When media muddy the waters
Last night, I caught the last half of 20/20's special "The Last Days of Earth." Much of what they said was pretty accurate, albeit seriously lacking in depth, detail, and source citation. The problem I have with the show, however, is that even I as a layman could see some things they said (or, more often showed) did not help the cause of good science.
If you didn't see it, you can probably guess what it was about by the title and the fact I'm writing about it on this blog -- various forms of apocalypse. They looked at seven, but I can't remember them all and only caught the last four: asteroids, nuclear war, global pandemic, and climate change, ranking the last as the most serious threat.
Common sense says all of those things are in fact real threats; but I'm not sure I'd give them the same order. To me, the most serious in terms of what it can ultimately do to humanity and nature is nuclear war, because, in a very real sense, it combines many of the effects of the other three. The combination of megadeaths plus long-term radiation plus a massive smoke pall plus other "synergies" would very likely destroy human civilization for a very long time and cause major changes in the genetics of human and natural communities alike.
Admittedly, I rank that a little higher than asteroids because, while a really big asteroid can actually sterilize Earth and I don't think we can nuke Earth into sterility, if a nuclear war happens it's our fault. Asteroids are impersonal; nuclear war is not.
Anyway, I'm digressing. 20/20's section on asteroids was simplistic but truthful about the prevailing theory that asteroids wiped out the dinosaurs, leaving mammals a chance to take over the reptiles' ecological niches. But the "reporters" then argued that an asteroid of the same size hitting Earth now would burn the crust to a depth of 60 miles. Obviously, that's crap: there's no way our mammalian ancestors would have survived such a strike. They lived semi-nocturnal, semi-underground lives, but not that far underground. The only lifeforms that have ever lived that far down are extremophile bacteria.
You can test the effects of various sizes of asteroids here or here.
It mentioned that people have found around 100,000 asteroids, but didn't mention that we occasionally lose some, are constantly finding some only when they cross Earth's orbit, and suspect there are countless more out there. Chances are, if one hits us, we won't see it until it's too close to do anything about.
Of course, they could be right about the one they mention specifically -- an asteroid that's due to make a close (within the Moon's orbit) pass in 2029. They don't say that will hit us -- general consensus is that it won't -- but that the near-miss might alter its orbit just enough to cause a hit the next time around in 2037. What they don't mention is just how small the risk really is: 1 in 26,000 in 2029 and cumulatively just .00023% chance between now and 2054, during which time it'll have three close approaches. The show doesn't identify that chunk of rock, but astronomers know it as 2004 MN4 or Apophis.
The show's discussion of what people are likely to do if faced with a probable direct hit was kind of interesting, but also fairly predictable. It's pretty safe to assume chaos would reign as the time drew near as people try to do things they'd never before attempted (for good and ill). Nobody said they'd go out and commit crimes (obviously, they wouldn't say it on national TV even if they would do it), but a few said they'd want to have children. Excuse me?!? How can someone be so supremely narcissistic as to bring children into a world they knew was going to get walloped by an extinction-level-huge asteroid?
What was equally troubling was what the show didn't mention -- the probability that some people would try to organize a major space effort to keep humanity alive off-world. Such an effort may well be the only thing that could prevent such widespread chaos, and I've said before that I believe we need a good global space program as insurance against just such a catastrophe.
The section on nukes was woefully vague and much shorter than the subject warranted. It didn't say anything about radiation or various other ill effects, although it did point out (accurately, I think) that the nuke threat from places like Iran and North Korea is being blown out of proportion to the risk caused by the thousands of nukes the US and Russia still have on "launch on warning" status. It failed to mention, however, that both nations are trying to create new, smaller, more mobile nukes, especially the U.S. Add that to the simmering problems in the Middle East, and it may be time to revisit the Doomsday Clock's setting of 7 minutes to midnight, which hasn't changed since 1992.
The one really questionable assertion they made was that "an exchange of just 20 missiles would cause nuclear winter for several years." The problem here is that the number of missiles is irrelevant, what matters is the number and strength of the warheads and where they explode -- urban or rural, airburst or groundburst. Burning cities are significantly more likely to spew the toxic smoke into the sky that can block sunlight and cool the land, especially if hit by warheads that explode close enough to the surface for soil and debris to get sucked into the fireball. Even the TTAPS study of the early 1980s predicted a 5,000 MT threshold for nuclear winters, which requires significantly more than 20 missiles.
