It’s ‘extremely annoying when all of these extreme events occur, whether it’s a wildfire or an extreme hurricane like this, and there’s no mention of the fact that climate change has actually exacerbated the situation,’ says Dr. Kevin Trenberth of the National Center for Atmospheric Research
DIMITRI LASCARIS: This is Dimitri Lascaris for The Real News. Tropical Storm Harvey has brought catastrophic flooding and killed at least 14 people. The death toll regrettably will certainly climb, and perhaps dramatically. Most of Houston, the fourth populous city in the United States, is submerged in flood water, and tens of thousands have been driven from their homes. Rescue workers helped evacuees reach safety after hundreds were stranded in the storm. Damage caused by Harvey will cost tens of billions of dollars, and rebuilding is likely to last years. At this stage, it’s not unreasonable to ask whether Houston will ever fully recover from this calamity. Meanwhile in India, Nepal, and Bangladesh, millions are said to be affected by the worst monsoon season in years. Monsoons and the massive flooding they have caused have left over 1,200 people dead and many more thousands without food or clean water. As extreme water devastates lives around the world, extreme weather I should say, another type of storm is raging in the media. The question that is provoking some controversy is whether the media is doing justice to the question of climate change, and whether now is the time for us to be having a discussion about the links between climate change and these historic storms. With us to explore these questions is Dr. Kevin Trenberth. Dr. Trenberth is a distinguished senior scientist in the Climate Analysis Section at the National Center for Atmospheric Research. He obtained his science doctorate in meteorology in 1972 from the Massachusetts Institute of Technology. He was the lead author of the 1995, 2001, and 2007 Scientific Assessment of Climate Change Report from the Intergovernmental Panel on Climate Change and shared the 2007 Nobel Peace Prize, which went to the IPCC. Dr. Trenberth joins us today from Boulder, Colorado. Thank you for joining us today. KEVIN TRENBERTH: You’re most welcome. DIMITRI LASCARIS: There appears to be some hesitation of mainstream media to link the severity and duration of Harvey to climate change. I’d like to start by showing you a clip from a very recent exchange on CNN which addressed this issue. Why don’t we have a look at this clip. REPORTER: One of the things we’ve heard from scientists over the last 10 years is that climate change does impact the intensity of many of the storms that we see. SPEAKER: I probably wouldn’t attribute what we’re looking at here. This is not an uncommon occurrence to see storms grow and intensify rapidly in the Western Gulf of Mexico. As long as we’ve been tracking them, that has occurred. The why for the big rain is the stationarity, the fact that the storm is going to come in and not move. While it has happened in some cases, to have a really big storm come and stall, I guess, is really rare. DIMITRI LASCARIS: Dr. Trenberth, how do you regard the answer of the former director of the Hurricane Center? Do you view that as a complete answer to the question that was put to him by the CNN anchor as to what’s going on in terms of climate change and Harvey? KEVIN TRENBERTH: While what he said was certainly true, there’s a tremendous amount of natural variability and these storms can certainly form without the influence of climate change, what he didn’t address is the fact that there is climate change, the oceans are warmer, the sea surface temperatures are higher, the air above the oceans is warmer and moister than it used to be, and the environment in which all of these storms are occurring is simply different than it used to be. This adds to the rainfalls in particular, it adds to the activity in a general sense, and that activity is usually manifest in the forms of more intense, larger, and longer-lived storms. On the other hand, one big storm can play the role of three or four smaller storms. We don’t actually expect more storms, rather we expect there may be fewer storms but they’re bigger and more intense with climate change. DIMITRI LASCARIS: Not too long ago, we at The Real News were covering the BC wildfires. We were talking about the linkage between climate change and the wildfires as the wildfires were raging in BC, and some of the commentary was to the effect that that was not the time to be having that discussion. This point of view has again emerged as Harvey has unfolded. Naomi Klein just authored a piece in The Intercept in which she responded to assertions that now is not the time to “politicize” the catastrophe in Houston. According to Ms. Klein, it’s imperative that we have a discussion now about the true causes of this catastrophe, and she argues that a decision to ignore or downplay the role of climate change