santer at lawrence livermore national lab. thank you for joining us. >> you are very welcome.that you mentioned trickle-down ignorance, there was a political ignorance inference with it. some of it is just that we do not really learn about it. we do not know where the trusted sources are, which is why you are here. tell us, what are we seeing this summer that is absolutely related to the change? >> we know beyond a shadow of a doubt that by burning fossil fuels, we increased levels of heat trapping greenhouse gases and the planet has warmed. what we are seeing this summer is not a scientific surprise. this was expected behavior. and we have been studying this and warning about this for well over 40 or 50 years. >> all right, so this is not anything new, actually. let's talk about that. i was reading something very fascinating about lake mead and the colorado river and there were choices that were made hundred years ago by political leaders to say we do not need to do that action, that course of action, because we will have enough water. we still seem to be on that track of say