Days of Future Past

Updated: Dec 6, 2021

How to Live with Long-Term Climate Change in Mind

Past Present Future by Oliver Vernon. Retrieved from David B. Smith Gallery

Abstract: Scientists have been sounding the alarm on climate change for over fifty years. Evidence of anthropogenic influence as the leading architect in the disruption of climatic processes soon became irrefutable. Despite the elevated confidence in the body of expanding data pointing to Homo sapiens, progress in mitigation and adaptation has been close to none, although the public appears to take the scientist's warnings concerning climate change to be serious and in need of immediate action. However, this awareness is mostly applicable to present extreme conditions and changes to traditionally predictable contingencies of the climate and to a certain extent, short-term consequences. This work aims to examine how humans could think about long-term climate change, by drawing inspiration from chapter 12: "Long-term Climate Change: Projections, Commitments, and Irreversibility” by the Intergovernmental Panel on Climate Change.

Keywords: climate-change; Anthropocene; IPCC;



“In times of change, learners inherit the Earth, while the learned find themselves beautifully equipped to deal with a world that no longer exists.”

- Eric Hoffer in, ‘The True Believer: Thoughts on the Nature of Mass Movements’ (1961)

The year is 1143 CE. Among the many things that humanity is currently engaged with, one particular event is worth highlighting. At the time, the Kingdom of Portugal is being officially recognized by the treaty of Zamora, and independence from the Kingdom of León, assured (Waisberg, 2017). It is the birth of – possibly – the oldest nation-state in Europe (Mira, 1999).

Aside from the exceptional historical nature of this occurrence, I do not mention the event as a medium for distant and vicarious self-gloating. Instead, the reason to bring up the inception of the Portuguese nation is due to the fact that from its humble beginnings - almost a millennia ago – that time window coincidently corresponds to roughly the same period used in the long-term climate change projections by the Intergovernmental Panel on Climate Change (IPCC) in their Fifth Assessment Report (AR5).

In such a manner, the choice to employ the example of the Portuguese is designed to facilitate the analysis of such a complex issue as long-term projections on climate change, and hopefully, to establish some empathy. With this in mind, one could be inclined to generate a thought experiment and pose some crucial questions regarding posterity and any rectitude owned to future generations.

For example, let us assume that the Portuguese of the previous nine hundred years were being endowed, generation after generation, with the double-edged gift of foresight. Such an ability would allow these ancestors to contemplate all the scientific and humanistic progress just waiting to be brought to light, but also, all the consequences of unearthing the untapped potential that has caused our current predicaments.

It begs the question:

- Would they have sacrificed their capacity to enhance the quality of their lives in exchange for the collective existence of their descendants?


- If we ourselves in the present could access the lives of our millennia-old-heirs (presuming large-scale human existence on Earth is still possible (Morgan, 2009; Tonn, 2009; Lopes et al, 2009)) would we cede our privileged status that Steven Pinker (2018) calls the “safer, healthier, freer and happier than in any other point in history” generation, in exchange for their ability to live?

Science says we must (Clark et al. 2016; IPCC, 2018). Human nature is telling a different story (Saxifrage, 2019; Climate Action Tracker, 2019).

This work shall attempt to disentangle the intricate essence of that which is the culmination of human knowledge regarding climate science and what exactly scientists are envisioning for our time to come. However, before we can make sense of the future, we need to examine the past.


The Good Old Days

"Human beings are now carrying out a large-scale geophysical experiment of a kind that could not have happened in the past nor be reproduced in the future.”

- Revelle, R. & Suess E. Hans (1957)

In their 1981 paper published in Science, ‘Climate impact of increasing atmospheric carbon dioxide,’ James Hansen and colleagues opened the floodgates to what would be regarded as the emergence of the public and political concern over the greenhouse effect (Rich, 2018) (the first mention of the term dates back to a report for President Lyndon Johnson) (Kolbert, 2018). Already at the time, Hansen et al. foreshadowed the rise in Earth’s temperature and the grim prospect of human life walking on thin ice as the conditions that led to the Holocene – and the evolution of Homo sapiens – could be irreparably lost.

