Worst-case scenario

Climate science today is suffering from an acute crisis of confidence. You could point to the “ClimateGate” conspiracy-that-wasn’t, or the occasional mis-statements, over-estimates and outright exaggerations in the writings and statements of prominent climate change activists, from Tim Flannery to the IPCC itself. But put aside the ad hominem attacks, ignore the wilfully misconstrued attacks on the impartiality of science, and at the root of the problem is the nature of the science itself. Climate science, like so much else in our modern world, relies upon models in order to predict outcomes on the basis of changed starting conditions.

In this, climate science is not dissimilar to virtually any other discipline of science. There are very few sciences that rest solely upon observation of the natural world. Our understanding of everything from meteorology to the physics of light and electromagnetism, from chemistry to biochemistry, to genetics and growth… virtually every scientific endeavour operates within modelled frameworks that allow us to understand, make sense of and frame the raw data. But in the case of climate science, the politics and entrenched interests with an intent to discredit the science have latched upon the “falsifiability” component of modern scientific practice as a means to challenge the outcomes. Climate science appears to be uniquely privileged in this way: we don’t hear armchair critics arguing that the law of gravity might be wrong because it’s built on models.

It doesn’t help that scientists, and increasingly policymakers, usually err on the side of caution and moderation. Scientists are trained by the sheer nature of science to frame their statements in terms of “may”, “likely” and “possible”. Given a set of possible models or extrapolations, they may often choose the middle course, or even the least severe outcome. Partly this is to avoid being seen as a doomsayer or an alarmist; partly it might be in the hopes that a moderate but manageable situation might be more likely to spur action than an all-or-nothing existential crisis. Partly this may be an attempt not to make firm predictions, because even the firmest likelihood still has a chance of error and every error is latched upon by sceptics. All of this means that the current debate around climate change is not actually looking at the worst that could happen. It’s not even looking at the most likely outcomes at present. When governments and think-tanks and the IPCC talk about restraining global warming to 2 degrees C above pre-industrial levels, they’re already looking through rose-coloured glasses.

At the risk of seeming a doomsayer or an alarmist, it is prudent once in a while to look at the worst-case scenario: what could happen.

It’s not just academic. Some would argue that the worst-case scenario is actually the most-likely scenario. After all, actual measurements of carbon emissions and climate change are consistently meeting or exceeding the worst-case scenarios considered by the IPCC and climate scientists. They have been for years. In September 2012, a scholarly article was published: Climate Disruption – Are We Beyond the Worst Case Scenario? It’s well worth a read. For the sake of interest, here’s an extract from the abstract:

The inability of world governments to agree on and implement effective mitigation response policy for anthropogenic climate change has resulted in the continuation of an exponential growth in greenhouse gas emissions (GHGs) that averages 3.1 per cent per year since 1870. With the exception of 2009, world GHG emission levels surpassed the Intergovernmental Panel on Climate Change (IPCC) (2000) worst case scenario every year since 2004. Because of increasing temperatures due to GHG emissions a suite of amplifying feedback mechanisms, such as massive methane leaks from the sub-sea Arctic Ocean, have engaged and are probably unstoppable. These processes, acting in concert with the biological and physical inertia of the Earth system in responding to atmospheric loading of GHGs, along with economic, political and social barriers to emission reduction, currently place Earth’s climate trajectory well within the IPCC’s A1FI future climate change scenario. There is a rapidly diminishing chance of altering this trajectory as time goes on. There is also now a very real risk of sudden climate change. The pace of this quickly advancing situation, along with our scientific understanding of it, has substantially outstripped policy discussion.

It’s clear that we must turn things around, and very quickly. But it’s not going to happen. 80% of known fossil fuel reserves must stay in the ground – but this can’t be done. Too many people with too much power have too much invested in the value of those fuels to allow them to go unused. Late last year, Rolling Stone published an article on this, and it’s a must-read: Global Warming’s Terrifying New Math.

Looking at the worst-case scenarios may help us to frame the debate, and to prepare for mitigation. So what are the worst-case scenarios with runaway, catastrophic, irreversible climate change?

Extreme climate events

We hear about heat waves, cold snaps, coldest winters on record and hottest summers on record, on a regular basis now. From wildfires in America to deadly cold seasons across Europe, to record-breaking tornadoes in the US midwest, extreme climate events the world across are increasingly being linked to ongoing climate change. But this is hardly worst-case scenario. Even as tornadoes and fires and frozen winters become more common, as weather patterns across the globe change to a new normal (it’s not a passing phase and it’s not going to get better, folks), human misery and the readjustment of natural ecosystems will occur. But climate has changed before, and mankind is very good at suffering through and either adapting to, or mitigating through technology, inclement climates and situations. So, discomfort and small-scale, localised death and disaster are the outcomes here. We can live with that.