Elsewhere Sagan (as cited by Alan Phillips), notes it could happen with as few as 100 warheads if the targets are predominantly oil refineries and associated structures. Obviously, we don't know for sure... and sane folks don't want to. There's some controversy over the TTAPS calculations, sparking some of the theory's supporters to acknowledge that there needs to be more research done in this area. We've got better climate-study technology and computer simulation capability than we did in the 1980s, let's target it on this threat.
Desmond Ball of the Australian Nat'l University argues even more specifically that even a full-scale war hitting both cities and strategic weapons sites, which Ball estimates at 4140 to 4650 MT, would throw up less smoke than Sagan's nuclear winter threshold of 100 million tons, largely because of where those missile silos are -- in farmfields and tundra, not forest.
Obviously, I'm not citing him to downplay nuclear war's horrors. Even without nuclear winter, it would be by far the worst calamity to have ever hit mankind, and for that reason, I'm still in favor of banning the bomb.
My guess is that a full-scale nuclear holocaust would actually leave most people alive in the short-term, but hundreds of millions, if not billions, would not survive the social, economic, and agricultural disruption, radiation, temporary loss of the ozone layer, diseases, and other problems that can reasonably be expected after such a catastrophe, even if the temperature change is minimal. (Imagine what shape Europe or Japan would've been in for years after WW2 if the US had not created the Marshall Plan. That's the catch -- global nuclear war isn't likely to leave anyone untouched, even nations that don't get bombed, simply due to the nature of fallout and our world's high level of economic interconnectedness.) But I suspect humans will still be here long term, reduced in numbers and cultural complexity and possibly permanently unable to regain today's level of technology, science, and the possibility of reaching the stars.
I can't claim to have anything resembling detailed knowledge of this subject, since I'm not a doctor and have no medical experience of any sort. But as a layman with some knowledge of history, I noticed a couple of things that seemed a little out of whack. In one place, they claim the 1918 Flu Pandemic "killed only 3% of those who caught it." That figure didn't ring true ... but it was. If anything, it was higher than the actual percentage (I came up with about 2.5%). The New England Journal of Medicine reports that "the pandemic of 1918 and 1919 killed 50 million to 100 million people" worldwide. NPR adds, "About 25 percent of the population was infected, with perhaps 650,000 people dying from the virus." At that time, US population was about 104,550,000.
According to the same NEJM article, "more than half the deaths occurred among largely healthy people between 18 and 40 years of age and were caused by a virus-induced cytokine storm (see diagram) that led to the acute respiratory distress syndrome (ARDS). ...If we translate the rate of death associated with the 1918 influenza virus to that in the current population, there could be 1.7 million deaths in the United States and 180 million to 360 million deaths globally."
The show also notes that smallpox & other germs could be used as weapons. In its present state, the show said, smallpox kills about 30% of its victims -- a significantly higher rate than the 1918 Flu. Under some circumstances, it's even more deadly -- some evidence suggests the death rate among the biologically unprotected Native American population exceeded 65%.
This was an unfortunate mixture of mostly good spoken fact and grossly misleading imagery. Most obvious was when they spoken of sea level rising if Greenland and West Antarctic ice sheets melt -- 20 feet individually, 40 feet together. That's a pretty severe rise, one that would (as their sources, which includes climatologists and Al Gore, said) inundate south Florida, southern Louisiana, Bangladesh, parts of Manhattan and possibly London, and many other coastal areas. but teh graphics shown at teh same time exaggerated the flooding immensely: they showed blue covering over half of FLorida, huge stretches of the UK, and even mountainous regions of Southeast Asia and Africa far from the coasts.
As TV studios know quite well, people pay far more attention to images than words, a fact that makes such a presentation a major league disservice to the work the scientists are doing. By so exaggerating a threat that is serious enough on its own, it only provides ammunition to the very naysayers the show largely (and accurately) discounted verbally.
Instead of hyped up graphics of biblical proportions, they should have taken the time to show realistic maps of the potential sea level rise, scenery from areas that are already seeing problems, etc. Among those available are these ones from the EPA (note that they only show a 3.5 m rise), or go to places like this (USGS) or any decent topographic map of seashore regions and figure it out yourself from the contours.