Between Iraq and a hard place

Dedicated to the memory of Andrew Bacevich, Jr.

There's little to say about Iraq that hasn't already been said, although a lot of what has been said so far is nonsense. It's depressing to think about what's left to try and what might happen when US troops leave. Iraq is now experiencing a limited civil war - war with the emergency brake on. Without outside troops to serve as peacekeepers and deterrents, that civil war is almost certain to get much nastier before it ends. Stop thinking Vietnam; start thinking Lebanon, only bigger and badder. Already civil conflict in Iraq has stimulated one of the largest movements of Middle East refugees in the last century; only the Iran-Iraq and Soviet-Afghan wars of the 1980s were larger.

The essential practical problem is summarized by the words, "Too few troops." There have never been more than 150,000 coalition troops total, in a country of about 24 million - about four times too few by reasonable historical measures. Even excluding the fairly peaceful Kurdish north, that's one soldier per 130,000 population, still more than three times too few. And the Kurdish north is peaceful only because it has its own unified semi-professional militia to police it. A proper occupation of Iraq would require half a million soldiers. Such an army was available in 1990, but not today. Almost every problem from April 2003 on - the Sunni insurgency, the overuse of the National Guard and reserves, the misuse of non-uniformed contractors (the root cause of the Abu Ghraib scandal), etc., - is a result of "too few troops."

"Too few troops" means that the troops now there are just enough to serve as targets, but not enough to provide a consistently successful counterforce. The so-called "surge" cannot mitigate that outcome except in a limited and temporary way - "here and there for a while." The cruel irony of this situation is that, while Iraq has too few troops for a classical occupation of overwhelming force (like Yugoslavia in the 1990s or Germany and Japan in the 1940s), it has too many for a classical counterinsurgency. The latter strategy would need about 20 to 30,000 troops, with few support troops, no Green Zone or "force protection" (Pentagonese for "build a fort and stay inside"), no typically American long logistical tail, and so on.* Americans have used this strategy before - in the Philippines and in Vietnam - and, to the extent it was tried, it worked. The British did it even more successfully in Malaysia in the 1950s, a positive contrast to the contemporary French mess in Indochina and Algeria.**

If you're expecting me to complain about WMDs, I won't, because the issue is entirely irrelevant. If Saddam had restarted his advanced weapons programs, and the coalition had bulldozed them into the Euphrates in April 2003, the situation a few months later would not have differed in the slightest from what it's actually become. The core problem of the Bush thinking was not WMDs, but magical thinking: the fantasy that Iraq would instantly snap into functioning as a modern state after Saddam was deposed. In fact, Iraq is an artificial country assembled, like Yugoslavia, after World War One and held together only by strongmen and intimidation. Remove the intimidation and, surprise, surprise, you get a civil war.

What's happening now in and around Baghdad (where virtually all of the violence occurs) is the long-postponed, final disintegration of another piece of the Ottoman empire. The process started long ago in the early 19th century, when Greece and Serbia became independent. The European part of the disintegration didn't finally end until the war in Kosovo in 1999. As historian Niall Ferguson points out in his recent, depressing tome, War of the World, virtually all of the massive violence of the last century has been concentrated in and around the world's long-lasting empires, as they underwent collapse or internal revolution. The first, European wave of violence ran from the late 19th century to the 1950s; the second ran from the late 1950s through the 1990s and, in the Middle East and Africa at least, hasn't ended yet.

In and around Baghdad, the practical result is the influx of Shi'ites and the outflux of Sunnis. The Sunnis were about 18% of Iraq's population in 2003, although they had virtually all of the power; now they're down to 16% and dropping. Such ethnic cleansing is one of the most regular features of the familiar and dreary script of empire-disintegration covered in mind-numbing detail by Ferguson. The 2003 invasion enabled the return of the Shi'ites (mainly from Iran). The 2005 Iraqi elections made it clear just how large the Shi'ite population is and that the Sunnis would never regain their control of the country; the Sunni exodus ensued.

There are many lessons to take away from this debacle. Some of them have already been preached by others, so I'll mention a few of my own here.

• Don't put soldiers in impossible situations. Soldiers will take big risks and die for feasible goals. It's criminal to put them in a bottomless tunnel with no exit.
  
• If another military action should prove necessary in the near future - for example, against Iran - it must be, like the wars in Yugoslavia and the bulk of the Persian Gulf war, an air-naval war, involving no ground troops. Ground troops should be sent in only on condition of an organized and complete surrender of enemy forces, with some continuity of government.
• Think long and hard before "uncorking" another bottle under high pressure. For example, Iran is only about half Persian; the rest is Azeri Turk and Arab.
• Resist the temptation to play favorites. The goal of peacemaking, if and when it becomes possible, should be that no one side wins outright. For example, the Iraqi Sunnis will never again control Iraq and dominate the Shi'ites the way they did between 1931 and 2003; but that doesn't give the Shi'ites license to trample all over the Sunnis. No place in the world is more prone to endless and often pointless payback than the Middle East; no need to stimulate more.
  
• Avoid being used by and taking information from only one faction in someone else's civil war without having a larger, independent picture. Develop your own sources and analysis of intelligence. Otherwise, you're flying blind in a dark cloud.

And it would help to have an administration not permeated by the frat boy spirit. At the frat house, you can get by cheating on homework and exams and calling home for more money; in the real world, Daddy's not always there to bail you out.
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* Such a counterinsurgency proposal was contained in an important Atlantic article by Bing West, journalist, Vietnam veteran, and author of No True Glory, one of the best books to emerge from the current Iraq war.

** Part of the reason the British decolonization strategy worked was because the British were clear that their post-1945 goal was indeed successful decolonization, not holding on indefinitely as the French tried to. Since the Treaty of Versailles changed the equation of empires versus nations in 1919 with Wilson's principle of "self-determination," every empire has acquired a built-in time limit. Only China's is left.

Digging out

What does American politics hold in the next couple years, as the Bush era (mercifully) limps to an end? The GOP's degeneration in the last eight years has been astonishing - if Bush is not the worst president ever, this is definitely the worst GOP ever. Neither liberal nor conservative, it's become a bad - incompetently, if unintentionally, bad - parody of liberalism.

I could spend this posting telling you about what 2008 will be like ... so you can roll over and go back to sleep. The Republican nominee will probably be Rudy, although Romney has a significant chance as a darkhorse - and would make a better president than Giuliani. The Democratic nominee will almost certainly be Hillary. It might thus be a cross-town World Series for New Yorkers, with Rudy the more likely to win.

But that would be trite crystal-ball gazing. Let's instead survey the forces and dynamics and apply the kinematics and boundary conditions as best we can.

