In January, Interior Secretary Sally Jewell put an immediate moratorium on all new leasing of coal from federal land.

Coal from public land represents about 40 percent of US coal supply, but critics have long charged that it’s being leased to private developers for too cheap, at a rate that does not account for its current market price or its impact on climate change. The "programmatic review" is intended, in part, to make sure taxpayers get their money’s worth.

The public comment period on the review has just ended. As expected, environmentalists flooded the Department of the Interior with hundreds of thousands of comments supporting the moratorium; the usual suspects (Republicans and the coal industry) are opposed.

We’ll have to wait to see what the results of the review are — a draft report is expected later this year, with another opportunity for public comment — but in the meantime, it’s worth taking a step back and asking a simple question.

In a climate-constrained world, there’s not much room for coal

The US, along with the other major nations of the world, has agreed to a simple climate target: Restrain global average temperature rise to no more than 2 degrees Celsius above preindustrial levels.

That target is very, very ambitious. It would mean rapid, aggressive decarbonization in every country in the world, especially developed nations like the US.

So here’s our simple question: What would it mean for coal on public land? How much coal could the feds lease if they were serious about the 2 degree target?

Green billionaire Tom Steyer’s climate advocacy group, NextGen Climate America, got curious about this, so it asked research outfit Carbon Tracker to look into it. The resulting report was just released.

The answer to the simple question? None. Zilch. Zero.

If the US government were serious about the 2 degree target, the moratorium on coal leasing would be total and permanent. No new leases.

What’s more, a lot of the coal that’s already been leased from public land would have to go unmined and unburned. Limiting temperature to 2 degrees entails such a steep decline in coal that we would have to stop burning it entirely before the coal now leased is even fully mined.

The US carbon budget has very little room left for coal

The study design was pretty simple. Carbon Tracker looked at the demand profile for coal in the International Energy Agency’s 2 degree scenario — a model of the fossil fuel phase-down necessary for a reasonable chance of avoiding 2 degrees.

Then it looked at the supply forecast for Powder River Basin coal from Wyoming and Montana (which comprises about 90 percent of federally leased coal).

The conclusion:

Demand for coal over the period is found to be far outweighed by supply from existing leases alone, meaning that no new federal acreage in the Powder River Basin is required to be leased by the Federal government through the end of our assessment period in 2040.

To put it more plainly: Under a 2 degree scenario, all the coal that the US will ever be allowed to burn has already been leased.

Here’s a visual. On the left is cumulative production from existing (blue) and potential new (orange) federal coal leases, from 2016 to 2040. The gray bars on the right show the demand for coal in a 2 degree scenario — here called a "450 scenario," referring to carbon concentrations in the atmosphere — varying with different assumptions about the viability of carbon capture and sequestration (CCS) later this century.

In my view, CCS on a scale that could make a difference is probably a pipe dream, so the gray bar on the right is likely the real target. Either way, the federal coal already leased vastly exceeds what’s permissible under a 2 degrees scenario.

A permanent coal-leasing moratorium has become speakable, but what about other fossil fuels?

It is considerations like this that led the Bloomberg News editorial board to take a stance last month that even five years ago would have been unthinkable: Make the moratorium permanent. As the editors note, even the public-health benefits of reducing local pollution more than justify ending coal production on public land. The climate imperative just reinforces the case.

They are not alone. Last month, a group of 65 prominent scientists sent Obama a letter urging him to make the coal-leasing moratorium permanent.

An end to federal coal leasing has at least entered the political conversation. But about oil and gas?

The government leases them too, lots of them. And many of the same problems that face the coal leasing program also face these programs — they’re leasing fossil fuels for too cheap, not taking climate into account. A 2 degree scenario doesn’t leave much room for new oil or gas supply either.

So why not extend at least a temporary moratorium to oil and gas leasing as well? Why not force them to undergo a similar programmatic review?

There are, in brief, two reasons. The first is practical, which Bloomberg editors note as they tiptoe gingerly in that direction. "Eventually, it might make sense to also stop new federal leases for other carbon-intensive fuels, chiefly oil," they write. "But the alternatives to gasoline-powered cars aren't nearly as far advanced as they are for coal-fired power."

Coal is on the decline, and alternatives (including, ahem, natural gas) are increasingly cheap, so restricting coal supply is only going to accelerate market shifts already underway. No one (except coal companies) is likely to suffer much.

But alternatives to oil, especially for transportation, are less cheap and available, so restricting oil supply is likely to be experienced primarily as a rise in consumer prices and an economic drag. That’s not necessarily prohibitive — it is, after all, how a carbon price is supposed to work — but it makes it a much heavier lift.

(Some political context: Oil production on public land has risen under Obama, from 581 million barrels in 2008 to 782 million in 2015, but even that hasn’t saved him from ceaseless attack.)

The same is true for gas leasing. Gas is the main thing killing coal on the market. Constricting gas supply might raise prices and, perversely, help coal. Or it might push manufacturing out of the country. It’s hard to say what the effects would be without further study, but they would certainly bite harder than a coal moratorium.

That’s the practical reason. The second reason is political.

The US coal industry is on the ropes, facing a wave of bankruptcies. Its political power is at an all-time low. The oil industry, by contrast, is healthy, feisty, and well-versed in throwing its weight around. Witness the power it has wielded in California, the nation’s bluest (and greenest) state. Just earlier this year, it blocked an effort that would have aimed to halve the state’s oil consumption.

Coal is politically vulnerable. Oil and gas are not, at least not nearly as much. Ending oil and gas leasing would be an enormous political risk and entail a gigantic political shitstorm. That doesn’t really sound like Hillary Clinton’s kind of thing.

Taking climate change seriously would be transformational

Still, difficulties aside, it doesn’t seem crazy to call a time out on oil and gas leasing while they are assessed with climate in mind. After all, just last week Obama’s Council on Environmental Quality released a guidance instructing all federal agencies to account for the climate impacts of their decisions.

CEQ's guidance on National Environmental Policy Act (NEPA) reviews even says specifically:

Examples of project- or site-specific actions that may benefit from being able to tier to a programmatic NEPA review include: constructing transmission lines; conducting prescribed burns; approving grazing leases; granting rights-of-way; issuing leases for oil and gas drilling; authorizing construction of wind, solar or geothermal projects; and approving hard rock mineral extraction.

Note the bit I highlighted.

Historically (and currently), federal oil and gas leasing decisions take virtually no account of climate at all. Shouldn’t they?

Dan Lashof of NextGen Climate America thinks it’s time to cut through the confusion with a simple rule:

Management decisions of all fossil fuels owned by the American public should be subject to a climate test: Are they consistent with our carbon reduction goals and our international climate commitments? If not, the fossils should be left in the ground.

It’s one thing to say this, as CEQ basically has. But it’s another entirely to put it into action.

As the Carbon Tracker study suggests, taking our climate commitments into account — taking the 2 degree target seriously — would likely entail an immediate halt to all federal fossil fuel leasing. And that's just the tip of the iceberg of what it would entail.

If you’d asked me a few years ago, I would have said that’s a political pipe dream. But then, I probably would have said the same thing about an end to coal leasing, which has, rather quickly, become a viable political possibility. Things are moving quickly around climate change. There just might come a day, sooner than anyone expects, when the US government gets out of the fossil fuel business entirely.