影／Johan Rockström教授在 TED 的演說
文／楊為植(國際科學理事會會長特別助理，原題："Boundaries for Managing the Human Enterprise: An Afternoon at a Symposium")
“Humanity must begin bending the curves…” It was a grey afternoon on November 4th, 2010. 200 or so students, scholars and citizens sat in a symposium hosted by the Institute of Atomic and Molecular Sciences at the National Taiwan University (NTU) (中央研究院原子分子研究所). They were listening intently to a presentation given by Professor Johan Rockstrom – head of the Stockholm Environment Institute (SEI) and the Stockholm Resilience Center; 2009 Swedish person of the year; and one of the world’s top scientists on resilience and sustainability issues.
The experts sharing the floor with him in this symposium were no less distinguished: Professor Shaw-Chen Liu from Academia Sinica’s Research Center for Environmental Changes (中央研究院環境變遷研究中心主任劉紹臣教授)；Professor Chen-Tung Arthur Chen of the Institute of Marine Geology and Chemistry at the National Sun Yat-sen University (中山大學亞太海洋中心陳鎮東教授), Professor Jiunn-Rong Yeh of the National Taiwan University College of Law (台灣大學法律系葉俊榮教授)，and the Moderator, former Academia Sinica President and a Nobel Laureate in Chemistry, Professor Yuan-Tseh Lee (引言人, 前中研院院長李遠哲).
“In nature, surprise is the norm, not the exception”
A year before, Professor Rockstrom had led an eminent group of scientists who published an influential paper in the journal Nature titled “A Safe Operating Space for Humanity.” And he is now here to share their groundbreaking findings. The premise of their research was simple enough. For the past 10,000 years – the Holocene – the global climate was remarkably stable. There is scientific evidence to suggest that this equilibrium is the only state of the planet we know of that can support human development as we know it. They reasoned, therefore, that keeping the planet in this stable state would be wise. Yet, everywhere we look, humans are rapidly altering their natural surroundings.
It’s not just our emission of greenhouse gases that displays the famous “hockey-stick figure” (flat for most of history, then steep rise within the last 1-2 centuries – similar to the curve of a hockey stick). Species extinction, deforestation, land degradation, air pollution, population growth, etc… all conform to this “hockey-stick” trend. Mankind is changing the environment at a rate without historical precedent. The Nobel-winning scientist Paul Crutzen (a co-author on the paper) thus believes that we have entered the “Anthropocene” – an age where humans are now the single biggest driver of environmental change.
So what is so problematic about these man-made changes? Professor Lee says that he is often asked: “What’s the big deal about two degrees? Temperatures change much more than that from season to season, or even from morning to evening!” “But look at the human body,” replies Prof. Lee. If our body temperature rises by a mere one degree, we have a fever; if it rises by 2-3 degrees beyond that, we may die. And the Earth, like the human body, is a finely-tuned system.
Man-made change is also problematic because of what Prof. Rockstrom calls “sudden regime shifts”, or “tipping points.” Most of us think of change as linear – for instance, if we put a given amount of pollutant into the environment, we should expect a proportional increase in pollution, not much more, and not much less. Prof. Rockstrom observes, however, that “in nature, surprise is not the exception, it’s the norm.” He raises as examples the sudden collapse of coral reef systems after decades of over-fishing, tourism and climate change, and the totally unforeseen loss of 30-40% of the Arctic’s summer ice-cover in 2007 due to climate change. In these and many other systems, conditions appear to be relatively stable despite a barrage of external forces; but then, all of a sudden, the systems shift to a completely different state. (Professor Chen added: “even within the stable Holocene, there are surprises!”)
As human development places more and more pressure on natural systems, these systems become less “resilient.” Whereas before, a natural system could withstand shocks while remaining relatively stable, now even a slight “push” could tip them over abruptly and dramatically into a state that is unable to provide for human welfare. And this change may be irreversible. Prof. Rockstrom states, for example, that we have no idea how to “re-freeze” the arctic. Similarly, it is virtually impossible to restore an ecosystem once it’s been lost.