The Republicans: confused and in disarray. The "disillusioned conservative" trend ("conservative" not to be confused with "Republican") has grown from the cottage industry of 2002-03 to boom times. Well-known conservatives like William Buckley, George Will, Robert Novak, Christopher Caldwell, Irwin Stelzer, Andrew Sullivan, Tucker Carlson, P. J. O'Rourke, and Peggy Noonan have been expressing their dismay and displeasure for several years running. A more recent crop of the disillusioned are now cranking out books: they include Bernard Goldberg's Crazies to the Left of Me, Wimps to the Right, Richard Viguerie's Conservatives Betrayed, Larry Diamond's Squandered Victory, and Bruce Bartlett's Impostor. The most striking thing about the post-1998 years, as Bartlett acutely points out, has been the sharp decline of ideology and serious policy debate, as evidenced by the silence of the Washington think tanks (except for Cato - see below). The liberal-conservative debate about the proper scope of government that reached fever pitch in the 1960s and 70s - and dominated through the 90s and a Democratic presidency - has vanished. The danger that the then-approaching GOP majority posed was predicted more than 12 years ago by David Frum in his Dead Right, just before the Republicans took control of Congress: Republicans would learn to love big government - for ostensibly conservative purposes - and lose sight of any larger goals, especially pruning and reforming the welfare state and readjusting America's foreign commitments post-Cold War. Instead, he suspected they would develop a strong taste for big government, as long as they were running it. The conservative movement was even then (in 1994) confused about the difference between the conservative message and being Republican partisans. And in 1994, no one foresaw, say, Jack Abramoff's future career or the explosion of earmarks and pork-barrel.

The Republicans faced a difficult choice in 1995, one that becoming the majority party forced on them: after talking conservative for years, they had to put or shut up. Four years later, in 1998-99, we got the answer. Newt resigned and the conservative era came to an end, with some accomplishments (welfare reform, reigning in farm subsidies) that would soon be partly undone. The Republicans then drifted into a new direction. Unwilling to really be a conservative party, they stumbled into the big government Republicanism that Frum predicted: socially conservative, patriotic, mildly authoritarian, more government - and more pork. They settled on a presidential candidate (Bush) answering to this description, and a campaign strategist (Rove) determined to permanently win over the Catholic and white southern vote for good with big government. With a Republican White House and Congress, everything seemed set. Congress would not interfere with Bush, and Bush would sign everything Congress sent him - including two new major middle-class entitlements (Medicare D and Leave No Child's Behind). Congressional Republicans would vote themselves enough pork to guarantee their re-election in perpetuity. A new era seemed at hand - the new politics was anti-ideological, but intensely partisan. In place of small-government conservatism or the liberal Republican devotion to "good government" would come "loyalism" and vote-buying: government as frat house.*

Unlike liberalism, conservatism did not die a natural death. And conservatives didn't disappear either. Instead they were marginalized by the only force that could marginalize them - the Republican party itself. Conservative fixtures of the House and Senate retired from politics, their place taken by right-leaning Democrats newly converted to the GOP. The conservative base became confused, hesitant, then more and more angry. Something had gone wrong.

The Democrats: desperate, still a bit unhinged. They want the White House back so badly, it hurts. Many still suffer from Bush-derangement syndrome. Now that they control the Congress, controlling all the elected branches of government again would be sweet - not that they deserve to. The modern Democratic party went off the rails in the 1960s and 70s and has never recovered. The distinction between the left fringe and the mainstream has become more and more blurred - it's the Democratic party's biggest long-term vulnerability. And the real problem with that left fringe is not that they're stupid and juvenile (they are); it's that they crave power but no longer know what it's good for. The implicit signal they emit is very obvious: they don't like or understand power, and they don't know what to do with it. Voters have been picking up this message for more than three decades and reacting accordingly.

And this from the party that invented modern big government to serve broad public goals - it's no longer sure what the public good is or whether it even exists. Only special interest group and identity politics push their buttons now. The Democrats have been politically, morally, and intellectually braindead for thirty years, and they lack coherent rationales for the very things they invented - the modern welfare state and an interventionist, globalist foreign policy. A striking example of their incoherence is immigration; see Mickey Kaus' discussion for more about the Democrats' apparent indifference to all the worrisome trends of the last 15 years: rising inequality, state and local government bankruptcy, and the failure of sovereignty. It shows that while the US is not in the dire straits of denial that Europe is in, it's not all smooth sailing here. The religion of political correctness is powerful in the US as well, as is the role of elites in suppressing politically touchy but critical issues.

This bankruptcy was again on display in the Democrats' 2006 campaign themes: no mention of the desperate need for entitlement and welfare-state reform, for curbing Congress' appetite for pork, or changing the entrenchment of incumbency. Of the three serious Democratic candidates, only Hillary has any realistic awareness of these issues, and what she will make of them is anyone's guess - she'll be coy about them for as long as she can. Forget about Obama: he's callow, too young, and has no experience. The Democratic candidate with the most depth (Richardson) has no chance of being nominated.**

For the Democrats, 2008 promises to be their last hurrah for the forseeable future, so they should make the most of it. Against a background of disillusionment with Bush, their victories in 2006 were due far more to Republican confusion and cluelessness (and conservative voters staying home) than anything else. Once Bush & Co. are gone, it will be springtime for Republicans, who are more likely than not to retake the Senate in 2008. But it will not be a new conservative era: the 20-year era of conservative ideological dominance, from the late 70s to the late 90s, will probably not return in our lifetimes. Everyone now loves big government. Only the doughty libertarian Cato Institute has had the balls to consistently sound the alarm, best seen in their two major studies of the Bush years, Buck Wild and Leviathan on the Right.

Will the liberal Republicans ride to the rescue? Maybe. Liberal Republicans like politics and don't suffer from the conservatives' fatal ambivalence about being in charge of modern government. And unlike Bush, they value competence above machine politics and loyalty. They also lack Bush's faith-based, blindfolded, trust-walk style, and are not tainted with same. Although liberal Republicans are the smallest faction of the Republican party, they sit the closest to the center of gravity of American politics - unlike the conservatives or the Bush fraternity house. To update what I said last year: the future of the Republican party, if it belongs to anyone, belongs to them.***
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* Rove is the bespeckled, geeky schemer that many frat houses seem to have.

** Note to Hillary: Richardson would make an excellent VP choice.

*** Apparently the New Republic is now saying the same thing.

Further thoughts on immigration

The earlier postings on inequality mentioned illegal immigration as one of the three major sources of the "new inequality" in the US in the last 30 years. (The other two are the education and marriage bifurcations.) It's an important aspect of both the inequality and immigration issues, one strangely neglected by most liberal commentators, who seem very confused on this point, as they're often confused about many things. (Although Kaus is one liberal commentator who's been consistent and persistent in his opposition to illegal immigration; he too wonders why many liberals are confused.) Of course, the whole issue really only registered nationally in the last year or so, a testimony to the ability of political elites to live in their own world and the power of news media "blackout."

But it would be wrong to view immigration as a whole this way. After all, America was built, following the earliest generations of colonial settlers, by immigrants, and immigration has been a largely positive force in American life. The earlier inequality discussion should also have made clear that the problem is with illegal immigrants. The problem is not just that they're breaking the law by coming here; their whole way of life here depends on chronic lawbreaking by themselves and practically everyone dealing with them. Even more unsettling is that the combination of illegals having welfare state claims, while remaining outside the tax system, puts a permanent lopsided burden on local and state governments. In locales with large numbers of illegals, those lower levels of government have faced year after year of fiscal crisis directly a result of a situation caused by a serious federal failure. Voters are rightly angry about it, and they're largely angry (correctly) at the politicians and political elites, more than at illegal immigrants per se. (The supposed economic benefits of illegal immigration are more than offset by these costs, as well as by the downward pressure on wages of unskilled labor.) Finally, there is the serious problem of the development of permanent ghettos of residents unwilling and uninterested in integration with the rest of American society. You only need to look at, say, France to see where that leads.

