JEFFREY BROWN:And now a resignation brings an assessment of President Obama's environmental policies in his first term and a look ahead to his second.

LISA JACKSON,Environmental Protection Agency: I'm very proud to be a part of his administration.

JEFFREY BROWN:She's been the president's point person on the environment for four years, but, today, Lisa Jackson announced she's stepping down as administrator of the Environmental Protection Agency.

In a statement, Jackson said, "I will leave the EPA confident the ship is sailing in the right direction."

Jackson's tenure was defined in part by efforts to curb carbon emissions. In 2009, she formally declared greenhouse gases, including carbon dioxide, a threat to public health.

That same day, she spoke on the NewsHour.

LISA JACKSON:I join the president in calling for clean energy and climate legislation. And that's because I think having economy-wide legislation sends an unequivocal signal to the private sector that we really mean it, that we're moving towards green energy.

JEFFREY BROWN:But a bill to cap greenhouse gases foundered in the Democratic-controlled Senate and never made it to the president's desk.

Jackson also pushed a rule to reduce smog, but it faced bitter opposition from Republicans and industry over the cost and potential effect on jobs. And, last year, President Obama ordered it withdrawn.

Still, environmental groups praised Jackson for shepherding the first-ever national standards governing power plant emissions of mercury and other toxic pollutants.

On her watch, the president also signed new fuel economy standards, doubling average gas mileage for new vehicles to more than 54 miles per gallon by 2023.

And Jackson helped persuade the administration to delay the Keystone oil pipeline, designed to bring oil from Canada to refineries in Texas.

We debate the Obama administration's environmental record under Jackson's tenure with Michael Brune, executive director of the Sierra Club, one of the oldest environmental groups in the country, and Kenneth Green, senior fellow on energy and natural resources for the Fraser Institute, a Canadian-based think tank.

Michael Brune, let me start with you, a quick overview first. Four years in, has the Obama administration has the Obama administration achieved what you had hoped for?

MICHAEL BRUNE, Sierra Club: Four years in, the Obama administration has done a great job.

And they do have some unfinished business. But when you look at doubling the vehicle efficiency in just four years, that's a remarkable achievement. Taking the amount of mercury and arsenic and dioxins and other air toxics out of the atmosphere from coal-fired power plants, that's an amazing victory.

And when you add on top of that the rule that was just announced last month to limit the amount of soot coming from power plant facilities across the country, those are just three rules among dozens that have had a big impact on keeping our air clean, our water safe and starting to reduce greenhouse gas emissions, so it's a good record to build on.

JEFFREY BROWN:All right, let me ask you Kenneth Green.

What's—well, Kenneth Green, what's your overview?

KENNETH GREEN, Fraser Institute: I think that when history looks back, it won't give Lisa Jackson a particularly good record as EPA administrator, for, when she came in, she was overshadowed somewhat by Carol Browner, who was a czar at that point, who is actually the one who gets the credit for the fuel economy standards, I believe.

And she's maintained a very adversarial relationship with industry. The EPA's culture of anti-industry, anti-business mentality continues.

And so it was under Lisa Jackson's watch that we had somebody saying that we're going to crucify some companies to set examples—an EPA regional administrator—that we're going to crucify companies in order to set examples and terrorize them into doing what we want.

JEFFREY BROWN:Crucify and terror?

KENNETH GREEN:Crucify and terror.

And so this is the kind of culture Lisa Jackson has overseen. Now, she's gotten some regulations through, but she also was publicly slapped back on the ozone standard in a way that it is inconceivable Carol Browner would have stayed in as head of the EPA if she had gotten brushed back that badly.

JEFFREY BROWN:Well, Michael Brune, you focused on some of the successes. There seem to be cases where Lisa Jackson wanted to go further than the president or White House advisers were willing to go.

MICHAEL BRUNE:Yes, I think that that's probably—probably true.

But, look, we have to acknowledge, if history has any judgment on the last term, what history will say is that we are living in historically partisan times, and it's just not possible for any member of the administration to not get attacks, certainly from the fossil fuel industry and certainly from members of the Republican Party.

But if you look carefully at what Lisa Jackson and the entire EPA was able to accomplish in just four years, and if you compare that to the eight years of the Bush administration, and if you can compare it to almost any—almost administration since EPA was created more than 40 years ago, you would say, fairly, that this has been an outstanding four years.

