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The Science

"We are on course for 4°C of heating. “A 4°C future is incompatible with an organised global community, is likely to go beyond ‘adaptation’, is devastating to the majority of ecosystems and has a high probability of not being stable”

General Principles of Climate Science

Every object in the Universe radiates energy (heat); how fast it does so depends on how hot it is, with hotter objects emitting energy faster. When you put on a blanket, the fabric traps some heat from your body – you warm up until the rate at which heat escapes matches the rate at which your body adds heat. This is called thermal equilibrium. Radiation from the Sun warms the Earth’s surface. That energy is re-radiated into space, but the Earth’s atmosphere traps heat like a blanket. It has been known since the 1850s that some gases trap more heat than others – these are called greenhouse gases. As human activity adds greenhouse gases (such as CO2 and methane) to the atmosphere, the total trapped heat energy increases, and so the Earth warms up. The thicker the blanket, the warmer one will ultimately get but, like boiling a giant kettle, the warming process takes time. The last time there was this much CO2 in the Earth’s atmosphere, the Earth was 1-3°C warmer than today.

Some processes thicken the blanket (burning fossil fuels, emissions from animals such as methane); others can reduce its thickness. Some CO2 dissolves into the oceans; some is sequestered by photosynthesising life (plants and algae), which extract carbon from the atmosphere and store it in their bodies. Some of this carbon ends up trapped in forests, in soils, on ocean floors and so life can be an extraordinary ally in slowing climate change. However, whilst almost doubling the amount of atmospheric CO2, industrial activity has decimated life across the planet. This ecological destruction effectively cuts the brakes, accelerating the Earth rapidly into a new state that is alien to human systems, while threatening the ecosystems which supply humans with food, water, and some defence from natural disasters.

The climate literature typically discusses average global temperatures, but this can give a false sense of security. Land and oceans heat up at different rates, so average temperature increases inland tend to be 2-3x higher than the global average. Meanwhile, as average temperatures increase, climate variability grows accordingly. This means that if, for example, the Earth warms by an average of 4°C, inland temperatures could be raised by >10°C, with catastrophic consequences.

Recommended Reading

  1. Foster et al., 2017, Future climate forcing potentially without precedent in the last 420 million years, Nature Comms, 8, 14845 –
  2. David Spratt, 2020, Climate Reality Check 2020 –
  3. Schurer et al., 2018, Interpretations of the Paris climate target, Nature Geo, 11, 220 –
  4. United In Science 2020 – UN Climate Report – 10.13140/RG.2.2.12801.28004
  5. Xu & Ramanathan, 2017, Well below 2 °C: Mitigation strategies for avoiding dangerous to catastrophic climate changes, PNAS, 114, 10315 –
  6. Sherwood et al., 2020, An assessment of Earth’s climate sensitivity using multiple lines of evidence, Reviews of Geophysics –
  7. IPCC. Global Warming of 1.5°C –
  8. IPCC. IPCC Special Report on the Ocean and Cryosphere in a Changing Climate, 2019 –

Climate Feedbacks

Feedbacks are natural mechanisms within the climate system which reinforce some process, i.e. accelerate it, once some climate threshold, or tipping point, is crossed. For instance, arctic sea ice has declined dramatically over the last few decades, accelerating in recent years. Ice acts as an excellent mirror, reflecting around 90% of Solar radiation, while water absorbs around 90%. This means that, as the ice retreats, far more heat is absorbed by the polar regions, driving accelerated warming. There are dozens of such tipping points known, and likely others not yet recognised. Other prominent examples of feedback sources include:

  • thawing permafrost (a layer of frozen soil which contains enough carbon and methane to raise global temperatures by perhaps 2°C, were it to thaw).
  • peatland fires (peatlands are boggy regions which store more carbon than all the world’s forests).
  • collapse and subsequent desertification of the Amazon rainforest (the Amazon collapse tipping point is believed to exist at around 20-40% deforestation: it is currently at ~17%.)
  • ecological destruction (such as the staggering recent loss of coral reefs, or boreal forests, destroying carbon reserves).