Much of the debate, especially on the right, but on the liberal side as well, has also been carried on under the false doctrine of economic determinism. All three sides of the issue - political/legal, social, and economic - need to be considered together; each has ramifications for the other two. Economics is not the fundamental dog that wags the tail of the other two.*

But back to the positives: One of the few good things about the new immigration bill is that goes a long way towards fixing the other thing that's broken, the legal immigration system. It's currently a mess and makes immigration by legal immigrants - people who seriously want to become part of American society and who should be welcomed - much more of a hassle than it should be. This hassle in turn has created a whole cottage industry of immigration law that rakes in money from people caught in the resulting limbo. The only problem is that the new bill implements a more rational system over the next decade. It should be phased in immediately, or within a few years, at most.

While welcoming legal immigrants - especially those with skills and possibly capital - we should pause to consider the effect massive immigration from poorer countries on those countries of origin. The earlier postings also pointed out that the illegal immigration problem - like our lopsided trade deficits with Japan and China - cannot be fully solved here. There is also the failure of the countries-of-origin to develop. When their best-and-brightest immigrate here, does that not have the effect of "country-stripping"?

POSTSCRIPT: Related thoughts from Charles Krauthammer, over at the WaPo.
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* That's the purplest passage of weird metaphors you'll ever see on this blog :)

Midwest peace still elusive

It's Lutherans versus Presbyterians: Iowahawk reports.

Chag Shavuot sameach

It's the Festival of Weeks, or Shavuot, sometimes known as Pentecost. Traditionally, the Israelites arrived at Mount Sinai about seven weeks after leaving Egypt, and this is that holiday. A few days after arriving, they and Moses hear the Decalogue, then Moses ascends the mountain to receive the rest of the Torah.

They didn't eat blintzes in the wilderness, but it is traditional to eat dairy foods and put out flowers. Shavuot is also an agricultural festival, marking the harvest of the winter grain and the end of the Omer count, and like Passover and other holidays, it has its own special book, the Book of Ruth. The book alludes to the winter harvest - and its heroine, Ruth, is a convert. All of Israel "converted" to Judaism, as it were, at Sinai. Ruth is also the great-grand-mother of David - something messianic in the air here ....

More climate sanity resources

Anyone interested in Earth's climate and climate change should read the excellent World Climate Report, the best overall climate blog and the world's longest-running as well. They have a large number of postings running back to 2004; their older content, running back to 1995, is organized as periodic issues in PDF format. The postings are organized chronologically but also tagged under topics ranging over many specialized areas of climate.

(Even WCR, like Homer, nods now and then. They recently referred to methane as the second most important IR-active gas in the Earth's atmosphere. Readers of Kavanna know that it's the third, after carbon dioxide - and our old friend, water.)

New climate books come to our attention now and then. A fairly recent entry is Leroux and Comby's fine Global Warming: Myth or Reality? The Erring Ways of Climatology (2005). The authors are French climatologists, the second an ecologist as well.

Longer and more involved than Essex and McKitrick, the book's early part is directed at a non-technical audience, with an incisive analysis of the role of the news media and powerful crusading politicians, while the later parts amount to giving a good spanking to the whole assembled congregation of climatologists, meteorologists, and geophysicists to task for allowing themselves to be dragged in, often against their better judgment. Leroux and Comby's scientific case against global warming is less theoretical and more widely-ranging and empirical, although they also discuss the many faults of computer climate models. They wrap up with an alternative list of "things climatologists should be doing instead of worrying about global warming." This blog will also return to that theme periodically - as well as touch base with a number of methods for diagnosing global climate that are better founded than those (strictly speaking) meaningless temperature averages you keep hearing about.

The book is published by Springer - it's one of the large and expensive scientific tomes for which the German publisher is famous. It's not the sort of thing you want to buy for yourself, but it is an excellent addition for libraries - especially academic libraries.

Skeptics and opponents of the global warming hysteria are not all American, nor does the issue neatly divide America from the rest of the world, contrary to activist and media sanctimony. Actually, second and third thoughts are spreading rapidly in Canada and the EU about both the flimsy science of global warming and the immense cost of implementing the Kyoto treaty. The danger in the US is that, having seen the science case collapse, the politico-journalistic side will just decide that "something must be done" anyway, regardless of science or of cost. The cause has long had a pseudo-religious aura; this will strip away its last intellectual pretensions and turn it into something more like the war on drugs - a crusade designed largely to make people in it feel good about themselves.

Aren't there cheaper and better ways of feeling good about ourselves?

Iran: What is to be done?

A recent issue (April 23) of the New Republic contained an excellent overview of Iran, its regional ambitions, and its nuclear program. Unfortunately, it's behind their subscriber firewall, so you have to find a print copy. But it is well worth it. Four authors contributed to it, but two especially - former ambassador Dennis Ross and Iranian-American author Azar Nafisi - should be listened to.*

The Iranian problem is headed towards a dénoument in the next 18 months, so it's important to understand what's happening. Condeleeza Rice has made it her final almost-impossible task in office to prevent a nuclear Middle East. Everyone should wish her success - failure (which is likely) means the end of nuclear non-proliferation and a regional military-nuclear competition. The first countries under threat are Iran's Sunni neighbors, followed by Israel. Rice is working to some extent at cross-purposes with her boss. Bush and Cheney have clearly given up trying anything more about Iran and now simply want the crisis to happen after they leave office. It's the final, rotten fruit of an administration that never had much interest in policy or much time horizon beyond the next election.

Nafisi indirectly comments on this trend:

The most important weapon in the U.S. arsenal is not its military might but its culture. Vigorously defending and promoting those values the United States was long thought to represent - freedom of expression, freedom of movement, freedom of conscience - will do a great deal more than any missile to neutralize Iranian radicals. And, though this wide-ranging task is probably beyond the capability of American politicians, it is not beyond the capability of America.

How did we go in twenty years from achievements like ending the Cold War, with giants like Reagan and Gorbachev, to a political landscape overrun by pygmies?
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* Of the other two, Robert Kagan is a little disconnected from reality, and the New York Times' Laura Secor is an example (sadly, not unique) of reporter-turned-apologist.

Pseudo-crypto-quasi-neo-saturated

Like heat transport mechanisms, different sorts of atmospheres can be confusing, so a comparative list might be helpful. One practical consequence of the physical differences is different lapse rates (in the presence of gravity, downward temperature slopes). Another is that the relationship among temperature, pressure, and density profiles is different.*

(Dry) adiabatic atmosphere. This is the simple case given in all the basic textbooks: heat energy (proportional to temperature) declining with altitude, as gravitational potential energy increases. It's adiabatic because no heat is being added from or removed to the outside.

This atmosphere is steady in time and has no matter or energy flows traversing it. Each layer satisfies local thermodynamic equilibrium (LTE).

(Wet) saturated adiabatic atmosphere. This is a more complicated case. The heat released by condensation of water vapor shallows the downward temperature slope. The action of gravity in converting heat energy to potential energy is still at work, however. The temperature still falls with altitude, just not as fast.

If you take wet air as a unit (water and dry air together), this atmosphere is still adiabatic. No heat is exchanged with the outside. The atmosphere is still steady, and there are no matter or energy flows. LTE is satisfied mechanically (pressure up against gravity down) and thermally (local temperature). Phase equilibrium is satisfied where water liquid and vapor are in equilibrium (in the clouds), although the ratio of liquid (or crystal) to vapor changes with altitude.

Pseudoadiabatic atmosphere, saturated or not. This is the most complex case. The atmosphere is steady, but there are now steady energy and possibly matter flows as "through-put." In practice, the energy flows are convective or radiative or both; the matter flows are water diffusing up as vapor and occasionally precipitating down as drops or crystrals.

