It seems both mainstream, cable, and even social media are consumed with discussions of past disasters (9/11, floods, COVID-19) or speculations on impending disasters (AI gone rogue). The United Nations has confirmed that disasters are increasing in frequency and intensity.
Harvard professor George Santayana once wrote, “Progress, far from consisting in change, depends on retentiveness … and when experience is not retained, infancy is perpetual. Those who cannot remember the past are condemned to repeat it.”
This is a valuable warning. But more valuable yet is the admonition of Alvin Toffler, who said, “If we do not learn from history, we shall be compelled to relive it. True. But if we do not change the future, we shall be compelled to endure it. And that could be worse.”
Disasters are devastating, but perhaps we can learn valuable lessons from them to help shape the future. This post looks at four modern disasters that changed the world and the lessons we can take from them that might prepare us for the future. Failure to do so could be unimaginable.
Tokyo Sarin Gas Attack
On March 20, 1995, members of Aum Shinrikyo punctured bags of sarin. Sarin is a potentially fatal nerve agent that causes acute cholinergic reactions, especially feelings of suffocation. The release killed 12 people and caused more than 5,000 to seek medical care, causing chaos across the subway system and overwhelming hospitals with about 1,000 victims physically exposed and over 4,000 people who feared they had been exposed.
The disaster revealed two phenomena: psychological contagion and the psychological iceberg effect. Psychological contagion refers to the spread of fear, general distress, and even physical reactions that mimic actual exposure to the pathogen, but absent any actual exposure. The psychological iceberg effect refers to the fact that psychological casualties can (and almost always do) vastly outnumber physical casualties in the wake of disasters by a ratio of 50:1 or more. This is especially true in the case of radiation, chemical, and biological agents.
The disaster taught two powerful lessons: 1) the importance of ongoing crisis communications to the affected community to combat uncertainty and fear, and 2) the importance of both physical and psychological triage to direct survivors to the most efficient and effective resources. Finally, crisis communications should follow the 3-T guidance: truthful, transparent, timely.
Hurricane Katrina
Hurricane Katrina was referred to as an example of catastrophic leadership failure. Katrina made landfall on August 29, 2005, as a Category 3 hurricane. It devastated the Gulf Coast of the United States—especially New Orleans—costing 1800 lives and displacing over 100,000 people.
Even though evacuation was recommended by federal weather authorities, the mayor delayed until evacuation was no longer an option. There was no clear-cut evacuation mechanism for over 100,000 people who did not have cars. State authorities delayed allowing access to external logistical and medical resources for fear of adverse legal ramifications. Federal authorities underestimated the severity of the impact. Temporary housing was abandoned for fear of toxicity, potentially leaving thousands homeless.
Perhaps the greatest lesson learned from Katrina was that “he who hesitates is lost.” Surely, the moment of absolute certainty never arrives. The only failure in crisis leadership is the failure to lead. Finally, paralysis by analysis or out of fear can be deadly.
September 11, 2001 (9/11)
On September 11, 2001, Al‑Qaeda terrorists, in a coordinated effort, hijacked four jet passenger planes and crashed them into the World Trade Center, the Pentagon, and a field near Shanksville, Pennsylvania. It goes without saying that those attacks reshaped the entire world for the following 25 years and will continue to do so. Over 3,000 people were killed as a direct result of the attacks, but many more have died as indirect victims through illness and retaliatory warfare. According to a September 10, 2026 report on CBS News, the Mt. Sinai medical system continues to treat over 25,000 first responders for mental health issues.
Perhaps the greatest lessons from 9/11 were the destruction of a national sense of invulnerability (we seemed to forget the previous attempt to destroy the World Trade Center on February 26, 1996) and how enduring and widespread traumatic stress, depression, and grief can be in the wake of disaster.
The COVID-19 Pandemic
The COVID‑19 pandemic was a global infectious‑disease disaster caused by the SARS‑CoV‑2 virus, beginning in late 2019. It disrupted every aspect of daily life worldwide—health systems, economies, communities, and even interpersonal social functioning. There were over 775,000,000 confirmed cases with over 7,000,000 confirmed deaths.
Lessons learned from COVID-19 were numerous. Psychologically, COVID was a disaster of uncertainty. Uncertainty was revealed to be the foundation for the subsequent psychological pandemic of anxiety and depression. Reviews found the prevalence of anxiety rose from 8 to 23 percent and depression rose from 5 to 25 percent (Hou et al., 2025). COVID-19 exposed systemic weaknesses in global governance, international cooperation, national policy formation, and crisis leadership. COVID-19 was a textbook case of failure in all of Everly’s five factors of effective crisis leadership (Everly & Athey, 2023). Moral injury, once thought to be primarily related to combat, became epidemic amongst healthcare workers. Perhaps the three greatest mistakes made during the pandemic were failed crisis communications, allowing persistent social isolation to destroy social infrastructures, and politicizing the pandemic.
As the Phoenix arises from disaster stronger than before, learning from the adversity and mistakes made in disaster, we too can arise stronger than before. The failure to learn from our mistakes, however, condemns us to repeat them.
© 2026. George S. Everly, Jr., PhD, MA