McKinsey & Co. published a really interesting, if geeky, report today on what it will cost to curb greenhouse gases in the U.S. It’s dense and complicated and 83 pages long, and I have to be honest and say I haven’t had time to read it all carefully yet. But I have written about it! That’s how Internet journalism works.

My first take on the report in today’s CNNmoney.com column is that it offers encouraging news—not the least of which is that roughly 40% of the carbon reductions needed to cut GHG back by 35 to 50% will pay for themselves, over time. This is a complicated way of saying that there is an enormous amount of energy waste in the U.S. economy.

Squeezing out the waste won’t be easy. Adam Smith nothwithstanding, markets alone don’t seem able to do it—if they worked as they should, most light bulbs in America would be a CFL bulbs because they are cheaper, in terms of their lifecycle costs, than old-fashioned incandescent bulbs. But they cost more upfront and so many people shy away from them.

Likewise, we don’t think much about the lifecycle energy costs of the homes we buy or the computers, plasma TVs, VCRs, DVRs, iPods and cell phone charges that stay plugged in (and draw power) round the clock.

In any case, if the economy can find a way to realize big savings from efficiency, it should be able to absorb the higher costs, at least in the near term, of renewable energy, clean coal and nuclear power, which are among the other options analyzed in the report.

Another encouraging thing about the report is that it assumes no big changes in consumer behavior. If we can get people to drive smaller cars, live in smaller homes, buy less stuff and recycle more—none of which, I understand, will be easy—then the projected costs of GHG reductions will be even less.

Energy-environment geeks like me will want to read the report, which can be found here. For the rest of you, here’s how the column begins.

The United States could reduce its projected greenhouse gas emissions by up to half in the next 20 or so years at a “manageable cost” to the economy, according to the most comprehensive report to date of the steps needed to curb global warming.

What’s more, according to the study released Thursday by management consulting firm McKinsey & Company, people will not necessarily have to change their lifestyles by taking public transport, driving compact cars or living in smaller homes.

But consumers, and businesses, will have to adopt other energy-efficient measures – a task that will be much harder than it sounds.

You can read the rest here.