At each layer, LTE is satisfied completely if there is phase equilibrium, as in clouds. (In the clear air, phase equilibrium is violated.) But because of the flows, this atmosphere cannot be called adiabatic. The LTE condition has to be supplemented by a list of the flows and the relevant boundary conditions on them, either at the surface or at the atmospheric top.

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There's a funny Greek or Latin name for everything in physics - including physics, from the Greek physis, meaning "change" or "growth" - roughly what we call "evolution" today, used in a very broad way. In thermodynamics, fluid processes can be labeled by what remains constant, using the prefix iso- meaning "same." Isothermal means constant temperature (Greek therme for heat); isobaric means constant pressure (Greek baros for pressure); isochoric means constant volume (Greek choros for space); and isentropic means no change in entropy (Greek entropos for "turning inside"). Adiabatic comes from a-diabatos, not pass-through-able.

So what do we call a pseudoadiabatic atmosphere, one with LTE and steady flows? (BTW, pseudos in Greek means fake or mistaken. ) A cute adjective I thought of comes from the Greek rheos, for flow (as in rheostat) - we'll call it isorheoic.
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* For experts: this is difference between different effective polytropic exponents connecting pressure and density, respectively, to temperature. For the dry adiabatic atmosphere, it's 7/5 (ratio of specific heats); for the actual pseudoadiabatic atmosphere, it's just shy of 5/4.

More about Herod, the mad king

Another photo essay about Herod's tomb, this time from the German Der Spiegel.

More from the site of the Biblical Archaeology Society here as well.

A-a-a-a-a-h-h-h-h-h-h !!!

The Economist explains.

Adjusting the thermostat

I've been working with heat flows and not temperatures mainly, because energy is conserved: I can add and subtract power flows and even create an "energy flow" or "heat budget." I can't do that with temperatures. Contrary to the nonsense of averaging temperatures over space, temperature is not a simple proxy for heat content or heat flow.

All of the discussion during the "climate weeks" on this blog has been based on a reconstructed heat budget for the Earth's atmosphere. Alternative climates have involved at most switching various heat sources and flows on and off.* Cause-and-effect (dynamical) explanations have not entered the picture, except in a limited way. For this and the next posting, this restriction will be relaxed somewhat. In this posting, causal mechanisms will be examined in a qualitative way, without numerical details. The underlying question is, what happens if different mechanisms are modified, either alone or in combination? It's impossible to give a general answer, but the questions can be broken down into more tractable pieces. In some cases, fairly exact answers are possible; in others, decent estimates; and finally, in yet others, only vague guesses - plausible hand-waving. Even this is progress, because it isolates the sources of uncertainty.

Generating and redistributing heat: Summary. There are only two sources of atmospheric heat: incoming solar radiation and the extra latent heat of water liberated by the evaporation-condensation cycle (which itself is catalyzed by the incoming solar radiation). Adding heat to the lower atmosphere requires either reducing cloud cover or accelerating the evaporation-condensation cycle. The other mechanisms mentioned over the months (adding clouds, steepening the lapse rate by enhancing convection or radiative transport) redistribute the heat flow, circulating it in the lower atmosphere or accelerating its departure. Consider each in turn.

Accelerating the evaporation-condensation cycle, while changing nothing else. Accelerating this cycle releases more latent heat from water and definitely raises atmospheric temperatures.

Adding clouds, while changing nothing else. Adding clouds - and making no changes in the hydrologic cycle and neglecting convection - definitely reduces atmospheric temperatures. The clouds at their tops reflect more solar radiation back into space than they absorb and re-emit below.

Accelerating radiative heat transport, while changing nothing else means raising the rad term and steepening the lapse rate. At first sight, it might seem that this should lower the temperatures, but it actually raises them. The reason has to do with where the temperature slope is anchored (the boundary condition). For radiation, the anchoring point is the top of the atmosphere. Only radiation gets out into space, and the total radiative power flow out has to equal what went in (what wasn't reflected from the cloudtops to start with) plus the injection of net heat from the water cycle. Follow a steeper temperature slope from the edge of space down, and you end up with a higher temperature at the surface, and an elevated temperature profile the whole way.

Enhancing convection, while changing nothing else, OTOH, accelerates the departure of heat from the lower atmosphere and lowers the temperatures. The difference between radiative and convective heat transport here stems from the fact that convection has to be anchored (have its boundary condition) at the surface, because the heating that drives it comes from below.

Turbulence is the wildcard. Convection is a form of heat transport. But it looks different from the point of view of fluid mechanics. There it's just a special case of fluid currents. If it's slow and not turbulent, convection can be understood theoretically in a complete way. But generally the flow is moderately to extremely fast - then convection overlaps with turbulence. Turbulence becomes more important if the fluid viscosity is smaller, and viscosity is much smaller in gases than in liquids. Convection in our atmosphere is moderately turbulent - not that fast in terms of speed (a tenth of a meter per second).** The approximate "mixing length" model used to represent convection (like a waterwheel, except it's air parcels that lift up and deposit heat before coming back down) is a decent approximation for convection in clouds. For the inefficient convection in clear air, the model shouldn't be taken as anything more than suggestive. There is no general theoretical solution for fluid turbulence; various approximation schemes, starting with the "mixing length" picture and moving on to more sophisticated cousins of same, are commonly used to fill this gap.

Conditions for convection. For convection to happen at all, the Schwarzschild criterion must be satisfied, meaning that it "pays," thermodynamically speaking, to move heat in an organized motion from higher to lower temperature; the entropy gained thereby is larger than the entropy lost in organizing the flow, and everything's copacetic with the Second Law. In a continuous atmosphere, the Schwarzschild criterion requires that the vertical temperature profile be steeper than a certain critical steepness: the temperature has to fall faster with altitude than it would if the atmosphere were perfectly adiabatic (no heat flow). When the slope (dT/dz) is more than that steep, an overheated air parcel feels an upward bouyancy force. The actual criterion is a little tougher: the slope has to be more negative than the adiabatic lapse rate by some amount related to the viscosity of air. Viscosity holds the overheated parcel down when it rubs past the surrounding air. The bouyancy force has to not only be positive, it has to reach a critical value above zero to overcome viscosity. These criteria are just the minimum to get convection going. Once it's going, it can be slow or wildly turbulent, largely depending on the viscosity and the size of the heat flow to be transported.

Efficiency of convection. There's no guarantee that, once it starts, convection has to be an efficient trasporter of heat. The efficiency is a direct result of whether or not the parcel loses much of its extra heat before it travels one mixing length and loses its identity. Convection in clear air is inefficient, because the overheated parcel radiates its excess heat quickly in the relatively transparent surroundings. (The surroundings have free water vapor and are partly opaque to infrared (IR) radiation - but only mildly.) Convection in clouds is a little faster and a whole lot more efficient: the parcel doesn't radiate much heat when surrounded by IR-opaque clouds.

Combined changes of evaporation and clouds. While it might sound perverse, accelerating this cycle has nothing to do with making more clouds, at least not directly. The whole cycle is meant here, evaporation followed by condensation - which can make a lot of rain, or just stay up there as clouds.

Combined changes of convection and clouds. Clear-air convection without clouds cools things off and lowers temperatures. With clouds, it does raise the temperature of the cloud bottoms. But within the clouds, it also reroutes heat up to the cloudtops, where it radiates away into space. On the whole, enhanced convection, with or without (realistic) clouds, lowers the temperatures.

