"Climate‐Change Science and Policy: What Do We Know? What Should We Do"
Presented September 6, 2010; Gamle Festsal, Oslo, Norway
JOHN P. HOLDREN is Science Advisor to President Barack Obama and Director of the White House Office of Science and Technology Policy, Executive Office of the President, and Co-Chair of the President's Council of Advisors on Science and Technology (PCAST). Prior to joining the Obama administration Dr. Holdren was Teresa and John Heinz Professor of Environmental Policy and Director of the Program on Science, Technology, and Public Policy at Harvard University's Kennedy School of Government, as well as professor in Harvard's Department of Earth and Planetary Sciences and Director of the independent, nonprofit Woods Hole Research Center. (FULL PROFILE [2])
On September 6, Dr. Holdren addressed the Kavli Prize Science Forum, [3] a biennial international forum to facilitate high-level, global discussion of major topics on science and science policy, held in conjunction with the Kavli Prize Science Week and Ceremony. The audio and PowerPoint presentation is available in two formats: as a video (above) and as a written transcript with downloadable presentation (PDF format). [4]
TRANSCRIPT AND SLIDES (CLICK IMAGE BELOW FOR POWERPOINT PRESENTATION)
Ministers, Ambassador White, Mr. Kavli, distinguished colleagues, ladies and gentlemen. My topic today, as is obvious from the screen, is climate change science and policy: what do we know, what should we do. And the secret bottom line is what is the Obama administration doing.
[4] CLICK TO DOWNLOAD SLIDES (PDF) [4]
[SLIDE 1] I will get to that, but I want to make a few general observations first to put these remarks in context. I’ve given the broad focus of this symposium on international cooperation in science. President Obama was clear from the very outset -- clear in his campaign, clear in his inaugural speech, clear on many, many occasions since – that he places a very high priority on science and technology, on the federal government’s stewardship of an investment in science and technology, of international cooperation in science and technology, and the reason he places such a high priority on these activities — and indeed on science, technology, engineering and mathematics education – is that he recognizes with crystal clarity the relevance of science and technology to the full array of great challenges that we face in the United States and indeed that most societies around the world face in common. Of the challenges of maintaining viable and growing economies; the challenge of delivering better health care outcomes to all citizens at affordable cost; the challenge of addressing the great problems at the intersection of energy and environment; above all, the challenge of climate change; the problems of maintaining peace and security in the world.
And the President recognizes as well, and this is particularly important I think in the context of the priorities of The Kavli Foundation – he recognizes the fundamental underpinnings that basic research provides the science and technology enterprise. That was particularly visible when the President spoke at the annual meeting of the National Academy of Sciences in 2009, the first annual meeting following his inauguration. He was the first president since John F. Kennedy to do that, and if you read that speech, which is still on the web I believe – both at the Academy web site and my friend Ralph Cicerone, president of the National Academy of Sciences, is in the front row – and it’s also on the White House web site – what you will find is although the president was clear about the practical applications of science and technology to our great challenges as I’ve mentioned, he probably spent two thirds of that talk talking about the importance of basic science; the importance of fundamental research in science and technology to our national well-being; and the importance of science, technology, engineering, and mathematics education.
And he has been emphatic as well – emphatic with me in our initial conversations, emphatic ever since about my responsibility and my office’s responsibility – for fomenting increased international cooperation in science and technology, including in basic research. At the first cabinet meeting, the President said to his full cabinet, “I’m willing to accept and to listen to any sort of bad news that you’ve got to bring me, except the bad news that you’re not cooperating.” He said, “the challenges we face are too big, and our resources are too limited, for us to be able to afford noncooperation,” and that holds internationally as well as domestically among our agencies, among the private sector, the public sector, the philanthropic sector – it holds among nations. We cannot solve the great problems of our time alone – any of us – as individual nations. We need to solve them together, and science and technology pursued together are going to be immensely important elements of those solutions.
[5]John P. Holdren, science advisor to US President Barack Obama, presenting his keynote address at the 2010 Kavli Prize Science Forum. (Scanpix)
[SLIDE 2] My remarks today on climate change science and policy are in a sense an illustration of this wider phenomenon. I’m going to cover a lot of ground, I’m going to cover it quickly, I’m going to use a wordy PowerPoint because I’m happy then to make that available and anybody who finds the presentation too fast I’ll be happy to send them one and we’ll post it on the White House website as we usually do.