Before long, Hansen was giving ground-breaking testimony in front of US Congress (Yale Climate Connections, 2018) declaring that for the first time, human action could be directly pin-pointed outside of the natural variability of climate, in effect, putting anthropogenic action on the radar. The first IPCC report followed shortly after in 1990, and the latest Fifth Assessment Report (IPCC, 2014) clearly stated:

“Anthropogenic greenhouse gas emissions have increased since the pre-industrial era, driven largely by economic and population growth, and are now higher than ever. This has led to atmospheric concentrations of carbon dioxide, methane and nitrous oxide that are unprecedented in at least the last 800,000 years. Their effects, together with those of other anthropogenic drivers, have been detected throughout the climate system and are extremely likely to have been the dominant cause of the observed warming since the mid-20th century.” (Bold added)
Figure 1: Atmospheric CO2 reaches 415 ppm. Data from Lüthi et al. 2008 plus Mauna Loa, 2018. Plotted by Peter Gleick 2019. Retrieved from Twitter, 2019

Correspondingly, the issue of the abruptness of observable changes in the temperature (and atmospheric CO2 concentrations) has also been a focus of extensive research (NASA Earth Observatory, 2010; Fisher et al. 2018). As the paleoclimate record (past climate) and global models reveal, the Earth's climate underwent profound changes, without any anthropogenic assistance (figure 2). In contrast, human activity has not just unleashed enough carbon dioxide to the atmosphere to mirror a state the planet last experienced roughly three million years ago when humans weren't even around (Willeit, Ganopolski, Calov & Brovkin, 2019), but the speed of this change is completely unprecedented in the paleoclimate record. As the NASA Earth Observatory (2010) stated:

“As the Earth moved out of ice ages over the past million years, the global temperature rose a total of 4 to 7 degrees Celsius over about 5,000 years. In the past century alone, the temperature has climbed 0.7 degrees Celsius, roughly ten times faster than the average rate of ice-age-recovery warming.”

To put it another way, humanity has produced an unparalleled rise of 1ºC in temperature in roughly 50 years. Above all, what is alarming is not so much the change itself, but rather the speed at which this transformation is occurring (Tomorrow, 2019).

As the IPCC asserts in their recent report Global Warming of 1.5ºC – Summary for Policymakers (2018) and as it can be examined in figure 2:

“Human activities are estimated to have caused approximately 1.0ºC of global warming above pre-industrial levels, with a likely range of 0.8ºC to 1.2ºC. Global warming is likely to reach 1.5ºC between 2030 and 2052 if it continues to increase at the current rate (high confidence).”

Following from the IPCC's assertion, Schurer and colleagues (2017) have argued in Nature Climate Change, that if on the other hand, one considers the cumulative warming of the Earth for all the historic human activity (not just since the Industrial Revolution), an extra ~0.2ºC would have to be added to the rise in global temperature. The team defies the IPCC's stance, arguing that using a baseline dating back solely to the 19th century is an inaccurate approach to estimate anthropogenic heating of the Earth, and, consequently, our remaining carbon budget (maximum amount of carbon released into the atmosphere to prevent - with a degree of confidence - a given temperature from rising).

Figure 2: Global Land-Ocean Temperature Index. Data source: NASA's Goddard Institute for Space Studies (GISS). Credit: NASA/GISS, 2019

Nevertheless, since the industrial revolution began, Homo sapiens have consumed enough fossil fuels - coal, oil, and natural gas - to supplement the atmosphere with somewhere around 365 billion metric tons of carbon. Deforestation has filled out another 180 billion tons, and each year, humanity amplifies this by another nine billion and a half Gigatons of Carbon (GtC) (CO2.Earth, 2019) - correspondingly to roughly 40 billion GtCO2 of carbon dioxide (McSweeney & Pearce, 2016) - an amount that has been enlarging by as much as 6 percent every year, as population and economic growth rise (Kolbert, 2014).

