Sparks: This road map could help us decide whether to deploy solar geoengineering

For half a century I have watched men study the machine that turns sunlight away, and still no philosophy has been written for a civilization that must choose its own weather.

All I know is what I read in the papers: some fellows drew a map for deciding whether to fiddle with the sky, which is one thing Congress never needed a map to do.

Forget the road map. Here is who has leverage: whoever controls the thermostats of the stratosphere; here is who is constrained: every nation that breathes the same air and was never asked.

We are told the plan was chosen; it accumulated, one experiment and one white paper at a time, until shading the earth looked like a decision instead of a survivor of fifty years of drift.

The road map promises a decision, but beneath it two forces strain: the heat already committed and the sunlight they propose to withhold, and no diagram holds that bow forever.

Before the experiment, map the wager: refuse to shade the earth and we lose the harvest; shade it wrongly and we lose the sky - and certainty is offered on neither side of my ledger.

Trace the conditions on which this decision depends - emissions still rising, institutions still divided - and the choosing dissolves into the very crisis it pretends to judge.

They call it a road map to informed decision, but a name is true only when the duty it names is performed; call the spraying of the sky what it is, and deliberation begins honestly.

Any physician who has watched a profession resist evidence knows the pattern: fifty years of cases collected, and the consensus still prefers the elegance of its fears to the data on the breakfast table.

How charming, that after half a century of warming the globe ourselves, we have at last prepared a courteous little document for deciding whether to dim the sun our own smoke has betrayed.

Scientists speak of experiments and politicians of deployment; the conflict dissolves once you distinguish what the stratosphere demonstrably does from who may rhetorically be trusted with it.

From the committee's side of the door, the road map describes governance; from a farmer's side, a dimmed sky is weather, and no one has gone inside to live under it first.

Having educated the public for a century to obey experts rather than reason, they declare it incapable of judging planetary engineering - then cite the obedience as proof the judgment must stay with them.

Petitioners describe a road map for deciding in the language of public interest, which is the language every concentrated interest has always used; the question is whose hand holds a thermostat no competition can constrain.

Announcements concern aerosols and decision frameworks; what they mean for the smallholder whose monsoon shifts a season earlier is a different document entirely, and no one has drawn that map.

Things that are elegant: a plan that lists first what must be learned. Things that are hateful: a sky whose color is a committee's line item, and rains that keep its schedule.

They offer us a road map to decide the sky's brightness inside the same structure that produced the warming; we are invited to manage the fever without examining the hand that lit the fire.

The board approved its roadmap for dimming the sun with the same unhurried courtesy it brought to the wine list, which is how the guests at the garden party failed to notice the wolf.

Read the headline again: the sky is to be 'deployed,' the decision an infrastructure project - and somewhere between the infinitive and the noun, the planet disappeared.