I’m going to cover the basic science fairly quickly – the essence of the challenge we face in the climate domain. Talk about five rather conspicuous myths propagated in large part by what the foreign minister has rightly called “the merchants of doubt,” talk about the risks and impacts we are likely to face going forward in the climate domain, and then turn in a little more depth to what we should do: the options available to us, what we need in the way of mitigation – how much, how soon; looking at the implications of our options for mitigation for the policy needs for bringing that mitigation about, and finally what the Obama administration is doing.
[SLIDE 3] I like to present the essence of the challenge this way: without energy there is no economy; without climate there is no environment; without economy and environment there is no material well being, there’s no civil society, there’s no personal or national security. And the problem is that the world is getting most of the energy its economies need in ways that are wrecking the climate its environment needs. That is the fundamental dilemma and the fundamental challenge we face.
[SLIDE 4] And here are the five myths I want to talk about.
The first one: a little global warming can’t hurt anything.
The second: the Earth has warmed since 1998 anyway.
The third: Any warming that has occurred has been natural.
The fourth: If there is any danger, it’s far in the future.
And the fifth: That the emails stolen from the climate research unit at the University of East Anglia and the mistakes that the IPCC made have shown that mainstream climate science is deeply flawed.
[SLIDE 5] So let me start with the proposition that global warming itself is a misnomer and indeed a dangerous misnomer. Global warming implies something that’s uniform across the planet; it’s mainly about temperature that’s gradual; and it is quite possibly benign. What could be wrong with a little bit of warming? What’s actually happening is none of these things. It’s highly nonuniform geographically. It’s not just about temperature, but as we’ll see in a moment about a whole panoply of variables that make out the climate. It is rapid compared to the capacities for adjustment, the capacities of ecosystems, and the capacity of social and economic systems to adjust, and it is going to be harmful for most places and most times. Some places for some time will get some benefits from climate change, but most places for most times and increasingly so going forward will suffer harm. We should therefore not be calling it global warming at all. It was indeed I think a strategic mistake to call it global warming. We should be calling it global climate disruption, even though that is a larger mouthful than global warming.
[SLIDE 6] Now let me turn to why average temperature is not in fact the whole story. We do use the average surface temperature of the Earth as a proxy for climatic conditions that are much more complicated, but we need to understand as a society that climate is the patterns of weather – meaning the averages, the extremes, the timing and the spatial distribution of not just hot and cold, but cloudy and clear, humid and dry, how much precipitation we get and what forms, when it melts, when it snow, how hard the wind blows – and again, when you’re talking about climate change, what it really means is disruption of the patterns. The global average temperature is just an index of the state of global climate in the same way that the temperature of your body is an index of the state of your body. When your body temperature goes up a mere two or three degrees Celsius – a mere two or three degrees Celsius – you know you’ve got a problem. It’s telling you something about the state of your body. And when the temperature of the planet goes up two or three degrees Celsius, that’s telling us we have a problem also in the same way. Small changes in that index correspond to big changes in climatic patterns.
[SLIDE 7] Can it hurt anything? Well again, I think most people are perhaps not sufficiently aware of the number of ways in which climate affects our well being. Climate governs and therefore climate disruption affects: the availability of water around the planet; the productivity of farms, forests and fisheries; the prevalence of oppressive heat and humidity; the formation and dispersation of air pollutants; the geography of disease – what vectors and pathogens can live in what abundance at what times of the year in what places; the damages we have to expect from storms, floods, droughts and wildfires; the property losses we have to expect from sea level rise; the amounts of money we have to spend on engineered environments; how much of our environment do we need air conditioned; what dykes, dams and so on do we need to build. And indeed the distribution and abundance of species – the ones we love, like polar bears; the ones we hate, like mosquitoes; and everything in between.
[SLIDE 8] And the fact is that the earth is getting hotter. This is the global average surface temperature land-and-ocean combined index with an arbitrary zero, and what you see there is that 2005 remains the hottest year on record –although 2010 may be on a course to surpass it; 2009 the second and so on through the list. The fifteen hottest years have all occurred since 1990.
