Health-Care Service Providers. The contrarian view is that a warming world would, on balance, improve public health in high-latitude areas. Though hot regions in the developing world experience high rates of communicable diseases that scare us, people are still far more likely to die from the cold than from heat—overall death rates in winter are much higher than those in summer. Retirees living in Florida, for instance, have less reason to fear a hot summer than those living in Vermont have to fear a cold winter. If the cold areas of affluent nations became less cold, we would expect longevity to increase. That would be good for society, and also a reason to hold health-care (and pharmaceutical) stocks, since the elderly require far more in the way of hospital services and drugs. The assisted-care industry might also be in for a long bullish run.

Electricity Producers. The World Energy Council has estimated that global demand for electricity will triple by 2050. The lion’s share of the increased demand will be in developing nations, but the United States and the European Union nations will need more megawatts too—and that’s even assuming increases in energy efficiency. It is all but certain that some form of greenhouse-gas regulation will come to the United States; many Fortune 500 CEOs already assume this. The result will be an electricity sector that’s much more technology- and knowledge-sensitive than today’s. Lots of brainpower and skill will be required to increase electricity generation and reduce greenhouse-gas emissions at the same time. It’s reasonable to guess that power-production firms with a track record of innovation, such as Duke Energy (which pioneered many techniques to improve the efficiency of nuclear-power plants), will be the kind of energy-sector stocks to own. Don’t be surprised if nuclear energy, which is nearly greenhouse- gas-free, enjoys a boom in coming decades. General Electric, Westinghouse, and Siemens are some of the leading producers of new “inherently safe” power reactors designed so they can’t melt down even if all safety systems are turned off.

“Green” Energy. Renewable-energy industries—such as solar energy and biofuels—might seem like a promising place for 401(k) chips, but bear in mind that no form of green energy is yet cost-competitive with fossil energy, and no one knows which may eventually win in the marketplace. Solar-cell production, for example, is an expanding sector, but nearly all large solar cells for residential and commercial applications are currently sold in California, Japan, or Germany, which heavily subsidize the installation of solar power. Many investors today are racing to ethanol, but wariness seems advisable. Bill Gates has already invested $84 million in a start-up called Pacific Ethanol; venture-capital firms have moved into the ethanol “space.” If the smart money is already there, you’re too late. Besides, BP and DuPont are now looking past ethanol to bet on butanol, a crop-derived petroleum substitute with superior technical properties.