moderator(P) Welcome to our special chat on climate change. Today's guest speaker is Dr. Jeff Severinghaus, who is a professor of geosciences in the Geosciences Research Division at Scripps Institution of Oceanography, University of California, San Diego. His current research interests center on using trapped bubbles of gases contained in ice cores to track changes in ancient climate. Born in Kentfield, CA, on Aug. 26, 1959, Severinghaus received a bachelor's degree in geology from Oberlin College in 1983, a master's degree in geological sciences from UC Santa Barbara in 1988, and a PhD in geological sciences from Columbia University's Lamont-Doherty Earth Observatory in 1995. Severinghaus' analysis of isotopes of nitrogen and argon contained in Greenland ice core bubbles have revealed that the earth went through a period of rapid warming at the end of the last ice age, some 11,000 years ago. He found that the region experienced a 15-degree-Fahrenheit jump in temperature in less than a decade, the impact of which was felt throughout the Northern Hemisphere. His research raises the question of whether the addition of carbon dioxide to the atmosphere through the burning of fossil fuels could also produce a rapid change in climate, rather than the slow, steady rise in temperature many computer models of global climate now predict. Severinghaus was awarded a Comer Science and Education Fellowship (2002), a Packard Foundation Fellowship (2001), a NOAA Climate and Global Change Graduate Fellowship (1992), and a University of California Regents Fellowship (1985).
Dr_Jeff_Severinghaus(P) Welcome, I'm here for any questions about global warming that you might have.
moderator(Q) This question was submitted via e-mail by Alan Benner: Why do we not capitalize on the problem by producing energy from solar, wind and other resources? The cost cannot be a factor because the value is high then the jobs produced and work required will be of high value and the process will buoy our economy rather than hold it down. The next obvious step would be a plug-in car in every garage.Tell me why this doesn't work or are we just stuck on old tech. that we refuse to give up?
Dr_Jeff_Severinghaus(A) Alan, your question is an excellent one. I'm a natural scientist so I'm not qualified to answer it, but as a citizen I can offer my opinion. I've heard, probably as you have, that plug-in cars will be available in two years in this country. I understand they are already available in Japan. So perhaps the changes you outline indeed are happening.
gac(Q) Global temp over the past century is some aggregate of measurements. An aggragate from what places? And what is the error or standard deviation of a global average temp?
Dr_Jeff_Severinghaus(A) Dear gac, This is a good question. Land surface temperatures are measured in a vast number of places and as you say, it is necessary to aggregate the data to make any sense of it. However, oceans cover 3/4 of the surface of the Earth, so it is important not to forget them. The oceans can be much more precisely measured, it turns out, than the land, because water holds heat so well and because the temperature swings in the ocean are so much less than on land. So the error, that you ask about, is tiny when it comes to the ocean measurements - far less than 0.1 degree Celsius.
moderator(Q) This question was submitted via e-mail by Grant Lockie: Which of the following are incorrect? Water vapour is a greenhouse gas. Water vapour is up to 40,000 ppm(vol) in the air. Water vapour is on average about 10,000 ppm(vol) in the air. The water vapour molecule has a greenhouse effect many times that of the carbon dioxide molecule. Carbon dioxide is only about 380ppm(vol) in air. If these are all correct - and they are! - how can carbon dioxide be considered to be of any signifigance at all in determining the Earth's temperature?
Dr_Jeff_Severinghaus(A) Dear Grant, Yes, this is a commonly asked question and I'm glad you brought it up. These are indeed all correct. The reason that carbon dioxide plays a critical role in determining Earth's temperature is that water vapor comes from the ocean, which covers 3/4 of the planet's surface. Think of the vast ocean as a nearly inexhaustible source of potential "greenhouse gas", just waiting to be converted to water vapor whenever the temperature rises a tiny bit. This is what we scientists call a "feedback". Humans have absolutely no way to control the water vapor content of the atmosphere because the liquid water (ocean) covers so much of the Earth's surface. On an imaginary desert planet, this would not be true - water vapor emitted by some civilization living on that planet would indeed change the climate. But if we emit water vapor it just gets rained out in a few days and cannot compete with the ocean as a source. So carbon dioxide is critical because it is not subject to this "feedback", and in fact drives this "feedback".