[SLIDE 9] If you look at it in a different way, you see that the 1980s were the warmest decade on record at the time, but every year in the 1990s was warmer than the 1980s average and every year in the 2000s have been warmer than the 1990s average. The notion that the world has not been getting warmer is simply incorrect.
[SLIDE 10] The heating of course is not uniform geographically – I mentioned this before. This shows the surface temperature average over 2001 to 2005 versus the average for 1951 to 1980. The average temperature increase for the globe in this period was only half a degree Celsius, but you see looking at the scale that in the central continental regions and particularly in the far north and the Antarctic peninsula, the temperature increases were two to three times the global average, and we expect that to continue; it’s well understood for the most part why it happens.
[SLIDE 11] Other indicators of climate have been changing apace. This shows annual precipitation trends over the 20th century. Green places getting wetter, orange places getting drier, and the size of the circles indicating the percentage change over the century. On average the world gets wetter in a warmer world because more water evaporates. What goes up must come down, so it rains more. But that is highly nonuniform and again, some places that you can see get drier while some places get wetter. Another aspect of this phenomenon is that in a warmer, wetter world a larger proportion of the precipitation falls in extreme events.
[SLIDE 12] The ocean heat content has been growing, as would be expected under these circumstances. Coastal glaciers have been retreating. Lots of before and after pictures available on the web.
[SLIDE 13] This is a prominent glacier, a coastal glacier in Alaska. [19]41 to 2004.
[SLIDE 14] This is the Himalayas. The largest glacier on Mt. Everest’s northern slope. Practically gone over the period between 1968 at the top and 2007 at the bottom.
[6]The 2010 Kavli Prize Science Forum, held in the Gamle Festsal at the University of Oslo, Norway. (Scanpix)
[SLIDE 15] Arctic sea ice is not only shrinking at its late summer minimum, which takes place later this month, but it’s also thinning. If you look at these figures – the 1981 to 2000 average, then 2007 which looked like the record low year in terms of extent, when you take thinning into account, 2008 had even less summer sea ice than in 2007; 2009 less still.
[SLIDE 16] Greenland and the Antarctic ice sheets are losing mass. When the sea ice disappears, sea level doesn’t change because that was floating ice. But these land ice masses have the potential to raise sea level when they lose mass and we now know that the Antarctic ice sheet as well as the Greenland ice sheet is losing mass. It was only relatively recently that we got the data to understand that Antarctica as well is losing mass.
[SLIDE 17] And so not surprisingly sea level is rising as a result not only of the loss of mountain glaciers and the great land ice sheets – losses from the great land ice sheets; but also thermal expansion of sea water because the ocean is getting warmer. And you see the red is tidal gages. Late in the last century we had the capacity to start to sense sea level from satellite observations. You can see the overlap of the red lines from the satellite observations. They’re in good agreement. And you can also see the satellite observations are right at the upper end of the range of IPCC projections.
[SLIDE 18] So do we have good reason to believe that humans are causing this primarily? Yes, we do. This is the IPCC’s assessment in the 2007 report. No part of this has been called into question by the way. The best estimates of the forcings – literally how hard we’re pushing on the climate over the period from 1750 to 2005, both human causes and the principle known natural caused changes in the amount of sunlight reaching the earth over this period – overwhelming the human causes are prevailing. The human causes are both positive and negative. Reflective particles and the cloud-forming effects of particles have an overall negative effect which masks part of the warming from the greenhouse gases and absorptive particles, but the warmth is winning over the cooling as has long been understood and expected. And if you compare the warming influence of the human-caused greenhouse gasses and the absorbing particles, it’s over this period about 30 times the warming influence of the estimated change in input from the Sun. If you look at the recent data where we have particularly good satellite measurements of what the Sun is doing, there is no increasing trend in the solar output to explain the rapid, recent increases in surface temperature of the Earth.
