Demetrios Karis

Executive Summary

Human civilization will not collapse from the direct effects of climate change, but rather from the secondary effects of crop failures, infectious diseases, and armed conflict. The root cause of the climate crisis is the earth’s energy imbalance: more energy is arriving at the earth from the sun than is being radiated back out into space.  This is occurring because we have been cutting down forests and burning fossil fuels for the last 150 years at a furious rate, leading to a greenhouse effect and the consequent warming of the earth’s land, oceans, and atmosphere. There is now general agreement that continuing to burn fossil fuels will lead to catastrophic consequences for human civilization as well as thousands of other species. We know how to reduce greenhouse gas (GHG) emissions and transition to other sources of power, but we are not doing this at a rate that will prevent catastrophe. The problems at this point are not scientific or technical but rather political, which is why individuals should focus on changing policies at the national and international level rather than focusing on reducing their individual carbon footprint.

This paper reviews the latest scientific findings on our climate, and provides evidence that not only is the biophysical situation much worse than reported by much of the scientific community, but that the consequences for human societies are also much worse. In summary: the situation is already critical, and it will get much worse in the near future. Climate change mitigation (the effort to limit greenhouse gases) has failed, risks are consistently underestimated, and the required rapid decarbonization is unlikely to occur. Staying below the 1.5°C limit of the 2015 Paris Agreement is impossible at this point, and it is also very unlikely that we will be able to stay below 2°C. A 2°C increase will be catastrophic in multiple areas and in multiple ways. Considering just ice sheets, “2°C will result in extensive, potentially rapid, irreversible sea-level rise from Earth’s ice sheets” (eventually up to 20 meters), and “Many ice sheet scientists now believe that by 2°C, nearly all of Greenland, much of West Antarctica, and even vulnerable portions of East Antarctica will be triggered to very long-term, inexorable sea-level rise, even if air temperatures later decrease” (International Cryosphere Climate Initiative, 2023). In fact, we may have already crossed a point of no return for many earth systems. 

The probability that there will be a global societal collapse is high because the second and third order effects of climate change, such as crop failures leading to starvation, are not fully appreciated and will lead to intra- and interstate conflict. Compound hazards and cascading effects will also increase the damage to individuals and society, and there are interconnections among risks arising from environmental, economic, technological, geopolitical, and societal factors that will increase the probability of societal collapse.

Although a global mobilization is required to deal with climate change, political forces in many countries, as well as resistance from fossil fuel companies, are preventing the required action. As climate disasters become even more extreme than those in 2023 and continue to multiply around the world, mass movements demanding meaningful climate action will increase, and eco-terrorism will, unfortunately, become inevitable. Eco-anxiety, already common, will increase dramatically.

The direct effects of climate change will result in millions of deaths from floods, droughts, heat waves, tropical storms, wildfires, and rising sea levels, but many more will die from starvation, infectious diseases, and especially from civil unrest and regional and international conflicts. The extreme consequences of climate change will start first in “fragile” states, as they have less resilience and adaptive capacity. Climate change has been described as a “threat multiplier,” and it will exacerbate existing political instability via fights over water, mass migration, and from the pressures of crop failures and extreme weather events. In addition, any economic or political problems are likely to derail mitigation efforts or at a minimum make them more difficult. Armed conflict often leads to environmental disasters and is incredibly carbon intensive, but is rarely mentioned as a contributor to climate change. The Israel-Gaza war, for example, is likely to end up emitting more GHGs than the annual emissions of over 100 countries (Neimark et al., 2024).

The rapid introduction of renewable energy will not prevent societal collapse. Planting trees will not save us, reducing methane will not save us, and removing CO2 from the atmosphere via direct air capture will not save us. At this point, the only thing that really matters is the amount of greenhouse gases we are emitting. This is a critical point that many people don’t seem to understand. The amount, and price, of renewable energy is basically meaningless with respect to the climate emergency if we continue to pour carbon dioxide and other greenhouse gases into the atmosphere. It is also essentially meaningless what you as an individual in a rich country do so long as other countries continue to build coal-fired power plants, cut down forests, and degrade the other natural carbon “sinks” on our planet.