Here, not only is uncertainty not a reason to rest easy and wait until scientists are sure, it is a frightening reason for worry. We know we are changing the planet, more often than not in negative ways. And we have witnessed the wholesale collapse of natural systems after years of human influence. What we do not know is at what point these collapses may happen. If that does not seem scary, imagine that you are in a snowstorm, trying to find a way home. You know there are cliffs nearby, but you cannot see where they are.
Planetary Boundaries: a Safe Operating Space for Humanity
In the Nature paper, Prof. Rockstrom and his colleagues propose a solution to this problem of not knowing where the tipping points are: we set safe boundaries that make it unlikely we would get close to them. Prof. Rockstrom illustrates this point with a picture of a man standing at the edge of a waterfall: “You do not want to be standing where he is. In fact, it’s illegal to stand there.” A little further upstream, there are fences that keep people away from the brink. Planetary boundaries would function much like these fences, keeping humanity away from points of danger.
Taking Earth as one system, their research identifies nine “processes” that are central to the functioning of the Earth system. These are: stratospheric ozone layer; biodiversity; chemical dispersion; climate change; ocean acidification; freshwater and the global hydrological cycle; nitrogen and phosphorous inputs into the biosphere and oceans; and aerosol loading in the atmosphere. Every one of these needs to be in good health for our planet to remain stable. For each of the nine, they try to determine, according to the best science, where the “danger zones” are. They then set the “boundaries” at the lower end of the danger zones, warning humanity not to cross beyond.
What makes their effort truly new is that they attempt to come up with specific numbers for these boundaries. Thus, they set the boundary for climate change at 350 parts per million of carbon dioxide concentration in the atmosphere; go above this level, and we risk incurring climate disasters. For biodiversity, the threshold we need to stay below is 10 out of every million species going extinct per year. For the ozone layer, its boundary is a concentration level of 276 “Dobson units”, and so forth. And we have already “transgressed” three of them – climate change (we are at ~390 ppm), biodiversity (the current extinction rate is already over 100 out of a million species), and the nitrogen cycle.
As Prof. Rockstrom would tell you himself, where to set the boundaries is still a subject of much debate among experts, and will be for a long time to come. And in fact, the science is not yet capable of assigning a number to two of the boundaries: atmospheric aerosol and chemical pollution. Yet remarkably, when they shared their proposed boundaries for review by many top scientists in the nine areas, not even once did anyone question the basic idea of setting boundaries.
“Humanity must begin bending the curves”
While the precise locations of the boundaries are still up for debate, the experts at the symposium leave no room for debating whether humanity needs to change course. Referring to the many “hockey-stick curves”, Prof. Rockstrom emphatically declares that we simply have to start bending those curves downward. After all, severe impacts from climate change are already happening.
Professor Shaw-Chen Liu (中研院環變中心主任劉紹臣教授) quickly brought this point home to the largely Taiwanese audience. His recent research reveals some terrifying trends. The relationship between temperature and extreme rain events is alarmingly more sensitive to global warming than previous projections by climate models, particularly at low latitude areas such as Taiwan. Here, when temperature rises by one degree Celsius, the strongest 10% of rain increases by 150%! This is much worse than the Intergovernmental Panel on Climate Change (IPCC) projections, and brings deadly disasters with which the Taiwanese public has become painfully familiar. Yet ironically, light to moderate rain has been happening less and less frequently at the same time, leading to droughts, sometimes after a year of storms and floods.
So we have to bend the curves. And the challenge is daunting. Prof. Rockstrom cites a study finding that, to have a good chance of limiting post-industrial temperature rise to within 2 degrees C, global carbon emission would have to approach zero by 2050 (this is in agreement with most scientific studies on the subject). But this is complicated by the question of equity and justice, an issue that loomed large in the symposium discussions.
