Our Final Warning

Mark Lynas

• Editorial: Fourth Estate
• Año: 2020
• ISBN:
  9780008308582
• Categoría: Ciencias biológicas
• Categoría: Conservación y Protección del Medio Ambiente

1°

Headline of the century

It happened in 2015. The event made the news, although only for a day or two, before normal service – terrorism, politics, sport, celebrity gossip – resumed. You could therefore be almost forgiven for not having noticed what might be considered the most important news story of the entire century so far.

To its credit, the Met Office (the UK’s meteorological service) did put out a press release. This noted that, ‘for the first time, global mean temperature at the Earth’s surface is set to reach 1°C above pre-industrial levels’ (‘pre-industrial’ was defined by the Met Office as 1850–1900). Human activities had, the scientists pointed out, now managed to cause a degree of global warming over and above what would have been the planet’s natural temperature otherwise. There was no mystery about the main driver: look no further than the two trillion tonnes of carbon dioxide gas (henceforth CO2) that have been poured into the Earth’s atmosphere mainly through the combustion of fossil fuels since the start of the Industrial Revolution.

With one degree already in the bag, some historical comparisons are in order. In just over a century of unbridled fossil fuel use, humanity has returned atmospheric CO2 concentrations to levels last seen in the Pliocene, around three to five million years ago. As a result, global surface temperatures can be expected to go on rising for a long time yet, but the thermal inertia of the planet – the centuries to millennia it takes to warm the abyssal depths of the oceans and melt the colossal bulk of the Greenland and Antarctic ice sheets – means that the temperature rise lags some way behind the ‘forcing’ effect of increased greenhouse gases. As we will see, there is much more still to come.

Most of the global warming has gone into increasing the heat content of the oceans. The latest estimates published in 2019 by the IPCC are that about 6 zettajoules of additional energy are accumulating in the upper oceans every year. A zetta is a big number: 6x1021 is a 6 followed by 21 zeroes, or 6,000,000,000,000,000,000,000 joules. For comparison, humans use about half a zettajoule per year in our total global energy consumption. A better visualisation might be to quantify all this extra energy in a more evocative unit: the heat released by the Hiroshima atomic bomb. Six zettajoules of energy equates to the same amount of heat as three Hiroshima atomic bombs exploding in the oceans every second. Count them: 3, 6, 9, 12, 15, 18 …

In late November 2018 the World Meteorological Organization (WMO) confirmed the UK Met Office’s preliminary diagnosis. Based on five independently maintained global temperature data sets, the WMO in its annual State of the Climate report revealed that the global average temperature between 2014 and 2018 was 1.04°C above pre-industrial levels. In other words, we are now definitively living in the one-degree world. For me, seeing this announcement was a particularly significant moment, because when I wrote the original Six Degrees book nearly a decade and a half ago this one-degree world still lay in the future. For the purposes of this book it is as if we have moved forward a chapter: what was once the future is now the present. If we don’t succeed in cutting back carbon emissions in time, the increasingly terrifying impacts detailed in later chapters – of two, three, four degrees and even higher – will also one day become our present. This really is our final warning.

The view from Mauna Loa

Mauna Loa, the gigantic shield volcano that sits at the centre of the Big Island of Hawai’i, is so tall that its summit protrudes above most of the island’s active weather. On the east side of the mountain, as the trade winds hit and are forced to climb the slopes, they cool, form clouds and drop torrents of tropical rainfall. This makes Hilo, the island’s biggest town, one of the wettest settlements in the United States. Drive through the glassy lava flows on the long haul up the flanks of the volcano, however, and you will quickly leave the rain clouds far below you. Conditions close to the summit are sub-Arctic, with only an inch or two of precipitation each year, much of that in the form of snow.

The paved road ends at the 3,200-metre contour line, where a group of antiquated buildings scattered across the volcanic debris together comprise the Mauna Loa Observatory. The Observatory is not as high as the solar telescopes that cluster atop the 4,207-metre summit of Mauna Kea, visible seemingly floating above the cloud layer 40 kilometres to the north. It is, however, arguably more historic, certainly from an earthly perspective. It was here that atmospheric chemist Charles Keeling first began collecting samples of airborne CO2 in 1958, seemingly on a whim and with little official support, using pioneering monitoring equipment that he designed himself.