Combined changes of evaporation and convection. Near the Earth's surface, where liquid water is evaporating, the water has to absorb the heat of vaporization from somewhere to change to a gas. While some of the heat comes from direct solar radiation - and that's enough to evaporate small puddles - the heat needed to evaporate large bodies of water comes from the air right above the surface, the inversion layer. Enhanced convection above the inversion layer undercuts the evaporative heat flow downward, slows evaporation, and lowers the heat flow from the hydrologic cycle.
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* In physics language, the analysis so far has been kinematic (descriptive), not dynamical (causal).

** It's important to again distinguish convection (here restricted to mean a type of heat transport) from general fluid flow. General updraft speeds in the atmosphere are about a meter per second, larger - sometimes much larger - in clouds, but the updraft speeds actually cover a large range of speeds. One small part (and not even a representative part) of that speed range convects heat.

She turned me into a newt

But I got better.

Here's a fake media uproar: Newt Gingrich recently declared that bilingual education keeps its students in a ghetto and expressed concern over official multilingual policies in, for example, drivers' licenses and ballots.

On the first point, Newt knows what he's talking about, certainly far more than the ignorant talking heads who attempted to criticize him. The only problem is that Newt is pretty late to the anti-bilingual party. Bilingual education - as a means for integrating non-speakers of English into American society - is a three-plus-decade failure. Everyone in education has known this for a long time. Furthermore, bilingual education in is controlled, not by non-anglophone students or parents, but by a small ideological activist lobby that wants to keep immigrant children ghettoized and has made no secret of it. How they managed to "capture" politicians into going along with them is another chapter in the story of special-interest group politics shortcircuiting democratic politics.

The political movement against bilingual education started over a decade ago, with great subsequent success in most states. Immigrant parents are overwhelmingly opposed to bilingual education. The anti-bi-ed movement succeeded in placing the question on ballots in all the states where that was possible. The only states where these initiatives ran into trouble were Colorado and Arizona, where many non-immigrant voters wanted bilingual education to continue to ghettoize immigrant children and prevent them from integrating into American society. Get it? Only the media, suffocating with myopic white guilt - the curse of postmodern liberalism - is unable to.

On the broader point of multilingualism, Newt is on shakier ground. For anyone older than mid-teens, learning a new language well is hard. Furthermore, the real issue isn't bi- or trilingualism, but having mono-lingual ghettos, where the monolingua in question is not English - which is probably what Newt meant to criticize. As long as American citizens have a common access to English, they can function well both politically and economically. For immigrants not to have English is to hobble them (viz. the Colorado and Arizona voters who understood this point better than the chattering classes). Otherwise, bilingual, trilingual - the more, the merrier. Bring it on.

Digression on evaporation, condensation, & precipitation

Because the evaporation-condensation cycle is the only source of heat other than solar radiation in the Earth's atmosphere, it's worth discussing in a little more detail.*

The essential overall fact about this cycle is that liquid and evaporated water coexist in phase equilibrium, with water vapor at saturation pressure, only right at the surface and up in the clouds. In between, the water vapor is not in equilibrium and in fact has a pressure below saturation pressure for a given temperature. Equivalently, between the sea and clouds, the relative humidity is less than 100%.

The most striking thing about this cycle is that it releases net heat, even while the amount of water cycled remains essentially fixed. A small part of the effect is due to the fact that the latent heat of water rises at lower temperatures. Condensation at lower temperatures in the clouds releases more heat than it originally took to evaporate the water originally at higher temperatures at the surface. However, this effect is only a small part of the total net heat released (22 units relative to 100 units of total incoming solar radiation).

A much more important part is due to the fact that the water evaporates and condenses in the presence of dry air pressure, not just water vapor. A given mass of water vapor takes up far more space than does the same mass of water as liquid. To transform water from liquid to vapor "at pressure" requires doing work against that pressure: if the pressure is constant (and at a fixed altitude, it is), then the work needed is the pressure times the change in volume. That energy has to come from somewhere - it comes from the same source as the latent heat of vaporization, namely, the daytime temperature inversion right above the surface water. In the clouds, the atmosphere gains back the work done when the water vapor "collapses" to form water droplets. However, at the cloud temperatures, the saturation pressure and density of water vapor are far smaller than at the surface. (Recall that the equilibrium or saturation pressure and density of water vapor is a very sensitive function of temperature.) The total work done in reverse - "collapsing" the vapor into droplets - is larger than the work done in "expanding" the liquid surface water into vapor, in spite of the lower air pressure in the clouds.

The total net heat released by the evaporation-condensation cycle is the sum of these two effects, although the second is much larger than the first. Precipitation and the formation of the highest clouds (the wispy cirrus type) actually involve the conversion of water vapor into ice crystals. That complicates the details, but doesn't change the conclusion.

Of course, the water also undergoes other energy transformations in this cycle from surface to clouds and thence back to surface. But those energy transformations do all add up to zero. They include the conversion of heat energy to gravitational potential energy (accompanied by a decline in temperature) on the way up, then the reverse on the way down. It's not quite as simple as it looks, though: Ever wonder why raindrops are usually cooler than the surrounding air? It's because the raindrops' heat energy is smaller than when the water molecules left the surface in the first place. What would have been thermal energy instead goes into the kinetic energy of the falling drops. That energy disappears when the drops hit the surface and reappears as heat energy - that is, the liquid water heats up again when it hits the surface, eventually back up to the surface temperature.

The surface evaporation is locally small (a few millionths of a kilogram of water per square meter per second). But it is global large, when multiplied by Earth's large water surface area: roughly a billion kilograms cycling through the lower atmosphere every second.
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* This ignores the small about heat emitted from the slow decay of radioactive elements in the Earth's core - the source of the Earth's vulcanism and other "hot" geophysical activity, like hot springs.

Temperature inverted

Two previous postings explained the temperatures of the lower atmosphere, first in terms of discrete entities (clouds, surface), then in terms of the lapse rate, the rate at which the temperature falls with altitude. Air temperature falls with altitude because some of the air's stored heat is converted to gravitational potential energy - or, equivalently, the air mass has to do work against gravity in order to rise. The condensation of water vapor complicates the details and ruins the simple heat content-temperature proportionality. But it doesn't change the essential point, that the temperature profile has a downward slope.

One more important qualification needs to be added to this picture. Depending whether it's ground or water and whether it's day or night, the temperature profile near the surface is often inverted. That means that the temperature rises with altitude in an inversion layer near the surface, then flips back to lapsing again at higher altitudes. Along with the inversion (where and when it exists) comes a downward heat flow near and at the surface, which is consistent with the temperature inversion: heat flows towards lower temperatures. Over water, this inversion is critical to enabling evaporation, which needs a constant source of heat flow downward into the water to "pay the heat of vaporization bill" that turns liquid water into vapor. Over land, the inversion keeps the ground warmer at night than would be otherwise. It also frequently leads to fog. The associated downward heat flow is all radiative, since convection can't happen if the temperature profile is upwardly-sloped: there is no bouyancy.

The inversion phenomenon arises from the different speeds at which water, air, and land both heat up and cool down. Water is the slowest, land the fastest, and air in the middle. An earlier posting touched on these differences in connection with the forces that drive climate.

Evaporation is one result. Another is an interesting complementarity - but not full symmetry - between land and convection on the one hand, and ocean and evaporation on the other.