is itself one that is political, and so that those who claim that we should not be politicizing the tragedy in Houston are in effect being disingenuous. What is your view of all of this? Do you think this is an appropriate time for us to be having the discussion about that linkage? KEVIN TRENBERTH: Yes, very much so. At least from the scientific standpoint, we can make very clear statements about the causes as to why this thing has happened, what the influences are that have come into play. It’s a different matter as to what you might do about those things, and that’s really where the politics comes in. The politics, that aspect of the politics, I would say, indeed, we should maybe try and set that aside, but it’s extremely annoying when all of these extreme events occur, whether it’s a wildfire or an extreme hurricane like this, and there’s no mention of the fact that climate change has actually exacerbated the situation. As a result, the general public, I think, is poorly informed about this kind of thing. DIMITRI LASCARIS: Let’s look at the way the Canadian media’s informing the public about this kind of thing. I’d like to show you a clip in particular from the flagship news program on Canada’s state broadcaster, the CBC, The National, which aired last night. Let’s have a look at what happened. REPORTER: A lot of people have been asking, is climate change a factor, and how much here? SPEAKER: We can’t take this entire event and connect it to climate change, but part of the reason why Harvey has already been so devastating is because it’s been forced to sit and spin off the coast. That in part is connected to these blocking systems to the north including a big high pressure system sitting right over British Columbia. That’s forced Harvey to sit in place, not allowing it to move forward or northward out of the hardest hit regions. More and more climate studies are connecting these blocked weather patterns with the jet stream that’s getting stuck in place thanks to a warming climate. It’s not moving weather systems forward in time. That’s part of new research that climate change is looking at, and that is the case with Harvey, again, being forced to sit off that coast, meandering in place until that high pressure ridge over BC finally moves out on Wednesday night. That will finally allow Harvey to move inland, hopefully giving some relief for the second half of the week. DIMITRI LASCARIS: Dr. Trenberth, how do you assess the answer given by the meteorologist in terms of accuracy and completeness in explaining the linkage? KEVIN TRENBERTH: I don’t think it was especially helpful, and some of the information she tried to pass along was probably not correct. The best understanding we have at the current time is that the track of these storms and whether or not it stalls is largely a function of the weather situation. She did make that clear, and she talked about it, but that weather situation is probably not greatly influenced at all by the climate change aspect. One of the examples might be Super Storm Sandy where it recurved in an unusual direction back into the Jersey Shore. There have been a number of experiments done with numerical models that have replicated the storm very, very well, and they’ve changed the sea temperatures, they’ve changed the environment in ways that would be happening with climate change. The track of the storm is identical, just about, in every case. The storm trackers determined by the weather situation where cold fronts are, where the jet stream is, and that’s largely by chance. The parts which she didn’t address are the parts relating to the intensity of the storm, the prodigious amounts of rainfall, and the fact that the oceans are warmer, they’re feeding more moisture into the storm. One of the things these storms do is to take the heat out of the ocean in the form of moisture, evaporative cooling of the ocean, and then moistening the atmosphere. Then when that moisture rains out with the excess amount of rains, that’s what causes the flooding and does the tremendous amount of damage. That’s certainly what’s happening in the case of Harvey, and there’s a strong climate change component to that. Climate change doesn’t cause these things, but climate change is making them worse by adding to the amounts. DIMITRI LASCARIS: Could you talk to us also about the question of sea level rise, which is obviously being affected by climate change? How is that playing into the catastrophe in Houston? KEVIN TRENBERTH: Since late 1992, we’ve had satellites in space that have altimeters on them that are measuring the global ocean locally to millimeter accuracy. We know what’s happening to global sea level, and it’s going up at a rate of about 3.4 millimeters per year. That’s about 15 inches per century. That’s the current rate. Sea level since 1993 has gone up 3.25 inches. That’s the global number, and that is caused by climate change. That’s because of global warming, the increased trapping of heat by carbon dioxide and other greenhouse gases in the atmosphere that is caused by humans. 