There are alarming signs that some of these tipping points have already been reached. Scientists fear is that one tipping point could trigger another, thus causing a cascade of collapsing environments, driving the planet irreversibly to a far hotter state. Such an outcome represents an existential threat to humanity. Policy makers often talk about “carbon budgets” (the amount of CO2 we could still release and hope to remain below certain temperature thresholds). This approach risks total civilisational collapse for the sake of continuing with the current system as long as possible. Furthermore, including the effect of feedbacks suggests the carbon budgets to avoid catastrophe may well already have been surpassed.

Recommended Reading

  1. Steffen et al., 2018, Trajectories of the Earth System in the Anthropocene, 115, 8252 –
  2. Lenton et al., 2019, Climate tipping points — too risky to bet against –
  3. Anthony et al., 2018, 21st-century modeled permafrost carbon emissions accelerated by abrupt thaw beneath lakes, Nature Comms, 9, 3262 –
  4. Lovejoy & Nobre, 2018, Amazon tipping points, Science Advances, 4, 2 –
  5. Feldmann & Levermann, 2015, Collapse of the West Antarctic Ice Sheet after local destabilization of the Amundsen Basin, PNSA, 112, 14191 –
  6. Schneider et al., 2019, Possible climate transitions from breakup of stratocumulus decks under greenhouse warming, Nature Geo, 12, 163 –
  7. Rocha et al., 2018, Cascading regime shifts within and across scales, Science, 362, 6421, 1379 –
  8. Gaurino et al., 2020, Sea-ice-free Arctic during the Last Interglacial supports fast future loss, Nature Climate Change, 10, 928 –

Rising Seas

Sea level rise is one of the most publicised aspects of climate breakdown – perhaps precisely because it is generally expected to be a relatively distant problem, implicitly justifying delay to action. Indeed, the full extent of sea level rise with rising temperatures will not be seen for thousands of years. Sea levels rise primarily due to two factors in a warming climate: ice-melt (from the polar ice caps and from glaciers), and thermal expansion (in warmer seas, water molecules have greater velocities which creates pressure and causes the body of water to expand).

The amount by which sea levels will rise in the next few decades or centuries is highly uncertain, due to cascading effects (e.g. a small rise in sea levels inundates previously elevated parts of an ice sheet, which may cause it to melt faster, destabilise and collapse, with knock-on effects in turn). Estimates of sea level rise this century have tended to increase over time as measurements and models improve, with the IPCC predicting up to 0.6m increase by 2100 in 2007, 0.9m in 2014, and with several recent studies predicting 2-3m or more. Either way, even small increases can have extraordinary impacts on human societies. A 10cm sea level rise approximately doubles the odds of extreme flooding. By 2050 it is likely that ‘historic’ floods will be exceeded annually in most parts of the world. Around 600 million people live less than 10m above sea level, and a third of the world in coastal communities. Hundreds of millions of these will become refugees as sea levels rise, while low-lying island nations are likely to be entirely submerged – a reality tantamount to genocide.

Recommended Reading

  1. Bamber et al., 2019, Ice sheet contributions to future sea-level rise from structured expert judgment, PNAS, 116, 11195 –
  2. WCRP Global Sea Level Budget Group, 2018, Global sea-level budget 1993–present, Earth Syst. Sci. Data, 10, 1551 –
  3. NOAA Technical Report NOS CO-OPS 083, 2017, Global and regional sea level rise scenarios for the United States –
  4. Post et al., 2019, The polar regions in a 2°C warmer world, Science Advances, 5, 12 –
  5. Bahr et al., 2009, Sea‐level rise from glaciers and ice caps: A lower bound, Geophysical Research Letters, 36, 3 –

Ecological Breakdown

Ecosystems continue to be devastated at an accelerating rate, driven overwhelmingly by industrial activity, in service to overconsumption by the world’s wealthiest (not due, despite much focus on it, to population growth). The causes of ecological collapse are many and varied, but are generally attributed to a mixture of global heating, habitat loss (due to deforestation, for instance), over-farming (particularly with marine life), and modern farming practices such as the wide-spread use of pesticides.

It is hard to ascertain precisely how many species or individual animals have already been lost, because the majority of species remain undocumented (existing in remote regions, such as deep in the Amazon for instance). However, it is estimated that over the last 5 decades vertebrate populations (fish, amphibians, reptiles, mammals and birds) have declined by around 70%, with around 20% of species wiped out. Only 4% of land animals today exist in the wild, while the other 96% are made up of humans (36%) and their livestock (60%). Around a third of the world’s trees have been cut down.

