Los Angeles has a new solution to climate change: painting streets white.

Well, not quite a solution to climate change. What it really addresses is what’s called the “urban heat island” (UHI) effect. Cities and towns, with lots of blacktop streets, absorb more energy from sunlight than rural areas, so their ambient air temperatures (especially at night) are warmer. Los Angeles will paint its streets white to reduce its UHI.

It might actually work, though with all those black rubber tires running over those streets 24/7/365 it’s going to be quite a challenge keeping them white enough to make much difference.

But if it has any measurable effect not on local (UHI) temperature but on global, it won’t be because actual global average temperature will be made less than it otherwise would be. Human emissions of greenhouse gases’ effect on global temperature is, though theoretically real, too small to measure. After controlling for solar, volcanic, and ocean current cycle variations, there’s no warming left to blame on carbon dioxide.

However, a significant portion of the apparent increase in global average temperature actually comes from UHI contaminating temperature data. If Los Angeles’s street-painting project really works and gets copied by lots of other cities, we could see “global average temperature” decline not because truly global temperature truly declines but because UHI itself declines.

And that could expose the fact that the increase in truly global temperature has been exaggerated all along.