Sunday, August 26, 2007

Dodging the Tipping Points?

By Timothy Den Herder-Thomas...

In the past couple months, the flurry of discussions around bold, visionary goals for global warming has gotten increasingly intense. We've been starting to realize that we have to be more ambitious if we're going to make it. I think this is a key question for movement introspection that's only the first stage in re-imagining a new society: what do we need to achieve?

We've been saying 80% by 2050 for over a year now. It sounds big, and significant, and is way beyond any of the 7% solutions Kyoto started with. But Kyoto phase 1 is over in 2012, after which we have to figure out the next step. I'll be nearing retirement by the time 2050 rolls around. We call it a science-based goal, but we're missing the risk assessment. Does the Intergovernmental Panel on Climate Change (IPCC) really hold the authority here? Before we go much farther, and define the post-Kyoto debate, we better take stock of the situation.

Here's a central challenge - why are we stopping at trying to prevent only those catastrophes that we are nearly sure of? Wouldn't it be prudent to avoid the risk of potential events, even if there's only a 50/50 chance that they'll happen. Considering that the things of which we're sure our tame compared to those that are still uncertain, I at least don't feel very comfortable taking our chance.

Department for International DevelopmentLet's face it, even if we were to stop emitting all carbon tomorrow, we are still going to lose large parts of Bangladesh, a country the size of Wisconsin home to 135 million people, and we are still going to have increasingly freakish storms and increasingly severe droughts (right where I am in MN too - for the second year in a row). Agriculture will face minor declines in some areas (like sub-Saharan Africa where people are already starving), and Venice is already a sitting duck (the Dutch are getting good at floating houses). It feels brutal to be callous, and we should use the knowledge to be ready when we do need to bail out places that get hit, but honestly, we just have to get used to the fact that yes, some of that is coming. These gradual, obvious changes will get us to the point where global warming will just be a massive global headache for the rest of my lifetime. Yeah, it's pretty annoying, but these types of things are not what we have to be worried about.

What we have to watch out for, are the really crazy changes that shake up everything.

We have to watch out for the tipping points. The really big, really bad changes that accelerate the problem, cause new positive reinforcement of climate change, and basically reshape the world.

There's a number of them that have been theorized, and many scientists believe that there are least decent chances that one or more could happen. More worrying still is the fact that the slow changes preceding these events are already starting to happen. Let's take a look at a few:

Die-back of Amazonia: the Amazon rainforest produces its own rainfall through the evapo-transpiration of the forest. As temperatures rise and we deforest the basin, less rain falls leading to drought. Since the soils hold very little water or nutrient reserves, just a few years of extreme drought could cause widespread die-back of forests. As the die-back accelerates, there are less trees to produce rain, less shade to cool the forest, and yet more drought and die-back. In addition to converting the Amazon into some combination of grassland and semi-desert conditions, this process would release massive amounts of carbon dioxide from decaying/ burning vegetation, turning one of the world's largest vegetative carbon sinks into a carbon source, thus causing more warming. Scientists in Amazonia have estimated that this die-back could be triggered with as little as three continuous years of extreme drought - The Amazon is in drought year number 2.

Gulf Stream disruption: we all know about the polar ice shrinking, and that the albedo effect with darker water keeps polar areas warming faster and faster than the rest of the world. But then there's the threat that collapse of large ice-masses like Greenland could send a massive rush of cold fresh water into the North Atlantic, threatening to cut off the Gulf Stream that keeps Europe warm (this is the disaster over-dramatized in The Day After Tomorrow). Scientists are now reducing the estimated risk of such on occurrence, but it should be noted that since the mid-1950s, the sinking of Gulf Stream water that drives the current has fallen by around 30% in response to colder fresher water. If you want a real shocker, go read The Weather Makers by Tim Flannery, where he discusses that fact that in past glacial periods, the Gulf Stream has collapsed in as little as a decade, throwing Europe and eastern North America into violent mini-ice ages even as main glacial periods were ebbing.

Or how about the problem in western Canada, where forest fires and bark beetles are ravaging the boreal forests, switching the nation from a net absorber of carbon to a net emitter in just a matter of years. Since the boreal forests are massive carbon sinks, this additional carbon is a huge loss, accelerating the feedback loops working against us.

How about a really freaky one: the melting of tundra permafrost in Alaska, Canada, and Russia. Permafrost holds massive quantities of carbon dioxide and methane that can be released only when the soil melts and begins to decay. With more carbon in these soils than the entire atmosphere, we could be looking at a nearly doubled potential for warming if this permafrost melts. While full release will almost certainly take over a century, it's beginning now, as endless reports of newly-swampy foundations, drunken trees, and melting Siberian peat bogs attest. Again, once started, the added carbon makes warming accelerate, meaning more melting ...

Shall I go on? Acidification of the world's oceans from increased carbonic acid concentrations resulting in dissolving carbonate rocks and the inability of ocean life to build protective shells? Massive collapse of methane hydrates (weird blogs of frozen-pressurized methane) from warming arctic seas? A rapid disintegration of the West Antarctic ice shelf sending sea levels up 10-20 feet? Loss of ice in the Himalayas causing massive drought and famine in the key food-producing river basins of the Indian subcontinent, China, and Southeast Asia?

I think we can all safely agree that we have to avoid this type of situation. Then there's a second key question: is any of this going to happen?

The answer is: we don't know. I'll be the first person to admit that any one of these 'tipping points' is uncertain: we know neither the timing of these tipping points, or even if they'll happen at all. Tipping points are inherently uncertain since they depend on complex non-linear responses that have little historical precedent (although they appear surprisingly common throughout the earth's history). But we should note that if one of them should occur, the result will both be disastrous, and will greatly increase the chances of others occurring. In other words, if we cross one of these thresholds, the world will never be the same again - and the chance of further drastic events will only increase. We have to dodge the tipping points.

