Ray Weiss, a geochemist at Scripps Institution of Oceanography, was at the climate talks in Copenhagen last December, and he had a big interview on the BBC approaching.

He only had two minutes to speak, and he needed a metaphor. One that would succinctly summarize his point — that the world needs a way to track whether countries pledging to cut greenhouse gas emissions are actually doing it. Because they have financial incentives to understate how much they’re releasing.

And right now, Weiss has found self-reported measurements are sometimes wildly inaccurate. He’s measured some gases — like one used primarily in aluminum smelting — and found much higher levels in the atmosphere than were supposed to be there.

So with the radio appearance nearing, he was looking for an alternative to a metaphor he didn’t like (it involved a car and a broken gas gauge). He called his wife, a trial attorney, who gave him this nugget: The countries’ unverifiable greenhouse gas pledges are like people going on a diet without having a scale to weigh themselves.

It stuck.

Let’s take that metaphor a step further. If the countries around the world are the people going on a carbon diet, Weiss is helping to design the scale. He and colleagues have since been awarded a $1.2 million federal grant to model California’s emissions.

By measuring greenhouse gases in the atmosphere and tracking wind direction, they’ll pinpoint what’s in the air, where it’s coming from and where additional monitoring stations are needed (the state currently has two).

We sat down with the Scripps vet — he’s been there since getting his doctorate in 1970 — to talk about how emissions can be verified, what else fuels climate change besides carbon dioxide and exactly how gases are warming the earth.

When we think about climate change, we often only discuss carbon dioxide. You’ve found other contributors. And there are some seemingly unusual things in there like termite fumigants and a chemical that comes from making solar panels.

Yes, those are things we discovered and were the first to measure in the atmosphere. But it’s been known for a long time that carbon dioxide is about 60 to 65 percent of the problem and that there are a host of other things. Methane, [chlorofluorocarbons], and a host of compounds we use because we banned CFCs (which contribute to the ozone hole).

Can you explain at an elementary level how one molecule can be a more potent greenhouse gas than another?

The molecules are effective as greenhouse gases because they absorb infrared radiation that comes off the earth after it’s heated by sunlight. They trap that radiation in the atmosphere and warm it.

Each molecule has different frequencies of light that it absorbs. A big factor is that the less abundant molecules in the atmosphere absorb more strongly because the atmosphere’s not saturated by that gas. If you took all the carbon dioxide out of the atmosphere and put it in a layer at sea level, it’d be about 10 feet thick. That’s millions of times thicker than the layer for some of these other gases. So adding a little bit more carbon dioxide has less of an effect than adding a little of another gas.

And it’s not just only how it absorbs infrared light, but how long it hangs around in the atmosphere. Some gases that are minor in concentration have very long life times. Carbon tetrafluoride, which is primarily from the aluminum industry, has a lifetime of 50,000 years in the atmosphere.

Versus soot from burning charcoal and wood, which is …

Very short-lived — a few days or a week.

You’ve described the negotiation about greenhouse gas reductions as being like going on a diet without having a scale.

The thing I’m really interested in is that when we measure things in the atmosphere and compare them to what people are reporting they emit, we find enormous discrepancies. With nitrogen trifluoride (used in the manufacturing of solar panels and flat-screens), it was a factor of four or five.

There’s four times more in the atmosphere than what’s reported?

Four times more than what they said was being emitted. It’s not regulated, so the emissions estimates are crude. But the uses are quite limited to high-tech stuff. So it isn’t like trying to figure out what every rural farmer in the world is doing. It should be pretty straightforward. And it wasn’t.

It’s a runaway problem. All the legislation is written by requiring people to add things up according to books full of recipes to report your emissions.

Both with California’s law and the Kyoto Protocol.

It’s all bottom-up (relying on emitters to report their emissions). And it doesn’t work that way. We ought to measure regionally in the atmosphere what’s accumulating and use computer models to figure out where it’s coming from. Those models exist. I’m hopeful that we could make the bottom-up recipes give the right number. Because right now, the discrepancies are so big, we have to do something. The climate doesn’t care what you say you admitted, it cares what you actually admitted.

This is a hard problem to solve. And if you’re a politician who’s proud of making progress in solving the problem, how badly do you want to know whether it’s working or not?

The key issue is being able to police the claims that countries make when pledging to cut greenhouse gases.

I might not use the word policing. Verification. This came to loggerheads between (Chinese premier) Wen Jiabao and Barack Obama in Copenhagen. It’s a problem everyone wants to get their arms around, but nobody’s done it yet.

I’m curious for your broad perspective on where the issue of climate change lies now — post-Copenhagen, post-Climategate (the criticism arising from the contents of several climate scientists’ stolen e-mails). Are we at the point of fatigue? Has the big legislative push been made and failed?

Climategate was unfortunate. But I don’t think it changes the thrust of the science significantly. It’s such a contentious issue that people who’d like not to believe the climate is changing would seize on things like that.

The main issue is what’s happening. And we tend to lose focus of that. That the atmosphere is changing is incontestable.

What was your takeaway from going to Copenhagen? You made a push there on the issue of verifying emissions. Did it get traction?

The opportunity the negotiations provide for scientists is that the world’s press is there, the attention is on it. If you stand on your soapbox and you’re not at the climate negotiations, no one will listen to you. But if you stand on it at the climate negotiations, someone will listen. Who do you want it to get out to? The average citizen. And the leaders. Both are possible — but difficult. I do think it’s fair to say there’s a reasonable chance that Barack Obama has read about [verification].

— Interview conducted and edited by ROB DAVIS

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