 My name is Kevin Trenberth. I'm from the National Center for Atmospheric Research in Boulder, Colorado. I'm a climate scientist. I specialize especially in changes in energy and water and how they are changing with climate change. I started, I'm from New Zealand and I was not particularly enamored with anything. I did an undergraduate degree in mathematics and was looking for a place to go and I ended up in the New Zealand Meteorological Service because the connection there was that I had done some work on fluid dynamics and this was the closest thing to it. But when I started there, there was a pattern I noticed to the weather and I actually noticed the El Nino phenomenon and its effects on New Zealand and I wrote a couple of papers about this long before most people had discovered the El Nino phenomenon and so I got into the climate realm mainly through these patterns of weather and their important influences on an inter-annual timescale and then eventually you start noticing that well, these inter-annual variations are beginning to change in various ways as well and so you run headlong into climate change. Well, the environment in which all events occur these days is different and so in fact every storm is different. Every event is actually different. It has to be. The trouble is that a lot of them look exactly like the ones that we've had in the past and the reason is because there's a lot of natural variability. There's a lot of spread in the values that can occur naturally but in actual fact they're all a little different but when they're at the high end or at the low end, well the low end, they don't occur so much in terms of temperature but at the high end then you start breaking records and that's what we're seeing around the world, increasing numbers of broken records and associated with the high temperatures often we have very intense droughts. Heat waves, wildfires and we're seeing increasing instances of that kind of thing as well. I got into this in a somewhat forced way through what happened after 2009 which was the Copenhagen Conference of Parties meeting when there was just before that this event called Climate Gate and I was a lead author in the IPCC 2007 report, a coordinating lead author of the main chapter. My fellow coordinating lead author was Phil Jones at the Climate Research Unit and that was the computer which was broken into and all of these emails were stolen and then made public including a whole bunch of mine and one of mine went viral and so I sort of had to deal with the public reaction to these things in various ways and I mean I already was answering many media questions but I made a deliberate decision at that point that I needed to step up and try and increase outreach relating to climate change and try to communicate especially with the masses of the general public as to why this is an important issue. So that's really how I got into the idea of trying to communicate more and I think I've had some success at least, I have a few fans. So the research I was doing at the time was very much related to Earth's energy imbalance so when you have increases in greenhouse gases, carbon dioxide in the atmosphere it traps more energy in the system and so this is one of the symptoms that you expect but we have measurements from satellites at the top of the atmosphere that are supposedly measuring these things and then the question is where does this energy imbalance go? Where does the actual energy go? Most of it goes into the ocean and so the ocean heat content increases, that expands the ocean so sea level goes up, some of it goes into melting Arctic sea ice some of it goes into warming the land, warming the atmosphere and this is where some of the effects on the weather occur and so one can in principle try to track all of these pieces put all of these pieces together, see how much extra energy there is in the system and trying to make it add up to the values that we think we're measuring at the top of the atmosphere and at the time we were quite frustrated because they weren't matching up especially well and so that's what that quote was actually about the lack of an adequate observing system in a number of ways especially the ocean observing system but also the top of the atmosphere measurements that were being made and the apparent discrepancies between those so that we couldn't track what I called the global warming which was the actual energy imbalance at the time that's what the vernacular that I was referring to was dealing with and of course it was a private email to colleagues who understood the context and then when it gets out of that context it maybe doesn't make as much sense I thought it was ironic that it was a private email but it was talking about a paper that had been published so even though everyone was getting excited about this secret email you were just talking about published research well some of it was published but in actual fact I subsequently wrote an article a perspective that was published in Science Magazine about tracking Earth's energy and that's been a quite popular article as it turns out but that was really more of an explanation as to what all of this was really about most of the energy imbalance at the top of the atmosphere ends up in the ocean and so the ocean data sets were not very good they're getting better one of the reasons they're getting better is we have a new ocean observing system called Argo which provides a lot better information all over the world but that really only applies to after about 2005 it doesn't give you the record further back in time but using that information it's possible to improve the analyses that are being made of the ocean temperatures the ocean heat content and so this has been done there are so-called ocean re-analyses that you can take a comprehensive framework a climate model or an ocean model with all of the components that are forcing it the changes in the winds estimates of the surface exchanges with the atmosphere in terms of temperature and moisture and so on and create along with sea level measurements and sea surface temperature