 Good afternoon So if any of you noticed how strange the weather has been lately We just come through three of the hottest years on record We just emerged from a major drought and in fact this last year in the American West was the second wettest and recorded history So we're now in a phase where climate change has become a reality of our daily lives And what I'm going to describe to you today Are some pathways for getting down off the up escalator of climate change and it's critical that we engage in this collectively This is a story that really links energy the environment Society and climate together, and I'm going to start by describing the link between society and climate So we've been very fortunate to establish our cities our agriculture our industry in a period of very stable climate and of course the weather bounces around around the Mediterranean climate that we have here in the American West and the climates under which people have set up their cities and their agriculture and their Industries all over the world and that stability has lasted for literally thousands of years Now imagine what would happen if suddenly the climate changed underneath you and that's the situation that we're facing now None of the students in our classes have grown up in a normal climate They've been growing up in a situation where we have much more rapid heat waves occurring much more frequently Really dramatic flooding events that have greatly accelerated over the last 50 years Dramatic droughts like the one with it. We just emerged from and also Increased sea level rise imagine you're the poor pedestrian here on the Embarcadero here in San Francisco dealing with a combination of a king tide rising sea level and a winter storm So what's driving this climate change is something that many of us here at Berkeley have been studying rather intensively and we're now very confident that humankind is The primary responsible agent for the change that we've been observing in our own lifetimes and There are a few key culprits that I want to call out The first is black carbon and carbon dioxide Carbon dioxide so shown by the smoke stacks in these pictures is the main culprit but black carbon that comes from just ordinary diesel combustion is also a major agent of climate change and I Illustrated this shows it is showing a particularly intrepid runner from a recent Marathon in Beijing wearing what was apparently appropriate personal protection gear Given the level of smog in that city So black black carbon contributes significantly to smog as well It also contributes to health problems as well as to global warming my group at Berkeley has now directly shown the link between carbon dioxide and The greenhouse effect as shown in this figure the blue is the carbon dioxide and the orange is the forcing or the greenhouse effect And as you can see The forcing increases in lock-stop with the carbon dioxide so the two are very closely linked This is the first time this direct linkage has been shown from observations we've also began looking at the effects of Methane methane is another and very important greenhouse gas about 30 times more effective than co2 and We've just now concluded our work to show the direct linkage between methane and The greenhouse effect So this is a time series or a plot of the growth and the greenhouse effect or warming Due to methane with time and it shows how that warming has increased rapidly since the introduction of fracking So how do we get off this path that we're on? We're currently on a straight trajectory that connects increased emissions and increased temperature And this is a figure from the last intergovernmental panel on climate change report in which many of us participated That shows that direct one-to-one correspondence between increased emissions and increased temperature So we have to slow down our path down this curve because it's a very straight trajectory toward a much warmer and much stranger climate Well, I'm happy to say that there are success stories So if you look at Los Angeles the butt of jokes, right? So you can get smog in a can This was true of Los Angeles in the 1970s But if you fast forward to today, it is a much cleaner environment And this has to do with both an improvement in the air quality and also a reduction in the Particulates that cause global warming and serious human health issues. So this is a win-win Improvement for the city of Los Angeles and for other cities that have already taken really serious efforts to control their air quality And their greenhouse gases at the same time We are fortunate to have a state governor governor brown who's very serious about reducing the effects of climate change This is a meeting that we had with him recently in which he really took on the the duties as Governor and as the leader of the largest virtual nation that went to the Paris Accords To try to reduce the agents that drive global warming and I think thanks to this kind of initiative We can build a world that both embodies the sustainability that we think is so critical to human life And also embodies the diversity that we hold as a critical value. Thank you very much