3.25 inches you might say is not that much, but then when we have a storm surge from a storm like Harvey along with a high tide and the sea level rise, that’s when all of the damage occurs. It’s these things adding together that cause us to cross thresholds, and break records, and things break. DIMITRI LASCARIS: Of course, neither the increased moisture in the atmosphere nor sea level rise were mentioned in the CBC report, unfortunately. Many climate experts don’t seem particularly surprised by the intensity and duration of Harvey despite its unprecedented nature. Are you surprised in your professional capacity by either its intensity or its duration given the climate trends that you’ve been observing? KEVIN TRENBERTH: Yes, this has been quite amazing in a couple of different respects. Firstly, it was in the far western part of the Gulf, and so it was close enough to land next to Mexico on the west and the Texas coast on the north that some of the air that’s coming into Harvey was coming from over land, and therefore it’s very dry air. That doesn’t help the storm at all. There was tremendous amount of moisture coming from the south and from the east into the storm from over the Gulf, and the Gulf was very, very warm, about 87 degrees Fahrenheit, and tremendous amounts of moisture flowing into the storm that enabled it to get to a Category 4. That was pretty amazing given that it was already so close to land. If it had been further out over the Central Gulf, it could easily have become a Category 5 storm and even bigger still. Then it made landfall. The average time for a storm over land to last is about 27 hours, and then it peters out because it loses the connection to the ocean, and there’s greater friction over land. This storm was still going after 60 hours, and then it went back over the ocean again. The duration of this storm over land was one of the other very amazing things. What you could see was that there were these spiral arm bands that were bringing tremendous amounts of moisture, a lot of them actually flowing right over Houston into the storm. The size of the storm enabled it to reach out and still tap into all of this excess moisture over the Gulf and feed itself, and it didn’t peter out in the same way. Again, this is very likely a climate change aspect to it, the fact that it has maintained its identity for as long as it has. DIMTIRI LASCARIS: You mentioned the average survival time of these storms, I think you said, was in the range of 27 hours, and we’re now way beyond 60. What is your current best estimate as to how long this storm is going to last to the extent you can predict that at all? KEVIN TRENBERTH: These storms certainly depend on where they go, and this storm is now predicted to meander around a little bit and then move to the Northeast and go further over land. Once it does that, I think it’ll very quickly lose its circulation, the winds, but there will be a swath of heavy rains that will follow this storm perhaps all the way up into the Northeast. That’s going to take the next five days or something like that. I’m not the best person to ask about that. DIMITRI LASCARIS: Lastly, I understand that 2015 was the most active year globally for tropical storms, hurricanes, typhoons, but mostly in the Pacific. I understand that was related in no small part to El Nino. KEVIN TRENBERTH: Yes. DIMITRI LASCARIS: What, if anything, does it say that we are getting this type of a storm in a non-El Nino year? KEVIN TRENBERTH: The action in an El Nino year is in the Pacific. In fact, there were three hurricanes. There’s a classic picture of three hurricanes right in the vicinity of the Hawaiian Islands, and one of them actually went into the Big Island, I believe, very unusual situation. During El Nino years, the Atlantic activity, the Atlantic hurricanes tend to be suppressed. In fact, that’s one of the things which perhaps leads to more activity this year because there’s some pent up action. There’s a bit more ocean heat in the Atlantic that hasn’t been taken out in the previous years because all of the action was in the Pacific. This is one of the components of the natural variability that comes into play and helps to cause some of the variability from one year to the next. Yeah, there are very active El Nino years. The second most active year is probably still 1997, was again a major El Nino year. All of the action was in the Pacific, and it was a very quiet year in the Atlantic. DIMITRI LASCARIS: This has been Dimitri Lascaris speaking to Dr. Kevin Trenberth about the linkage between climate change and current unprecedented storms happening in Houston and elsewhere. Thank you very much for joining us today, Dr. Trenberth. KEVIN TRENBERTH: You’re most welcome. DIMITRI LASCARIS: This is Dimitri Lascaris for The Real News.