Karl(Q) What about effects of global warming on birds and mammals, I heard that penguins might not be able to get their food because ice melting and polar bears need ice. Do we need artificial polar bear places or is ocean just too big??
Dr_Jeff_Severinghaus(A) Dear Karl, These are accurate reports you have heard. Penguins and polar bears are indeed under threat because of global warming. But it is important not to focus too much on just these two (loveable) species. Recall that global warming will cause tens of thousands, perhaps millions, of species to go extinct. These are facts that are difficult for the human mind to comprehend, they are so staggering, and so spread out in time (hundreds of years) that it is difficult for us to get a grasp on them. But they are undeniably true.
moderator(Q) This question was submitted via e-mail by Joe: Climate change ... do you feel the IPCC reports accurately reflect what is really happening as to the rate of warming? My hunch tells me that all their reports err on the side of caution and conservatism in terms of how fast glaciers are melting, etc. There's a US ice and snow expert in CO, I believe, Ted Scambos (?) who thinks the arctic ice cap may be gone by 2020 ... that the rate of melting is much faster than we generally are led to believe. True?
Dr_Jeff_Severinghaus(A) Dear Joe, Stefan Rahmstorf published an interesting paper in Science magazine last year, showing that the IPCC's projections from 1995 onward, made in 1995, actually were on the conservative side in the subsequent 12 years. When compared with what actually happened, the IPCC's error envelope for both sea level rise and temperature just barely contained the actual records. So this tells us that you are generally correct - the IPCC is a conservative organization and does not engage in speculation or science that is in progress (with a few very notable exceptions, such as the infamous "hockey stick", which indeed was a work in progress when they used it). Ted Scambos has his finger on the pulse better than anyone I know. I would take his word seriously if he thinks 2020... I hear many people saying 2030. Anyway, you are correct that IPCC is conservative.
gac(Q) From Grant's question, if atmospheric circulation slows down, could not water vapor and clouds accumulate (rather than precipitate) and cause large climate change?
Dr_Jeff_Severinghaus(A) This is an interesting idea. There is already some evidence that the east-west atmospheric circulation in the tropical Pacific ocean is slowing down a little ( this is the circulation that brings us El Nino, among other things. It's called the Walker circulation.) It is tough to predict what clouds are going to do, because they are incredibly complicated beasts. Perhaps I'll redirect this question to my colleague Joel Norris, who works on clouds at Scripps (jnorris@ucsd.edu).
tassili(Q) While I believe in glaobal warming, and recycle and all that good stuff, I run into people who say, "No such thing. The earth has cycles of warming and cooling. Look at the ice age." What is good proof that this is a man made change?
Dr_Jeff_Severinghaus(A) Dear Tassili, This is an excellent question - I'm glad you asked it. The best proof that this is man-made comes from the isotopes (different flavors of an element, if you will) of carbon in atmospheric carbon dioxide. We've been measuring these for 41 years now at the Scripps Institution of Oceanography, continuing the pioneering work that Charles David Keeling began. These isotopes are like the "smoking gun" that shows that the CO2 rise is human-caused. Natural CO2 is rich in these isotopes (carbon-13 and carbon-14), but fossil fuel CO2 is depleted in them. So if you measure the atmospheric abundances of these, you can tell where the CO2 is coming from - natural or fossil. Indeed, the isotopes have been taking a nose dive over the past 150 years of the industrial revolution. So there is absolutely no doubt that humans have done it - in this "whodunit". Then you add in the basic physics, known from the laboratory for 140 years, that carbon dioxide traps heat. That is really an airtight case at that point - the evidence goes on and on but that is the key part.
moderator(Q) This question was submitted via e-mail by Joe: Do you have any opinion re: slowing down the rate of population growth to help combat global warming? I think it makes sense; but not sure how we'll agree on how to implement nat'l or global policies in furtherance of that concept.