Insect populations are relatively poorly studied, but around half of all insect species are thought to be at risk of extinction in the next few decades, with a decline in insect biomass over just the last few decades in excess of 75% in a number of geographically limited studies. Recent evidence suggests even plankton (which generate around 80% of the world’s oxygen and are the basis of all marine ecosystems) may be at risk of catastrophic decline as the planet heats up. The natural world is of simply incalculable importance to human society, providing the basis of our food, water, health, air and more. Without healthy ecosystems, human society cannot thrive. Without functioning ecosystems, human society cannot survive.

Recommended Reading

  1. Living Planet Report 2020 –
  2. Thomas et al., 2004, Extinction risk from climate change, Nature, 427, 145 –
  3. Parmesan & Yohe, 2003, A globally coherent fingerprint of climate change impacts across natural systems, Nature, 421, 37 –
  4. Sanchez-Bayo & Wyckhuys, 2019, Worldwide decline of the entomofauna: A review of its drivers, Biological Conservation, 232, 8 –
  5. Lister & Garcia, 2018, Climate-driven declines in arthropod abundance restructure a rainforest food web, PNAS, 115, E10397 –
  6. Hallman et al., 2017, More than 75 percent decline over 27 years in total flying insect biomass in protected areas, PLoS ONE 12 (10): e0185809 –
  7. Trubovitz et al., 2020, Marine plankton show threshold extinction response to Neogene climate change, Nature Comms, 11, 5069 –
  8. Rainforest facts –

Food and Water Security

Crops exhibit ‘critical temperatures’, above which they rapidly die; as a result, extreme heat waves can kill huge proportions of the crops in the affected region. Food supply chains in the modern world are global, and so failures in one region have global impact. Additionally, much of the world’s food is grown in concentrated centres, not evenly distributed geographically across the world (<25% of the total cropland produces >70% of the maize, wheat and rice), so it only requires a relatively small number of regions to simultaneously suffer extreme heatwaves for catastrophic failures in the global food supply to occur. As the climate heats up, the number of extreme heatwaves grows rapidly. The implication is that, without dramatic policy changes, food production this century will consistently fall short of demand, potentially causing the effective collapse of global society as an epidemic of starvation and food riots sweeps the world.

Since 1980, crop yields have consistently declined for most crops, and this decline is projected to accelerate – potentially dramatically – in coming years. While predictions vary, a number of studies predict declines in crop yields of around 50% within just a few decades (depending on the crop). Some studies suggest this may even be an underestimation because studies often only consider the effects of changing temperature and rainfall on crop yields, but not the effects of changing climate on human labour, the decline of pollinators, nor the effect on non-staple crops.

Droughts, too, are set to dramatically worsen. At 3°C of warming the global average drought duration is projected to last around 10 months, with vast swathes of the world in near-perpetual drought (in northern Africa the average drought is projected to last 5 years, for instance). It is hard to imagine a scenario in which these regions could sustain even a small fraction of their current populations in such a case.

Recommended Reading

  1. Watts et al., 2020, The 2020 report of The Lancet Countdown on health and climate change: responding to converging crises, The Lancet –
  2. Gourdji et al., 2013, Global crop exposure to critical high temperatures in the reproductive period: historical trends and future projections, Environ. Res. Lett., 8, 024041 –
  3. Arora, 2019, Impact of climate change on agriculture production and its sustainable solutions, Environmental Sustainability, 2, 95 –
  4. Hatfield & Prueger, 2015, Temperature extremes: Effect on plant growth and development, Weather and Climate Extremes, 10, 4 –
  5. Schlenker & Roberts, 2009, Nonlinear temperature effects indicate severe damages to U.S. crop yields under climate change, PNAS, 106, 15594 –
  6. Dai, 2013, Increasing drought under global warming in observations and models, Nature Climate Change, 3, 52 –
  7. Naumann et al., 2018, Global Changes in Drought Conditions Under Different Levels of Warming, Geophysical Research Letters,45, 7, 3285 –

The Human Cost

The net effect of drought, heat stress, crop failure, natural disasters, inundation, and consistently worsening catastrophes will be – without dramatic social, economic and political reorganisation of society – catastrophic for human societies. The first and hardest hit are those in the global south, with climate breakdown accentuating existing inequality and injustice, but essentially no community will avoid the consequences. Even the most devout optimist struggles to see much hope; and yet, by understanding what some of the consequences are likely to be, it is possible to prepare and mitigate for some of the worst effects of climate breakdown.

