a serious way?

• PAUL SOLMAN:

  But geologic samples of carbon dioxide going back millennia changed his mind.

• MARTIN WEITZMAN:

  We were way outside the historical range for at least 800,000 years, and we're climbing very strongly.

• PAUL SOLMAN:

  Today's higher concentrations of atmospheric carbon dioxide are shown here in red. And the historic correlation with high temperature implies, says Weitzman:

• MARTIN WEITZMAN:

  There's about almost a 10 percent chance of an increase of 4.5 degrees Centigrade.

• PAUL SOLMAN:

  And that's nine degrees Fahrenheit, roughly speaking?

• MARTIN WEITZMAN:

  Yes, something like that, and that would make outdoor living in many parts of the world impossible.

• GERNOT WAGNER:

  It doesn't sound like a lot, but think of the human body, right? If you have a fever of 4.5 degrees Centigrade, nine degrees Fahrenheit, you are dead.

• PAUL SOLMAN:

  But 10 percent, I mean, that is just one chance in 10. I have been at the racetrack long enough to know how rarely a 10-1 shot comes in.

• MARTIN WEITZMAN:

  Yes, but we — it's not that rare. You buy fire insurance for probabilities that are much lower than 10 percent. You buy car insurance for probabilities that are much lower than one in 10 over a lifetime.

  So, this is well within the range of things that we like to insure against.

• PAUL SOLMAN:

  OK, buy insurance against catastrophe. But how?

• GERNOT WAGNER:

  You price CO2. You price carbon dioxide.

• PAUL SOLMAN:

  You put a price on it?

• GERNOT WAGNER:

  That's the insurance premium, right? For every ton of CO2 we are emitting today, we cause at least about $40 worth of damages. When I board a cross-country flight to San Francisco and back, I emit about one ton of CO2, I personally, not the plane, just me personally. Meanwhile, I don't pay for that.

• PAUL SOLMAN:

  So you want the airline to charge an extra $40 on your ticket?

• GERNOT WAGNER:

  I want the government to put a price on CO2 that everybody pays, in order to set the right incentives.

• PAUL SOLMAN:

  But there isn't broad public support for taxing emissions.

  Meanwhile, a cheap, but controversial solution of last resort has emerged: a so-called geoengineering technique called solar radiation management, shooting particles into the sky to reflect sunlight back into space.

  Harvard environmental scientist David Keith.

• DAVID KEITH, Harvard University:

  The central idea is to make the planet a little bit more reflective, which tends to cool it down, because it will absorb less sunlight. And that will partially and imperfectly compensate for the buildup of greenhouse gases like carbon dioxide, which are tending to trap heat and make the Earth warmer.

• PAUL SOLMAN:

  Nature ran the experiment in 1991, when the eruption of Mount Pinatubo in the Philippines lofted a 20-million-ton sulfur dioxide cloud into the stratosphere, lowering global temperatures by a full degree Fahrenheit for two years.

  And mimicking the volcano's effect by spraying sulfates is relatively cheap, says Wagner.

• GERNOT WAGNER:

  It's somewhere between $1 and $10 billion to literally fly like Learjets 24/7, enough of them, to decrease global average temperatures back to where they were pre-industrial times.

• PAUL SOLMAN:

  But if the clear and future danger of climate change is some chance of calamity, what could sulfur particles in the stratosphere do? The premise of the sci-fi film "Snowpiercer," starring a train that circles the Earth with the last living humans, is a dramatization of skeptics' worst fears, a coolant shot into the upper atmosphere that freezes Earth.

• ACTOR:

  Dead, all dead.

• PAUL SOLMAN:

  Weitzman and Wagner have their own scare scenario: a rich, rogue geoengineer.

• ACTOR:

  Man has climbed Mount Everest, gone to the bottom of the ocean, achieved miracles in every field of human endeavor, except crime.

• PAUL SOLMAN:

  As James Bond's arch nemesis, Goldfinger, easily dispersed gas over Fort Knox, Weitzman and Wagner imagine a Greenfinger, sending 100 planes around the Earth around the clock.

• DAVID KEITH:

  I think it's very implausible that it would be done at large scale by a single person, a Goldfinger.

• PAUL SOLMAN:

  But, says Keith, countries could certainly do it. And if temperatures keep rising, some might ask, why not, risks be damned?

• DAVID KEITH:

  The big risks of this technology fundamentally aren't technical. They're political. They're the risk of how it gets used in a divided world. There's the basic question of how we set the thermostat in a world where we have many different countries and many different interests, and it's really cheap to adjust the thermostat.

• PAUL SOLMAN:

  With emissions rising, Keith and his colleagues are researching technical dangers, depleting the ozone layer and changes in weather patterns among them.

  They think geoengineering could become a desperation fallback. Consider the latest call for action from Pope Francis.

• POPE FRANCIS, (through interpreter):

  This home of ours is being ruined, and that damages everyone, especially the poor.

• PAUL SOLMAN:

  In his recent encyclical, the pope made the moral case for reducing the use of fossil fuels and for rethinking current definitions of economic growth. Scientist Keith agrees.

• DAVID KEITH:

  Even if I knew that stopping climate change would make the world on average a few percent poorer in 2100, I would still be in favor of stopping climate change.

  And that's because I want to leave future generations with a chance to enjoy the natural world more as I do. And that is fundamentally an ethical or moral or naturalistic view about the world that isn't easily captured in the equations of economists.

• MARTIN WEITZMAN:

  This was once a red cedar.

• PAUL SOLMAN:

  But Weitzman thinks there's an economic case for climate action, too, since, in the long run, the benefits to society of cutting emissions far outweigh the short-term costs. Meanwhile, the costs of inaction seem to be inching ever closer to home.

• MARTIN WEITZMAN:

  So here is a wooden walkway that has been lifted up by high tides that will come over it. That took a while to develop this curve, due to the pushing up of the water and the higher level of water.

• PAUL SOLMAN:

  So you mean this was flat before?

• MARTIN WEITZMAN:

  Yes, yes. When it was constructed, it was flat. Careful.

• PAUL SOLMAN:

  It isn't anymore.

  This is economics correspondent Paul Solman, reporting for the PBS NewsHour, from Gloucester, Massachusetts.