A Matter of Equity
As scientists are urging the world to go zero-carbon by 2050, developing countries are just ramping up. Many of them never enjoyed the fruits of high carbon-emitting development, and are unlikely to agree to carbon neutrality while many of their citizens are still struggling in poverty. And, Prof. Rockstrom says, they have a legitimate point. It would be unfair for us to deprive them of the development rich nations have long enjoyed. Plus, developing countries are bearing the brunt of the climate impact thus far. For instance, Professor Liu (劉紹臣教授) observes that higher temperatures appear to intensify precipitation in the lower latitudes more than the higher latitudes. And developing countries, unfortunately, reside mostly in the lower latitudes.
Prof. Yuan-Tseh Lee (李遠哲院士) recounts an exchange he had at a recent meeting overseas. A participant from a developing country said firmly that they would never agree to carbon neutrality. “We would rather that we all die together,” he said. However, the man relented a little when Prof. Lee said: “what about an annual per capita carbon emission of three tons?” This would still allow most poor countries to increase their emissions many-fold. “Ok, we might accept that,” the man replied.
An arrangement such as this would of course require even more drastic reductions from the developed countries. Prof. Rockstrom suggests: “If we were to leave room for a reasonable level of further development for the developing countries, the developed countries may have to go zero-carbon between 2020 and 2030.”
“We have nowhere to run”
However difficult, change must come nonetheless. The good news is that changes are already happening, often in surprising places. Professor Yeh (葉俊榮教授) notes that around the world, the number of lawsuits against large carbon-emitters, including governments, has been climbing rapidly. Here Prof. Rockstrom raises an intriguing scenario. In the future, we may see nation-states suing other nation-states for their carbon pollution. What if sea-level rise completely destroys an island nation, and scientists find a convincing link between this and the greenhouse gases emitted mainly by a few large states? This would surely pose an interesting question for international law.
Professor Yeh (葉俊榮教授) wonders also about the possibility of applying the boundaries concept to more specific areas of social, economic and environmental management. What if we could, by looking at sustainable development indices, derive boundaries that could tell us how much a certain industrial or economic activity is too much?
Whatever the case, Professor Chen (陳鎮東教授) argues, there has to be change at the government level. He suggests that at this moment, even some basic requirements on environmental monitoring in Taiwan are inadequate. Professor Y.T. Lee (李遠哲院士) comments further that our government still talks enthusiastically about raising per capita GDP to US$30,000, and about “dominating the market.” So there has to be a change in mindset.
But the government cannot act alone. Professor Yeh (葉俊榮教授)contends that “policy-makers” no longer mean just the President and the Ministers; it should include the public as well. If we wish to shift from the narrower “government” to the broader “governance,” the public has to play a part. For Professor Yeh (葉俊榮教授), the fact that international negotiations on climate are still centered around states is precisely the problem. The states maneuver and leverage their weights to pursue “the national interest”, but according to how the government interprets it.
The symposium concluded, and the crowd dispersed. But the bottom-line seemed clear: our societies are playing a dangerous experiment on the Earth system, one that may well overturn the environmental stability that has underpinned our development for the past 10,000 years. So putting some safety limits around this experiment would be a wise idea – perhaps through a series of boundaries at the planetary scale. The trouble is that our social, political and economic structures are so deeply committed to this experiment, the challenge of turning around almost boggles the mind. We need everyone to be actively involved, from the hallways of power to the boardrooms and the most local of communities. And we just may have to accomplish this while allowing the less-privileged majority of mankind to carry on a while longer.
Daunting to say the least. But we scarcely have a choice. “Taiwan is a small place,” Professor Chen (陳鎮東教授) remarked towards the end, “we have nowhere to run.”
楊為植。國際科學理事會 （International Council for Science) 會長特別助理。從小留學，旅居歐洲及美國。美國佛萊契學院 (The Fletcher School) 公共政策碩士，曾任職於國際發展組織及政策智庫，研究多項國際議題。