Catastrophic threats address events which could kill tens of millions of Americans and destroy the nation.

Two hundred people a year are killed by asteroid impacts. Actually, that is only a gross average, and it has not happened yet. But the geological record suggests that every 25 million years or so we can expect an impact of a magnitude that would kill most humans, perhaps 5 billion - an average of 200 a year. This is one of the catastrophic threats which the nation faces, events which could kill tens of millions of Americans and destroy the nation. This is an unusual catastrophic threat since we know enough to actually estimate both consequences and likelihood. Other catastrophic threats are also very unlikely to actually occur in the decades ahead, but it is generally impossible to quantify the probability. These threats include supervolcanoes, strategic nuclear exchanges, and virulent pandemics. Although unlikely, the potential consequences of these threats are so massive that a number of preliminary efforts are already in progress. These threats and actions are discussed in more detail below

Asteroid Impacts

This is a threat that earth has faced throughout its long history, a threat that can never be eliminated. Even a cursory glance at the moon's heavily cratered surface gives an immediate impression of the magnitude of impacts that earth must have suffered through the eons. Nor is this just a theoretical threat. One recent evaluation, for example, has identified a probable impact off the coast of Madagascar, an impact a mere 4,800 years ago, which raised a 600-foot tsunami and has been attributed to a large asteroid or comet, the kind which could kill a quarter of the world's population. A recent NASA calculation on near-Earth-asteroid 2004 VD17assesses it as 500 meters in diameter with a possible impact on May 4, 2102, while Russia assesses than an asteroid Number 2907, a kilometer-wide chunk of space rock, "with a large degree of certainty" will strike the Earth on December 16, 2880. Another recent calculation shows that a small asteroid will pass as close as 15,000 miles to earth (less than a tenth of the distance to the moon) on April 13, 2029; an impact is possible.

In fact, the direct effects of a large asteroid impact (physical destruction, enormous tsunamis, global earthquakes) are only the beginning. The great extinction which destroyed the dinosaurs resulted from massive amounts of dust thrown into the atmosphere, creating several years of Winter Night which collapsed the food chain and starved hundreds of species into extinction. A similar Winter Night now would inevitably starve the overwhelming majority of mankind.

NASA is addressing this impact hazard by carrying out a comprehensive telescopic search for near-Earth asteroids (NEAs). This program is called the Spaceguard Survey and its objective was to find 90% of the NEAs larger than one kilometer diameter by the end of 2008. It assesses no known asteroid on a verified collision course with the Earth, and the Spaceguard Survey does not expect to find any large asteroid that directly threatens us. But the apparent 25 million year cycle of impacts also raises the possibility that part of the threat is from more distant sources, with the solar system regularly encountering some cloud of galactic debris. At any rate, if an asteroid is discovered on a collision course, then NASA anticipates that we would apply appropriate technology to deflect it before it hits.

NASA's comment on applying appropriate technology is reassuring, except that such technology does not now exist. Anti-missile technology could be adapted to this task, but no such systems are currently configured to escape earth's gravity or to intercept an object traveling up to thousands of miles a second. Nor is it clear what such an intercept would really accomplish. Russia has also considered such development, so there is an opportunity for a cooperative effort. Other approaches have also been proposed, including a proposal for a craft to accompany incoming asteroid and use its small gravitational attraction to gradually deflect the asteroid's trajectory enough to cause it to miss Earth. Were a threatening asteroid to be identified today, there is little we could actually do. Developing a reliable anti-asteroid system would take substantial effort and years of time. Perhaps sometime in the future such an effort will be initiated.

Supervolcanoes

For a number of years, scientists puzzled over Yellowstone - its famous geysers and hot spots gave striking evidence of subsurface volcanic activity, but they were not able to identify any associated caldera -- a subsurface crater of magma characteristic of active volcanoes. Gradually, it became evident that their vision was too small, that the entire Yellowstone area is one gigantic caldera. Scientists now understand that this is a massive supervolcano which most recently erupted about 650,000 years ago when ground-hugging flows of hot volcanic ash, pumice, and gases swept across an area of more than 3,000 square miles. When these enormous pyroclastic flows finally stopped, they solidified to form a layer of rock called the Lava Creek Tuff with enough material to cover Wyoming with a layer 13 feet thick; ash was dropped as far away as the Gulf of Mexico.

