A dummy missile was launched from Alaska and 17 minutes later, it was destroyed by an 16-meter-long interceptor from California. The warhead was hit by a fridge-sized "kill vehicle" moving by the speed of 29,000 kilometers per hour. This $85 million test has increased the measured reliability of the system slightly above 50%. About $10 billion is spent on the program every year. That's a few percent of the global annual cost of the Kyoto protocol, and I am absolutely sure that a missile attack is a bigger threat than a few percent of global warming - and probably the whole global warming - even though the costly Kyoto protocol can only remove a few percent of this hypothetical warming.
I have never understood the comments that the missile defense system was impossible. It is possible: the only questions are the quantitative ones: how much does it cost and what it can do and how reliably. ;-)
The modern civilization faces all kinds of threats but it also has all kinds of tools and policies to fight against these threats. It is hard to quantify the relative importance of different scary scenarios but I believe that the old-fashioned missile attacks remain a likely threat. Countries that don't like the West are expected to have or acquire old-fashioned weapons.
Is it possible that Iran and North Korea already have nuclear bombs in the New York City, Boston, Chicago, Los Angeles, and San Francisco waiting to be activated? Is it possible that they will be capable to do so in the future? I don't know. Maybe. Such a thing has never happened but the responsible officials together with the intelligence services are already fighting against this potential threat and other threats they find imaginable. It is easier for them to supervise the U.S. territory than to check what's going on in countries that are not exactly friends.
An old-fashioned attack remains a possibility and it could be helpful to be protected against such a threat, even though the protection wouldn't be 100% reliable.
Imagine that a hostile country just develops nuclear weapons and its leader orders the U.S. to introduce communism, Sharia law, or to immediately stop all sources of carbon dioxide - or to face nuclear consequences. Many of these guys believe that their dreams are not only justified but also realistic. What will the U.S. president do? Surely, she won't accept such a deal. How could she sacrifice the market economy, religious freedom, or all of technology in the U.S.? It is better to be at risk that one or two U.S. cities will be destroyed before the whole attacking country will be flattened. No doubt about it. Neither Condi nor Hillary would surrender. You would have to elect Dennis Kucinich or someone like that to get a different answer and it is just terribly unlikely.
Fine. But the communists, islamists, and perhaps also the environmentalists can be dead serious. One can simply imagine that they launch the missile with a nuclear warhead. What will you do? You can't do much if you don't have a missile defense system.
Many people would argue that the U.S. government would never accept the risk of being attacked by nukes. I just don't believe it. In fact, it has done so in the past. All these questions are quantitative. It is clear that some demands will remain unacceptable and the risk will remain a better option in these cases. In such situations, you simply want to reduce the risk.
I believe that the reliability of the missile defense system will continue to increase. But even if you imagine that it will be 50%, such a reduction of the risk is priceless. The imperfect reliability only means that the average benefits are reduced by a factor of two, not more. Many people can't understand this reasoning. Many people think that if the safety is not 100%, it is worthless. Many people's reasoning has the form of zero times infinity, and what a surprise that most of their conclusions are crappy.
Imagine that in the next 50 years, there is a 10% probability that someone will send nukes against 5 large U.S. cities in average and there will be or won't be a 50% probability of intercepting each missile. What is the benefit of having the defense system?
To make a random order-of-magnitude estimate, consider 10 million casualties per attack. The value of a human life is really uncountable but let's find a lower bound. Imagine that one killed human being together with his or her fraction of the city plus the indirect losses for the rest of the country is evaluated as $200 thousand. The large attack against one city is thus above 2 trillions of U.S. dollars. I must divide it by 10 because the probability of the scary scenario is 10%; multiply by 5 which is the average number of missiles; and divide by 2 because the missile defense system is inefficient. You still save half a trillion or 500 billion of U.S. dollars.
That's the price of the missile defense system for 50 years, assuming that the annual spending will be constant. My calculation was designed to match the costs and benefits. It is up to you to decide which numbers should be adjusted and what your result will be. If the risky scenario is at least remotely acceptable, I think that the unbiased comparison of the average costs and benefits is the only rational way to decide whether an insurance is a good idea. However, when truly catastrophic scenarios are at stake, it may be better to be safe than sorry.
Consequently, I think that the missile defense system is a good investment for the U.S. Incidentally, the experts have found out that Czechia has better conditions for a missile defense base than Poland. However, most of the population oppose the base; the anti-base campaign is led by f$#$# young communists.
If you want to see an opposing opinion, see the nutcases at dailykos.com. Their description of the system reminds me of Peter Woit's description of modern theoretical physics. It's probably not an accident since dailykos.com is one of the primary sources of information for Peter Woit: he has learned a lot from them.