Together with this, in the absence of an agreement on implemented policies, the Earth is predicted to warm at least 4.1ºC – 4.8ºC above pre-industrial levels by the year 2100 (figure 3). In contrast, current commitments put us on a path of 3.0ºC - 3.4ºC warming above pre-industrial levels. As of September 2019, after world leaders reconvened in New York for COP24, their unconditional pledges, and targets, including their National Determined Contributions (NDC’s), would set a scenario of 2.6ºC-2.9ºC warming above pre-industrial levels. On the other hand, an optimistic scenario, in which governments meet these prospects, as well as those pledged but not yet implemented, would still create a median warming of 2.9ºC (Climate Action Tracker, 2019).

Figure 3: Addressing Global Warming. Emissions and expected warming based on pledges and current policies. Retrieved from Climate Action Tracker, 2019

However, many scientists are still convinced of the plausibility of curbing warming to 1.5ºC (Seneviratne et al. 2018; Millar et al. 2017; Kuramochi et al. 2018; Hausfather, 2018), maintaining that it is still a geophysical possibility, even though they stress the inherent hardships associated with such a goal. Nonetheless, it is crucial to highlight that checking warming to 1.5ºC would not just require an immediate reduction in carbon emissions, but also that these are brought to zero by mid-century (Climate Action Tracker, 2019).

At the same time, there are those who stress that the carbon budget to keep temperatures below the 1.5ºC limit can be spent as soon as 2021, with 2ºC as early as 2036 (McSweeney & Pearce, 2016). Reiteratively, the IPCC writes in Global Warming of 1.5ºC – Summary for Policymakers (2018) that:

"By the end of 2017, anthropogenic CO2 emissions since the pre-industrial period are estimated to have reduced the total carbon budget for 1.5°C by approximately 2200 ± 320 GtCO2 (medium confidence). The associated remaining budget is being depleted by current emissions of 42 ± 3 GtCO2 per year (high confidence) [...] [There is] an estimate of the remaining carbon budget of 580 GtCO2 for a 50% probability of limiting warming to 1.5°C, and 420 GtCO2 for a 66% probability (medium confidence)."

Regardless of the case, many of the mitigation scenarios to limit this warming also assume two accessory events. First, that global temperature will overshoot the 1.5ºC mark and be prolonged for a non-established time period during the 21st century (Rogelj et al. 2015; Schleussner et al. 2016; Seneviratne et al. 2018), before it can be ‘brought down.’ Reducing this temperature takes us to the greatest wager in climate history.

In effect, mitigation scenarios are relying on large amounts of carbon dioxide removal technology (or negative emission technology), such as bioenergy with carbon capture and storage (BECCS). Besides still being at an experimental stage in terms of feasibility, scale of deployment and construction (Carbon Brief, 2016), these technologies also carry serious social, environmental, political and economic risks (Holz et al. 2018).

In the light of this, during the presentation of the National Climate Assessment (Malakoff, 2018) at the American Association for the Advancement of Science (AAAS) in March 2018, Ben Sanderson from the National Centre for Atmospheric Research in Colorado gave a reality check (Williams, 2018), affirming:

To hit the 2ºC target it requires emissions to be cut substantially before 2040 to reach near zero or zero by the latter half of the century, with a likelihood for negative emissions thereafter […] any CO2 which is emitted into the atmosphere broadly has to be removed again in order to maintain a 1.5° stable climate […] it requires a lot of effort post-2030 […] rapid reductions in emissions after 2030 and then definitely negative emissions for the latter half of the century. And it has to be remembered that negative emissions and the ability to remove carbon dioxide from the atmosphere is not a technology which is currently available, or not one that can be deployed at scale. And so the assumption which is implicit in most of the future scenarios […] assume that carbon dioxide can be removed from the atmosphere in future, and that’s betting on a technology we don’t yet have available.” (Bold added)