Keeling had found that measuring CO2 lower down in the atmosphere was pointless, because the levels fluctuated constantly as a result of emissions from car exhausts, industrial chimneys, vegetation growth and so on. Thanks to its elevation, Mauna Loa rose above all that day-to-day noise, and Keeling’s measurements were the first in the world to show that CO2 mixed at high altitudes through the whole global atmosphere was increasing, in a sawtooth upwards seasonal pattern now known as the ‘Keeling Curve’ (probably the most famous global warming-related graph of all time). Charles Keeling died in 2005, but appropriately his efforts have been continued by his son Ralph, also an atmospheric chemist. Ralph Keeling has made his own subsequent discoveries, such as that the oxygen content of the air is decreasing commensurately with our consumption of fossil fuels, as airborne O2 is combined with carbon extracted from underground to form the gas CO2.

When Charles Keeling began his measurements in 1958, the rarefied air atop the lava fields of Mauna Loa contained CO2 at a ratio of 315 parts per million (ppm), already substantially higher than the pre-industrial concentration of about 278 ppm. On 10 May 2013 the Scripps Institution for Oceanography, which maintains the Observatory, made a landmark announcement. For the first time ever in human history, CO2 levels had briefly touched the 400 ppm threshold. ‘There’s no stopping CO2 from [permanently] reaching 400 ppm,’ commented Ralph Keeling sadly. ‘That’s now a done deal. But what happens from here on still matters to climate, and it’s still under our control. It mainly comes down to how much we continue to rely on fossil fuels for energy.’ Perhaps no one was listening, because at the time of writing the atmospheric concentration of CO2 has hit 408 ppm. This figure will already be out of date by the time you read this book. You can follow the relentless upwards progress of the Keeling Curve in real time on Twitter, via @Keeling_curve.

The Keeling Curve is a useful reality check, one that cuts through all the noise and confusion of the climate and energy debates. Unlike the slopes of the huge volcano on which it is measured, the initially gentle upward curve gets steeper the higher you go. That means that the rate of CO2 accumulation in the atmosphere is steadily increasing, from roughly 1 ppm in the early years to about 2 ppm annually today. There is no visible slowdown, no sudden downwards blip, to mark the implementation of the Kyoto Protocol, still less 2009’s Copenhagen ‘two degrees’ commitment or the landmark Paris Agreement of 2015. All those smiling heads of state shaking hands, the diplomats hugging on the podium after marathon sessions of all-night negotiating – none of that actually made any identifiable difference to the Keeling Curve, which is the only thing that actually matters to the planet’s temperature. All our solar panels, wind turbines, electric cars, lithium-ion batteries, LED lightbulbs, nuclear plants, biogas digesters, press conferences, declarations, pieces of paper; all our shouting and arguing, weeping and marching, reporting and ignoring, decrying and denying; all our speeches, movies, websites, lectures and books; our announcements, carbon-neutral targets, moments of joy and despair; none of these to date have so much as made the slightest dent in the steepening upward slope of the Keeling Curve.

This does not make us powerless prisoners of fortune. No trend continues for ever, and just because recent history has been all one way does not mean the future must necessarily follow suit. These emissions are not extra-terrestrial – they come from our everyday activities. Indeed they are an inescapable part of modern civilisation itself. We can get a sense of the sources, and the magnitudes, from the annual Global Carbon Project report. On average, every year over the last decade we humans transferred 35 billion tonnes of CO2 from the geological reservoirs (that’s coal, oil and gas) into the atmosphere. This was augmented by 6 billion tonnes of CO2 from ‘land-use change’ (that’s deforestation, ploughing up new farmland and so on). About 9 billion tonnes of this new CO2 dissolved in the oceans, and 12 billion tonnes was taken up on land by vegetation and soils. That left a remainder of about 18 billion tonnes to accumulate in the atmosphere and drive the relentless upward climb of the Keeling Curve. (The imbalance of 2 billion tonnes is due to uncertainties.)

There are small changes in the carbon budget year on year, which sometimes cause great excitement. In 2014, 2015 and 2016, for example, there was little to no annual growth in fossil fuel emissions, which seemed to have stabilised for the first time. Cue some premature celebrations. But had the world reached an early peak in emissions? No. In 2017 growth resumed again, reaching a new high of 36.8 billion tonnes despite a record installation of 161 gigawatts of renewable generating capacity in 2016 alone. In 2018 emissions continued to accelerate, however, increasing nearly 3% on the previous year and pushing CO2 levels to a new historic high. In 2019 growth slowed somewhat, to 0.6% above 2018, thanks to a reduction in coal use in Europe and the US. But what we need is carbon cuts, not slower growth – urgently.

