Over a five-decade career, climate scientist

became a foremost champion for climate change activists, who see him as a fearless truth teller, and a bête noire for global warming skeptics, who see him as a rash alarmist.

Hansen, 72, stepped down this month from

. He's speaking at the Portland Center for the Performing Arts Thursday night, part of the international speaker series from the

Hansen was one of the first scientists to sound unequivocal warnings about global warming, telling Congress in 1988 that it had begun. Since 2009, he's been arrested or cited several times at climate change protests, which he attended on NASA vacation time.

A registered independent, he has also alarmed many environmental activists, supporting nuclear power and speaking out against carbon tax plans that would shift money to the government.

In an interview this week, Hansen discussed the importance of raising prices on carbon, his plans to support lawsuits past and future – perhaps including suits against coal export to Asia from Northwest ports – and his fear of Democrats. Excerpts, edited for brevity and clarity:

Q: Why did you leave NASA?

A:

To avoid administrative duties and the government bureaucracy, which takes quite a bit of time – I hope I will have more time for science, not less. Activism is a second reason. I want to be able to testify in cases

is filing against the federal government and state government, and a government employee can't testify against the government. It just was inappropriate to stay as director when in my heart the emphasis is really to help address this climate change problem, rather than leading NASA research.

For tickets

Check with the

for ticket information

Q: Is the United States taking climate change seriously enough?

A:

In general, no. The current administration does say some of the right words about the fact we have a planet in peril and we need to take actions. But so far they're not effective. Improving vehicle efficiencies and EPA regulation on power plant emissions is useful. With the economic slowdown, U.S. emissions have declined. But if all you do is reduce your emissions, one effect is to reduce demand for fossil fuels, which lowers the price, and somebody else will burn it.

Q: What do you think should be done?

A:

We have to actually increase the costs of fossil fuels, and that is appropriate because presently they're subsidized and they do not include the costs to society, including the health effects of air and water pollution and the climate effects. If your child gets asthma, the fossil fuel industry doesn't pay. Or if there's a natural disaster, the bill is paid by the taxpayer, not the fossil fuel company.

Q: How would you increase costs?

A:

A (gradually increasing) carbon fee. It should be across the board and collected at the source, a domestic mine or port of entry. Money should be distributed to the public, a dividend in equal amounts to all legal residents. If we did that, there'd be a big incentive to limit fossil fuel use so you would get more in a dividend than you pay in increased (fuel) prices. Entrepreneurs would have opportunity to develop low-carbon or no-carbon energy sources and improve energy efficiency. It would spur the economy, make our technology more up to date and put us in a leadership role.

Q: Can that fly politically? Gas prices are a hot button already.

A:

We've had some success in persuading conservatives that this makes sense. If we're going to get a change in policy, it needs to, if not come from conservatives, at least have a strong endorsement from conservatives. It should not enlarge the government. That's why I'm a little afraid of Democrats. (U.S. Sens. Barbara Boxer and Bernie Sanders) introduced a bill, but it gave 40 percent of the money to the government, which means most people would not get more in their dividend (than they paid in increased fuel costs).

Q: Why are politicians reluctant?

A:

It's almost entirely due to the fossil fuel industry, which directly has an effect via its lobbying and the money it pours into Washington and state capitals. There's also the indirect effect of all the money they put in advertising. They have the public believing that things like (oil from

will create jobs. Compared with the economic development that would be spurred by gradually increasing carbon prices, the jobs associated with the (Keystone) pipeline are small and short term.

Q: The Northwest is debating whether to build shipping terminals to export coal to Asia. What do you think?

A:

It's analogous to the tar sands pipeline. Science makes it clear that the easily available oil and gas is enough to put us up to the limit of what we can put in the atmosphere ... without our children and grandchildren inheriting a situation that's out of their control. What that means is we can't burn most of the coal. (Natural) gas can be a transition fuel, but as long as there's no carbon fee, there's no limit.

Q: Global temperature has been relatively flat since 1998, despite rising C02 levels. Does that undermine warming predictions?

A:

The fact

in the last decade is partly due to natural forcings: We just completed the deepest solar minimum since the 1970s. We had the strongest El Nino in 1998, and then two strong La Ninas. There have been a few modest volcanoes contributing stratospheric aerosols (which cool the atmosphere). S02 (sulfur dioxide, an aerosol) continued to increase up until 2006 because of China's increased coal burning. When you add up the effects it's not surprising that temperatures have been flat in the last decade. We know more energy is coming in than going out (and) ocean heat content is increasing. The next decade is going to be warmer than the last, just as each decade has been for the last three or four decades.

Q: What about the effects of increased plant growth from higher levels of C02?

A:

Some carbon is being taken up by increased growth because of the fertilization of CO2 in the atmosphere and the nitrogen we're spreading around, which is a pollutant but in dilute amounts a nutrient for plant growth. But there's a limit to how much the biosphere can take up, and we've actually removed some by deforestation. The fact is fossil fuel carbon will stay in the surface climate system for millennia.

Q: What are the most certain climate change effects showing up now?

A:

Mountain glaciers all over the planet are melting, and the arctic sea ice in the summer has (dropped) almost half at the end of the melt season. What's most worrisome is the rapid acceleration of the mass load loss of both the Greenland and West Antarctic ice sheets. We've only really had precise data since 2003. But if that continues, it means we will get a multi-meter sea level rise this century. It's just a recognition that the climate dice are loaded.

Q: Is global warming causing specific droughts and extreme weather events?

A:

What you cannot blame on global warming is the location of individual events. In each case, you can look at meteorological situations and say they happened because of weather patterns, the distribution of sea level temperatures. But the point is that those blocking situations have always occurred. Now what we're seeing is an increase in intensity. Droughts are more intense. Scientists will say we can't blame global warming for any single event. In a sense that's right, but the fact that the frequency and intensity of these events is increasing you can blame on global warming

Q: What do you think is reasonable to expect by 2100 if we stay on the current emissions path?

A:

We would have passed the point where events would be burning out of control. For example, the ice sheets would be disintegrating and sea level would be going up and the shoreline would no longer be stable. When you get a sea level rise of a few meters, most coastal cities may be partly underwater. Climate zones would be shifting so rapidly it would combine with other pressures we're putting on species and drive extinctions in significant numbers. We really can't go down that path. I'm quite sure and hopeful we will realize that. But we better do it soon because we're running out of time.

Q: What's your plan for the future?

A:

I have submitted a major paper I've been working on the past few years, which provides the prescription for what's needed to stabilize the climate and the rationale for the lawsuits filed or being filed by Our Children's Trust. It will also be useful for the actions that are intended to try to block the expansion of coal exports on the West Coast and efforts to block the tar sands pipelines. I'm hopeful it will be accepted in a period of weeks, then I will use it for those specific purposes.

-- Scott Learn