Although negative carbon emissions are still a built-in supposition in the IPCC’s future scenarios and other Integrated Assessment Models (Mui et al. 2018), our current position is in no way a presage of a stable foundation. As the IPCC’s report Global Warming of 1.5ºC – Summary for Policymakers (2018) cautions, to avert a 1.5ºC rise, greenhouse pollution must be subsided by 45 percent - from 2010 levels - by 2030, and 100 percent by 2050. It also underlines that, by 2050, the use of coal as an energy source has to be reduced from our current use of 40 percent today, to between 1 and 7 percent, while renewables would have to increase from roughly 20 percent in 2018, to 67 percent (Davenport, 2018).

This becomes even more relevant when we take into account that humanity’s carbon emissions saw a surge of 2 percent in 2017 and 2.1 percent in 2018, when we should, by all means, be decreasing them (Carrington, 2018; Tollefson, 2019). Equally important, as Barry Saxifrage writes (2019) for Canada's National Observer, in his yearly analysis of BP's Statistical Review of World Energy Report (2019):

"Back in 1992, the world gathered at the Rio Summit promising to prevent fossil fuel pollution from unleashing a full-blown climate crisis onto future generations. As the chart shows (figure 4), humans burned 7.1 billion "tonnes of oil equivalent" in fossil fuels per year back then.
Since that original global climate conference, there have been 24 more. And yet, as the chart also makes clear, the amount of fossil fuels burned each year hasn't gone down. It hasn't levelled off. It has only surged upward.

Given these points, it is no wonder that Raftery et al. 2017 contend in their research published in the journal Nature Climate Change that the Earth has roughly a 5 percent probability of avoiding a 2ºC warming. According to the study, trends regarding global economic output, emissions, and population growth make it severely unlikely that the planet will remain below this limit established in Paris. Moreover, the goal to cap warming at 1.5ºC is examined to have just a 1 percent probability of success (Milman, 2017).

More importantly, perhaps, is what Fischer and colleagues alert in a study (2018) published in Nature Geoscience. In the paper, the researchers argue that climate models may be underestimating the ramifications of global temperature rise and sea-level rise. Identically, Hansen and Sato (2012) write about the dangers of the rise in temperature and its nonlinear effect on amplifying feedbacks:

"Goals to limit human-made warming to 2ºC are not sufficient - they are prescriptions for disaster."

Obviously, things are not looking good, and if our track record could provide any insight, it would be an indication that the future doesn't appear to hold any assurances either.


Perhaps, our first instinct would be to find fault with the ones that preceded us, claiming that their behaviors were the flame that kindled the climate and ecological monstrosities that confront us. 'Why'? we could ask, were they so oblivious to the reverberations of their actions? 'How?' we may ponder, could they have sentenced us to such a harsh fate, in which children march the streets seemingly echoing the concerns of Chuck Palahniuk in his novel Invisible Monsters (1999):

"When did the future switch from being a promise to being a threat?”

Yet, it would be misguided to hold our antecessors fully responsible for our current and prospective plights. As much as we would like to expiate ourselves of responsibility and moral agency by pinning it down on them, the contention just wouldn't hold up since more than half of all industrial CO2 has been emitted since 1988 (Frumhoff, 2014).

As much as it might pain us to admit, our predecessors weren't exceptional or shrouded in mystery as L.P. Hartley famously wrote that: "The past is a foreign country; they do things differently there." The truth is much more straightforward and speaks volumes about the pedestrian nature of human beings.

They - like us - had one shot at life. They - like us - did anything in their power to increase their odds of self-preservation, and invariably, reproduction. They - like us - turned to material wealth and engrossed capital to attain a better life. Ultimately, regardless of where or when, humans can't help but attempt to maximize the likelihood of their survival. Sadly for us (and non-human life (Abegão, 2019)), an existence with more comfort, prosperity, and opportunity hasn't been decoupled from a larger footprint left on Earth.

