In my previous post, I noted that a lot of us can imagine the end of the world more readily than we can imagine a future which is different in much smaller ways. I think that's because while conventional wisdom can't rule out the possibility that all things can end, conventional wisdom is pretty well set on "this is the best way to do X". The way we're currently doing it is the only good way to do it. That's why we do it this way. Resistance is futile.
Taking that train of alleged thought a step further, it's easy to point out that the way we currently do X fits just perfectly with the ways we do U, V, W, Y and Z. Clearly, if we change the way we do X, one or more related functions no longer fit smoothly and will have to change, and then functions related to those functions will be affected, and the ripples will just continue ad infinitum. Clearly, it's better just to leave X alone. Or to change it only at the margins. Slowly.
Now, there's value in that old Yankee chestnut: if it ain't broke, don't fix it. Change, merely for the sake of change (and the artificial stimulation of consumer demand) just gets you the fashion industry. And tail fins (for those of us old enough to remember). And New Coke (ditto).
But a reflexive loyalty to 'the way things are' readily overlooks aspects of the current situation which are, in fact, "broke". The powers that be don't want to point these aspects out -- after all, if things change too much, they might not be the powers any more -- but sometimes, the truth becomes readily evident.
One of those times occurs annually, when Lawrence Livermore Laboratories published its annual Energy Flow Chart  for the USA.
Energy generation and usage, of course, is a common topic of discussion when the subject of sustainability comes up. Alternatives get suggested and shot down. The way things currently happen gets attacked, and defended, and depicted as the only practical option. There's a lot of money at stake: honest money made by selling goods and services, less honest money made by influencing government subsidies and taxes, and immoral-if-not-illegal money made by speculation and market manipulation. So there are lots of paychecks (some of them very fat) dependent on folks maintaining a Panglossian complacency about how things are.
But take a look at that flowchart. Compare "energy services" (energy put to use) to "rejected energy" (energy put to no use at all -- energy wasted). We, as a country, are wasting about 58% of all the energy we generate. Almost three-fifths of all the fossil fuel, nuclear, hydro, wind and solar energy we capture goes up in smoke. Or, more realistically, in waste heat.
Think of all the heat that your car generates when it's running. Think of all the heat your computer generates when it's running. Think of every machine, every appliance, every electrical cord that gets a bit warm when it's being used -- all of that heat is energy, and most of it benefits absolutely no one.
If the people who go on and on about fraud, waste and mismanagement in the government were to look at energy as money, it would make their jaws drop. I don't think that even Boss Tweed managed to skim off 58% of public funds. Certainly, bureaucratic inefficiency can't accomplish anything nearly so costly.
Greenhouse gases get generated as a result of all fossil fuels burned, not just fossil fuels burned to good purpose. If we were able to make our energy industries more efficient, we could decrease our fuel needs considerably. If we were able to make our vehicles more efficient, our buildings more efficient, our whole society more efficient, our greenhouse gas emissions could (in theory) be cut almost in half even without major behavioral changes or major technological shifts.
What level of GHG reduction can realistically be achieved through improved mechanical efficiency? Through more efficient generation and distribution? The truth is, no one really knows. I certainly don't. But what I do know is that the answer will likely be far different if we start from the assumption that our current modes of generating and utilizing energy are grossly inefficient, than it will be if we start from the assumption that everything's for the best in this, the best of all possible worlds.