We should note that complex civilization only emerged after a climatic tipping point, common over the past few million years of glacial-interglacial cycles, ended the last Ice Age and ushered in an era of warmth and prosperity. During that tipping point, atmospheric carbon concentrations rose from in the low 200s to near 280 parts per million (ppm). This change was typical of the periodic glacial-interglacial reversals of the past few million years, where carbon concentrations ranged from near 200 ppm (glacial) to near 300 ppm (interglacial). Since the beginning of the Industrial Revolution, we've gone from 280 ppm to about 385 ppm, and we're rising at a higher rate than any time in recent geological history. Yet our climate has so far only changed gradually, slowly shifting from the recent past. A tipping point will be like a sudden flip as dramatic as the changes between warm periods and Ice Ages. The difference is that Ice Age to non-Ice Age flips have been common over the past few million years. A flip from an interglacial period to a warmer era has not happened for many millions of years - since before humanity. And the rate of growth in global carbon concentrations is almost unprecedented.

Funny then, that IPCC reports don't discuss tipping points very much. The reason is that they're uncertain. Since tipping points are all about non-linear processes (which can accelerate dramatically when only minor changes are made to the climate system), and are inherently unpredictable, they are naturally unlikely to be confirmed by scientific studies in general, which require rigorous certainty (usually 95% confidence that a predicted event will occur). While some research has suggested that this level of confidence can be expected for certain tipping points if we do nothing to slow carbon emissions, other studies are less conclusive and thus do not agree that these events are certain. Because the IPCC produces consensus-based reports, where all scientists (and later diplomats arguing on scientific grounds) must come to agreement on the final publication of the report, and events that do not have near-complete agreement in the research are omitted. Another way of saying this is that the types of events the IPCC predicts are 95% certain, or that there's only a 5% possibility of them not occurring. Given that the predictions of the IPCC are only those that are almost certain, we have to start wondering about what's being left out.

Let's say, for the sake of argument, that the chances of dramatically accelerating permafrost crossing a tipping point and thus causing vastly accelerated warming over existing predictions are 50%. This figure is completely made up (I sure hope its lower, though unless we change our course, the risk keeps rising) and the calculation of such a risk is so complicated based on a vast array of other variables as to be basically impossible to pinpoint accurately. Risk could also describe only a portion of the carbon released or a rate of release which changes the nature of the tipping point (its not like all the permafrost will melt at once), so this is a really simplistic example. The IPCC reports don't include this event because its not for sure, and thus can't be reported as scientific fact. Tipping point events vanish off consensus-based reports, leaving decision makers with no ability to assess the threat of such scenarios - most of our leaders aren't even aware of them. But would you like to base the future of the world on a coin flip?

Now let's imagine that the risk of that same tipping point event is only 1%. Pretty low, right? Small enough to ignore, right? Wrong. Homeowners typically buy home insurance even when the risk of their home being destroyed is vanishingly small - just a tiny fraction of one percent. We make a real investment in the security of our personal homes to avoid the risk of cataclysmic events. Why aren't we treating climate change the same way, and taking the problem seriously enough to avoid possible, though not certain, catastrophes? When the risks of all the possible tipping points are combined, they are far far higher than the risk of your individual home being destroyed by an accident. We can be sure that the risk is real, significant, and will only grow as we continue emitting more. The situation is also worse than on the personal level, since the effects shape our global home - the insurance industry can't use the financial weight of a wealthy society to bail out the unlucky homeowner. The victim in this case is the wealthy society, and we only have one home. With recovery out of the question, we only have one way to invest in our security: avoiding the crisis in the first place. Time for some prevention?

We can debate whatever level of risk we find appropriate as long as we like, but centrally, until we start looking at the risks, we're basing any policies we develop on the faulty assumption that the events we have to prevent are certain. And when you start looking at the risks for large scale impacts, the scale of the investment we have to make rises, the time-frame for doing so shrinks, and the cost of inaction soars sky-high. Taking a careful look at tipping points changes our frame - the 80% by 2050 reductions in the developed world that are necessary to prevent certain events become wholly inadequate in dealing with the risk of far worse ones.

For myself, I've decided I'm unwilling to accept any plan that will result in temperature rises that yield more than an estimated 1/3 chance of crossing a dangerous tipping point. A 2 out of 3 chance of making it through with only marginal impacts (like roughly a meter of sea level rise, temperatures a degree or so warmer, some amount of famine and a few more nasty hurricanes) that are for sure while avoiding real catastrophes seems the very maximum risk we can allow. I'd much prefer if the risk was 10% or 5%, 0r 1%, or even better 0.01%. We simply don't want to mess with this stuff.

To get to that low a risk, we're going to need to build a sustainable society, fast, collectively, and holistically. It will require everyone, which means it must also be done equitably, while taking into account the risks behind climate science. This is going to be intense.

I'll be following this up: as a teaser for next time, check out Colin Forrest's article about the degree of change that's needed. He's a layman analyzing a wide array of scientific documents. They're not consensus, but they've got risk analysis all over them. Similar conclusions have been popping up everywhere, so we have a lot to discuss. Next question: given risk, what should we aim for?

1 comment:

Phil said...

Great post ... in our attempt to "optimize" our response to this crisis, we're failing to leave ourselves any margin for error. But in fairness to the IPCC, they do have a lot of this info (eg. on permafrost melting), but it's buried in the full text, not in the summaries.