Former U.S. Energy Secretary Steven Chu has warned the world is on a “collision path” with climate damage – likening today’s course to the Titanic’s final hours – and pressed for immediate policies to speed deployment of proven solutions, especially solar plus long-duration battery storage.

A catastrophic outcome is not inevitable, Chu said on the opening day of Harvard Climate Action Week on September 15. He emphasized that the technologies to turn the climate ship around already exist or are well under development. But the rate at which nations are adopting the right technologies and policies is lagging far behind what is necessary.

Chu, the William R. Kenan Jr. Professor of Physics at Stanford University, received the 1997 Nobel Prize for laser cooling and optical trapping of atoms. He served as Energy Secretary from 2009 to 2013.

“Holding steady is not good enough,” he said, speaking at the first Climate Crossroads: Debating Energy’s Next Frontier lecture series.

Because the impact of greenhouse gases in the atmosphere is cumulative, the climate effects of today’s emissions will not be fully felt for generations. Measurements taken by buoys around the world show that 90 percent of the accumulated heat is stored in the deep ocean, rising only slowly to warm the air.

Chu described in detail the potential and limitations of different technological solutions. He emphasized that solar power is now the cheapest form of electricity production and, when combined with batteries or pumped storage, can provide a significant portion of the world’s power needs. “Long-term energy storage is crucial, absolutely crucial,” he said.

Rapidly spreading battery storage offers great potential. With the right incentives, the growing tide of electric vehicles could provide a major source of backup storage for the grid, he said: “We just need the regulation.”

Some emissions sources are harder to address than others. Twenty-five to 30 percent of global greenhouse gas emissions come from food production, and “we don’t have a solution” to that issue. “It’s an unsolved problem,” he said.

Construction materials, especially concrete and steel, are also major greenhouse gas producers, but solutions do exist, he said. For example, laminated wood construction can be used for buildings up to 20 stories; this not only avoids the emissions associated with steel and concrete production, but the wood itself also sequesters carbon. While people may think of wood as less durable, there are wooden buildings in London that are more than 1,000 years old, he said.

Hydrogen has great potential as a substitute for existing liquid and gaseous fuels, and there is promising work exploring natural sources of hydrogen underground, but the extent of this resource is still not well known. Transporting hydrogen – such a “leaky molecule” – remains a challenge.

Modular nuclear fission reactors are promising, he said. Such reactors could be built in a factory and trucked to their sites, which is far more efficient than building reactors in place. They could be designed to be “walk-away safe,” meaning they would not rely on any external power or water supply to prevent a meltdown. These could operate safely for up to 80 years; then the entire reactor would be buried and sequestered safely underground, limiting the need to transport waste to a central repository in Utah – a plan Chu described as “a really bad site.”

Fusion has potential, but the expense is likely to remain high, he said, and practical applications of that technology could still be 30 years off. Economic carbon sequestration – to enable continued use of fossil fuels while drastically reducing their greenhouse gas emissions – is possible but faces many obstacles.

While these promising technologies exist, he said, without stronger action and regulation “the world is still on a collision path.”

Continuing his Titanic analogy, Chu added: “It’s going to take 60 or 75 years to determine the outcome of this ship. It’s not going to be fast. So we should do a hard-right rudder right now, because you need all the time” for the effects to take hold.