[SLIDE 19] We also know that the key greenhouse gas increases that generated these forcings were caused by human activities. We have a couple of ways of knowing that. Here are the plots for carbon dioxide and methane, the two most important anthropogenic greenhouse gases over a 10,000 year period on the big scale and over the last couple hundred years on the small scale. And you see on the long time scale, there’s this utterly sharp turn where, with the industrial revolution and the large-scale influences humans in other ways of the surface of the earth, you find this extraordinary rate of increase. But we also know that humans are responsible for the CO2 spike because carbon dioxide from fossil fuels lack carbon 14, and when you dilute the atmospheric carbon dioxide with fossil carbon dioxide you can actually see the signal of the declining fraction of carbon 14 in atmospheric CO2.
[SLIDE 20] This is one of the busier slides here but I think is also one of the more compelling. I call this the fingerprint; in some presentations, I call it the smoking gun. What one has in the top panel is a plot for the period of the thermometer record – roughly from 1880 onward – of our best estimates of the known forcings of greenhouse gasses, solar output, volcanoes. The blue line that goes periodically downward in spikes are the cooling effects of volcanic eruptions which inject reflecting particulars into the stratosphere that stay there for two or three years. The red line at the top is the greenhouse gasses. And what you see at the bottom is what happens when you feed a state of the art climate model of those forcings and say, given these forcings, what should the climate have done over the last 125 years, and you see the various runs and then the observations in blue. The match is very good. It’s not perfect. We would never expect it to be perfect because the climate is a noisy and in some respects chaotic system. But the fit is very good. It’s very hard to look at this diagram and conclude we don’t fundamentally understand what is being done to the climate and by whom.
[SLIDE 21] Furthermore, models match the observed changes in temperature separately on every continent. This was a relatively new result in the period between the third and the fourth assessment by the IPCC.
[SLIDE 22] Are we seeing harm now? This is an interesting slide from some of my colleagues in China at Tsinghua University where they have concluded that a 30-year trend in the weakening of the East Asia monsoon, which they attribute to global climate change, has meant less moisture flow from south to north in the atmosphere over China, which is producing increased flooding in the south and drought in the north, already having serious impacts in China.
[SLIDE 23] Wildfires. Wildfires in the western United States up about six-fold in the last 30 years. Similar trends in other fire-prone regions, including this summer of course in Russia among other areas.
[7]Ernst-Ludwig Winnacker, the first Secretary General of the European Research Council and now the Secretary General of the Human Frontier Science Program, presentng his keynote address. (Scanpix)
[SLIDE 24] Pest outbreaks. This is a marvelous ecological story, where pine bark beetles, which got a longer breeding season courtesy of warming, could get four generations of beetles into a single season instead of three. That proved to be a tipping point for devastation of trees already weakened by heat and drought. A similar thing has happened with the spruce bug worm in Alaska where millions of hectares of spruce have been devastated.
[SLIDE 25] Melting permafrost; these of course are particularly evocative pictures, and this happens to be from the Norwegian Polar Institute which does wonderful research in the Arctic.
[SLIDE 26] Coastal erosion – this is the village of Shishmaref, in the far far north of Alaska, where the coastal erosion is not so much from rising sea level but the melting sea ice has reduced the protection from waves.
[SLIDE 27] And this kind of harm is widespread. We’re seeing variously in different places around the world more floods, more wildfires, more droughts, more heat waves, more pest outbreaks, more coral-bleaching events, increasing power of typhoons and hurricanes, expanded geographic range of tropical pathogens. All of these plausibly link to climate change by theory, by models and by observed fingerprints – namely the patterns matching what you would expect if climate change were the cause.
[SLIDE 28] And we do expect bigger impacts going forward. This again is from the fourth assessment of the intergovernmental panel on climate change – an immensely important international cooperative effort on characterizing, synthesizing and summarizing the science in this domain, not withstanding a modest number of mistakes which were bound to creep into any exercise of this magnitude. Looking at various trajectories going forward, history in black to the left, the European Union target of holding the global average surface temperature to less than or equal to 2 degrees C – the EU was the first to embrace that target; but as you’ll see, it’s now been embraced more widely. And you see under most of the trajectories we sail through that 2-degree target in the middle of this century. The gold curve at the bottom is what would happen if you could freeze the atmosphere instantaneously at its current composition. We have no way to do that, but it indicates the temperature continues to coast up for a while because largely the thermal inertia of the ocean – the ocean has a huge heat capacity and it takes the ocean decades to catch up to any change in the energy flux in the atmosphere.
