It was a memorable conclusion to the now-decade-old movie An Inconvenient Truth: After former Vice President Al Gore finished explaining the horrors that would be created by climate change, he said we hold the solution in our grasp — if only we have the will to follow it.

That solution, he said, included ramping up renewable energy as one important method of reducing greenhouse gas emissions.

But for a while there, that message appeared to be lost amid the Great Recession, as well as failed efforts to bring the world to a consensus on reducing emissions.

That consensus has now begun to take shape, and the marketplace has responded. “The renewable energy industry has experienced dramatic growth over the last couple of years,” says Arthur van Benthem, a professor of business economics and public policy at Wharton.

Wind and solar power prices have plunged, and projections about future wind and solar deployment have become decidedly more optimistic. Many well-respected sources have calculated that the cost of renewable generation is approaching parity with the cost of fossil-fueled electricity in a large number of places, van Benthem notes.

But van Benthem and other observers say a big increase in renewables is only one piece of the climate puzzle.

The growth in wind and solar will undoubtedly continue, but even at massive growth rates, it will take many decades to replace existing power plants, van Benthem says. “There’s inertia in the energy system, and coal-fired generation, and other forms of generation, don’t just disappear immediately,” adds Nathan Serota, senior analyst at Bloomberg New Energy Finance.

Which is to say that while one of Gore’s wishes appears to be coming to fruition, the climate change solution remains incomplete. The growth of renewables and solving the climate crisis: “These are two different things we’re talking about,” Serota points out.

Outpacing Expectations

Gore has compared the rise of renewables to the wireless telephone: As innovations have arisen, sales have outpaced anyone’s expectations.

In 2010, there were 35 gigawatts of wind capacity added globally; in 2015, 58 gigawatts were added, Serota says. And in 2010, there were just 18 gigawatts of solar added around the globe; in 2015, there were 56 gigawatts added, he notes.

“In the U.S., the momentum is on the renewable side in a way that it hasn’t been.”–Nathan Serota

That comes as the average U.S. contract price for wind has dropped an average of 60% since 2009, Serota says. Wind prices are regularly being signed at rates below the regular “brown” grid power, Serota points out. And solar module costs have fallen 69% since 2010, he adds.

Projections for future implementation, meanwhile, have taken a quantum leap. Bloomberg expects total installed solar will more than quadruple between now and 2022, on the strength of continued cost declines. And the projection made in the year 2000 by the International Energy Agency of how much wind power capacity there would be in 2040 has been revised upward, fivefold.

“In the U.S., the momentum is on the renewable side in a way that it hasn’t been,” Serota says.

That’s in part because of the renewal of tax credits at the end of 2015, which occurred as part of the deal that kept the government running, Serota says. Those credit extensions will guarantee continued growth in wind and solar over the next five years, Serota predicts.

In addition to cheaper panels, another important reason for the rise of solar in the U.S. is that companies such as SolarCity and Sunrun have found efficient ways to acquire customers, process the applications and install the panels on people’s roofs, van Benthem says.

On the policy side, the main driving forces are tax credits and renewable energy portfolio standards, van Benthem says. The latter are state-level mandates that a fixed amount or percentage of electricity be generated from renewable sources.

Nevertheless, stock in solar companies have traditionally been volatile, and this year has been no exception. Investors have expressed concern that major companies like SunEdison, SolarCity and Yingli have taken on too much debt, sending stock prices falling.

One Part of a Broader Solution

Gore has long acknowledged, as he did in An Inconvenient Truth, that ramping up renewable energy would only be a part of solving the climate change challenge. Gore also spoke of higher-mileage cars, and innovations in the transportation system, among other factors.

“It’s a clean energy miracle process. It will take many years.”–John Voelcker

Indeed, Serota says the power generation industry, significant as it is, is only responsible for a part of the nation’s greenhouse gas emissions. The other sectors combined — which include transportation, heating and cooling, cement making and industry — make up a larger share of emissions than power, he says.

Media reports have hailed a revolution for electric cars, with the falling price of battery packs, and an increasing second life for the battery packs as energy storage units.

John Voelcker, editor of GreenCarReports.com, says electric vehicles can help nations meet their emissions reductions targets. But for electric vehicles, the revolution isn’t quite here yet, Voelcker notes.

Sales of electric vehicles have been far lower than what some of the more optimistic observers in the industry had projected a few years back, Voelcker says. That’s because the range of the first generation of electric cars, now six years old, have been about 60-80 miles, he says. That’s a fine range for everyday driving purposes, but people want the security of knowing they could drive further if they needed to, he points out.

Chevy’s Bolt and the upcoming Tesla 3 are expected to have ranges of 200 miles, for the same price at which cars were selling six years ago, which should help, he says.

Other factors have held back electric vehicles, Voelcker notes. Low gas prices haven’t helped make the price argument to potential buyers. Dealerships generally take the path of least resistance and guide consumers toward more traditional, less expensive cars, especially since it takes longer to make a sale of an electric vehicle, he says.

And consumers will probably wait until electric vehicles are more competitive with their gas burning counterparts before buying them in greater numbers, Voelcker adds. That day is on its way — but it’s not here yet.

“I would say it’s a clean energy miracle process. It will take many years,” Voelcker says.

Growth Projections

Van Benthem has his own concern about electric vehicles: Right now, the electricity grid, including in the Midwest, still uses plenty of coal.

“Of course, the future grid will get cleaner as solar takes off,” van Benthem says. This, he adds, makes electric vehicles attractive in that they could plausibly lead to an almost pollution-free source of transportation, and batteries.

But for now, “policy makers have continued to ignore that they are massively over-counting their gains when presenting EV’s as ‘emissions free’ technologies,” van Benthem says.

Global growth projections for renewables have been linked to efforts among nations to meet the goals set out in the Paris climate change agreement, reached in December 2015. As part of the agreement, every nation pledged to reduce greenhouse gas emissions.

“As with any environmental problem, economists have long realized that the market cannot solve the climate crisis by itself.”–Arthur van Benthem

The cost declines in renewable energy are part of what made the Paris agreement possible, Serota says. They didn’t make as much business sense during previous climate talks, he points out.

Nevertheless, climate scientists say the agreement will only get the world halfway toward cutting the necessary emissions to avoiding the worst consequences, like flooding, droughts, food shortages and violent storms.

“The breakneck growth in renewables is certainly enabling relatively unprecedented declines in power-sector carbon dioxide emissions,” Serota notes. “But even at the current pace at which we’re going, it will likely leave us below the emissions trajectories that the U.N. and the climate science community have said we need to achieve if we are to avoid dangerous climate change.”

Even if renewables continue on the current trend and occupy a greater share of overall power use, the ongoing use of fossil fuels and other emitting sources “may still leave us with a really serious set of problems having to do with climate change,” says Brian Berkey, professor of legal studies and business ethics at Wharton.

In order for a true renewable energy revolution, governments need to cap fossil fuel emissions, says Noam Lior, professor of mechanical engineering and applied mechanics at Penn. But there is tremendous opposition from the oil industry, he says. The Obama administration attempted to cap emissions through the Clean Air Act, but the legislation is under review by the Supreme Court.

With low shale oil and gas prices in this country, it doesn’t help that we are exporting it to places like Turkey, Egypt and Europe, he says. Those kinds of moves suppress interest in renewables, Lior notes.

If government is serious about solving the problems that result from climate change, a cap-and-trade or carbon tax system will be necessary “to induce green innovations and foster emissions abatement technologies across a wide variety of industries,” van Benthem says.

“As with any environmental problem, economists have long realized that the market cannot solve the climate crisis by itself,” van Benthem notes.