Climate change is the greatest threat of our time.

I definitely challenge people. But hopefully, I am working harder than anybody else, and so people won't resent the fact that I want them to work hard, as well.

I love disagreements. I love the democratic process. If I'm in a room where everybody agrees, I start to nod off.

I think that one of our most difficult international challenges is clearly climate change and making sure that the Paris agreement goes forward. While I think the international community understands that President Trump is not taking the same position as President Obama.

I cannot shy away from controversy. I don't know if it's my Irish blood, but I love it.

The EPA's greenhouse gas regulations, along with a host of other onerous regulations, are unnecessarily driving out conventional fuels as part of America's energy mix. The consequences are higher energy prices for families and a contraction of our nation's economic growth.

When discussing overall impacts on employment, it is important not to overlook the new technologies and industries that can be driven by pollution control standards.

Critics play a dangerous game when they denounce the science and law EPA has used to defend clean air for more than 40 years. The American people know better.

If coal wants a place in a carbon-constrained future, they have to look at technology like this. And we think that our rule can help stimulate technology, growth, and innovation, bring those costs down, and allow coal a more stable opportunity to continue to be invested in.

Greenhouse gas pollution, through its contribution to global climate change, presents a significant threat to Americans health and to the environment upon which our economy and security depends.

There is no threshold level of fine particle pollution below which health risk reductions are not achieved by reduced exposure.

We need an international solution to the challenge of climate change, there's no question about it. But the real key is, can you actually get that - or get that solution - without the US' involvement? Can you not lead domestically, and expect the rest of the world will take action... the US needs to lead, we need to be out there.

EPA gets to set a standard for new. For the existing, EPA sets guidelines for what we think is appropriate, but then states develop plans that work for them, taking into consideration their specific energy mix.

Any first-generation technology will. But we are looking at carbon the same way we look at every pollutant under the Clean Air Act we look for the new technologies that are available. We recognize that these power plants are going to be around for decades.

The climate change is real today, but also the solutions that we have available to us that are cost-effective and beneficial to everyone are at our disposal now.

But I will tell you that I didn't go to Washington to sit around and wait for Congressional action. Never done that before, and don't plan to in the future.