So what’s going wrong? Well, it’s a matter of scale. The world is hungry for new energy: primary energy demand keeps on increasing, and 80% of that increase is supplied by new fossil fuels. Overall, renewables (not including hydro) in 2019 accounted for only 4% of global primary energy, still much too small a proportion to have any discernible effect on the upward trend in overall emissions. This is why solar and wind have so far not measurably dented the Keeling Curve. According to recent estimates, the installation rate for clean energy sources would have to increase tenfold to arrest the annual growth in fossil fuels.

Meanwhile, as the measurements conducted in the Observatory buildings continue to show relentlessly rising CO2, Mauna Loa itself is experiencing the effects of the resulting climate warming. Temperatures are gradually rising, and night frosts are rarer than they were when Charles Keeling first began to keep records with his home-made equipment. Mauna Loa may sit above most weather, but no part of the world can entirely escape global heating. Snowfall is less frequent – and the snow melts earlier in springtime – while plant life on the slopes of the mountain is changing with every year that passes. In 1958 Charles Keeling had to design complex and sensitive equipment to discern subtle changes to the Earth’s environment. Now these changes are plain for all to see.

Back to the future

With its official average temperature just over one degree above pre-industrial levels, 2015 was the warmest year on record. But what about much longer ago, before humans invented thermometers and started taking measurements? You have probably heard of the Little Ice Age spanning the 17th to 19th centuries, when frost fairs were held on the frozen River Thames in London, or the Medieval Warm Period, when the Vikings colonised Greenland. These are sometimes cited by climate sceptics as evidence of previous variations in the climate, with the accompanying assertion that today’s high temperatures are therefore not caused by humans (a logical fallacy: whatever changed climate in the past is not necessarily what is changing it today) and are nothing to worry about.

However, a 2019 Nature paper using temperature records from corals, lake sediments, glacier ice, sea shells and trees, collected across the globe from Antarctica to Australia and from Canada to Chile, demonstrates convincingly that these earlier temperature fluctuations were regional phenomena and not globally coherent. So while it is a historical fact that frost fairs were held on the Thames from the 1600s to the early 1800s (our romantic myth of the ideal white Christmas dates from this period), colder European winters at the time were balanced out by simultaneous warmer temperatures in the western half of North America that no one now remembers. This was not a global cooling event, just as the Viking occupation of Greenland or the Romans growing grapes in Britain is not evidence of pre-historic global warming. In fact, according to these multiple data sources, today’s global high temperatures are unprecedented for at least 2,000 years.

That’s just two millennia, however. What about even longer ago? One study, combining data from 73 different sources around the world, concluded that the early Holocene, from 10,000 to 5,000 years ago, was just over half a degree warmer than the pre-industrial era. Given that temperatures since 2015 have been one whole degree higher than then, it is reasonable to conclude that the globe is now almost certainly warmer than at any point since the end of the last ice age, 18,000 years ago. Indeed, to find an analogue for today’s anomalous warmth, you have to look beyond the last ice age to a period of time between 116,000 to 129,000 years ago often referred to by scientists as the Eemian.

In the first Six Degrees, I included studies about the climate of the Eemian in my second chapter, corresponding roughly with two degrees of warming. But more recent studies suggest that the Eemian was only about one degree warmer than the pre-industrial Holocene. In other words, it was roughly equivalent to global temperatures we are already experiencing now. Yet the Eemian world was radically different: the Arctic tree line was much further north and hippopotamuses bathed in rivers in southern England. The Eemian isn’t a perfect match with today, because with humans still confined to cave dwelling, atmospheric CO2 remained at pre-industrial levels of about 270 ppm. Why was it then so warm? Probably because slight variations in the Earth’s orbit changed the distribution of incoming solar energy, warming the higher latitudes but leaving the tropics little changed or even slightly cooler than now. Studies of preserved dead midges in lake sediments have found that local summer temperatures in parts of Greenland were somewhere between 5°C and 8°C higher than today, but it seems that there was still plenty of sea ice in the Arctic Ocean.

Perhaps the most ominous lesson from the Eemian is that even with CO2 at around 135 ppm lower than today, and worldwide temperatures about the same as modern averages, sea levels were six to ten metres higher than at present. Evidence from the Eemian suggests that about five metres of this sea level rise originated from the partial melting of the Greenland ice sheet, which shrank down to a largish remnant in the north-east of the landmass. The implication is pretty clear: it suggests that today’s temperatures are already high enough to eventually melt the majority of the Greenland ice sheet and deliver a multi-metre rise in sea levels. This seems hard to believe, until you travel to Greenland and witness what was once a frozen wasteland currently undergoing rapid, epochal change.