measurements put all of these things together and get a much better estimate of the ocean state and its changes over time and so in 2013 we published a new reconstruction of the ocean heat content over time prior to that I don't think the ocean heat content estimates were as good and so this helps to uncover and find some of this missing heat that we couldn't find earlier so that's one of the things and what we found was that some of the heat in recent years is going deeper into the ocean and we were able to trace that back to especially changes in wind patterns in the Pacific Ocean there have been very large changes associated with what is called a Pacific Decadal Oscillation a Pacific Decadal pattern where there have been increases in the trade winds that piled up more warm water in the far western Pacific but left the eastern Pacific relatively cool and as a part of that it has changed some of the ocean currents where some of the heat has gone and it has had some patterns that have emanated from that region around the world these tend to occur strongest in the winter time so in the northern hemisphere winter they affect the northern hemisphere regions and it turns out there was a connection into the Arctic and across into Europe and this we believe led to some of the cold outbreaks that occurred in Europe at the same time over the North Atlantic Ocean there were fewer cold outbreaks especially in places like the Labrador Sea and as a result there was less cooling of the ocean now normally in the winter time there are these cold dry air masses that come off of North America over the North Atlantic they produce very cold conditions over the North Atlantic a tremendous amount of cooling and they trigger convection in the ocean the ocean is stratified with warm at the top cool down below and as a result it's very hard to move heat down instead what you do is you can move cool water down through convection in the ocean but if you turn off that cool water going down the convection in the ocean is equivalent to warming the deeper ocean and this is partly what has happened in the North Atlantic and so the North Atlantic turned out to be one of the places where it has warmed more than many other places but we think it's origins we're actually back in the tropical Pacific and similarly in the southern hemisphere there's been some very distinctive patterns especially in the winter time that have affected the southern oceans the southern oceans are warming quite a bit yet at the same time Antarctic sea ice has spread out more in the South Pacific that relates to the winds having a component away from the continent that have pulled the ice further out and more ice gets generated and behind but in the places where the wave structure was from the north in the Antarctic Peninsula area there's been a huge loss of sea ice there but you can't push the loss of sea ice too far because you run into the continent and so there's an asymmetry in the southern hemisphere where you can only push the ice in one direction so far but it can spread out an enormous amount in the other direction it means that a lot of that sea ice is very thin but this kind of a pattern of the changes in sea ice in the southern hemisphere turns out also to be related to these large scale changes that have occurred in the Pacific in particular that have led to more heat going deeper into the ocean especially in the southern ocean in the North Atlantic partly in the Pacific at least below 300 meters down to maybe 700 meters or something like that kind of a depth redistributing the heat within the ocean and so this is a part of the nature of the changes that are going on we certainly think that the planet is still warming but that warmth is not necessarily being seen right at the surface where it gets manifested in the global mean surface temperature the jet stream is the eastward flowing current of air in the northern hemisphere it's very much associated with the warmer tropics and the higher latitudes and if there are major heating regionally in the tropics it produces meanders in the jet stream waves, large scale planetary waves in the jet stream the biggest source of those waves is associated with the El Nino phenomenon and this has occurred especially over the last year or two in December, January, February of 2013-14 there was the beginning of the current El Nino event which is going on and there was a tremendous amount of precipitation north of Australia or slightly northeast of Australia right on the equator and we believe that that was one of the triggers for one of these major waves that set up and so as an example in that particular case it spins up an anti-cyclonic flow in the upper part of the atmosphere right in that vicinity but then downstream there is a trough that forms as naturally occurs in the jet stream and then the next thing is downstream from that is a big ridge of high pressure which was this ridge of high pressure that went along the west coast of North America this is the very so-called persistent ridge that led to the that's the right, yes and a ridiculously resilient ridge that occurred that led to the drought in California at the same time it led to very warm air going right up into Alaska and up into the Arctic but if warm air goes up in that direction the cold air is going somewhere else and it came down in the next trough in the eastern parts, east of the Rockies in particular in the eastern parts of the United States very cold outbreaks breaking some records in some places but again having its origin back in the tropical Pacific so this large meander that got set up in the winter of 2013-14 led to record dry conditions in California the drought 2013 was the driest year on record in California and now this El Nino has been gradually developing and spreading a lot of warm water around over the northern hemisphere likely to make 2014 the warmest year on record but that warm water is sitting out there it had a very profound effect on the distribution of hurricanes around the northern hemisphere in the northern hemisphere summer very active about double normal