JEFFREY BROWN:And you're saying that in...

MICHAEL BRUNE:The result of that—well, the result of that is that thousands of lives are being saved every year. The quality of life for millions of Americans has been raised because our air is a little bit cleaner, our water is a lot cleaner, and now we have got a real shot at reducing greenhouse gas emissions. That's a record to be proud of.

JEFFREY BROWN:Kenneth Green?

KENNETH GREEN:Well, these trends of environmental improvement have been set for 35 years or better. Our air is getting cleaner and our water is getting cleaner as much because our technology is getting better as because we keep ratcheting down air standards from clean to super-clean to ultra-clean to pure.

This is one of the problems EPA—that also has come up over the last four years, is that EPA has played fast and loose with its benefit calculations, the claims it makes with regard to the benefit of these new rules.

JEFFREY BROWN:So, you're questioning whether they have actually accomplished what they say they have accomplished?

KENNETH GREEN:Whether the benefits of the regulation will be what they promised and whether the cost will be as low as they have estimated.

Outside analysts have looked at their methodology, and EPA seems to consistently overclaim benefits, health benefits especially, and underassess the cost to their regulations and the economic impacts that Americans will face in years to come.

JEFFREY BROWN:But what about this partisanship notion that Michael Brune brought up, that, in this political atmosphere, that's inevitably what's going to happen, and that's what she faced and what the administration faces?

KENNETH GREEN:I think that's a fair assessment.

But I would have to say she gave as good as she got. And when the administration came in, they set a certain tone. They said they were going to be the most transparent administration ever.

And then how did they do the vehicle fuel economy standards? In closed-door session, where no notes were allowed to be taken to record the series of events, usurping the traditional route of setting CAFE standards through the National Highway Traffic Safety Administration.

So, if there's credit to be given for polarization and partisanship, both sides get their share.

JEFFREY BROWN:Is that fair, Michael Brune?

MICHAEL BRUNE:No. We're reaching a level of silliness here. EPA has had countless public hearings to talk about those vehicle standards. I testified at one.

And, Kenneth, you probably should have done the same.

But let's look at the results. As a result of this standard, in which more than a million comments were submitted, by the way, as a result of this standard, consumers will save money at the pump, we will reduce our dependence on oil by several million barrels of oil per day, and this one rule will do—will cut greenhouse gas emissions by 10 percent economy-wide when it's fully implemented.

That's a huge victory. That's a huge victory. And it was done through a lengthy process that EPA drove. So, this has been...

MICHAEL BRUNE:Go ahead.

JEFFREY BROWN:Well, no, I just want to try to end by a little looking forward here.

And you can start, Kenneth Green.

What do you see as the biggest priority either to push forward or to stop, in your case, perhaps, in the coming -- in the next term?

KENNETH GREEN:Well, I think there's a pipeline now that is loaded up with regulations that have been somewhat delayed and slow.

And now if they feel they have carte blanche to push them, the kind of uncertainty they're going to create in the business economy and in the energy sector and the technology sector as well could overwhelmingly dampen economic growth, could really harm the country's trajectory.

For example, these new vehicle fuel economy standards, well, the Chevy Volt won't meet them. And it costs $40,000, twice the cost of a comparable vehicle. Your vehicle costs are going to be going up as a result of these rules over time, and they're going to up significantly.

JEFFREY BROWN:Michael Brune, a last word from you. What would you see as the biggest priority going forward?

MICHAEL BRUNE:Meeting the challenge that is posed by climate change.

The president has said that climate change will be one of his top three priorities. And what we're looking for from the president and EPA is an ambition to match the scale of the challenge. So that will manifest itself.

In the first couple months, it will manifest itself in two key tests. One is whether or not the tar sands pipeline gets approved or whether we invest in clean energy instead.

Of course, we think that clean energy will produce more jobs and improve the quality of our air and water at the same time.

And, then, secondly to regulate carbon pollution from existing power plants, all of the coal-fired facilities that you see across the country, the refineries as well, to make sure that we continue to invest in clean energy and begin to wrestle with the challenge of climate change, so that we have fewer droughts, fewer wildfires and fewer superstorms in the years ahead.

JEFFREY BROWN:All right, Michael Brune, Kenneth Green, thank you both very much.

KENNETH GREEN:Thank you.