“Net zero” refers to a state in which greenhouse gases entering the atmosphere are balanced by their removal from the atmosphere. Recent proclamations that after we reach net zero warming will quickly stop are disingenuous. Reaching net zero will take decades, and there are so many positive feedback loops and tipping points we may soon cross that it is likely that a variety of biophysical processes will continue to warm the earth even after we stop emitting greenhouse gases. 

When it is clear that it is impossible to adapt to our changing climate, geoengineering via solar radiation management or other means will become inevitable. In fact, some scientists now already argue that any realistic approach to the climate crisis must include “climate cooling” via geoengineering.

This paper just “connects the dots”: there is consensus that at 1.5°C the situation will be very bad, we are likely to cross several tipping points, and multiple feedback loops will increase the release of GHG emissions. Given the political realities in the world today, there will be no world-wide mobilization to rapidly transform our economies and power production to reduce GHG emissions. That means we will almost definitely cross 2°C, probably before 2050. The direct and indirect consequences of this increase will dramatically impact the climate around the world, leading to all the negative consequences listed above. As a result, societies around the world will start to collapse. 

Unfortunately, liberal democratic states with their market economies are ill-equipped to deal with a major crisis that requires immediate actions. During World War II, the War Production Board was established to convert civilian industry to war production. The United States had, during the war years, a centrally planned economy, with the federal government controlling and allocating resources, directing the conversion of factories, and even taking over some private companies. The current climate crisis is far more serious than a war, and similarly drastic actions are required.

Given the unlikelihood of immediate and drastic actions, there is really no chance of remaining below either 1.5° or 2°C. And despite what we are constantly told, we may now be at a point where every tenth of a degree no longer matters. Several scientific organizations and initiatives are trying to sound the alarm, proclaiming, for example, that, “As of 2023, some of the very lowest emission pathways from IPCC no longer remain possible” (ICCI, 2023). More dramatically, 

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  “The scale of the threats to the biosphere and all its lifeforms—including humanity—is in fact so great that it is difficult to grasp for even well-informed experts” (Bradshaw et al., 2021).

  
  


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  From coordinated editorials in over 200 health journals: “...climate change and biodiversity loss are one indivisible crisis and must be tackled together to preserve health and avoid catastrophe. This overall environmental crisis is now so severe as to be a global health emergency” (Abbasi et al., 2023).

  
  


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  “Sea level rise is unavoidable for centuries to millennia due to continuing deep ocean warming and ice sheet melt, and sea levels will remain elevated for thousands of years (high confidence)” (IPCC, 2023).

  
  


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  “Earth is now well outside of the safe operating space for humanity” (Richardson et al., 2023).

  
  


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  “The consequences of global heating are becoming increasingly extreme, and outcomes such as global societal collapse are plausible and dangerously underexplored” (Ripple et al., 2022).

  
  


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  “...the world in which we live is collapsing and may be nearing the breaking point” (Pope Francis, 2023).

  
  

Although global societal collapse is probable, it is not inevitable, and the paper ends by describing what you as an individual should do, and what we as a society should do. In the short term, political action, mass mobilization and civil resistance, plus working for a carbon tax will be the most effective actions for individuals. Only after there is agreement that a worldwide mobilization and extreme actions are required will it be worthwhile to focus on reducing one's carbon footprint. 

We are now on a “Hothouse Earth” trajectory that will, if we continue on it, end human civilization as we know it. Humans are capable, however, of creating a new pathway to what Steffen et al. (2018) call “Stabilized Earth.” As a society, we must, on a global scale, rapidly reduce greenhouse gas emissions. This must be our number one priority; it is necessary but not sufficient. Simultaneously, we must protect our biosphere’s carbon sinks and actively cool the earth using geoengineering techniques such as solar radiation management. Research and development on directly removing CO2 from the air should continue because in the future, even after net zero is reached, it will be necessary to remove massive amounts of CO2  from the atmosphere.

As Pope Francis (2023) writes in his Apostolic Exhortation, international politics and organizations must recover their credibility by agreeing to “binding forms of energy transition that meet three conditions: that they be efficient, obligatory and readily monitored.” Reaching such international agreements will be a challenge.