First, we should understand how immediate the issue of climate breakdown is.

  • Already more than 20 million people per year are estimated to be driven from their homes by environmental catastrophe.
  • Currently, there are around 85 million refugees in the world, up ∼240% compared to 10 years ago, and around half of these are children.
  • Meanwhile, refugees are treated with increasing hostility around the world, with a resurgence in the use of concentration camps, and ever more people left stateless and without support.
  • The number of refugees could well surge by billions over the next few decades: ‘unprecedented’ does not capture the depth of this crisis.

Social dynamics are hard to predict with accuracy, but we can seek guidance from a range of historical analogues and case studies. One illuminating example which ties together many elements of the climate crisis is the Syrian civil war. In that case, the worst drought on instrumental record (made possible by the rapidly changing climate) preceded and precipitated the war. Large regions of the country saw three quarters of their animal and crop populations die. More than a million fled to cities to find work and food, with the additional pressure sparking social unrest, which escalated into civil war. This collapse lead to half a million deaths and displaced ~5 million people from the country. That has fuelled fascism and human rights abuses across the world, fed into the rise of Trump, Brexit, the persecution of the Rohingya; this crisis is set to repeat a hundredfold in the coming decades.

The number of conflicts over water has grown over the last century, and exponentially in recent years. Syria is not an isolated case: historically, climate change has been a remarkably common driver of civilisational collapse. If we do not learn from these lessons and adapt accordingly, social collapse on a global scale beckons.

Recommended Reading

  1. UNHCR Report, 2019, Global trends forced displacement in 2018 –
  2. International Organization for Migration (IOM) – Outlook on migration, environment and climate change, 2014, Brief 5 –
  3. Xu et al., 2020, Future of the human climate niche, PNAS, 117, 11350 –
  4. Mora et al., 2017, Global risk of deadly heat, Nature Climate Change, 7, 501 –
  5. Oxfam, Extreme carbon inequality, 2015 –
  6. Weiss & Bradley, 2001, What Drives Societal Collapse?, Science, 291, 5504, 609 –
  7. deMenocal, 2001, Cultural Responses to Climate Change During the Late Holocene, Science, 292, 5517, 667 –
  8. Turchin, 2008, Arise ‘cliodynamics’, Nature, 454, 34 –
  9. Kelley et al., 2015, Climate change in the Fertile Crescent and implications of the recent Syrian drought, PNAS, 112, 11 –

Climate Solutions

There are no simple fixes to the climate crisis, but there are partial solutions which could be implemented today to slow the progression of climate breakdown, and societal elements which must be changed if total collapse is to be avoided. One aspect is practical (transforming our relationship to land, energy, food and resource use); another is cultural (economic, social, political).

To avoid climate breakdown, we must first name its causes. The current capitalist economic model of endless (exponential) growth on a finite planet is clearly unsustainable: by definition, that means that it must come to an end. The only question is whether we will choose to end it, or whether it ends via system collapse. Greenhouse gas emissions and environmental destruction are overwhelmingly driven by corporate expansion and industry. Most consumption – escalating massively during the neoliberal era – comes from the world’s richest, with the wealthiest 10% contributing around half of global personal emissions. Tackling gender, wealth, and social inequality are at the heart of combatting both climate breakdown and climate injustice. Though some would interpret these propositions as inherently ideological, they are conclusions that emerge out of robust scientific study. Capitalism – particularly in its modern neoliberal incarnation – must be abandoned or transformed beyond recognition if human civilisation is to survive.

The current economic model underpins virtually every aspect of society’s organisation, but is often invisiblised. Modern farms, in an effort to outcompete rivals, pump livestock full of antibiotics, use insect-destroying pesticides, and clear all available space of wildlife to sow profitable monocultures; technologies are often designed to break, so that replacements must be regularly purchased; relentless advertising creates discontent in order to push consumables upon the population. To escape the destruction of the natural world, the precepts underpinning this reality must be combatted.