Another catastrophic eruption is also possible. The effects of such a disaster are hard to even comprehend. One geohazard specialist, Bill McGuire of the University College of London, has estimated that "magma would be flung 50 kilometers into the atmosphere. Within a thousand kilometers virtually all life would be killed by falling ash, lava flows and the sheer explosive force of the eruption. One thousand cubic kilometers of lava would pour out of the volcano, enough to coat the whole USA with a layer 5 inches thick." This could again bring "the bitter cold of Volcanic Winter to Planet Earth. Mankind may become extinct."

Fortunately, the probability of an eruption occurring at Yellowstone within the next few thousand years is exceedingly low. A National Volcano Early Warning System being developed by the United States Geological Survey to monitor the most threatening volcanoes in the United States partly addresses this threat. It could provide some warning of such an event. However, as distinguished from the asteroid threat, there is no appropriate technology even waiting in the wings which could deflect a super volcano eruption. Moreover, since the core threat is a global Volcanic Winter, super volcanoes anywhere in the world pose a direct threat to the nation; at least seven have been identified. For now, this is a threat we simply have to live with. Perhaps with a gradually cooling earth, there will be no more supervolcano eruptions.

Strategic Nuclear Exchange

For many years, the United States lived with the threat of a comprehensive nuclear strike from the Soviet Union. Step-wise missile and warhead developments by both countries resulted in a posture of Mutually Assured Destruction in which each side had tens of thousands of warheads aimed at the other. In a full scale nuclear exchange, one researcher estimated that 100-160 million US citizens would die in the first few days. Firestorms and ozone depletion would add to this destruction, and a resulting Nuclear Winter would approximate the effects of an asteroid strike, spreading the destruction globally.

The potential for such an exchange to actually occur was higher than almost anyone realized. Robert McNamara, the US Secretary of Defense during the Cuban Missile Crisis, has recently outlined how that crisis came close to initiating nuclear war. In another chilling episode, a Russian colonel described how a false alert resulted in launch instructions for 5,000 Soviet missiles, instructions which the colonel declined to carry out.

With the demise of the Soviet Union and greatly improved US-Russian relations, the likelihood of this threat has significantly diminished. These improved relations led to the 2002 Moscow Treaty, in which each nation agreed to reduce strategic nuclear forces to about 2000 deployed warheads. Unfortunately, the treaty does not require the actual destruction of any weapons, merely their removal from deployed status. Moreover, these reduced levels to not have to be met until December 31, 2012, which happens to also be the very day the treaty expires. So, while it is a step in the right direction, thousands of missiles remain in place and some unexpected chain of events could still lead to catastrophe.

This is particularly troubling since relations between the two countries have continued to deteriorate while no additional nuclear reduction steps have been taken in over four years. In the meantime, Russia has pushed ahead with its most massive intercontinental ballistic missile testing and upgrading program since the collapse of communism. And the United States is still considering its own plans for new warhead developments.

So the threat of a comprehensive nuclear exchange with the Russians remains and once again grows. It is practically impossible to put any quantitative probability on this threat, though it would certainly seem to be higher than the probability of an asteroid strike or a supervolcano eruption, probably even larger than the proverbial "one-in-a-million" chance.

Currently, there are no other nations which pose a threat of a comprehensive nuclear exchange, and only China would seem to have any potential to pose such a threat in the future. At present China has perhaps as few as 100 nuclear weapons. Regardless of the present number, it is clear that China is not now in a nuclear race with the United States. This is consistent with China's historical inclination not to compete against opponent's strengths, but rather to focus on their weaknesses. A relatively small number of strategic nuclear weapons gives China essentially a countervalue capability against the United States. A significant increase in numbers would provide China little additional capability but would require a major refocusing of assets away from the economic development which is clearly occupying the leadership. Overall, the probability of a Chinese comprehensive nuclear strike in the years immediately ahead seems significantly lower than for a Russian strike.