[SLIDE 29] What do we expect in the future? We expect hotter summers. This is from the latest of a batch of National Academy, National Research Council studies of climate change that have come out in the last few months. This one is stabilization targets and this again – a wonderfully evocative picture – shows the percentage of summers that we expect to be warmer than the current 95th percentile in warm summers after two degrees Celsius of global average warming. The whole world is getting very substantially hotter.
[SLIDE 30] Heat waves. This again is a busy slide, but one worth understanding. This relates to the heat wave that occurred in southern and Western Europe in 2003, estimated to have caused something in the range of 35,000 premature deaths; also a significant drop in agricultural production. What you see in the left hand side of this diagram out to the early 2000’s is a combination of the observed temperatures – smooth, the black line; red, blue and green lines – simulations of the summer temperature in this part of Europe, using the UK Hadley Center’s model; and the yellow … is natural only. The red blue and green are natural plus human. And the spike at 2003 with an asterisk on top of it is that horrible heat wave in the summer of 2003. And then you have the same computer models projecting forward what is expected under a middle of the road scenario going forward; what some people call business as usual. And the stunning thing about this is, by 2050, the conditions of 2003 will be an average year, expected to happen roughly once in two years; and by 2060 or 2070, that will be an unusually cool summer in France, Spain, Italy, where that heat wave occurred.
[SLIDE 31] Wildfires. This is another stunning one from the new National Academy’s study on stabilization targets. These are the percentage increases in median annual area burned by wildfires in the western United States for a one degree C increase in global average temperature. Look at those percentages. 200%, 300%, 400% increases in expected area burned by wildfires in the western United States.
[SLIDE 32] We expect droughts to get worse. Some people find that paradoxical; that in a warmer, wetter world droughts could get worse. But it’s not hard to understand when you realize that more of the precipitation falls in extreme events. It’s uneven to start with. In extreme events, more of the precipitation runs off, the soil dries out sooner, there are longer gaps between precipitation events, and in some parts of the world we get greatly exacerbated droughts.
[SLIDE 33] Crop yields. Increasing evidence shows that crop yields are more sensitive to climatic conditions even than previously thought. At the bottom are global average surface temperature changes and then at the top are the changes expected to go with that at low latitudes and mid latitudes, and modeling again from the Academy’s study of the declines in crop yields expected under those circumstances.
[SLIDE 34] We are also decreasing the PH of the ocean, increasing the acidity of the ocean because some of the carbon dioxide we add to the atmosphere absorbed in the ocean forms weak carbonic acid. That is a problem potentially for organisms that make shells or skeletons out calcium carbonate including corals, and what you see here – 1870, 2003 and 2065 expected atmospheric concentrations and the associated condition as they effect the suitability of the water for supporting coral. And green is good, orange is bad, you see we’re on our way to making much of the ocean now supports coral reefs inhospitable to coral reefs by the middle of this century. Interestingly enough, coral reefs are the second largest habitat for biodiversity on the planet after the tropical forests. The tropical forests are also at risk. So, ironically, we are placing at risk both of the largest reservoirs of biodiversity.
[8]Jonas Gahr Støre, Minister of Foreign Affairs, Norway, presents his opening address. (Scanpix)
[SLIDE 35] This one’s a little hard to read on the screen. The color’s faded out, but what it shows is that recent projects of sea level rise in this century are much larger than those produced by the last assessment of the IPCC, which left out – and explained it left out — dynamic processes of rapid disintegration and slippage of ice from the Antarctic and Greenland ice sheets because they were not felt to be well understood enough to be modeled at that time. But the best current estimates are that you could see sea level rise in the range of a meter to 1.8 meters or so in this century depending on the scenario.