Land and convection: Inversion by night. Land heats up more quickly than air during the daytime. With the ground hotter than the air above it, strong upward convection results. Late summertime afternoon thunderstorms, sometimes with spectacular clouds rising into the stratosphere, are the most extreme sign of this. At night, however, the ground cools off faster than the air above it, and an inversion layer forms. Heat flows down from the air into the ground. Such inversion layers (and any associated fogs) typically disappear in the early morning, as the Sun starts to heat the ground again.

Water and evaporation: Inversion by day. Inversion develops during the daytime - the air heats up faster than the water - and peaks late in the daytime and early evening. At night, the ocean retains more heat than the air and cools off more slowly. The inversion disappears, only to reappear again the next day. The coolness of the daytime ocean air is one sign of the great heat sink that drives evaporation. Some evaporation happens by direct radiation from the Sun and clouds. But most of it is due to the downward heat flow in the atmosphere's lowest layer.

Cute climate analogies: Introducing opacity

And - unlike the "greenhouse" - these are even accurate.

My favorite is the analogy between temperature and heat flow on the one hand, and pressure and fluid flow on the other. The pressure one is easy to visualize: think of a vertical hose with water flowing in and out. The water pressure at any point in the hose is the result of:

• The mass of water in the hose at any instant
• The force of gravity downward
  
• The hose cross-sectional area available to the water
• The rate at which water is flowing through the hose

Assume a steady flow of water and incompressibility - that is, the water density at every point in the hose is the same constant. Then there's a water flow balance: kg of water flowing in per second = kg of water flowing out per second.

Back up for a moment and just have a mass of water in the hose, with no flow. If you squeeze the cross-sectional area down, the height of the top of the water must go up (to preserve the volume and thus the mass). But then the gravitational potential energy difference between the top of the water and the bottom must increase and the pressure difference between top and bottom decrease. If the water top is open to its environment, it must have the same pressure as the ambient air. The pressure difference becomes smaller by the pressure at the bottom of the hose increasing.*

This linear pressure-height relationship is analogous to the linear temperature-altitude relationship in an adiabatic atmosphere. The pressure falls linearly with height as the water does work against gravity, just as temperature falls linearly with height as the air's heat is converted to work against gravity. The analogue to the pressure boundary condition (pressure at the top = ambient air pressure) is the temperature boundary condition (heat flowing out the top of the atmosphere = heat that flowed in - not reflected by clouds - then supplemented by latent heat released in the water cycle).

Now switch on the flow and create an analogue to the pseudoadiabatic atmosphere, one with local thermodynamic equilibrium, but supplemented by steady flows in and out. Hold the flow of water (kg/sec) fixed. There's a new kind of energy in the system, namely the kinetic energy of the flowing water. Squeezing the cross-sectional area down again pushes more liquid up and increases the pressure at the bottom of the hose. But it also increases the fluid's velocity and kinetic energy. Again, the pressure at the top has to be equal to the ambient air pressure. It's the pressure at the bottom of the hose that rises.

If you decrease the cross-sectional area of the hose, but insist on keeping the flow rate unchanged, then something has to give, and that something is the pressure: it goes up. If you increase the cross-sectional area of the hose and leave everything else unchanged, the pressure goes down. OTOH, if you change the cross-sectional area and insist on the pressure remaining the same, then what gives is the flow rate.

The analogy with temperature and heat flow goes like this:

• Pressure > temperature
• Mass flow > heat flow
• Incompressibility > temperatures are steady
• Cross-sectional area > radiative opacity or thermal conductivity

A source of steady work (a pump) is needed to keep a steady water flow upward against gravity - just as steady heating from the Earth's surface is needed to keep heat flowing up in the air.

The analogy is misleading in one respect. In the Earth's atmosphere, the effect of gravity is dominant. The effect of radiative heat flow (as well as convective heat flow, for that matter) in the atmosphere's temperature distribution is small.** (In the earlier discussion of the lapse rate, those are the rad and conv terms.) That's where the radiative opacity comes in. (If we were talking about heat flow in a solid or liquid, we'd be talking about the thermal conductivity instead.) Upping the opacity - making the atmosphere more opaque to infrared radiation - is like squeezing the hose: with a constant heat or water flow, it raises the temperature or pressure at the bottom, respectively.

The Earth's atmosphere is like a very wide, vertical hose with a strong pump: gravity and heating from below dominate the picture. Changing the hose cross-section a bit only has a small effect on the pressure; we'll see soon that changing the opacity a bit in the air has a real but small effect on the temperature. Soon after that, we'll meet a different planet - Venus - whose atmospheric temperature profile is dominated by opacity, not by gravity, and whose heat flow is like a narrow hose at high pressure.

Further analogies of this type are possible. Opacity is also analogous to electrical resistance. Recall Ohm's law: voltage difference across two points in a circuit = resistance times electrical current flowing between the points. The analogy is:

• voltage difference > temperature difference
• electrical current > heat flow
• resistance > opacity (or thermal conductivity if the medium is a solid or liquid)

The one thing missing is an analogy to gravity. It would have to be a strong electric field parallel to the current wire, although that's not something typical in electrical circuits.**
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* If you drop the analogy to temperature for a moment and consider real temperature effects on the liquid, heating the liquid causes its pressure to increase and thus the height of the top of the fluid to rise. If the relation of pressure to temperature is proportionate (linear), then the linear relation between the pressure difference and the height yields: temperature change proportional to change in height of fluid column. That's a how a thermometer works.

** And unfortunately, there's no obvious analogy in these examples to evaporation, condensation, and the release of latent heat.

King Herod and his tomb

Herod the Great (or the Wicked) was the last independent king of ancient Judea before that province was taken over by the Romans upon his death in 4 BCE. He was a megalomaniac who killed much of his own family out of paranoia and built or rebuilt huge structures that still survive: Masada, the Herodion, and the Second Temple in Jerusalem (parts of which survived its destruction by the Romans in 70). Each one topped the last as the largest public works project of classical antiquity.

Israeli archaeologist and Hebrew University professor Ehud Netzer has confirmed that the large structure on a hill near Bethlehem (part of the Herodion complex) that has been under excavation for decades is in fact Herod's tomb. You can view a public photo essay here.

C'est matin en France

Congratulations et félicitations au nouvel Président de la République, from the land of le capitalisme neo-impérialiste et sauvage! :>)

It wasn't the landslide that some predicted - only 53% to 47% - but Nicolas Sarkozy, the center-right candidate did win France's election Sunday. And the turnout was massive, maybe the biggest in the history of the Fifth Republic. Here's English-language reporting from the Economist, and an interesting background article from Commentary. See earlier postings on Europe's crisis here, here, and here.

It's been clear since the hapless Jacques Chirac* was re-elected in 2002 that France's drift and decline would continue, unless and until a serious shakeup was at hand. The four main candidates this time were not ideal - and one, Le Pen, is really a disgrace - but they nonetheless signal that real change has finally arrived. Apart from Le Pen, they're considerably younger than Chirac, and all grasp that France has been sinking deeper and deeper into serious trouble.

