It would be fairly straightforward for the United States to keep its carbon dioxide emissions from rising between now and 2040. All Congress would have to do is keep most current energy policies in place.

That's according to a new analysis out today from the Energy Information Administration (EIA). The agency tries to project U.S. emissions in an "extended policies" scenario — in which all current energy policies are made permanent — and found that emissions would be 6 percent lower by 2040 than if those policies were allowed to sunset.

So what does this entail? The EIA's "extended policies" scenario is detailed here. It basically includes making a variety of tax credits for renewable energy permanent and regularly updating efficiency standards:

— Extend the production tax credit of 2.2 cents per kilowatt-hour for wind, geothermal, biomass, and hydroelectric indefinitely. (This tax credit is currently scheduled to expire at the end of 2013.)

— Extend the 30 percent investment tax credit for solar power indefinitely. (This is currently set to drop to 10 percent in 2016).

— In the buildings sector, make a tax credit for the purchase of renewable equipment permanent. (This is set to end in 2016.)

— Regularly update federal energy-efficiency standards and codes for equipment, homes, and buildings, as allowed under current law.

— Continuing to increase fuel-economy standards for new cars and light trucks after they reach 54.5 miles per gallon in 2025. In other words, the improvements would continue apace at "an annual average rate of 1.4 percent."

Some of these measures, such as re-upping the tax credits for clean energy,  would require Congress. (And that wouldn't be free; the recent one-year extension of the wind credit, for instance, will cost $1.2 billion per year for 10 years.) The energy-efficiency and fuel-economy standards, meanwhile, can be set by the White House.

The basic point here, however, is that none of these policies are new or drastic. They've all basically been in place for years. And during that time, the United States has seen a boom in wind and solar generation and an increase in vehicle fuel efficiency. That would continue indefinitely.

Now here's the gloomy news. As Joe Romm points out at Climate Progress, the United States would get nowhere near its climate-change goals if emissions simply flat-lined between now and 2040.

The Obama administration, after all, has set a goal of cutting greenhouse-gas emissions 17 percent by 2020 and 83 percent by 2050. That's in line with what the IPCC has recommended the U.S. do to do its part for limiting global warming below 2°C.

But the EIA's "extended policies" scenario won't get us anywhere close, even if emissions stayed flat:

That's why, as Trevor Houser and Shashank Mohan of the Rhodium Group wrote back in March, "Further emission reductions will require new policy, whether in the form of EPA regulation, congressional legislation (as called for in Obama's speech), or state-level action."

Now, Congress isn't likely to enact major climate-change legislation anytime soon, but environmental groups have been calling on the Obama administration to use EPA regulations to drive greenhouse gases down even further. That could include restrictions on carbon emissions from power plants as well as new regulations for methane leaks from natural-gas wells and pipelines.

That's all more difficult, technically and politically, than simply keeping current policies in place.