The Climate Crisis
I am a social scientist, not a climate scientist. I accept the biophysical basis of the climate crisis, but address the following question, which is rarely asked: What will happen to human societies when we consider not just the physical changes to our climate, but how these changes will interact with political, economic, military, health, and psychological factors? This page summarizes a comprehensive paper examining this question. The full paper presents the evidence and arguments behind each of the findings below.
- Staying below 1.5°C (Paris Agreement) is no longer possible, and even staying below 2°C is very unlikely — and 2°C will be catastrophic
- Extreme weather events are increasing in frequency and intensity, especially heatwaves and extreme rainfall. The impacts are devastating
- Climate risks are consistently underestimated
- Extremely rapid decarbonization is required but unlikely to occur
- We may have already crossed points of no return in multiple Earth systems
- The barriers to action are political, not scientific or technical
Renewable energy will not save us. The price of renewable energy has fallen dramatically, and is now often cheaper than fossil fuels. This is true, but it doesn't matter as long as we continue to pump enormous amounts of greenhouse gases into the atmosphere.
Overview
Photo by NASA
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.
As the earth warms, snow and ice in the cryosphere melt, albedo (reflectivity) is reduced, and more of the sun's energy is absorbed by the land and ocean. Melting permafrost and burning forests also release greenhouse gases (GHGs), while at the same time the ability of natural carbon sinks to sequester carbon is falling.
Root Cause
Photo by Patrick Hendry
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."
This is why individuals should focus on changing policies at the national and international level rather than focusing on reducing their individual carbon footprints. For meaningful change to occur there needs to be mass mobilizations for climate action, and one critical initial prerequisite is an honest assessment of the current situation, plus predictions about what we can realistically expect in the near future. The goal here is to provide that information.
Current Situation
Photo by Chris Gallagher
The paper below reviews the latest scientific findings on our climate, and provides evidence that not only is the biophysical situation much worse than reported by most 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. Rapid decarbonization is required but is unlikely to occur. Staying below the 1.5°C limit of the 2015 Paris Agreement is impossible at this point, and furthermore it is very unlikely that we will be able to stay below 2°C.
On Ice Sheets at 2°C
"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.
Assessment
Photo by Matt Palmer
It is possible to predict many astronomical and physical events quite accurately, but no one can predict the future of human societies. There are just too many variables and unknown future events. But given the evidence I have accumulated in the paper below, how likely is a societal collapse, and how strong is the evidence?
The Intergovernmental Panel on Climate Change (IPCC) uses "calibrated uncertainty" language to communicate certainty. There are two metrics, confidence and likelihood. Confidence reflects the strength of the evidence, while likelihood is the assessed probability of an outcome or result. Will climate change lead to societal collapse? Given the evidence and arguments in my paper, I estimate the likelihood level as "More likely than not" (greater than 50% chance), while my confidence in this estimate is "High confidence." See the paper for a definition of societal collapse.
Likelihood
More likely than not
>50% chance of societal collapse
Confidence
High Confidence
Strong evidence base for this estimate
Modeling the Crisis
Figure from IPCC
This figure shows climate-model scenarios, not predictions. It shows projected patterns of annual average surface warming near the end of this century, for 2081–2100 compared with 1995–2014. It compares two emissions pathways: SSP1-2.6, a low-emissions pathway with strong climate mitigation, and SSP5-8.5, a very-high-emissions pathway associated with intensive fossil-fuel use.
The projections come from CMIP6 climate-model simulations. CMIP6 stands for Coupled Model Intercomparison Project Phase 6, an international effort in which climate-modeling centers run models using common experimental designs so their results can be compared. “Coupled” means that the models link major parts of the Earth system, including the atmosphere, oceans, land surface, and sea ice.
“SSP” in the figure stands for Shared Socioeconomic Pathway. SSPs describe different possible human futures, including assumptions about population, economic development, technology, land use, energy use, and climate policy. In labels such as SSP1-2.6 and SSP5-8.5, the number after the dash refers to the approximate level of radiative forcing in 2100, measured in watts per square meter. Radiative forcing is a measure of how much human activity has changed Earth’s energy balance. A higher number means a stronger warming influence.
The columns of the figure compare different ways of representing warming within each emissions pathway. Panels (a) and (d) show the scaled CMIP6 multi-model mean, adjusted to match the IPCC’s assessed best estimate of global surface temperature change. Panels (b) and (e) show averages from selected high-warming models, meaning models whose global warming is near the upper end of the IPCC’s assessed very likely range. Panels (c) and (f) show very-high-warming models, meaning models that produce warming above that assessed very likely range. Climate-scenario researchers now believe that the high emission levels in SSP5-8.5 are implausible.
You can see that warming is not spatially uniform: land warms more than oceans, and the Arctic warms especially strongly. It also shows that, even under the same emissions pathway, different climate models can produce substantially different levels and patterns of warming.