One way of looking at Europe's problems is that, in many ways, the 1970s never ended there. The rise of the EU has brought some degree of governmental self-discipline to the old continent, but at the price of alienating democratic sovereignty and popular consent. Within Europe, the British, Irish, Dutch, and Nordic economies in the last generation have put themselves through a wringer of sometimes painful reform and renewal, with generally positive results. It's the heart of continental western Europe - France, Belgium, Germany, and Italy - that now lags. The interesting thing is that France now joins Germany in a center-right-leaning trend. Sarkozy's parole favorite is rupture, which means the same in English and French. There are no guarantees that these leaders can accomplish what they need to - Berlusconi's rightward coalition in Italy had some modest accomplishments, nothing dramatic. Perhaps only a consciousness that the hour is late will serve as a spur to change.
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* Best Chirac quote, on the Brits: "The only thing they have ever done for European agriculture is mad cow disease.… You can't trust people who cook as badly as that."

Is not their climate foggy, raw and dull,
On whom, as in despite, the sun looks pale,
Killing their fruit with frowns? Can sodden water,
A drench for sur-rein'd jades, their barley-broth,
Decoct their cold blood to such valiant heat?

- Henry V, III.v

Why weather is hard to predict

If my climate scenarios seem lifeless and idealized, they are. They're not real climates, but caricatures. Even the most complicated computer models of climate are caricatures, albeit caricatures with more details.

There is no sharp dividing line between "weather" and "climate." We all know weather is hard to predict, yet has repetitive features. But we tend to think that there is a long-term average of "climate" that is stable - but such a thing doesn't exist. "Climate" really just means "weather in the long run" - and it shares the same duality that we see in weather - repetitive, yet unpredictable.

It was the 19th century's physics that defined thermodynamic equilibrium and gave exact definition to now-familiar concepts like temperature and pressure and more esoteric notions like entropy. The atmosphere as a whole is not in thermodynamic equilibrium, because it has no one temperature or pressure, and its phase equilibrium of liquid and evaporated water shifts depending on temperature. The first half of the 20th century gave physics broader concepts that take us closer to what the atmosphere is really like. A local thermodynamic equilibrium (LTE) allows temperature, pressure, and phase equilibrium to change from one place and time to another, but still have exact definition at each point. It's a broader definition of thermodynamic state than equilibrium. Because of the variation of pressure, temperature, and phase, the LTE distributions of those fields must be supplemented by a list of the flowing matter, heat, radiation, and evaporation-condensation-precipitation. To really understand this steady state of nonequilibrium is to understand that the flows are causes and the local equilibria effects, not a cause.

But we're still not at the real atmosphere. In real life, equilibrium is always local, temporary, and approximate. Scientific education still biases the thinking even of scientists who should know better into an unconscious prejudice that equilibrium is more fundamental, instead of seeing the world as it actually is: equilibrium is a condition that will pass.

The flows of air, water vapor, and energy are not steady. Different components of the atmosphere, even at the same point in space and time, have slightly different temperatures. Phase equilibrium is frequently violated in a pretty serious way, at least outside clouds. The dynamics of the atmosphere is represented by a complicated set of nonlinear partial differential equations that describe how the thermodynamic and hydrodynamic fields change continuously and how cause and effect are linked on the stage of spacetime. They have no exact solution and even the most powerful computers are strained to the limit by attempts to solve them using approximate computation methods.

Buried in these equations is one of the greatest discoveries of 20th century science - why the world as we know it is both repetitive and yet shot through with a stream of unique, never-to-be-repeated events. In the last third of the 20th century, physicists, mathematicians, and others discovered chaos. It's a topic that deserves and will get its own full discussion. In fluids like the air, the chief manifestation of chaos is turbulence, of which our familiar heat convection is one part.

Chaos is what makes it impossible to predict weather much beyond two weeks. After trying naively and futilely in the 1950s and 60s to make exact predictions of weather with ever more computing power, meteorologists in the 70s and 80s abandoned the goal of a completely self-contained weather theory and instead invented sophisticated ways of combining present and past meteorological data (synoptic meteorology) with general physical principles (dynamic meteorology) into a fruitful symbiosis that draws on the strengths of each. Synoptic analysis uses the atmosphere itself as an analog computer - present and past observations suggest patterns and probable future evolution. Dynamic meteorology introduces physics into the picture, to enforce general laws of nature and veto predictions that would violate them - say, energy or mass conservation, or an approximate condition like hydrostatic equilibrium known to be satisfied to high accuracy. Computers are essential for this symbiosis, since they make it possible to store and compare vast numbers of atmospheric observations. In the old days, meteorologists had to rely on limited human memory and ability to compare similar situations.

The symbiosis of synoptic and dynamic meteorology began in the 1930s, but until the 1970s, the hope remained that the synoptic part could be eliminated and meteorology could be all dynamical, based on complete, self-contained theoretical predictions made from scratch (ab initio) using the complete theory of the atmopshere: fluid dynamics, geophysics, and radiation. The discovery of chaos dashed those hopes and made it clear that the symbiosis wasn't just practical - it was a deep necessity. Although the dream of complete theoretical weather predictions came to an end and the two-week limit had to be accepted, scientists have since learned to ask a different set of questions about the long-term behavior of chaotic systems. Chaos includes most of the non-trivial dynamical systems around you: the rushing stream, the human heart, the power grid, the stock market - and the weather.

Climate greenhouse: The power of bad metaphors

It's surely obvious by now that the full range of heat flow and temperature modifications in the lower atmosphere due to water and convection should add up to what is commonly called the "greenhouse effect" - and they do, more or less. But the metaphor and the implications latent in it badly distort the reasons for why the Earth is as warm as it is and lead to endless misunderstandings and exaggerations.

How a greenhouse works. A greenhouse is a hothouse for plants, specially equipped with a glass roof to let sunlight in. It's typically well-watered too. However, contrary to legend, it does not trap significant infrared (IR) radiation. The temperature enhancement in a greenhouse is partly due to the watering, but mainly due to the trapping of convective heat currents that rise but then can't escape through the roof. This was proved in 1909 by R. W. Wood's experiment with two greenhouses, one with a glass roof, the other with a rock-salt roof. The former absorbs heat radiation, the latter does not. There was only a small difference in temperature.

The lower atmosphere is not a greenhouse. It should also be obvious from the previous weeks' postings that the Earth's climate does not work this way. Convection plays an important but still secondary role in heat transport - its main role is to warm the cloud bottoms, but also to efficiently get rid of heat by transporting it through to the cloudtops, where it's radiated away into space. Because temperature stops falling with altitude at the tropopause, there is a greenhouse-like "lid" on convective heat flow. But at that altitude, virtually all heat transport is by radiation anyway, in air that's very dry and transparent to IR radiation. The heat gets out.

The lower atmosphere does not trap heat. The real damage that the misleading "greenhouse" metaphor is not only the wrong explicit analogy - the metaphor carries with it another, totally wrong implication that heat is somehow "trapped" in the lower atmosphere, like locking someone in a closet. You hear this constantly: carbon dioxide (CO2) - like water vapor, although that's mentioned far less often - is a "heat-trapping" gas, which is nonsense. Occasionally, someone will take stab in the right direction by calling them "heat-absorbing" gases, which is at least half-true. But the other half is that molecules good at absorbing IR radiation are also good at emitting it.* What these molecules really are is exceptionally good at passing the heat along, like an efficient bucket brigade. That's why they steepen the temperature slope (lapse rate). And so here on this blog, molecules of this type - like water, carbon dioxide, and methane (CH4) - will be henceforth referred to as "IR-active," a shorthand meaning they are very efficient at absorbing and emitting heat radiation. Very soon, we'll take a closer look at how steepening the lapse rate affects climate.