Dr_Jeff_Severinghaus(A) Dear Joe, This is a good question, and it comes up repeatedly so I'm glad to have a chance to address it. The problem is really consumption, not population. Think of it this way. The average person in China produces one-fifth as much global warming as the average American. If they produced the same amount as us, they would increase their impact fivefold. Population growth, on the other hand, is only going to increase by a doubling at the very most and more likely only a 50% increase so that we stabilize around 9 billion. So global warming is really driven by changes in per capita greenhouse gas emissions, rather than population per se.
rick(Q) To clarify my question further, I am involved in city planning and we are looking for code opportunities to help combat global warming... we are split on the issue of allowing outdoor (recreational) fireplaces at all, with some claiming that gas fireplaces would be a good alternative to wood burning fireplaces in the context of pollution and global warming.
Dr_Jeff_Severinghaus(A) Dear Rick, As far as global warming is concerned, wood is better because the trees remove carbon dioxide from the air as they grow. Natural gas, on the other hand, comes from fossil sources and so adds to the total amount of heat-trapping CO2 when it burns. But local air quality issues run the other way, of course, with gas being much cleaner for local ozone and smog problems. So this is a trade-off..
moderator(Q) This question was submitted via e-mail by Joe: Not too many are discussing food shortages as a result of climate change. Do you see this as a real danger as climate change impacts agribusiness in the future?
Dr_Jeff_Severinghaus(A) Dear Joe, Droughts in California are very likely due to global warming, and could be sustained for decades (so-called Mega-droughts). So yes, agribusiness is definitely vulnerable to global warming. There is too much attention paid to temperature, and not enough to water availability, in my opinion. This is an important topic and needs to have greater visibility.
drabo2000(Q) What is the best evidence that atmospheric CO2 rather than some other factor has caused the increase in temperature over the past 100 years? The two are correlated but this correlation does not prove causation, right?
Dr_Jeff_Severinghaus(A) Dear drabo2000, The best evidence is what I alluded to in a recent answer - basic physics. It has been possible for more than 100 years to calculate how much heat gets trapped by CO2. You can do this about as well as you can calculate how fast an apple will fall under Newton's Laws of Gravity. But we also know that nature on her own causes climate change, and that some of the 20th century warming was natural in origin. The warming of the 1920s and 1930s, that was associated with the famous "dust bowl", was caused by the sun. Solar activity peaked then, as we can easily tell from records of sunspots and cosmic ray fluxes. But all the solar indicators have been constant in the past 30 years, leaving no doubt that the current warming cannot be attributed to the Sun.
ramoslol(Q) Whatever happen to "Global Cooling?" We were feed this a couple of years ago. Also, what do you think about tax on Carbon? Seems like a way to tax the American people.
Dr_Jeff_Severinghaus(A) Dear ramoslol, The notion that "global cooling" would happen was very briefly (and speculatively) mentioned in a few papers in the 1970s, as you say. But this really was pure speculation. Good scientists did not buy this. It is sort of like comparing the very few papers published in the 1950s that found no evidence linking smoking to cancer, with the vast and unassailable body of evidence that smoking causes cancer. I won't comment on the tax on carbon - I'm a physical scientist and not an economist. But my economist friends tell me that reducing the payroll tax at the same time that you increase the carbon tax would result in no net increase in taxes. But it would relieve the regressive burden that payroll taxes impose on average working people, at the same time that it encourages innovation and technological advancement.
drabo2000(Q) Jeff, Thanks. Temperature changes led CO2 changes over glacial-interglacial cycles so the idea is that a different scenario explains the rise in temperature over the past 100 years, right? Could you explain? Thanks.
Dr_Jeff_Severinghaus(A) Dear drabo2000, Yes, this is an often-mentioned fact that is worth explaining, because it is so widely misunderstood. The ice ages are caused by the Earth's orbit around the sun - when we go farther from the sun in June (when most ice melts), ice sheets grow and you get an ice age. A few hundred years after the ice sheets change, due to the decrease in June sunshine, the ocean reacts to the change and takes up more carbon dioxide. This then causes slightly more cooling - what we call a "feedback". But it is clear from the isotopes of the carbon dioxide, that we have measured, that the ocean is the source of this CO2. In other words, it is clearly natural CO2. The current increase in CO2, on the other hand, is clearly from fossil fuels, based on the isotopes as I mentioned in an earlier post. So the "smoking gun" is really the isotopes of carbon.
jeff(Q) What are the most important things individuals can do to curb Climate Change?
