Future generations face sea-level rises of 18 to 27 feet, extinction of 30 percent to 50 percent of animal species and other catastrophes if carbon-based fuels continue to be used at the same rate as today, a climate scientist told a group at the Santa Fe Institute on Thursday.

James Hansen, physicist, astronomer and adjunct professor at Columbia University’s Earth Institute, said average temperatures have risen eight-tenths of a degree centigrade over the last century, and efforts to stem climate change will be ineffectual as long as fossil fuels remain the cheapest form of energy.

“They’re not really cheapest,” he said. “They only appear to be cheapest because we don’t make them pay for their costs. We actually subsidize them to protect them. We don’t make them pay for the human health effects … and climate change.”

Hansen proposed a new tax for carbon emissions from oil, gas and coal, collected at the wellhead, mine or port of entry, increasing $10 per ton annually for 30 years, with proceeds distributed directly to the public, which in a decade would mean $2,000 to $3,000 per resident, or $6,000 to $9,000 per family.

“About 60 percent of the people would get more in this dividend than they would pay for the increased price of everything, but it would do it in a way they would want to,” he said. “So, for example, if you get your food from the farm next door as opposed to importing it from New Zealand, as this tax gets higher, it’s not going to make sense to import your food from New Zealand.

“This would affect your lifestyle and you could make changes. When you get your new car, you better consider a more efficient one. … Are you going to commute 50 miles a day every day?”

Hansen said economic modeling has shown that such a system would decrease carbon-fuels use by 30 percent — 11 times the amount that would carried by the Keystone pipeline from Canada’s tar sands to Texas refineries. But he said today’s politics, influenced by energy companies, bodes against such a system.

He said when he spoke about this idea with John Kerry, former Massachusetts senator, 2004 Democratic presidential nominee and now secretary of state, Kerry told him, “Well, of course, you’re right, but that’s politically nonviable. … I can’t get one vote in the Senate for that.” Instead, Democrats propose “3,000 pages of this cap and trade with offsets, which gives the big banks marvelous opportunity to make huge amounts of money on the fluctuating cap-and-trade market,” Hansen said.

Even the hybrid version of a carbon tax proposed recently by U.S. Sens. Barbara Boxer, D-Calif., and Bernie Sanders, I-Vermont, is faulty because 35 percent of the money would go to deficit reduction, Hansen said.

“Government shouldn’t be making decisions as to what the next energy sources are,” he said. “Let the marketplace make the decision. We’ve got to the point that our government is so incompetent that the Energy Department does not develop the next generation of nuclear power.

“Bill Gates is financing the fourth generation of nuclear power out of his own pocket because that’s the only hope of doing it on a time scale that would help with this problem of climate change. So he’s going to build his reactor in South Korea. He can’t build it in the United States because of the way our government works. The [Nuclear Regulatory Commission] has become too much, in effect, antinuclear, making it so difficult that you can’t advance the technology.”