Sea level rises

We’re not talking merely about the loss of prime beach-front property. During the pliocene era, with global temperatures 2-3 degrees higher than now, sea levels were 25-30 metres higher than at present. You might wonder at the relevance of conditions three million years ago, but our atmospheric carbon and our projected climate have their closest precedent in the time of the dinosaurs.  In a world with the sea 25 metres higher than now, low-lying islands across the world are simply gone, naturally, with the displacement of smallish populations – terrible individually, but not terribly substantial in historical terms. What’s more important is that the vast majority of human civilisation is built on the coastlines. Most major cities. About 40% of the world’s population overall lives in coastal areas, defined as within 100km of a coastline. With a major rise in ocean levels, most or all of these people will have to move. Most major cities in the world will either grow inland or cease to exist entirely. There are physical limitations to the amount of sea level rise possible in each year, so a 25m increase will likely take a long time to occur, giving us time to adapt and mitigate. This is probably a good thing. Some scientists now think that this outcome is inevitable.

Mass human death

Now we start to come to some of the more unpalatable possibilities of runaway climate change. Unfortunately, here is where we start meeting those who have been labelled extremists and alarmists, even paranoid or deluded. But we need to put our judgmental attitudes aside for the purpose of this investigation and look dispassionately at the worst possible outcomes, if only to confirm that they are indeed baseless and nothing to worry about.

A small number of climate scientists and other activists have been willing to put their reputations on the line and make predictions of the future that sound like edge cases. Among them are ex-NASA scientist James Hansen, and the famous Professor James Lovelock, whose claim to fame is that he proposed the Gaia hypothesis. He’s also a widely published independent scientist. Lovelock argues that rapid climate change will lead to the deaths of most people on the planet, and require mass migration of those who survive to the few areas of the world that are still (or have become) habitable.  He’s not alone in thinking a hotter Earth can only support a small proportion of the current human population. Lovelock argues that the outcome will be large-scale unrest and conflict; defence experts in the US and elsewhere would seem to tacitly agree.

This scenario sees the dregs of mankind eking out a living at the tropical green poles of the planet. These would be no garden of Eden conditions: the models argue that the tropical temperatures in the few areas of the planet not turned into desert would be too high for sustainable large-scale agriculture. This is a nightmare vision of the Earth that would take literally thousands of years to remedy, as the de-industrialisation of the world allows the Earth to gradually find a new equilibrium.

Oxygen depletion from deforestation and loss of phytoplankton

Believe it or not, the death of eighty percent of the current human population, the extinction of the vast majority of species on the planet, and the contraction of habitable areas of the globe to a few spots on the poles is not the worst that could happen. Some scientists speak seriously of the planet running out of breathable air. Before we laughingly dismiss this possibility, we should at least look at the theory and its supporting evidence.

Oxygen makes up about 20% of the Earth’s atmosphere. But there’s evidence that the amount of oxygen in the atmosphere in recent decades has been declining. The evidence for declining oxygen levels includes oceanic dead zones and forest fire charcoal levels. Both of these measures are currently bearing out the theory. Measured oxygen levels in some highly industrialised cities have fallen to 15%, indicating that oxygen can be “crowded out” by CO2 and CO. In a world with runaway climate change, with methane, carbon and other GHGs released from geological stores by ice melts and other feedback mechanisms, it’s conceivable that the proportion of O2 in the air could decline markedly. Some estimates go as low as 5%, which is not enough to support basic human functions like breathing.

Compounding the problem of a decline in O2 is the risk to our current sources of oxygen. Some atmospheric oxygen is produced by the planet’s forests, but the forests are under continued attack from urban expansion, logging and other exploitation, and global warming itself. But even if the last tree were chopped down, it would not be the end for us. At least 50% of Earth’s oxygen is generated by phytoplankton, microorganisms in most oceans and bodies of fresh water that live at the surface and survive via photosynthesis.

There have been arguments that phytoplankton is at risk from ocean acidification, again due to rising levels of CO2. In 2010 a study was published in Nature that reported substantial declines in marine phytoplankton. If the phytoplankton were to die, it would be catastrophic. Apart from generating oxygen, phytoplankton is at the base of the marine food chain; the cradle of life on this planet could become barren.

Even the worst case scenario here is possibly not a death knell for the human species. By some models, if all photosynthesis were to cease, atmospheric oxygen would be depleted in 5000 years due to respiration, weathering,  and combustion. There are studies that dispute the premise that acidification or warming are reducing phytoplankton levels. In this specific instance of climate science, the jury actually is still out. But the worst case scenario leaves us little cause for optimism.

The good news

If there’s anything positive to come out of this litany of woe, it’s this. Even under the worst outcomes currently envisaged, humanity as a species is likely to survive in some fashion. We’ve done it before. Three million years ago, environmental pressures and evolutionary competition whittled the progenitors of current humans down to a mere ten thousand individuals. Oh, wait – there’s that three million years again. There have been other population bottlenecks affecting specific racial groups, more recently – as recently as 20,000 years ago for some groups. But the point is that even if humanity were reduced to a rump, given enough time and appropriate conditions, we are likely to spring back. Humans are clever like that.

So there we have it. A few models that outline what could be in store if the climate scientists are right (they are) and countries and populations around the globe don’t moderate their behaviour (they won’t). So when a climate change skeptic next argues that we should just adapt to the new conditions and get on with life, you could ask them if this is what they had in mind.


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