Dr_Jeff_Severinghaus(A) Dear Jeff, Again I'll have to take off my scientist's hat - I am not qualified to speak on these topics. But I am a citizen, so I'll give you my own opinion (realizing that this is NOT science). I think individuals can change their lifestyles, insulating their homes so that they use less energy in summer when it's hot, or winter when it's cold, and buy an efficient car. When plug-in cars are on the market in the next two years, they can buy these (producing electricity in a central huge power plant is more efficient than an internal combustion engine). They can write letters to elected representatives, especially congressmen. There needs to be some top-down solutions as well as individual efforts, because much of the CO2 is emitted by corporations. Those corporations need a level playing field, and predictability that comes from having a schedule of emissions reductions laid out clearly and fairly for the next 30 years or so, so that planning can take place and investments can proceed. There is nothing worse for investments than uncertainty.
moderator(Q) This question was submitted via e-mail by Bill: What have you to say about the unusually quit period of the sun spots we are in the midst of? Surely you recognize the sun is a far greater factor than all tailpipes and smokestacks - in fact it was just a few hundred years ago we had a mini ice age because of this same phenomenon.
Dr_Jeff_Severinghaus(A) Dear Bill, This is an excellent question. The sun goes through an 11-year cycle of activity, and this is not news. It has been known since Galileo invented the telescope. So what does this have to do with climate? The warming of the past 30 years can't be explained by the sun because there is no trend in solar activity over this time. In other words, the sun's activity has gone down just as much as it has gone up during these 11-year cycles, leading to zero overall net change with time averaged over the 30 year period. This wasn't true in the 1920s and 1930s as I mentioned in an earlier post.
Lippy_(Q) Some people say that global warming is causing hurricanes and excessive rains, but you say it may cause droughts. Which is it?
Dr_Jeff_Severinghaus(A) Dear Lippy, It is both, in different places and at different times. As you know, the southwestern US is rather dry, but Florida is quite wet. The projections are that Florida will get wetter and California will get dryer - sort of like the "rich get richer and the poor get poorer". Midcontinents (think Kansas) will get drier, but Alaska will get wetter. So it is not terribly useful to think about moisture in global terms - we only really care about how much water we have locally, not globally. In fact, simple physics tells us that a hotter world must create more evaporation, which means that there must be more total rain. But most of that rainfall increase will be in the tropical rain belts (think Amazon, Indonesia). So it really doesn't have that much to do with water availability where we care about it most.
Lippy_(Q) Do you have a solution to combat global warming that is in line with the realistic energy needs of the world?
Dr_Jeff_Severinghaus(A) Dear Lippy (again!), This is an excellent question. All too often discussions of solutions focus on unrealistic options. I am not qualified to comment on a solution to combat global warming, but again I can take off my expert's hat and tell you what I think as a citizen. A combination of carbon sequestration underground and in deep ocean sediments, where stable clathrates are formed, using our abundant coal resources, plus some nuclear power, plus some conservation, plus some solar and wind, when taken all together, is I think a realistic solution. Coal is pretty hard to beat as a cheap energy source. So using that coal, but keeping the CO2 and mercury and other pollutants out of the atmosphere, makes good economic sense. We can gasify the coal, making hydrogen and synthetic liquid fuels as salable products, and sequester the CO2 so produced. This is called Integrated Gasification Combined Cycle, or IGCC.
moderator(Q) This question was sent via e-mail by Jim: How much greenhouse gasses does the landfill in miramar produce everday, every year? Is methane more harmful than tailpipe emissions?
Dr_Jeff_Severinghaus(A) Dear Jim, Methane is currently about one-third as important as carbon dioxide in causing climate change. But it only has a lifetime of 8 years, compared to a century or more for CO2. So for future generations, I think methane is really not all that significant, and we can let that one go to some extent.
Dr_Jeff_Severinghaus(P) This is goodbye, and thanks to those of you who participated. I'm always pleased when I get such excellent questions. Thanks again.
moderator(P) We are out of time, but thank you for participating in today's chat with Dr. Jeff Severinghaus. Please remember to check the schedule for our other upcoming chats, which can be found at http://www.signonsandiego.com/chat. If you don't have time to join a chat, just use the link on the chat page to e-mail a question to the moderator. Then, when you have time, return to the chat page (www.signonsandiego.com/chat) to read the transcript. We can't answer every question, but we will do our best.
