john, thank you for your reporting there. this has been described as a sweeping agreement. for an environmental law professor that we spoke to earlier, this is very sobering. here's what patrick parenteau had to say. >> this is more of a political agreement than legal document, frankly. it's important, certainly for the nations to commit to what they've committed to and to commit to ratcheting up the pledges that have been made. but the time frame is very short. the amount of carbon that we're putting into the atmosphere every year on order of 36 billion tons is still going into the atmosphere. it will be there for centuries. the science is telling us that the climate systems of the earth are actually more sensitive than we thought. the rate of melting of the ice sheets, the warm fgt oceans, the sea level rise.