[SLIDE 36] Now the question: do recent disclosures about emails in the IPCC cast doubt on these conclusions? Well, the emails do show that climate scientists are human too, and they show that more efforts at openness and transparency are warranted. The IPCC’s missteps – and there were a few – show the need for increased rigor in adhering to the already strict review procedures, and there are improvements that have been suggested in the procedures in the newly released review of the interacademy panel. But the errors discovered so far are relatively few, and they are unimportant in terms of the fundamental understandings that I have been conveying here. And I kind of think it’s important to understand -- some people imagine that the IPCC is the source of our understanding of climate –but in fact the IPCC is just one of the messengers. [SLIDE 37] A very sophisticated and high powered and organized messenger to be sure; but the sources of the global community of climate scientists and the peer-reviewed literature that they have produced over decades, and nothing in the email or the IPCC controversies rises to a level that would call into question the core understandings in that body of literature. Of course it is true – and again the foreign minister mentioned this – all science is contingent. There are always uncertainties. There are always need for refinement. And there’s always a chance that new observations and analyses will not just refine but overturn previous conclusions. That does happen from time to time.
[SLIDE 38] But those overturnings are unlikely when the body of data and analysis supporting the generally accepted conclusions is extensive and has been much reviewed, and that is certainly the case with climate science today, with the body of data and analysis that support our conclusions. Because of their relevance to policy choices in part, key findings from climate science have been subjected to unprecedentedly extensive peer review. And so it’s highly unlikely that new data or insights will alter those findings in a fundamental way. They’ll get altered in all kinds of ways but in a really fundamental way that says for example “humans are not the main cause of this,” that is exceedingly unlikely. And I suggest that policy makers should not bet the public’s welfare against such long odds. That is, they should not bet that the mainstream science view is wrong. That would be a bad bet.
[SLIDE 39] What should we do? We have only three options. Mitigation: steps to take to reduce the pace of the magnitude of changes in global climate that we’re causing. Adaptation: measures you take to reduce the adverse impacts from changes that do occur that you fail to prevent with mitigation. And the third option is suffering: suffering the adverse impacts that are not avoided by mitigation or adaptation.
[SLIDE 40] And concerning those, it’s important to understand: number one, we’re doing some of each already. We’re doing some mitigation, we’re doing some adaptation, we’re doing some suffering, as I’ve already shown. What’s up for grabs – what’s at stake – is the future mix of mitigation and adaptation and suffering. And minimizing the amount of suffering in that mix, which is certainly what we want to do, can only be achieved by doing a lot of mitigation and a lot of adaptation. That’s true, because mitigation alone won’t work because climate change is already happening and can’t be stopped quickly; can’t be stopped overnight no matter what we do. Adaptation alone won’t work because adaptation gets more costly, more difficult and less effective as the size of the climatic changes to which you’re trying to adjust get bigger. And therefore what we need is enough mitigation to avoid unmanageable climate change and enough adaptation to manage unavoidable climate change. That particular formulation is due to my German colleague John Schellenhover; we ended up using it as the subtitle of her report to the Secretary General of the United Nations on this topic just a few years ago, “Avoiding the Unmanageable, and Managing the Unavoidable” – a symmetric look at mitigation and adaptation.
[9]2010 Kavli Prize Science Forum panelists. Left to right: Charles M. Vest (moderator), President, US National Academy; Nils Christian Stenseth, President, Norwegian Academy of Science and Letters; Ralph Cicerone, President, US National Academy of Sciences; Ichiro Kanazawa, President, Science Council of Japan; Steven E. Koonin, Under Secretary of Science, US Department of Energy; Yongxiang Lu, President, Chinese Academy of Sciences; Martin ReesPresident, The Royal Society, United Kingdom; keynote speakers Holdren and Winnecker. (Scanpix)
[SLIDE 41] Lots of possibilities for mitigation: reducing the emissions from the energy sector, reducing deforestation, modifying agricultural practices. Some things we might do if we got desperate enough: scrub greenhouse gasses from the atmosphere technologically, geo-engineering to create cooling effects to offset greenhouse heating, [SLIDE 42] lots of adaptation policies, cropping patterns, heat drought and salt-resistant crops, strengthen public health and environmental engineering defenses against tropical disease, new water projects for flood control and drought management, dyke storm surge barriers, avoiding further development on flood plains in near sea level. [The] important point here is that many of these are win/win strategies. They make sense in any case. We should be strengthening public health and environmental engineering defenses against tropical diseases even if we weren’t worried about the climate change, we should be avoiding further development on flood plains at next to sea level just because of storm damage even in an unchanging climate.
