To see global warming in action, look around.

America has just experienced its warmest fi rst half-year on record.

This means more energy in the atmosphere, which drives storms, lightning strikes (causing fi res) and violent winds. Warmth also causes droughts that harm farmers in Arkansas and elsewhere.

Hurricane-force straightline storms hit the eastern states two weeks ago, killing 20 and knocking out power to millions during a sweltering heat wave. Heat, drought, early snowpack melt and pine beetles migrating northward fueled western wildfi res, burning 2.1 million acres and hundreds of homes.

By the end of June, 113 million Americans were living under extreme heat advisories and twothirds of the country was experiencing drought.

Earlier in June, deluges fl ooded Minnesotaand Florida.

This is what global warming looks like.

If you think humans are too puny to cause such havoc, consider this: The energy going into the atmosphere each day from human-caused greenhouse gas emissions is equivalent to the energy release of half a million Hiroshimasized nuclear bombs.

And if you have any doubt recent weather events are far outside the norm, consider this: In normal times, the number of broken hightemperature records in one year is roughly equal to the number of broken low-temperature records.

In recent years, the number of broken hightemperature records has been more than 10 times the number of broken lowtemperature records.

Sure, there will be some colder-than-usual days, but there will be many more hotter-then-usual days. This is not a normal weather “fl uctuation.” Global warming is loading the dice.

But ya ain’t seen nothin’ yet. Global temperatures are up by “only” 0.8 degrees Celsius (1.5 degrees Fahrenheit) so far. As I wrote three weeks ago, scientists predict there is now no way to stop global warming short of 2 degrees Celsius. We’d better stop believing the antiscientifi c fairy tales people like Sen. James Inhofe, R-Okla., who calls global warming a “hoax,” foist on us.

Two readers of my previous column told me, since I had depressed them with the news about global warming, I should explain what to do about it. It’s a good suggestion.

Being green is admirableand helpful. I try to do it, and so should you. But it’s not enough, and will never by itself come close to being enough.

Greenhouse gas emissions are driven by “business as usual,” in other words by economics.

The structural problem is a market system not pricing in the environmental costs of doing business.

Economics 101 teaches us free goods are consumed rapidly. As Garrett Hardin pointed out in his trail-blazing 1968 Science essay, “The Tragedy of the Commons,” a healthy environment nearly free for the taking will be consumed rapidly.

If capitalism is going to work in this era of huge “environmental externalities,” these environmental costs have got to be included in the market price.

There must be a price on greenhouse gas emissions. There are two ways to do this, both proven, both feasible, and both orders ofmagnitude cheaper than the alternative (continued global warming). One is cap-and-trade and the other is a “carbon” (greenhouse gas) tax.

Cap-and-trade limits the amount of greenhouse gases humans will be permitted to emit, and issues tradable emission permits to companies allowing certain emission totals. Companies emitting less can sell their excess certifi cates to companies emitting more. Cap-andtrade quite eff ectively reduced power plant sulfur emissions two decades ago, ending severe acid rain. This cost far less than industry had predicted, because of the market economics inherent in capand-trade.

A carbon tax would simply levy a per-ton tax on all greenhouse gas emissions, raising the priceand thus reducing the amount of emissions.

Essentially all economists favor a carbon tax over cap-and-trade, for at least three reasons.

First, its effects are clear and immediate, as we see from the way higher gasoline prices always cause a drop in gasoline consumption.

Second, a carbon tax can’t be easily “gamed” but cap-and-trade can.

The costs of permits, the proper measurement of emissions, the granting of permits, etc., are all subject to political and fi nancial manipulation.

Third, the cash raised by a tax could subsidize the energy needs of lowincome people who are fi nancially distressed by rising energy costs during our transition to non-greenhouse gas fuels, and the rest could be returned to Americans as income tax reductions.

The philosophy here is, tax “bads” (greenhouse gases) rather than “goods” (work).

We’d better start using our brains. It’s getting hot. ART HOBSON IS A PROFESSOR EMERITUS OF PHYSICS AT THE UNIVERSITY OF ARKANSAS.

Opinion, Pages 15 on 07/15/2012