In the long run, be it the Portuguese of today, of past centuries, or of tomorrow, this is the only certainty that we have, that humans will do anything in their power to exist. The question is, if they will be able to do so as Lester Lave testified before the US Congress in 1982 (Rich, 2018):

“Carbon dioxide stands as a symbol now of our willingness to confront the future.”

From Here to Eternity

Unfortunately, the clock is ticking, the hours are going by. The past increases, the future recedes. Possibilities decreasing, regrets mounting.”

Haruki Murakami, in Dance Dance Dance (1988)

In the acclaimed science-fiction romance The Left Hand of Darkness (1969) the late Ursula K. Le Guin left us with an immortal token of wisdom, saying:

"The only thing that makes life possible is permanent, intolerable uncertainty: not knowing what comes next."

In effect, in the IPCC's Working Group I contribution to the Fifth Assessment Report, specifically the chapter "Long-term Climate Change: Projections, Commitments and Irreversibility," the scientists write (Collins et al. 2013):

"Projections of future climate change are not like weather forecasts. It is not possible to make deterministic, definitive predictions of how climate will evolve over the next century and beyond [...] Projections of climate change are uncertain, because they are dependent on scenarios of future anthropogenic and natural forcings that are uncertain, second because of incomplete understanding and imprecise models of the climate system and finally because of the existence of internal climate variability. The term climate projection tacitly implies these uncertainties and dependencies." (bold added)

Unexpectedly, Le Guin's prose and the IPCC's science are remarkably in synch, as both associate the future with uncertainty. Yet, where the poet found purpose and significance for one's life in this incertitude, for the scientists it might be the difference between a turbulent hereafter or the questionably permanency of our complete human aggregate. That is to say, the 'Potentially Abrupt and Irreversible Changes' [p. 1114] or even 'The Seventh Mass-Extinction' (Carperter & Bishop, 2009) which might spell disaster in our uncertain days to come.

However, there is one aspect of this work by the IPCC that is not embedded in uncertainty, which is, coincidentally reflected in one of the most gripping and thought-provoking assertions made in the entire chapter. The researchers write:

“Abruptly setting CO2 emissions to zero results in approximately constant global temperature for several centuries onward […] past emissions commit us to persistent warming for hundreds of years, continuing at about the level of warming that has been realized…” (Page 1104).

This is as much as saying that CO2-induced warming is, in essence, everlasting on the perspective of human timescales (Millar & Friedlingstein, 2018; Matthews & Caldeira, 2008), and why the IPCC have constructed Representative Concentration Pathways (RCPs) (figure 5) to make better sense of the future.

The RCPs encompass several scenarios including time series of emissions and concentrations of GHGs - as well as aerosols, other chemical active gases and land use/land cover (volatile to socioeconomic factors such as geopolitical agreements), but for simplicity sake, the focus in here is on CO2 – which have different radiative forcings (RFs), a crucial concept describing the net change in radiative flux (expressed in Watts per square meter; W m-2) for each climatic factor (anthropogenic or natural), which impinge upon the Earth’s surface by downward-directed radiant energy. It is worth highlighting that CO2 is linked to roughly 80 to 90% of the total anthropogenic forcing in all RCP scenarios through the 21st century (Collins et al. 2013).

It is worth comparing these long-term predictions (as well as levels of confidence and likelihood) to the predictions being made until the end of the 21st century. The researchers write (Collins et al. 2013) regarding temperature changes:

“Global temperatures averaged over the period 2081-2100 are projected to likely exceed 1.5ºC above 1850-1900 for RCP4.5, RCP6.0 and RCP8.5 (high confidence), are likely to exceed 2ºC above 1850-1900 for RCP6.0 and RCP8.5 (high confidence) and are more than likely than not to exceed 2ºC for RCP4.5 (medium confidence). Temperature change above 2ºC under RCP2.6 is unlikely (medium confidence). Warming above 4ºC by 2081-2100 is unlikely in all RCPs (high confidence) except for RCP8.5, where it is about as likely as not (medium confidence) [page 1031].

