very friendly audience in a lot of ways on capitol hill. his speech was very -- it was fairly small. this comes some months after a very detailed date meant that really says this is something that must be, that climate change must be confronted, and it really addressed a lot of different issues. i did not read the whole thing. it really talked about how we need to look at consumer culture, how we need to look at the moral responsibility to the earth, how we need to look at the effects of capitalism. that is something that i think for people on the left was quite heartening that he confronted that issue sort of head-on. what remains to be seen is how much this is going to sway people in the long-term. i was looking at some polling among catholics in particular that was taken just before the release of the encyclical, and

that with some few polling, -- some pew polling, and about 1/3 of catholics felt that combating climate change was at all central to their catholic identity, so what i would be curious to see is one, how much pope francis discusses this two, going forward, and whether it has any type of ripple effect among the faithful worldwide and really among the worldwide. climate change is not something that tends to register -- in the u.s. anyway -- as a top concern for the public in general. if you ask people sort of open ended what are the biggest problems in the country, global warming does not tend to be -- it is at the bottom of the list. if you ask a direct question -- do you think we should be imposing limits on emissions from power plants? and the answer will be quite affirmative. which side of that coin on the polling ultimately wins the day

will say about where climate change goes in the future. host: the pope taking his message from the south lawn of the white house to the house chamber to the united states -- nations.ited he said any harm done to the environment therefore is harm done to humanity. we are talking about a big week in climate energy news. if you want to call in, you can do so. we will put our lines on the screen. tom in pittsburgh, pennsylvania, line for republicans. tom, good morning. caller: good morning, and thanks for c-span. my opinion is of the climate is changing, but the climate is always changing, and we have no definitive proof that it is man-made changes. that man is causing this changes. people are getting rich over this climate change issue, like al gore is. he has made hundreds of millions of dollars from what i

understand from this. and others -- money is a big part of it. like the caller that mentioned college professors are getting these big grants to come up with statistics that the government, you know, favorable to the government's stance, and one of those is michael mann at penn state, a professor of there who came up with the, hockey stick graph, and it came out to be bogus. he is still there and getting grants and making money for the university, so that is why he is still there. i think it is all about money. it is not about the environment. climate is always going to change, and that is my opinion. host: tom from pittsburgh, pennsylvania. carol is expressing similar concerns. our all want to protect planet," she writes, "but the caveat is how."

mentioned caller michael mann at penn state university. one thing i would say to the caller, his research, because it has been so controversial, this is research that essentially , reconstructs temperatures going back over about a millennia and shows a sharpening of take over the last century. uptick over the last century. his research has been probed, and the allegations of academic that has never come to anything at all. is know, honestly it something you hear quite a lot of people are sort of doctoring science in the name of somehow getting rich. i was fine that theory interesting because it seems to me if you are smart enough to say, perhaps atmospheric physics, if your only goal is money, why would you not be creating algorithms for goldman sachs?

i do not agree, with all the , thatt, to the caller studies in climate change are only in it to get grant money. i am not sure there is a lot of evidence for that. host: greg is next. caller: good morning. it is about time i got in. it has been almost 10 years. host: glad to have you back, greg. caller: this is really a tax on life. when you think -- what is a tax todit? -- that is permission pollute. of course we will have differential of seasons if our shifting, and i think that has something to do with our galaxy, which is a lot more serious. talking about the chemicals that they spray up there every other day.

the money is already out of the bag. when are we going to address that? host: frank in union city, georgia. -- greg in union city, georgia. any comments on greg? guest: the research goes back quite a long time. the issue has a political and social salience that is somewhat higher than it has been, but there is a lot of research going back quite a long time, and the consensus view among the scientific community is that the production of greenhouse gases through activities such as cutting down and burning forests, and most notably the burning of fossil fuels -- coal, oil, and to a lesser extent natural gas -- is creating an effect that is leading to a long-term warming trend of the atmosphere. there is not much disagreement on that point any scientific realm.

now in the political realm, it is hotly debated for a couple of reasons. ,ne, notably among republicans presidential candidates and lawmakers, there is dispute about the extent to which there is global warming. that is the dominant or largest driver of warming you see going back a ways. staying on the political round, there has been a huge and very legitimate debate about what should the appropriate the p are youce will have one or's and losers created -- force be. you will have winners and losers created. host: kerry clinton making a lot of news this week coming out with her -- hillary clinton making a lot of news this week coming out opposing the keystone

xl pipeline. talk about the timing on that. guest: this has been fascinating. the keystone is under review at the state department, which clinton led under president obama's first term. back in late 2010, she seems to be heading in a different direction on the keystone pipeline. -- now somewhat famously then secretary clinton said she was inclined to approved the pipeline. it blew up into becoming the high profile climate change and energy policy fight of president obama -- of the obama presidency, and the administration has been slow walking businesses in four slowalking this for years. her suck answer was, well, while this was under review while i was at the state department, it would not be appropriate for me

to weigh in. might change her tune because she was getting impatient with the last decision from the obama administration. host: to be clear, this is what she comes out with this week. "i am opposed to the construction of the keystone xl pipeline. we should not be building a pipeline dedicated to moving north america's dirtiest fuel through our communities -- we should be focused on what it will take to make america the clean energy superpower of the 21st century." a pretty definitive answer. guest: very definitive. very much like literature from environmental magazines -- "the dirtiest fuel." this was a huge piece of news because again clinton have been so silent on this for such a long time. one thing that was interesting, though, because this issue splits and a lot of weight the environmental community -- in a lot of ways the environmental community, clinton the very next day was quick to come out with a on severalement

