Once a professor, always a professor.

Steven Chu, the energy secretary, winner of the Nobel Prize and former physics teacher at Berkeley, spoke tonight at a Washington fundraising dinner for Conservation International, the global NGO.

Actually, he delivered a lecture, deploying a long, detailed PowerPoint presentation, with charts and graphs explaining temperature fluctuations over decades, rising CO2 concentrations in the atmosphere over the last 800,000 years, changes in sea levels, payback for investments in energy efficiency, even a diagram of a new battery technology that included this caption:

Battery about to charged: Positive Mg ions and negative Sb ions are dissolved in electrolyte (green)

Battery fully charged: Mg (blue) and SB (yellow) become the anode and cathode

It was another one of those all-too-frequent moments when I wish I had taken more science classes in college. And remembered why I hadn't.

By coincidence, Michele Obama visited the energy department earlier in the day and said, "My husband loves his Cabinet. He was extremely excited that he had a real nerd on his team. He talked about it for weeks on end."

It's easy to see why the cerebral president and his brainy energy secretary would bond.

Chu wasn't spellbinding at the CI dinner but in this city of politicians and special interest groups, with climate change legislation again on the front burner, it was actually refreshing to study a Power Point instead of being bombarded with talking points. Spin doctors marshal facts to support their arguments. Chu starts with the science and works his way from there to solutions.

He argued for three broad approaches to the climate crisis – a major commitment to energy efficiency requiring government regulations and financing, changes in forestry and agricultural practices and still-to-be-discovered breakthroughs in clean energy technology. Some highlights:

Energy efficiency: Chu said market failures –- among them lack of knowledge and lack of financing -– stand in the way of efficiency to commercial and industrial buildings and to homes which deliver relatively quick paybacks.

"How many University of Chicago economists does it take to change a light bulb?" he asked.

"None," he replied. "If the light bulb needed changing, the free market would have done it."

Calling himself "an energy conservation nut," Chu displayed a chart showing that efficiency standards for refrigerators adopted years ago in California had reduced annual energy costs, on average, from $1272 to $462 a year. "Even though refrigerators have gone up in size, energy usage has gone down by 70%," he said.

The simple step of painting roofs white could cut air conditioning costs by 15% in warm weather regions, he noted.

Forestry and agriculture: Together, deforestation and agriculture account for about 31% of annual greenhouse gas emissions, Chu (and his pie chart) said. "To achieve our energy and climate goals," he said. "We've got to solve deforestation and change our agricultural practices."

Some of this can be quite complicated: Rich countries, rather than cutting their own emissions, could finance alternative livelihoods for people in the tropics so they don't cut down trees. Other ideas are simpler: If you provide poor people in the global south with solar or highly-efficient cook stoves, then they don't have to burn as much wood to heat their homes or cook food. An efficient stove avoids the equivalent of two tons of carbon emissions, about half the amount emitted by a typical car in a year.

Protecting forests is "the least expensive way to decrease carbon emissions," Chu said.

Technology breakthroughs: The energy department recently announced $151 million in grants for transformative technology under a program called ARPA-E, which stands for Advanced Research Projects Agency-Energy, and is modeled after the federal defense spending project that led to the invention of the Internet. "We don't have all the technologies we need," Chu said.

Interestingly, I listened to Chu chat with several venture capitalists just before the dinner in Union Station and he asked them how they thought his department was doing at reviewing grant applications from startup firms. He said he had a feeling that the DOE staffers who review the grants might be too conservative and risk-averse, and that he intended to urge them to take more chances on long-shot ideas that could deliver big breakthroughs.

Only near the end of his talk did Chu revealed a bit of the passion that he brings to the topic of climate change.

The costs of enacting climate-change legislation, he said, are about 45 cents a day for a family of four.

And the cost of doing nothing?

One is that the U.S., which recently fell behind China in high-tech manufacturing, will fall even farther behind. "Very recently, China turned a corner," he said. "China and other countries will pass us by."

"And the other cost," he said, "is that we will expose our children and grandchildren to unconscionable risk."

No PowerPoint slide was required to explain that.

GreenBiz.com Senior Writer Marc Gunther is a longtime journalist and speaker whose focus is business and sustainability. Marc maintains a blog at MarcGunther.com. You can follow him on Twitter @marcGunther.