On 6 degrees of climate change
Climate change is all about degrees. Six degrees Celsius of warming may not sound like much probably because temperatures can swing by 6 degrees within an hour if a warm front passes, and it doesnt mean the end of the world, said Mark Lynas, author of a book called Six Degrees: Our Future on a Hotter Planet. But if we raise global average surface temperatures by just 6 degrees above pre-industrial levels, Lynas told me, well create a scenario which is so extreme its almost unimaginable. Most of the planetary surface would be functionally uninhabitable, he said. Agriculture would cease to exist everywhere, apart for the polar and sub-polar regions, and perhaps the mid-latitudes for extremely heat-tolerant crops. Its difficult to see how crops could be grown elsewhere. Theres a certain level above which plants just cant survive. Theres a certain level where humans biologically cant survive outside as well ... The oceans would probably stratify, so the oceans would become oxygen-deficient, which would cause a mass extinction and a die off in the oceans, as well which would then release gases and affect land. So its pretty much equivalent of a meteorite striking the planet, in terms of the overall impacts. I chatted with Lynas, a science writer in the UK, about how to avoid a 6-degree world, the international goal of limiting global warming to 2 degrees and how to talk to kids about climate change. The following is an edited transcript of our conversation. For background: This interview came about because of you. Lynass book was one of 12 chosen by readers for a book club as part of my 2 degrees series on climate change. To follow along, and shape the coverage, sign up for the 2 degrees newsletter. Lynas has agreed to take your questions the week of June 8. Lynas: Sure, sure. Ill do my best. In the marine environment, I think the most threatened ecosystems are coral reefs. (Theyre) threatened both by coral bleaching, due to rising temperatures and ocean acidification, plus the general degradation of everyday, general human activity. Its very tough to imagine that the worlds coral reefs will continue to exist in their present day form in a 2-degree warmer world. The other most-threatened environments probably are the mountain ecosystems where species will be left marooned in shrinking islands of habitat. As temperature rises, you can imagine biomes rising up the sides of the mountains, and species which are dependent on a certain level of temperature and humidity will get left with nowhere to go. Theres really a lot of uncertainty about this. Its possible to imagine hurricanes will become less frequent but more intense, and possibly (form) over new areas. Lynas: The overall global picture is kind of, unto them that have with be given more and unto them have not shall be taken away if you want to get biblical. That maps out as the subtropics, which are already the drier parts of the globe, will become more water-deficient. The deep tropics will actually get more rainfall, as well as some of the mid-latitudes. But the subtropics which is the southwest of the U.S. would expect to see less rainfall, which indeed seems to be whats happening. That does call into question, really, the development model that large areas of the southwestern U.S. have adopted expecting a large amount of freshwater to be available to urban areas and agriculture, which are already in a pretty arid location. So I do think its going to be hard to adapt to that change. Lynas: I used to be adviser to president of the Maldives, who is, by the way, now in jail due to there having been a coup. But his challenge, and his main agenda, when he was president, was to bring to attention the fate of the small island states especially those that are coral atolls. For the Maldives, the entire country exists at a meter or less above sea level, and little more. Its difficult to imagine the survival of coral atoll nations at 2 degrees, it has to be said. Although the extinction process depends on the rate of sea level rise. It might take decades, it might take centuries, its not clear at the moment. But I dont think they have a very long term future. Lynas: Its a scenario which is so extreme its almost unimaginable. Not many studies have addressed this because its so far off the scale of what can be envisaged. I found myself looking back at the really serious traumatic events in the Earths geological history, which have led to mass extinctions, such as the one at the end of the Permian period, 250 million years ago, which wiped out nearly 90% of life on Earth. Actually, a lot of the mass extinctions seem to have been associated with very rapid global warming events. Humans are releasing carbon more rapidly even than took place during mass extinctions. We havent gotten there in terms of the overall amount, but were certainly moving in that direction. So its not a planet that I think any of us would want to live in, and it doesnt have to happen. While I think its important to try to visualize what a 6-degree world would look like, its also important to remember that we dont have to go there. Lynas: Most of the planetary surface would be functionally uninhabitable. Agriculture would cease to exist everywhere, apart for the polar and subpolar regions, and perhaps the mid-latitudes for extremely heat-tolerant crops. Its difficult to see how crops could be grown elsewhere. Theres a certain level above which plants just cant survive. Theres a certain level where humans biologically cant survive outside, as well. We get close enough already in the Arabian Peninsula and some other parts of the world. Remember, 6 degrees is a global average. It would be probably twice that over land and somewhat less than that over the oceans. The oceans would probably stratify, so the oceans would become oxygen deficient, which would cause a mass extinction and a die off in the oceans, as well which would then release gases and affect land. So its pretty much equivalent of a meteorite striking the planet, in terms of the overall impacts. Lynas: A lot of people want to know what warming we get with what emissions path, or what warming we might get by what date. Thats pretty fundamentally uncertain because they depend on different factors which arent very well quantified. I felt that looking at it degree by degree was much more robust. If the temperature rises by X amount then what will be Y impacts? There are three major sources of information about that. One is the observational changes were already seeing in terms of impacts in temperature rise. The second is computer models showing different ecosystem changes or whatever. And the third is paleoclimate sources so looking at how the climate was different in earlier hotter periods in geologic time. So piecing those together and mapping them onto a degree by degree