Extinction—nuclear war and ecological breakdown—feedback loops make adaptation impossible

Climate change is an existential risk to human civilisation: that is, an adverse outcome that would either annihilate intelligent life or permanently and drastically curtail its potential.

Temperature rises that are now in prospect, after the Paris Agreement, are in the range of 3–5°C. At present, the Paris Agreement voluntary emission reduction commitments, if implemented, would result in planetary warming of 3.4°C by 2100,30 without taking into account “long-term” carboncycle feedbacks. With a higher climate sensitivity figure of 4.5°C, for example, which would account for such feedbacks, the Paris path would result in around 5°C of warming, according to a MIT study.31 A study by Schroder Investment Management published in June 2017 found — after taking into account indicators across a wide range of the political, financial, energy and regulatory sectors — the average temperature increase implied for the Paris Agreement across all sectors was 4.1°C.32 Yet 3°C of warming already constitutes an existential risk. A 2007 study by two US national security think-tanks concluded that 3°C of warming and a 0.5 metre sea-level rise would likely lead to “outright chaos” and “nuclear war is possible”, emphasising how “massive non-linear events in the global environment give rise to massive nonlinear societal events”.33 The Global Challenges Foundation (GCF) explains what could happen:

“If climate change was to reach 3°C, most of Bangladesh and Florida would drown, while major coastal cities — Shanghai, Lagos, Mumbai — would be swamped, likely creating large flows of climate refugees. Most regions in the world would see a significant drop in food production and increasing numbers of extreme weather events, whether heat waves, floods or storms. This likely scenario for a 3°C rise does not take into account the considerable risk that self-reinforcing feedback loops set in when a certain threshold is reached, leading to an ever increasing rise in temperature. Potential thresholds include the melting of the Arctic permafrost releasing methane into the atmosphere, forest dieback releasing the carbon currently stored in the Amazon and boreal forests, or the melting of polar ice caps that would no longer reflect away light and heat from the sun.”34

Warming of 4°C or more could reduce the global human population by 80% or 90%,35 and the World Bank reports “there is no certainty that adaptation to a 4°C world is possible”.36 Prof. Kevin Anderson says a 4°C future “is incompatible with an organized global community, is likely to be beyond ‘adaptation’, is devastating to the majority of ecosystems, and has a high probability of not being stable”.37 This is a commonly-held sentiment amongst climate scientists. A recent study by the European Commission’s Joint Research Centre found that if the global temperature rose 4°C, then extreme heatwaves with “apparent temperatures” peaking at over 55°C will begin to regularly affect many densely populated parts of the world, forcing much activity in the modern industrial world to stop.38 (“Apparent temperatures” refers to the Heat Index, which quantifies the combined effect of heat and humidity to provide people with a means of avoiding dangerous conditions.) In 2017, one of the first research papers to focus explicitly on existential climate risks proposed that “mitigation goals be set in terms of climate risk category instead of a temperature threshold”, and established a “dangerous” risk category of warming greater than 1.5°C, and a “catastrophic” category for warming of 3°C or more. The authors focussed on the impacts on the world’s poorest three billion people, on health and heat stress, and the impacts of climate extremes on such people with limited adaptation resources. They found that a 2°C warming “would double the land area subject to deadly heat and expose 48% of the population (to deadly heat). A 4°C warming by 2100 would subject 47% of the land area and almost 74% of the world population to deadly heat, which could pose existential risks to humans and mammals alike unless massive adaptation measures are implemented.”39 A 2017 survey of global catastrophic risks by the Global Challenges Foundation found that: “In high-end [climate] scenarios, the scale of destruction is beyond our capacity to model, with a high likelihood of human civilization coming to an end.”40 84% of 8000 people in eight countries surveyed for the Foundation considered climate change a “global catastrophic risk”.41 Existential risk may arise from a fast rate of system change, since the capacity to adapt, in both the natural and human worlds, is inversely proportional to the pace of change, amongst other factors. In 2004, researchers reported on the rate of warming as a driver of extinction.42 Given we are now on a 3–5°C warming path this century, their findings are instructive:

• If the rate of change is 0.3°C per decade (3°C per century), 15% of ecosystems will not be able to adapt.

• If the rate should exceed 0.4°C per decade, all ecosystems will be quickly destroyed, opportunistic species will dominate, and the breakdown of biological material will lead to even greater emissions of CO2.

At 4°C of warming “the limits for adaptation for natural systems would largely be exceeded throughout the world”.43 Ecological breakdown of this scale would ensure an existential human crisis. By slow degrees, these existential risks are being recognised. In May 2018, an inquiry by the Australian Senate into national security and global warming recognised “climate change as a current and existential national security risk… defined as ‘one that threatens the premature extinction of Earth-originating intelligent life or the permanent and drastic destruction of its potential for desirable future development’”.44 In April 2018, the Intelligence on European Pensions and Institutional Investment think-tank warned business leaders that “climate change is an existential risk whose elimination must become a corporate objective”.45 However the most recent IPCC Assessment Report did not consider the issue. Whilst the term “risk management” appears in the 2014 IPCC Synthesis Report fourteen times, the terms “existential” and “catastrophic” do not appear.

Existential risks require a particular approach to risk management. They are not amenable to the reactive (learn from failure) approach of conventional risk management, and we cannot necessarily rely on the institutions, moral norms, or social attitudes developed from our experience with managing other sorts of risks. Because the consequences are so severe — perhaps the end of global human civilisation as we know it — “even for an honest, truth-seeking, and well-intentioned investigator it is difficult to think and act rationally in regard to… existential risks”. 1NC—AI vs eBay