The latest shocking news about Gulf Stream instability reinforces the idea that we need to be more alarmist – not less
Bill McGuire is Professor Emeritus of Geophysical & Climate Hazards at UCL, and a co-director of the New Weather Institute. His current book is Waking the Giant: how a changing climate triggers earthquakes, tsunamis and volcanoes.
Cross-posted from Bill’s substack website
Have you noticed how the term ‘alarmist’ has been high-jacked? In the context of climate breakdown, habitat and wildlife loss and other environmental issues, it has become synonymous with scaremongering; with the voice of doom. In certain circles it is frowned upon, judged to be a hindrance to getting the global heating argument across, or tarred with the brush ‘climate porn.’ Even iconic broadcaster David Attenborough has expressed the view that ‘alarmism’ in the context of the environment can be a ‘turn-off’ rather than a call to action.
But are such viewpoints justified, especially when our world and our society teeter on the edge of catastrophe? After all, the simplest, most straightforward, meaning of an ‘alarmist’ is someone who raises the alarm. Is this not what we need now more than ever; to be told the whole story – warts and all? The alternative, it seems to me, is to play down the seriousness of our predicament, to send a message that is incomplete, and to conveniently avoid or marginalise predictions and forecasts that paint a picture regarded as too bleak for general consumption. Surely, such climate appeasement is the last thing we need at this critical time?
No-one could ever accuse the IPCC (Inter-governmental Panel on Climate Change) of being alarmist. Because every sentence of IPCC report drafts is pored over by representatives of national governments – some of whom are luke-warm or even antagonistic to the whole idea of anthropogenic climate change – the final versions are inevitably conservative. The closest the IPCC has come to sounding an alarm bell can be found in its report Global Warming of 1.5ºC, published in 2018. Here it warns that emissions must be slashed within 12 years (by 2030) – if there is to be any chance whatsoever of keeping the global average temperature rise (since pre-industrial times) below 1.5ºC – and fall to zero by 2050.
Notwithstanding the unlikelihood of achieving net zero global emissions in a little more than three decades, the pace and degree of climate change are about more than just anthropogenic emissions. They are also influenced by tipping points and feedback loops; sudden changes in the behaviour of ice sheets, carbon sources and sinks, and ocean currents, which can accelerate warming and its consequences way beyond the expected. In addition there may well be other effects and consequences that have not yet made themselves known and of which we have, as yet, no inkling.
Depressingly, but perhaps not surprisingly, the Global Warming of 1.5ºC report’s Summary for Policymakers – let’s face it, the only bit likely to be read by the movers and shakers – includes just one brief mention of feedbacks and has nothing at all to say about tipping points. The justification for this appears to be that because it is not possible to assign levels of confidence to such known unknowns – as the late Donald Rumsfeld would likely have called them – they cannot be included. But it is difficult not to conclude that the real reason is to tone down the threat in order to appease those governments that view global heating and ensuing climate breakdown as nuisances that they would like to go away.
The decision – conscious or otherwise – to bury concerns over tipping points and feedbacks in the depths of the full report rather than flagging them in the Summary is nonsensical. Touting the critical importance of drastic action while at the same time soft peddling the threat has the potential to backfire, providing the obvious get out: well, if the situation is not so bad, maybe the response doesn’t need to be that urgent. If drastic, life-changing, action is being mooted, people need to know – have a right to know – why. They need to be presented with a complete picture showing how bad things might get – however scary or poorly constrained. They need, in other words, to be alarmed.
Bringing the potential ramifications of tipping points and feedbacks into the equation, alongside unlooked for and unexpected consequences, inevitably transforms perceptions of the dangers we face. Suddenly, climate change ceases to be something vaguely inconvenient that we can leave future generations to deal with. Instead, it becomes far more of an immediate threat capable of tearing our world apart. Most recently, this has been highlighted by the shocking, and unpredicted, news that the Amazon Rainforest, has already switched from carbon sink to carbon source; a conspiracy of changing climatic conditions and extensive burning now pumping out an excess of more than a billion tonnes of carbon every year.