Virulent Pandemic

A global epidemic of some newly evolved infective agent, one that is both highly virulent and highly transmissible, could conceivably kill tens of millions Americans. Past pandemics show the potential for such an effect. The Black Death which swept through Europe in the mid-14th century killed about half of Europe's population. Although modern antibiotics would probably reduce the impact of such a bacterial disease, this is not assured. More recently the influenza pandemic of 1918 killed an estimated 50 million people worldwide; it infected some 28% of the US population, killing nearly 700,000 with a lethality rate of 2.5%, much higher than the 0.1% of previous epidemics.

Against this background, recent outbreaks of avian influenza have been very sobering. By 2007, it had infected only 256 people in 10 countries -- mostly people in close contact with chickens in Asia -- but the pathogen had a staggering 60% lethality. Conditions also exist for the disease to become highly contagious. One possibility would be for the avian influenza virus to exchange genes with a common form of flu which routinely infects people. Should this happen, it could acquire the basic genetic blueprint for spreading quickly -- and explosively -- through human populations. Scientists believe a similar exchange of genetic material occurred prior to 1918.

Although this is the most prominent candidate for a new pandemic, it is not the only one. In November, 2002, the first new severe infectious disease to appear in the twenty-first century surfaced in China. As it spread to several hundred people, the World Health Organization became alarmed at this previously unrecognized disease which became referred to as Severe Acute Respiratory Syndrome (SARS). By July 2003, there had been 8,096 known cases in 29 countries and 774 deaths (a mortality rate of 9.6%). By late 2003, the disease seemed to have run its course, thanks to close and proactive international cooperation. There was no vaccine or treatment; it responded to traditional treatment tools: isolation, infection control, and contact tracing. An epidemic does not seem likely, but development of effective drugs and vaccines will likely take considerable time. The virus has been characterized as sufficiently transmissible to be able to cause a large epidemic, but not so contagious as to be uncontrollable with good public health measures. Overall, SARS certainly remains a pressing concern; as with avian flu, viral mutations could result in a severe global threat.

Acquired Immune Deficiency Syndrome (AIDS) first came to the attention of medical authorities in June, 1981. Since then, the virus has infected some 65 million people and killed 25 million of them. Initially it was invariably fatal. Now drugs have made it treatable in many cases, but it continues to take a heavy toll, especially in Africa. Mankind is fortunate that at the very time the disease was first emerging, medical science was also beginning to understand DNA and viral diseases. Had AIDS emerged a mere couple decades earlier, it may well have spread widely before even being recognized, thanks to its long incubation time. Development of effective drugs would have been practically impossible. Mankind is also fortunate that AIDS requires intimate contact for transmission. But AIDS is a stark reminder that new and highly virulent diseases can emerge unexpectedly. Another new disease, just as virulent but readily transmissible, could certainly wreak havoc with world health.

There are also a number of African filoviruses (including Marburg fever and ebola) which have a potential for causing global disaster, particularly if viral mutations make them more transmissible.

Overall, it is clear that virulent pandemics pose a catastrophic threat not just to the United States but globally. With widespread international travel now common, one lesson of the SARS epidemic was how quickly it spread to almost 30 countries, despite being under international medical scrutiny. A disease with a longer incubation period could spread nationally and even globally before anyone even recognized its presence. Once such a pandemic got started, the deaths of tens of millions of Americans is certainly within the spectrum of possibilities. The probability of such an occurrence is also not quantifiable due to the variability of both pathogen lethality and transmissibility. But considering the variety of possible infective agents and the record of past and current epidemics, the probability would seem to be definitely higher than for a strategic nuclear exchange.

These are all natural threats. It seems unlikely that a terrorist group would be able to initiate a medical disaster of such magnitude, or even that they would want to as it would inevitably affect their own preferred populations. Nevertheless, the widespread availability of sophisticated biogenetic equipment and the worldwide availability of many lethal viruses, including those originally collected for biowarfare purposes, means that this is a possibility. Some extremist group or even some perverted scientist could produce an agent which turns out to be much more lethal or effective than anticipated.

The US government recognizes the urgency of this threat, particularly the threat of avian influenza. In late 2005, President Bush proposed a $7.1 billion program for pandemic flu protection and issued a new National Strategy for Pandemic Flu.

