The Evolution Of An Eco-Prophet

If a good gauge of Gore's enthusiasm for something is how voluble and technical he gets, then you can be sure that he loves biofuels. There is some irony in that, since biofuels were the subject of his worst political mistake on the environment. As vice president, he cast the tie-breaking vote in the Senate in 1994 to institute an ambitious federal ethanol program even though, he admits in the book, "there were already ample warnings" that production of corn ethanol is responsible for more greenhouse gases than the gasoline it displaces. But next-generation biofuels are a different story, he says. "The pathway that I think is likely to be the winner is enzymatic hydrolysis, which essentially uses engineered enzymes to break down the cellulose, the lignin, into fermentable compounds that would then yield many more liters per hectare than any of the first-generation ethanol options," Gore tells me. "I think it's going to play a significant role … One of the many advantages of third-generation biofuels is that they can yield fuels like biobutanol that don't have any blending problems. You just burn them directly. Enzymatic hydrolysis, if I can make another point about that: there is no theoretical upper limit to how efficient they can become. So I think there might be some pleasant surprises on enzymatic hydrolysis."

Gore loves plants and soils as only a former farm boy can (well, a summertime farm boy: as a kid he spent the school year in Washington, where his father was a senator). He regales you with numbers: more CO2 is emitted from burning and destroying forests—20 to 23 percent of the annual total—than from all the world's cars and trucks; only by the 1980s did CO2 from fossil fuels overtake that from deforestation, which accounts for 40 percent of the CO2 increase since the 1800s.

The potential for soils to absorb more of the CO2 that our utilities, factories, and vehicles spew poses a dilemma for Gore, one of two where his scientific and political instincts collide. With better management, soils could sequester much more carbon than they do now. The question is how much more. Soils scientist Rattan Lal of Ohio State University was surprised to get a call last summer ("Vice President Gore would like to talk to you") that began, "I have 15 or 20 questions about soils and climate for you." Lal calculates that if more farmers adopted mulching, no-till farming, and the use of cover crops and manure, 3,700 million acres worldwide could sequester 1 gigaton per year of CO2, roughly 12 percent of annual global emissions. Other experts are even more sanguine. "If we feed the biology and manage grasslands appropriately, we could sequester as much carbon as we emit," says Timothy LaSalle, CEO of the Rodale Institute, who presented at two summits. The political clash is this: if you tell people soils can be managed to suck up lots of our carbon emissions, it sounds like a get-out-of-jail-free card, and could decrease what little enthusiasm there is for reducing those emissions—as one of Gore's assistants told LaSalle in asking him to dial down his estimate. (He didn't.)

To his credit, Gore sides with the science, letting the political chips fall where they may. He writes that soils could sequester an additional 15 percent of annual global CO2 emissions from fossil fuels. That could cut 50 parts per million of CO2 from the atmosphere over the next 50 years. (We are now at 387, up from 280 before the industrial era, with 450 ppm or even less a dangerous level.) To encourage changes in agriculture that would foster carbon sequestration, Gore advocates moving away from price supports and toward paying farmers for "how much carbon they can put into and keep in their soil," he says. Paying farmers to sequester carbon might jump-start the use of biochar, which Gore calls "one of the most exciting new strategies for restoring carbon to depleted soils, and sequestering significant amounts of CO2." Biochar, which he learned about during a 1989 trip to the Amazon, is basically porous charcoal. Made by burning switch grass, corn husks, and other waste, it can absorb CO2 like a charcoal filter in a cigarette absorbs gases. Gore estimates that biochar could sequester 40 percent of annual CO2 emissions.

The other issue where science could be an inconvenient truth for climate politics is the basic question of what is causing the greenhouse effect. Earlier this year Gore phoned two scientists at NASA's Goddard Institute, which is above the Manhattan coffee shop where the Seinfeld characters hung out. Drew Shindell, Schmidt, and colleagues run state-of-the-art computer calculations on how much various greenhouse gases contribute to global warming. The relative impact of each, they were finding, was different from what simpler models had suggested. As they reported last week in Science—findings that Gore got hold of last spring—methane accounts for about 27 percent of the man-made warming so far, largely because of how it interacts with atmospheric aerosols. Halocarbons have caused 8 percent of the warming; black carbon (sooty emissions from burning wood, dung, and diesel), 12 percent; carbon monoxide and volatile organics, 7 percent—and carbon dioxide, 43 percent.

Depending on your bent, you can append an "only" to that last number. On the one hand, the NASA calculations provide a glimmer of hope. Reducing CO2 emissions strikes at the lifeblood of the global economy—namely fossil fuels, which provide 86.5 percent of the world's energy. But targeting other greenhouse gases is "likely to be much more cost-effective than CO2-only strategies," the NASA team writes in Science. For example, methane emissions could be cut by changing farm practices and by capturing the huge quantities that are flared at oil wells. And "removing one ton of black carbon will have the same [climate] effect as removing 2,000 to 3,000 tons of CO2," says climatologist Veerabhadran Ramanathan of the Scripps Institution of Oceanography, who talked to Gore for hours about it. "The technology is there—you can buy a $250 diesel filter for your Mercedes—and the beauty of black carbon is that if you cut it today, it's gone in a month because rain causes it to fall out. [CO2 stays up for decades.] By going after other greenhouse gases we can buy the planet time, postponing by 30 to 50 years the day when warming exceeds 2 degrees." At 2 degrees, sea-level rise, droughts, floods, and other climate disasters will likely kick in with a vengeance.

On the other hand, the prospect of what Schmidt calls "this low-hanging fruit, which may be bigger than we think," could—like biochar—diminish enthusiasm for cutting CO2. Does that worry Gore? "Over the years I have been among those who focused most of all on CO2, and I think that's still justified," he says on his patio. "But a comprehensive plan to solve the climate crisis has to widen the focus to encompass strategies for all" of the greenhouse culprits identified in the NASA study.