And there are plenty of other situations too, where observations flag threats that appear to be building far more rapidly than models have forecast. Take sea level rise, for example. The IPCC’s 5th Assessment Report, published in 2013 and 2014, predicts – for a worst case scenario – that global mean sea level could be about a metre higher by the end of the century. Bad enough for millions of coastal dwellers, but nothing compared to what our descendants might experience if a tipping point is crossed that sees the Greenland and/or West Antarctic ice sheets start to disintegrate in earnest. Models that incorporate this point to sea level rising far more rapidly. One suggests that the ice loss in Antarctica could occur at a much faster rate than expected, leading to global average sea level being more than 3m higher at the end of the century. Another, based upon correlations between temperature and sea levels during the last interglacial, which ended around 115,000 years ago, proposes that sea level – in theory at least – could climb by as much as 5m by 2100.
Observations of what sea-level is actually doing confirms that we should be alarmed. Between 1900 and 1990, global average sea level rose by 1.4 mm/yr, hardly sufficient to bother with. But look at what’s been happening over the last fifty years or so. For the period 1970 – 2015, the figure was 2.1 mm/yr and for 2006 –2015, it was 3.6 mm/yr (IPCC, 2019). Between 2015 and 2019, the annual rate of global average sea-level rise reached 5 mm (WMO, 2019). Scariest of all, is the serious possibility that sea-level rise might now be following a pattern that sees the rate doubling every 20 years or so. This would mean that by 2040, we could expect it to be rising by a full centimetre a year, increasing to 2cm by 2060, 4cm by 2080 and 8cm annually by the century’s end. Such a scenario is far more inline with more ‘alarmist’ predictions, than with the conservative and consensus estimates published by the IPCC.
Of course, for sea level rise to accelerate at these sorts of rates, a similar pattern would need to be matched by ice melting at the poles. Let’s look at what has happened recently. During the 1990s, and up to 2011, Antarctica – mainly the West Antarctic Ice Sheet – was shedding around 76 billion tonnes of ice a year, enough to raise global sea level by a tiny 0.2mm a year. Between 2012 and 2017, however, the rate of melting tripled to a staggering 219 billion tonnes annually, sufficient to add 0.6mm to rising sea level. Even at the new rate, the contribution over the next 25 years would only be 1.5cm. Not enough to worry about in its own right. If, however, the rate of increase is maintained over this period – in other words if the melting rate continues to triple every five years – the result would be very different. In these circumstances, the annual rise – as soon as the early-2040s – would be close to a catastrophic five centimetres a year. And this is without any growing contribution from Greenland and from the increasing expansion of sea water as the oceans warm.
It might be that the rates of sea-level rise, and ice melting at high latitudes, could begin to slow once again. I can’t, myself, think of any convincing reason why this should happen, but then again mechanisms of ice-melting is not one of my areas of expertise. As global temperatures continue to ramp up, on the other hand, it would be no surprise to see them accelerate further.
Another reason for concern is the behaviour of the Gulf Stream and associated currents (together making up the AMOC – Atlantic Meridional Overturning Circulation) that warm north-west Europe and also have a big influence on global weather patterns. In the distant past, surges of meltwater from shrinking ice sheets caused the AMOC to shut down. Now, it looks as if it might be in danger of doing so again as huge volumes of freshwater from the crumbling Greenland Ice Sheet pour into the North Atlantic, feeding a so-called ‘cold blob’ in the North Atlantic.
The IPCC’s official line is that another complete shutdown is ‘very unlikely’, but this is not the same as ruling it out. And there are certainly some worrying signs. The AMOC has slowed by 15 – 20 percent since the middle of the 20th century and is now at its weakest for at least 1600 years. The AMOC has a tipping point, and – evidence from the past shows – it can shut down in just a few years when this is crossed. The problem is that no-one knows when – or even if – this will happen. If it does, the ramifications will be sudden and widespread. The North Atlantic region will cool dramatically, particularly across the UK, Iceland and North West Europe, while sea ice will expand southwards. Sea-levels along the eastern seaboard of North America could rise at three to four times the global average rate. Further afield, changes to weather patterns are forecast to include a weakening of Indian and east Asian monsoons, which could have devastating consequences for crop yields. Even as I write this a new research paper has been widely flagged, which argues that the AMOC has experienced an ‘almost complete loss of stability’ over the last century, and may be nearing a shutdown.
Of the many and varied feedback loops and tipping points linked with rapid anthropogenic warming, perhaps the most disquieting relates to the vast tracts of permafrost at high latitudes – both on land and beneath the sea. Trapped beneath this frozen crust are colossal quantities of methane, a greenhouse gas that has a warming effect 86 times greater than carbon dioxide. Fortunately, methane has a relatively short residence time in the atmosphere and breaks down to carbon dioxide within a few decades. Nonetheless, concerns have been raised by some researchers about the possibility of major outbursts of methane from the rapidly thawing permafrost – so-called methane ‘bombs’ – capable of causing sudden climate mayhem, perhaps with little or no warning.