Other

Other catastrophic threats can be identified, but none of them seem to have a probability above the level of negligible. These include:

- Impact not with an asteroid but with a planetoid. Indeed, Uranus's moon Miranda might have had just such an experience, being shattered into major fragments which gravity reassembled into a new heavenly body.

- The sun will eventually explode in a gigantic nova fireball which will incinerate and maybe even vaporize Earth. Thankfully astronomers assure us that this is some billions of years in the future. However, the sun is also capable of sudden, energetic outbursts. A massive solar flare, for example, could toast the sunny side of Earth or bathe it in lethal radiation.

- Earth has an active Search for Extraterrestrial Intelligence (SERI) program screening distant astronomical bodies for electromagnetic radiation patterns indicating intelligent direction. So far we have not found any. But our own societies emit a prodigious amount of electromagnetic radiation at thousands of frequencies. So Earth would stand out like a bright beacon for any extraterrestrial beings looking for a new home on some hospitable planet. If SERI itself makes any sense, then clearly so would a wariness about what such a contact might bode for humanity.

None of these minimal threats seem to pose any real threat to the nation. Nevertheless, they remind us that we cannot really identify all the threats we face. There is always a possibility that some unforeseen event will emerge to wreck havoc.

Summary

The nation faces only a few catastrophic threats. Of these, only two (virulent pandemic and strategic nuclear exchange) pose any significant short-term threat. The US government recognizes the urgency of both and has taken steps to address them. In both cases, intensified efforts are needed.

A virulent pandemic poses a clear and present danger. The National Response Plan for homeland security designates the US Department of Health and Human Services as the lead government agency for disease issues. The department, in turn, has prepared a detailed report on action to address avian flu, including research on faster identification of pathogens and stocking of anti-viral medicines, including tamiflu, with a planned goal of 81 million doses. This is an anti-flu drug, but its efficacy against a mutated avian flu is questionable. Obviously, until a mutated virus arises, specific drugs cannot be tailored to its specific characteristics, so tamiflu is probably the best that can be done at the moment, so extensive vaccine research is also under way.

Project Bioshield, signed into law by President Bush on July 21, 2004, implements a number of the planned actions, but it is specifically focused on terrorist actions, as is the policy behind it, Biodefense for the 21st Century. Medically, these programs only address avian flu; they do not encompass other threats such as SARS, though obviously many of the efforts to strengthen public health response would be useful for any health emergency. Collectively these efforts to modify and upgrade public health activities are relatively costly. But the improvements they fund are also socially useful as they support broader public health efforts.

A strategic nuclear exchange with the Russians poses a very different threat. If a pandemic kills 100 million Americans, once the bodies have been disposed of, the country will still have its cities and towns, its ports and power plants, its homes and office buildings, its infrastructure and farmland. The survivors can pick themselves up, dust themselves off, and move forward to revive the nation. On the other hand, if a strategic nuclear exchange kills 100 million Americans, once the bodies are disposed of the nation will be left with radioactive rubble, radioactivity which will kill many of the initial survivors. And all survivors will face the uncertain effects of Nuclear Winter. There will be no way to simply dust off and move forward. Because of this, the nuclear threat is much more alarming than a pandemic.

Arms reduction efforts are also much less costly. In fact by decreasing weapon requirements and deployments there would be significant cost savings. Such efforts could also visibly improve US-Russian relations and support cooperative efforts including efforts to secure nuclear and other materials from terrorists and radicals. Simply reducing the size of the nuclear complexes on both sides would also reduce the potential for leakage to terrorists or unauthorized actions by some deranged individual within the complex.

Mutual arms reductions would also support nuclear nonproliferation at a time when it is under a lot of stress from Iranian and North Korean programs. One result is that other numerous nations are apparently considering their own nuclear programs. Invigorated US-Russian nuclear cooperation could do much to blunt this threat.

Although neither of these threats has a high probability of occurrence, the potential damage they pose calls for a higher priority response. And in both cases, actions to directly address the threats will also help address other less pressing threats, such as terrorists and other potential medical crises.