picture seemed to me to be a way to try to convey this in a visual and intuitive but also highly scientifically appropriate way. Lynas: I think its important to have a target because it focuses policy and it focuses peoples efforts. And it makes sense also to have a target based on the temperature. But its not something we can meet, by definition. We dont have a simple thermostat where we can decide exactly how much carbon to emit and have an exact temperature result dependent on that. So, theres uncertainty, really, about what level of emissions will lead to what temperature outcomes, by when. However, I think that 2 degrees is really the absolute upper limit of whats tolerable in terms of ecosystems and, probably, adaptive capacities of human societies. A 2-degree world is a world without coral reefs, and with much less snow and ice and with fairly dramatic heatwaves and other impacts. So, I would like to see a global warming future in which warming actually is lower than that, personally. Lynas: I think its possible. Its not very likely. If our current understanding of climate sensitivity is broadly correct then were probably going to come in between 2 and 3 degrees, somewhere, by the end of the century. I guess the good news is the absolutely calamitous 5 and 6 degree outcomes are particularly unlikely, too, although still possible. And certainly, the risk of them happening is higher than the risk of an airplane crashing when we get onto it. Lynas: Well, the likelihood of an airplane crashing is, I dont know, one in 1 million or something on that order of magnitude. Whereas the likelihood of coming within 5 or 6 degrees of warming is probably more than 1 in 100. Its the sort of risk that one would not tolerate at a personal level. But, perhaps because we can diffuse responsibility, we feel that its tolerable for our species to take that gamble with the whole planet. Maybe its because we just think theres nothing we can do about it. And we have an in-built optimism bias, myself included, where we like to think that things will just turn out all right, because they often tend to. And meantime well go on with our lives as normal. Its a big ask, I guess, to make society as a whole forgo the main energy source we all enjoy, which is fossil fuels, in order to forestall uncertain impacts decades into the future. It doesnt really matter whether you find it depressing or not, its the scientific reality. We have to deal with it. A thing like climate change is known as a wicked problem. Its seen differently by different people, according to their psychological, political and cultural biases. You can frame it as just a technology challenge: Lets get off of fossil fuels and lets get onto renewables and nuclear easy. Or you can frame it as a moral challenge: Were trespassing on the rights of future generations and how dare we do that. Or you can see it as a political challenge that somehow these big fossil fuel corporations are transgressing democracy and forcing us to stay hooked on oil and coal and gas. Different people, according to their politics, will see climate change fundamentally in this way. Its not a simple problem to understand. Well, Im a pragmatist. I think its a solvable problem. I dont think we need to abandon capitalism or change our entire political system in order to tackle this challenge. Other people do, and I disagree with them on that. And we have debates late into the night. But I think with next-generation nuclear technologies, and particularly with the way solar power is developing so rapidly, and how rapidly its coming down in cost, and how quickly the technology is improving, there are zero-carbon options now becoming much more widely available, which will bring down our emissions much more rapidly than people think or than people thought just a few years ago. I dont think theres any point being pessimistic about that. Pessimistic people dont achieve anything. Its important to do whats possible and to do it quickly. Lynas: We are now inhabiting a human-dominated planet. We are in a new epoch known as the Anthropocene. The Holocene is now considered to be over. And I dont think theres really been another species that has had that effect on the planet before maybe the first bacteria that emitted oxygen, or photosynthesizing microorganisms. But we really are into terra incognita looking forward. That gives our species a serious level of responsibility for planetary management that people just dont really appreciate at any kind of fundamental physiological or political level. We are in charge. Its up to us. We actually do have an overall effect on the earths temp. Its not up to Mother Nature anymore to run the show. Lynas: Yeah. The reason I was distracted just a minute ago was my kids just came back from school. Lynas: I talk to them a bit. They know what I do. Younger generations have grown up with this specter. Its a bit like how those of us who are older grew up with the Cold War and the threat of nuclear annihilation ... So theyre not entirely in a different situation, I suppose, from previous generations. You could feel bad for future generations, but on the other hand Im not sure their future is any worse than the future for somebody born in, say, 1900, who in all likelihood, in Europe, would have killed in one of the world wars. Its a manageable problem. Were beginning to get the grips of it. There are some positive signs already China and the U.S. agreeing to peak emissions, and things like that. So its not a counsel of despair. And I think its important to talk to kids at that level not to make them think that somehow theyre fundamentally doomed. That isnt the case and doesnt have to be the case. Lynas: Well, Im a ecomodernist, which is a new label a lot of environmental thinkers are beginning to attach to themselves because its a bit different from more traditional environmentalism, which thought we were somehow doomed or we were fundamentally a destructive species. We can turn this around this and other problems as well, if we have a more pragmatic approach to politics, economist and especially technology. We need to have a price on carbon, so that emitting carbon dioxide isnt cheaper than other energy sources. We need to invest heavily in research and development in zero-carbon sources, including next-generation nuclear renewable energies, especially solar. And we need to deploy them on an ever wider scale, with increased financing. We also need to have a political agreement so theres a sense the whole world is moving in the right direction. All of those things are not just possible, but I think theyre fundamentally achievable, and likely. But we need to keep the pressure up on politicians and on everyone else. Email questions to: climate [at] cnn.com. Subscribe to the 2 degrees newsletter. Follow the project on Facebook, Twitter and Instagram.