Greenland’s lakes

Greenland is turning blue. Hundreds of thousands of iridescent blue lakes now dot the fringes of the rapidly melting ice sheet throughout the summer months, and the melt area has been creeping steadily upwards and inwards towards the interior as global heating bites. The direct impacts of this increased thaw can be dramatic – in late July 2012 so much meltwater was sluicing off the south-western portion of the ice sheet that a bridge was washed away on the Watson River, which empties into a fjord just to the south of the town of Kangerlussuaq. Footage shared on YouTube shows a grey-brown torrent resembling a tsunami washing away a tractor and tearing through the bridge and the road leading up to it in just a matter of minutes.

This episode is more than just a revealing anecdote. Meltwater flows in the Watson River have been steadily rising in recent years, and on average are now nearly 50% higher than they were in the 1950s. The tattered, debris-covered edge of the giant ice sheet lies just a few kilometres up the valley from Kangerlussuaq, and most of the hundreds of blue lakes that pepper its surface in summer drain into the Watson River, which is fed by a 12,000-square kilometre catchment across the south-western portion of Greenland. In terms of annual averages, the three largest discharge years on record are 2010, 2012 and 2016, with the largest single discharge peak coming in July 2012, explaining why it was then that the bridge over the Watson at Kangerlussuaq succumbed to the dramatic flood.

The timing of this glacial torrent was no great mystery either. For the first time in living memory unprecedented melting had penetrated right up to the summit of the giant ice sheet, located at 3,216 m in altitude. Summit is classed as a polar desert, an inhospitable place of frigid thin air and snow as dry as dust. On 12 July 2012, however, temperatures edged above freezing at the summit for the first time in recorded history, and the automated weather instruments permanently located there were surrounded by slush. Lower down, on the western side of the ice sheet, climate researchers were forced to rebuild their camp when snow and ice supports melted away. Things were no better in North Greenland where Danish scientists logged six consecutive days of above-freezing temperatures at the surface between 10 and 15 July. It even rained on 11 and 13 July, with melt and rainwater percolating down into what had previously been permanent snow.

When the first satellite data came in about the July 2012 melt event, scientists analysing it thought their instruments must have malfunctioned. Later visuals showed the entire ice sheet coloured deep red, indicating pervasive melt conditions. When the scientists checked their data with output from other satellites, they found that on 8 July the temperature of about 40% of the ice sheet surface was above freezing. On 12 July the figure was 98.6%. Virtually the whole of Greenland was in the melt zone, the first time any of the scientists studying the colossal ice sheet had seen such a thing.

Longer-term data show that all-Greenland melt events are extraordinarily rare. A December 2018 paper concluded that the 2012 melt rates were exceptional and ‘likely also to be unprecedented over the last 6,800–7,800 years’. The same paper stated that there has been a 500% increase in melt intensity at the ice core site in just the past 20 years. The latest data show that the fastest-expanding melt zones are now in the northern portion of Greenland, in what should be the coldest area closest to the North Pole.

Once the domain almost exclusively of ice and snow, Greenland has begun to see more rain, even in the depths of winter. While fresh snow is brilliant white, reflecting most of the sun’s radiation back out to space, thawing slush is less reflective, and the bare ice sheet with snow removed is darker still. All around Greenland the snowline has retreated uphill, exposing more uncovered ice to the full heat of the summer sun. As the fringes of the ice sheet gradually shrink inland, bare rock and glacial debris are revealed, leading to an increase in dust storms. Plants have begun to colonise new areas, and are now coming into leaf a week or two earlier as spring temperatures rise.

It has long been clear from ice core records that the climate in Greenland can do sudden and strange things. About 11,700 years ago, at the end of a colder period called the Younger Dryas, temperatures shot up by 15°C over a few decades. A similarly dramatic warming, of 9°C in less than 70 years, took place 14,760 years ago during the last ice age. Scientists fear that Greenland may currently be crossing a similar threshold of rapid climate change, one that could lead to the eventual loss over centuries of the entire ic...

Índice

• Title Page
• Copyright
• In Memoriam
• Contents
• Foreword
• 1 Degree
• 2 Degrees
• 3 Degrees
• 4 Degrees
• 5 Degrees
• 6 Degrees
• 7 – The Endgame
• Acknowledgements
• Notes
• Index
• Also by Mark Lynas
• About the Author
• About the Publisher