Heat is not trapped in the lower atmosphere, and the energy flows in and out are never far from balance. Visible light flows in and is used in certain ways, is transformed into longer-wavelength radiation or temporarily converted to convection, catalyzes the release of latent heat from water, then flows out. The temperature distribution is a result of this interlocked network of heat flows.

Don't settle for bad metaphors. Textbooks often do flag the faulty "greenhouse" metaphor and at least attempt to substitute something less objectionable, like "atmosphere effect." Even that, improvement that it is, doesn't convey the real complexity of the Earth's enhanced temperatures. The enhancement, as the recent postings have explained, is the net result of a whole bundle of effects that both raise and lower temperature. With the exception of clear-air convection, all of them are associated with water.** If we want to give an accurate name to this collection of heat-flow modifications, the best bet is something like "The Water-Convection Effect." Each piece of it should get its own metaphor - like "steambath effect" (evaporation-condensation cycle), "shiny blanket effect" (clouds), "boiling effect" (convection), and "tropospheric lid" (tropopause).

Proper points of comparison. Finally, two further distortions are dragged along with the "greenhouse." The first is the misleading comparison of the actual surface of 288 ^oK to the fictitious 250 ^oK surface with infinitely thin but still reflective clouds - the Earth's surface with only the solar radiation coming in that doesn't get reflected, but missing the latent heat of evaporation-condensation. While useful as an accounting device, the comparison is physically meaningless. The right comparisons are:

• Dry atmosphere: T(surface) = 279 ^oK = 6 ^oC = 43 ^oF
  
• Wet atmosphere with evaporation, but no clouds: T(surface) = 304 ^oK = 31 ^oC = 89 ^oF
  
• Wet atmosphere, with evaporation and thin, reflective clouds, but no convection: T(surface) = 269 ^oK = -4 ^oC = 25 ^oF, T(clouds) = 247 ^oK = -26 ^oC = -15 ^oF
  
• Wet atmosphere, with all the effects of water included, plus convection (our climate): T(surface) = 288 ^oK = 15 ^oC = 59 ^oF, T(cloudbottoms) = 275 ^oK = 2 ^oC = 36 ^oF, T(cloudtops) = 250 ^oK = -23 ^oC = -9 ^oF
  

Water vapor is overwhelmingly the most important "greenhouse" gas. The second misbegotten notion is a direct result of the hysteria surrounding carbon dioxide, a minor constituent of Earth's atmosphere - everyone forgets, water is the main star when it comes to temperature enhancement, withe the key supporting role played by convection. Carbon dioxide is like the bit-part actor who gets a couple lines.***

Where did the "greenhouse" come from? The "greenhouse" idea regarding IR-active gases has been around in some form for over a century. But the modern version was hatched in the 1950s with attempts to understand the intense heat of Venus. An upcoming posting about Venus will delve into this history a bit. We'll see then why Venus' atmosphere has little to tell us about Earth's, they're so radically different - but we'll also see that Venus' atmosphere does hold one important lesson rarely noted. We'll also meet Mars' more Earth-like atmosphere and learn a different but equally important lesson.
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* Kirchhoff's law of radiation again.

** Convection can exist without clouds, but clouds as we know them cannot exist without convection.

*** Methane is then like the silent character in the back who looks menacing, but never actually does anything.

Climate summary, with pretty pictures

I never know how much of what I say is true. - Bette Midler

Here's a summary of the heat flows in the Earth's lower atmosphere, surface, and clouds. If the total incoming solar radiation power stream is 100 units,*

• Solar radiation in reflected by clouds = 35
• Solar radiation in absorbed by clouds = 19
• Solar radiation that reaches surface = 46
• Atmospheric heat flow downward to surface = 49
  
• Net latent heat of water released = 22
• Heat convected upward from surface = 10

Astute readers might have noticed that the evaporation-condensation (hydrologic) cycle adds 22 units on net to the heat flow in. But shouldn't that be zero? The full cycle brings water back to the surface as precipitation - why not the heat released back to zero as well? The answer is another one of those subtle and beautiful properties of water. The energy change for liquid-vapor phase conversion is larger at lower temperatures and pressures and smaller at higher temperatures and pressures. Thus water condensing at lower temperatures and pressures in clouds releases more heat than was originally absorbed by the same water evaporating at higher temperatures and pressures at the surface. To use the language of chemists, the whole cycle is exothermic.**

Look at just surfaces, clouds, and lower atmosphere as wholes: six mechanisms modify the pure incoming solar radiation, three enhancing, three anti-enhancing:

    Modification of heat flow                      Effect on temps
--------------------------------------------------------------------------
Net latent heat released from
 water evaporation-condensation                        up
Convection in clear air                                up (clouds only)
Clouds as radiators down                               up
Clouds as reflectors up                                down
Clouds as efficient convectors up                      down
Clouds as radiators up                                 down

Look at the whole temperature profile and consider the lapse rate: four mechanisms modify the dry adiabatic lapse rate:

    Modification of heat distribution              Effect on lapse rate
--------------------------------------------------------------------------
Condensation: release of latent heat                   shallows
Condensation: loss of water vapor pressure             steepens
Convective heat transport                              steepens
Radiative heat transport thru water vapor              steepens

Overall, condensation (release of latent heat) wins, and the dry adiabatic lapse rate of 9.8 ^oK/km is moderated to about 6.5 ^oK/km. Two previous postings, on tropospheric temperatures and lapse rates, contain more details and have been revised somewhat for accuracy and clarity.

The water- and convection-driven temperature enhancements are frequently compared to the 250 ^oK = -23 ^oC = -9 ^oF climate with reflective but otherwise unreal clouds and no evaporation, implying internal enhancement of surface temperature of +38 ^oK, to 288 ^oK. But a better baseline is the 279 ^oK = 6 ^oC = 43 ^oF dry atmosphere, with a +9 ^oK net enhancement due to all the effects of water and convection taken together, both enhancements and diminutions. This baseline is well-defined physically, while the other is based on isolating one effect of water (cloud reflectivity) and leaving the others out.

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I've been asked to leaven the steep scientific climbing of the last couple weeks' postings on climate with something a little easier. Here's a neat graph of the atmosphere's temperature profile. The troposphere shows off its 6.5 ^oK/km lapse rate:

(From Lyndon State College, Vermont, meteorology notes.) The height is marked in both miles and kilometers. The pressure is marked in millibars: the surface pressure is about 1010 millibars. Of course, there's more going on above the troposphere - an upcoming posting will explain what happens in the upper atmosphere and why it's important for us down here. And here's a nice summary of all the heat flows into and out of the atmosphere. This diagram divides up the energy flows in a different and more detailed way from our approach, but the results are nearly the same.

Finally, there are clouds:

(From the exquisite online photo archive of Redvest.) Clouds are wonderful things - like snowflakes and people, no two are alike. The theory I've used in the last month to explain clouds isn't the full theory - no one can solve it - but a highly simplified model that treats clouds as stable horizontal slabs of dense water droplets. Real clouds are everyday reminders of dynamical chaos and pointers to the deep reasons why weather is repetitive and yet unpredictable.
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* These numbers closely match the classic results of Budyko, with slight differences due to a different "solar constant" (incoming radiation power flux, watts per square meter) and including the effect of the cloudier southern hemisphere. I've ignored the tiny absorption of incoming radiation by the upper atmosphere. Mean cloudiness = 0.54.

** Water really is a miracle compound. (See here.) On alternate Tuesdays, it's enough to make me believe in a just and benevolent G-d.