[SLIDE 43] How much mitigation, how soon? Limiting the global average change in surface temperature from preindustrial times to less than or equal to 2 degrees C is now considered by many people – not by everybody but by many people – to be the most prudent target that is still attainable. You might like to do better, but it will be very hard to do better. Indeed it will be very hard to do this. The European Union embraced this target in 2002; the G-8 and G-20 embraced it in 2009. But just to have a 50% chance of staying below 2 degrees C, developed country emissions would need to keep no later than 20105 and decline rapidly after that, and developing country emissions would need to peak no later than 2025 and decline rapidly after that, and that is a huge challenge.
[SLIDE 44] Some of the relevant realities – carbon dioxide emissions are the biggest piece of the problem. Fifty percent roughly and growing as a share. Eighty-five percent of those CO2 emissions come from burning coal, oil and natural gas, which are providing more than 80% of the world’s energy; most of the rest coming from deforestation. Industrialized and developing countries are now, in total, about equal in CO2 emissions. The global energy system is immensely ponderous – about a 15- trillion dollar replacement cost if you tried to replace the full global energy system over night. The power plants, the oil refineries, the drilling rigs, transmission lines, would cost you 15 trillion dollars. The normal turnover time of that investment is about four decades. That means if you want the energy system in 2050 to look very different from what it looks like today, you better start changing it now. And deforestation isn’t easy to change either.
[SLIDE 45] There are, however, things we can do. This is a curve produced by the McKensey company, looking at a supply curve for the amount of abatement you would need by 2030 worldwide to beyond that trajectory that gives you a 50% chance of staying below a global temperature increase of 2 degree C. Below the line on the left are measures that actually make money under current circumstances; that is, the money you invest mostly in improved energy efficiency measures gets more than paid back by the savings in energy, and you get the carbon savings for free. As you move to the right, you find a variety of approaches – some in the energy domain, some in the land management domain – that have modest costs; and as you get very far to the right –all the way to where you need to be on this curve – you are doing some very expensive things. Carbon capture and sequestration in various kinds of plants, solar photovoltaics, and so on and so forth.
[SLIDE 46] Now here’s what this tells you about policy. We need in essence three kinds of policies to be on such a curve. On the left, you have a lot of things that people would be doing anyway if there weren’t barriers for them doing it: information barriers, tax barriers, financing barriers, perverse incentives of various kinds. So we need policies to remove the barriers to picking what we often call the low hanging fruit. Fruit tree metaphors are widely used in this domain. In the middle, where there’s a price that you have to pay to reduce the carbon emissions, you need an economic incentive to do that and the way you get that economic incentive is you put a price on carbon emissions that make it worthwhile to avoid them, or more worthwhile than it is under today’s circumstances wherein most places – most countries – there is not a significant price on carbon. So this is to motivate if you will reaching higher into the tree past low-hanging fruit. And on the right, we need research development and demonstration to lower the highest hanging fruit into reach. This is the research domain where we need to make these things cheaper because currently carbon prices are not likely to get high enough to motivate these things any time soon. …
[SLIDE 47] Very quickly, can we afford it? Actually, we can afford it. If we paid an average of 100 dollars a ton of carbon to avoid half the current emissions, that would be half a trillion dollars a year, which is less than 1 percent of current gross world product. If you use the McKensey cost curve for what we need to be doing in 2030 to be on that stabilization trajectory that gives you a 50% chance of staying below two degrees C, the net cost is only about a tenth of a trillion dollars a year. If you use current economic models, you see that stabilizing at that level probably means that two to three percent gross world product loss in 2030, about the same in 2100, the range is one to five percent that most of the models cluster at between two to three; that’s a lot of money in absolute terms. But if the world economy is still growing at three percent per year as most economists say it will be, then you’re talking about people waiting until 2031 to be as rich as they otherwise would have been in 2030. In round numbers that does not seem like too high a price to pay for a manageable climate change. And for comparison, the world now spends 2.5 percent of gross world product on defense, five percent in [the United States where] …we spend 2% on environmental protection already.