other energy-related things that i think is more favorable to unions, so she talked about how to would be very aggressive as president in a large national initiative to fix modern infrastructures, specifically the pipelines and rail infrastructure, modernizing the power grid. i think what she was signaling is that, as she pointed out quite forcefully, in the energy space more generally, i will try to be more aggressive on things that unions would have very good reason to like. host: dennis is in west palm beach, florida, line for republicans. dennis, good morning. caller: good morning. my questions have to do with whether there is such a thing as "man-made climate change" as opposed to global warming or whatever. one of my questions is, number one, can reasonable people actually disagree on this issue as to whether it actually exists or not? this bewo, showuldn't

decided as a scientific issue as opposed to a political issue? i know somebody many people who want to fight to the death on whether this is an issue or not but do not have a clue on how to spell the word "science." for aing back to the pope moment, in one of his writings, he pointed out that there could be a situation where businesses are making tremendous amounts of money, let's say south of the so making alln these profits, they are leaving behind phenomenal amounts of work to do in the future that are based on damage to the environment, and they are leaving that work for future generations. he is saying this is not fair. does climate control actually exist? can reasonable people actually disagree as to whether oit does? and should it be a scientific issue or a political issue? guest: it is an issue in both

spheres. on the question of -- does it exist? i think that is something that finance has spoken to their he definitively at this point. -- spoken to their he definitively at this point. science has spoken to a number of scores, but that is different to flatly -- does exist. now the question of what will the long-term impact the, what will the rate increased be, if you have x amount of increase in carbon dioxide emissions, what exactly will the temperature response be? these things are very legitimate questions for debate, but as far as the threshold question of is there a human-induced climate change, i think the scientific community has spoken fairly strongly on that. i want to mention on clinton and keystone for a moment, that was interesting, there is more than one democrat in the democratic riemer he -- democratic primaries. senator bernie sanders has been

surging in the polls, and he has long been against the keystone pipelines, one of the more active members of congress opposing it. martin o'malley also opposes the keystone pipeline, and they were very quick to come out with statements to kind of limit the, i suppose, political traction that clinton gained or could gain from finally coming out on this. sanders said very pointedly, "i am glad she is finally coming to a decision on this," and o'malley was quick to point out that he also has been out on this for a long time. but clinton really is making sort of a role to look to left on the environment in a couple of ways. it was not just the keystone pipeline, but a couple of weeks before that, she made an announcement that was not quite as high profile but almost equally interesting, maybe even more consequential in terms of our energy system and policies going forward. she said, look, i do not support drilling in the arctic ocean off of the alaska coast. the obama administration has not been all that favorable to it.

they have really given shell permission after years of kind of regulatory maneuvering, permission to drill so far just a single well off the coast of alaska, but clinton's position was much stronger on this then even president obama's. keystone pipeline, her views on arctic drilling -- i think she is starting to answer some of the questions that i frankly a s have of environmentalist had for her. you can call in and send us tweets. that have come in, one fewer wrote that the pope was quite welcome when it comes to environmental questions that he put in. another wrote -- someone should remind the boat that in "the bible," god leaves earth a burnt center. i guess god is the worst offender. next call on our line for democrats. ralph, are you with us?

caller: they have the harp weather machine, and they can keep that to 15,000 degrees. how warm do wanted to go? certainly hold off on the heart and less you want to address the situation. guest: it is not something i know much about. host: warren is next. -- a rapid rate of which it was going the past. host: what was the question? i did not catch it. caller: people are denying the problem with climate change, if the polls are melting at such a rapid rate. host: do you want to talk about polar melts? guest: there are a number of different indications that climate change is having an

effect on the ecosystem. if you look at sea ice in the arctic, it is always moving around, and future and will be linear, the same every year, but certainly the scope of the arctic is something that has been declining over time, and that is one of several symbols of climate change we see. a few weeks ago, we chatted about that. one of the issues he spoke about a lot is the level of coastal erosion that is really something that -- a huge threat and problem for coastal villages in alaska. we're certain to see as the caller points out some really affects of this already, let alone what some of the warning signs are for decades and centuries in the future. host: joe on our line for democrats, go ahead. caller: did you say joe? that is me. thank you, sir.

briefly, i think science is using too small of a window for proximally 200 years to come up with and say this is "settled science." a couple of comments that i have never heard anybody else say or comment on -- how many ice ages have we had -- and science does agree on this -- there have been five. after two of those five ice ages, there was no ice anywhere on this earth. likef course, if anything that happened today, of course everybody would go nuts. the second thing is, it is in the same vein. if it is settled science, why can't they figure out what caused the dial 250 million years ago, or virtually, 90% of every living thing on this earth? man was nowhere in sight that

time. thank you, sir. host: a couple of questions on the history of the research. guest: some of his questions are beyond the scope of my authority -- way beyond. [laughs] scientists do not argue that there was not climate change before humans. the more is that recent climactic changes we have seen set in motion and the more recent temperature trends dating back probably toward midcentury, the mid, if you look at the theresince then, i think is very widespread agreement in the scientific community that if you are looking typically of the warming trend we are seeing now, bear the very strong footprint of human activities. sure, obviously going back over millions and millions of years, you have had a number of changes in the climate system that has by definition nothing to do with

humans, but since we are looking at some of the much more recent changes and the much more recent spikes in atmospheric carbon and whatoncentrations, the impact of that will be in the future, especially if we keep continuing at the present rate, i think that is something that does be

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