Then again, two models published by French laboratories (CNRS, 2019) challenge the IPCC’s conclusions, admitting to greater warming in 2100 compared to previous outcomes. For one thing, the researchers predict that the RCP8.5 scenario will reach an increase in the global average temperature between 6ª to 7ºC by 2100, a 1ºC rise compared with previous assessments. The researchers also remark that only the most optimistic of scenarios, marked by a determined and aggressive international cooperation would make it possible to not breach the 2ºC Paris Agreement (Institut Pierre Simon Laplace, 2019). It is reasonable to infer that such predictions might also carry implications to longer-term climatic changes.

Regardless, even if anthropogenic greenhouses gas emissions were to –unrealistically – be stopped at this moment, the relationship between the radiative forcing and the long permanency of these gases in the atmosphere would still trap the planet in a state of enhanced warming. This is mainly caused by an inertia driven by the ocean, since it takes several centuries for this large body to warm and reach a state of equilibrium with the altered radiative forcing.

Aside from this, there is still the possibility of unleashing ‘Potentially Abrupt or Irreversible Changes’ (Collins et al. 2013, p. 1114), which can occur due to ‘tipping points.’ These are better described as various components or phenomena operating in our planet which are bound by critical thresholds, which when breached can induce large-scale changes in a short period of time (Lenton, 2011; Lenton et al, 2008). The IPCC has reviewed several of these components, such as the Atlantic Meridional Overturning, the ice sheet collapse, the carbon release from the permafrost, the clathrate methane release, tropical and boreal forests dieback, among others. What all of these have in common is that they are irreversible for millennia, or at the very least for centuries (timing for the Atlantic Meridional overturning is unknown).

Lastly, there are processes that can either magnify or curtail the effects of forcings (solar irradiance, greenhouse gas emissions as well as aerosols, dust, smoke and soot), which are called feedbacks. These feedbacks have been described to be affected by clouds, precipitation, greening of forests, ice albedo, among others. As a result, the feedbacks can in turn become self-reinforcing, creating vicious circles of warming that can spiral out of control (NASA Global Climate Change, 2019; Madson, 2018).


Conclusive Remarks

We can only see a short distance ahead, but we can see plenty there that needs to be done.”

- Alan Turing, in Computing machinery and intelligence

On the whole, anthropogenic action has been so sudden and massive, that destabilization of the natural systems of the planet will linger for centuries or even millennia with many of the impacts already locked in (Clark et al. 2016; Steinberg, 2019), stressing the need to include negative emissions technologies in these scenarios.

In the event of an absence of such technology - or harder still, the voluntary abstention to emit more greenhouse gases by leading more frugal lives (Moser & Kleinhückelkotten, 2017; Bleys, Defloor, Ootegem & Verhofstadt, 2017; Gatersleben, Steg & Vlek, 2002) – humanity will have to come to terms with a near-certainty in their future: That the climatic changes of the Holocene (known as the “Long-Summer” (Fagan, 2004)) which enabled Homo sapiens to evolve, geographically distribute itself through the surface of the planet and create a global and thriving civilization might be coming full-circle, and disturb the relatively harmonious condition enjoyed so far.

With this in mind, it might be time to focus on a “Deep Adaptation Agenda” as suggested by Bendell (2018), in which the three key aspects of Resilience, Relinquishment and Restoration are championed. As more literature emerges (Read & Alexander, 2019; Wallace-Wells, 2019; Scranton, 2015; 2018; Frazen, 2019) making a case for a new civilization and renewed ethical and values system, humanity will need to grasp how to survive and thrive on the face of a profoundly changed planet. We owe it not just to the countless generations of Portuguese which will come after me, but to the whole of humanity. That future starts today.

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