On the immediate, pragmatic level, carbon emissions must be cut with urgency. Everything possible should be done to restore and sustain ecological systems: doing so could draw down around a third of the necessary carbon emissions and provide incalculable additional benefits (in terms of health, water and food security, resilience to environmental disasters, and more). The agricultural sector must be transformed to revolutionise our relationship to food and land. Housing must be reformed with efficiency front and centre. Energy systems must be overhauled so that power comes from sustainable technologies. These solutions require investment, but ultimately leave us wealthier, healthier and happier. At any rate, the cost of inaction is approximately the sum total of everything built over the past several thousand years, so inaction loses out in any conceivable cost-benefit analysis.

Recommended Reading

  1. Schröder & Storm, 2020, Economic Growth and Carbon Emissions: The Road to “Hothouse Earth” is Paved with Good Intentions, International Journal of Political Economy, 49, 153 –
  2. Hickel & Kallis, 2019, Is green growth possible?, New Political Economy, 25, 4, 469 –
  3. Otto et al., 2020, Social tipping dynamics for stabilizing Earth’s climate by 2050, PNAS, 117, 2354 –
  4. New Weather Institute, Advertising’s role in climate and ecological degradation –
  5. Griscom et al., 2017, Natural climate solutions, PNAS, 114, 44, 11645 – pnas.1710465114
  6. Ramanathan et al., 2019, Bending the Curve: Climate Change Solutions –
  7. The Drawdown Review 2020 –

Non-Violent Resistance

Activists, in order to achieve success, must be motivated both by ethical and practical considerations. While the why of resistance is intimately tied to questions of principle, the how of resistance is also an ideal question for scientific inquiry. By considering historical uprisings and campaigns we can assess different tactics and approaches to resistance in order to ascertain what works, and what are common themes of success.

Non-violent resistance is predicated on the application of human stubbornness: the refusal to cooperate, to defy and disrupt.

  • It employs a wide set of strategies: protests, demonstrations, direct actions, strikes, non-cooperation etc.
  • It can include the development of alternative institutions, such as mutual aid and educational networks.

All governments rely on cooperation and obedience in order to persist. When that cooperation is withheld, governments can find themselves surprisingly fragile.

In a groundbreaking series of studies, led by Erica Chenoweth, the common assumption that violent resistance is more effective than non-violence was scrutinised, and ultimately rejected. Studying hundreds of uprisings since 1900, they find that non-violent resistance is more successful than violent resistance (in democracies, autocracies and monarchies alike), achieving success around twice as often. Virtually no regime has withstood the participation of 3.5% of the population at the campaign’s peak, while even campaigns which mobilise around just 0.1% are successful nearly half the time. The primary reasons for this can be summarised twofold:

  • non-violent tactics can mobilise far broader sects of society, being seen as more legitimate (rather than mobilising overwhelmingly young, able-bodied males – indeed, the wide-spread participation of women is a strong predictor of campaign success)
  • and repression of non-violent campaigns is likely to backfire, driving people into the movement (including defections from state actors) and reducing the legitimacy of the regime which they seek to overthrow.

Furthermore, successful instances of non-violent resistance are far more likely to be followed by desirable conditions (e.g. increased stability, democracy, freedom) than their violent counterparts. Overall, the scientific literature strongly indicates that activists should strictly opt for non-violent resistance if they wish to achieve success, even in the absence of ethical considerations. 

Recommended Reading

  1. Sharp, 2003, There Are Realistic Alternatives, The Albert Einstein Institution –
  2. Stephan & Chenoweth, 2008, Why Civil Resistance Works, The Strategic Logic of Nonviolent Conflict, International Security, 33, 1, 7 –
  3. Chenoweth, 2019, Women’s Participation and The Fate Of Nonviolent Campaigns, One Earth Future Foundation –
  4. Chenoweth, 2020, Questions, Answers, and Some Cautionary Updates Regarding the 3.5% Rule, Carr Center for Human Rights Policy –
  5. Chenoweth, 2020, The Future of Nonviolent Resistance, Journal of Democracy, 31, 3, 69 –