activity in the central and eastern Pacific a couple of hurricanes went through Hawaii very inactive set of hurricanes in the Atlantic as a consequence of this and so it has already had big changes across the northern hemisphere into the Atlantic in the summertime and now we're seeing some of this the developing El Nino helps to pull the jet stream further down into California we're seeing some benefits of that if you like this week where it's going to be a fairly rainy week and it was flooding in San Francisco last week as I speak at least and so conditions are very different this year than they were last year the storms that are coming in are benefiting from the fact that the sea temperatures are very warm and as a result there's extra evaporation of moisture that goes into those storms and a lot of rains that are occurring are prodigious and there's been some flooding there's a real risk of major coastal erosion associated with these kinds of things and we're seeing this kind of thing going on so this is certainly being driven in part by the developing El Nino this inter-annual variability but it seems to maybe setting the stage for the end of this pattern has led to the very strong trade winds and the build-up of heat in the far west and Pacific that led in part to this super typhoon high-end late last year and so that pattern now has changed and the real question is this a blip is this a one-year thing associated with the El Nino or is this really signaling the end of this so-called hiatus in global warming we're really going into a new pattern where we'll see some more consistent warming from this point on the way I think of both the drought and the storms is that these are for the most part unchanged with regard to climate change but once they occur their impacts tend to be much greater than they used to be and so on the wet side there's more moisture that gets involved in the storms it rains harder and there's very good statistics to support that but in the case where you have dry conditions strong ridiculously resilient ridges being set up along the west coast then things dry out a little quicker there's a little bit of extra heat it's not a great deal but it accumulates over time because there's no evaporative cooling there's no moisture to take up this heat and so things begin to dry out and then once they've dried out then heat begins to form and you end up with heat waves then the risk of heat wildfire goes up and we've seen a lot of wildfires in California over the last year or so and some really big wildfires and so this has major costs attached to it so what one expects then is that the droughts set in a little quicker they become more intense they potentially are a little bit longer lasting because it takes a bit more to get rid of them and once you've got a drought the soil character tends to change so that even if you do get some rains the rains often don't soak into the soil they tend to run off more readily and so it takes quite a bit typically the best thing is moderate rains really heavy rains are very apt to run off but a prolonged period of moderate rains are apt to begin to soak into the soils and then change the pattern of the drought I think the drought has already changed in major ways but people refer to it in different ways so from the standpoint of soil moisture and many plants the drought is probably over in many respects but in terms of the lakes and the rivers and the major reservoirs and so on they're still way down and it's going to take quite a few more storms to help end the drought in that sense this is a tricky aspect because sometimes scientists are seeing only a little piece of the puzzle and maybe the piece they're dealing with is fine but they're not seeing other aspects of it and so how one can communicate that without discrediting them altogether especially if they're just misinformed or their intent is fine I mean there are a few people who are deniers of climate change and who deliberately go out of their way to misinform the public and mislead the public in various ways and there's always weather going on so you can always pick upon a cold outbreak or something which seems not to be consistent with the idea that there's global warming going on and so that's very easy to do if you want to do that and so when I try to deal with the public in general I'm really trying to reach I suppose what you might call the large uninformed masses maybe that's a derogatory term but many people are just not very well informed about climate change the small percentage of the deniers I'm not going to convince them and so I've sort of given up on that small cadre but I think building the general idea that the climate is indeed changing it has big consequences as we go further along this is what is needed in order to provide the goodwill behind politicians who then may be able to address some of these concerns through policy changes of various kinds this is quite worrying in the United States because there's a tremendous amount of vested interests especially on the fossil fuel side of things that has brought huge amounts of money to, I'm tempted to say, pay off the Congress in many respects or to influence the arguments in various ways and certainly have distorted the public's view of just what is going on global mean temperature is not the best indicator of global warming if you wanted to choose a single thing it's probably global mean sea level so global mean sea level is going up it's going up at a rate of over a foot per century we've got very good measurements of that since 1992 when we've had satellites in space with instruments that have altimeters on it that are measuring the sea level to millimeter accuracy and so that's the rate of climate change sea level's gone up two and a half inches since that time part of that is because the ocean is expanding because the ocean's getting warmer we can actually measure that and part of it's because of melting glaciers and melting Greenland and so on that's putting more water into the ocean and so there's no doubt that the planet is warming and this has consequences