The geographic region of most concern seems to be the submarine permafrost that floors the East Siberian Continental Shelf and locks in prodigious volumes of methane. Alarm bells were raised almost a decade ago when a pair of papers transported the whole issue into the limelight. The first proposed that as much as 50 billion tonnes of methane could be available for sudden release at any time, which would – at a stroke – hike the methane content of the atmosphere 12 times. The second suggested that a discrete methane ‘burp’ on this scale could advance global heating by 30 years and cost the global economy USD60 trillion – a figure close to four times the US national debt.
The findings of both papers have been strongly contested. In particular, the likelihood of an imminent major methane expulsion has been downplayed for a number of reasons, most notably because there is no evidence of a significant surge in methane during the last interglacial, when Arctic temperatures were higher than they are now.
Notwithstanding this, there remains much to be learned and understood about methane release in permafrost terrain. As such, it continues to be a clear and present danger that should be flagged rather than downplayed, so that the threat of augmentation of climate breakdown by methane outbursts is made clear to everyone.
It is surprising, as it now invariably tops the news agenda, that some aspects of the impact of global heating and climate breakdown have barely registered, and none less than the response of the solid Earth. The issue was very briefly addressed for the first time in the IPCC SREX report on climate change and extreme events, published in 2012, but it’s profile – even within the scientific community – remains negligible. Nonetheless, the so-called geosphere (our planet from surface to core)is already responding to anthropogenic climate change.
In southern Alaska, where more than a vertical kilometre of ice has been lost in just a hundred years or so, the removal of the ice load has already been implicated in ‘freeing-up’ active faults beneath and triggering earthquakes. In northern India, the massive load of monsoon rains soaking into the sediments of the Ganges Plain is promoting an increase in seismicity in the vicinity of the Himalayan Front.
Looking ahead, large-scale loss of ice mass is forecast to play a role in promoting earthquakes wherever faults lie beneath rapidly melting ice loads, including in the Himalayas, Andes and southern Alps. In Iceland, the continuing melting of the Vatnajökull Ice Cap is predicted to increase both the volume of magma generated below and the amount erupted at the surface.
Most worryingly, rapid melting of the Greenland Ice Sheet is already driving the accelerating uplift of the whole northern Atlantic region. As the ice continues to melt and its load on the crust beneath is reduced, so Greenland may well become increasingly seismically active. Strong seismic shaking associated with future quakes would have the potential to trigger submarine sediment slides capable of launching tsunamis across the North Atlantic. Such an event happened around 8,200 years ago off the coast of Norway, when an earthquake linked to post-glacial uplift of Scandinavia triggered one of the biggest submarine slides on the planet, and a huge tsunami that would have been devastating had it happened today.
Everything I have considered above is – to some extent at least – on the radar, and supported to a greater or lesser extent by observational evidence, either contemporary or from past episodes of rapid climate change. Little if any, consideration has been given, however, to unforeseen and unexpected ramifications of global heating – the late Donald Rumsfeld’s ‘unknown unknowns.’
One unpredicted instance that would seem to fit the bill is a link between a northern polar jet stream that climate change has caused to slow and meander, and the recent especially severe incidences of extreme weather. While the connection remains to be unequivocally established, it is beginning to look as though a climate-changed jet stream is driving conditions that lead to episodes of extreme weather being ‘locked in’, so that both their intensity and duration are elevated. If confirmed, the corollary of this is that we are seeing, and will continue to see, conditions that are more extreme than forecast, occurring more frequently and having far greater impact.
The bottom line to all this is that being alarmist, in the sense of drawing attention to how bad things can get as the planet continues to heat up, is a good thing. It fits with the precautionary principle and also with the idea that we need to know our enemy – in this case the climate emergency – if we want to defeat it. Currently, I don’t think that most members of the public, and indeed most governments, do.
Playing down the potential worst effects of global heating and climate breakdown is nothing less than climate appeasement. It does nothing to help spur the urgent action that is required, and by underplaying the climate threat, works – intentionally or not – to encourage a grudging and cautionary approach to emissions cuts that we simply can no longer afford.
Yes, people will fear, in particular for their children and grandchildren. But fear does not have to be paralysing. Indeed, it is often the driver of effective action. No-one ever won a war while knowing no fear, and make no mistake, this is a war.