 So I'm this really lucky person I get to ride my bicycle when I go places and that's a great thing But suppose you have to drive a car You may run into problems and you might have very few problems They're really low and you might have bad problems way over here on the right So this is problems getting worse and this is how likely this is highly likely You're really going to get this and this is rare down here So what we're going to look at is what does a commuter encounter if you go out in your car in the real? Well, the most likely thing that happens and so we show way up here because it's likely is That you get caught in traffic and you kill some time and you turn on the radio and it's just sort of boring It's not something that you really wanted to listen to that's really what most of us experience when we have to drive somewhere Be perfectly honest It is possible that you will get to a situation that nobody's in your way and you turn on the radio and they're playing the Beach Boys Festival And you're just grooving as you run down the road It's a wonderful thing and you're having a ball It is also possible that you get stuck in lots of traffic You're sitting there for an hour you turn on the radio and they're testing the emergency broadcast system And they are screaming out of the radio and this is no fun at all But recognize that there's slight possibility that you're sitting there stuck in traffic listening to the emergency broadcast system And a drunk driver comes running over the top of you and you know you get I'm sorry, you could be seriously damaged or you could end up dead and that is indeed possible It's not very likely But it's possible What do we do about that we buy cars that have airbags in them that have crumple zones We put on our seatbelts if we have kids we put them in a kid's seat We take out catastrophic insurance we pay mothers against drunk driving to try to reduce drunks We pay engineers to make the roads safer We put a fair chunk of our Transportation budget into something that we do not expect to happen because it's so devastating if it happens now When we start talking to Congress or to what have you about the the cost of global warming we have a best estimate What is the most likely thing and when we take that? Problems that go with that best estimate and you put them in an economic model We are better off if we deal with it than if we pretend it doesn't exist Now be very clear. This is science. It is not revealed truth It is indeed possible that we will see smaller or slower changes Absolutely correct that could happen. It's also possible. We could see larger or faster changes We simply do not see any way that simply adding co2 to the air We'll turn the earth into the greatest place to live that could possibly be imagined You can't make Eden with just one thing because building Paradise would take getting a lot of things right so there's really not much chance that we get Wonderful no problems great benefits just from cranking up co2 But there's a slight chance that we actually make the tropics too hot to live in for unprotected peace pool That we could have dead zones belching out poison gas that we could shut down the North Atlantic and dry out the monsoon belts That we could dump a ice sheet in the ocean and flood the coasts in our hurry These are all considered to be very unlikely at this point but we can't rule them out and co2 might by itself do that and So if you look at the picture, yes, it could be a little better. It could be a little worse It could be a lot worse, but we don't See any way to make it a lot better Now this is an opinion But the the last times that I have sort of talked to high policy makers about this that I've Testified to Congress or what have you my impression is that we spent a lot of time having this argument I present what we know best from the science and someone says it could be better This is our best estimate. It could be better. This is our best estimate. This could be better. Yes, that is not both sides Be very clear the best scientific evidence versus don't worry is not showing you both sides And if we scientists are wrong, it's more likely to be on the bad side than it is on the good side