The Wall Street Journal

By: Bjorn Lomborg

June 16, 2017 10:36 a.m. ET

Environmentalists were aghast when President Donald Trump withdrew the U.S. from the Paris climate treaty, with some declaring that the very survival of our civilization was at stake. But is the Paris accord really all that stands between the planet and the worst of climate change? Certainly not.

This is not to deny that President Trump’s announcement was problematic. He failed to acknowledge that global warming is real and wrongly claimed that China and India are the “world’s leading polluters.” (China and the U.S. are the largest emitters of carbon dioxide, and the U.S. is the biggest per capita.) It was far-fetched for him to suggest that the treaty will be “renegotiated.” Worse, the White House now has no response to climate change.

But the global consensus about the Paris treaty is wrongheaded too. It risks wasting huge resources to do almost nothing to fix the climate problem while shortchanging approaches that promise the most transformative results.

Consider the Paris agreement’s preamble, which states that signatories will work to keep the rise in average global temperature “well below” 2 degrees Celsius and even suggests that the increase could be kept to 1.5 degrees. This is empty political rhetoric. Based on current carbon dioxide emissions, achieving the target of 1.5 degrees would require the entire planet to abandon fossil fuels in four years.

But the treaty has deeper problems. The United Nations organization in charge of the accord counted up the national carbon-cut pledges for 2016 to 2030 and estimated that, if every country met them, carbon dioxide emissions would be cut by 56 gigatons. It is widely accepted that restricting temperature rises to 2 degrees Celsius would require a cut of some 6,000 gigatons, that is, about a hundredfold more.

The Paris treaty is not, then, just slightly imperfect. Even in an implausibly optimistic, best-case scenario, the Paris accord leaves the problem virtually unchanged. Those who claim otherwise are forced to look beyond the period covered by the treaty and to hope for a huge effort thereafter.

The treaty commits nations to specific and reasonably verifiable (but nonbinding) cuts in carbon emissions until the year 2030. After that, nothing really is concrete, for a very understandable reason: Could you imagine a carbon-cutting promise made by President Bill Clinton being fulfilled by Mr. Trump? Could you see a Democrat in 2035 feeling honor-bound by policies set by Mr. Trump today?

Now ask the same sort of questions about every country that has signed the treaty. Rose-tinted hopes for the accord’s success rely on heroic assumptions about what tomorrow’s world leaders will do. If what we need is a carbon diet, the Paris treaty is just a promise to eat one salad today, pushing all the hard self-restraint far into the future.

History gives us cause for skepticism about overly optimistic forecasts, even over much shorter spans. In 1993, Mr. Clinton committed the U.S. to cutting emissions by 2000, but he ditched the promise seven years later. In 1992, the industrialized nations promised that they would lower their emissions to 1990 levels by 2000. Nearly every country failed. Before the Paris treaty, the Kyoto Protocol was sold as a key part of the solution to global warming, but a recent study in the Journal of Environmental Economics and Management shows that it achieved virtually nothing.

In the wake of Mr. Trump’s exit from the Paris treaty, there have been many claims that solar and wind energy will soon be ready to power the world. This also isn’t true.

Just 0.6% of the world’s energy needs are currently met by solar and wind, according to the International Energy Agency. Even with implementation of the Paris treaty, solar and wind are expected to contribute less than 3% of world energy by 2040. Fossil fuels will go from meeting 81% of our energy needs to three-quarters. The energy expert Vaclav Smil of the University of Manitoba puts it bluntly: “Claims of a rapid transition to a zero-carbon society are plain nonsense.”

Though there are contexts in which solar and wind energy are efficient, in most situations they depend on subsidies. These will cost $125 billion this year and $3 trillion over the next 25 years, to meet less than 3% of world energy needs. If solar and wind truly out-competed fossil fuels, the Paris treaty would be unnecessary.

On this issue, even the climate scientist James Hansen, who advises former Vice President Al Gore, agrees: “Suggesting that renewables will let us phase rapidly off fossil fuels in the U.S., China, India, or the world as a whole is almost the equivalent of believing in the Easter Bunny and Tooth Fairy.”

Advocates of global carbon cuts fail to acknowledge the wider costs of subsidizing certain energy sources. A global pact in which governments promise to use more expensive energy ensures that the world economy will develop at a slower pace. This adds up to an immense expense: $1 to $2 trillion by 2030 and each year for the rest of the century, mostly in lost GDP growth. This represents $150 to $300 for every person in the world, every year.

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Taxpayers in wealthy nations may well ask whether this money could be better spent on schools, hospitals or care for the elderly. In developing countries with more immediate problems, there are definitely more productive ways to use the money. A global poll of almost 10 million people conducted by the U.N. finds that climate change is the lowest priority behind health, education, food and 11 other priorities. Work by the Copenhagen Consensus, which I oversee, has highlighted the many investments in nutrition, health and other areas that would help vulnerable communities much more than would any possible benefits from carbon cuts.

Acknowledging the Paris treaty’s flaws does not mean endorsing the Trump administration’s apparent intention to ignore climate change. Real progress in reducing carbon emissions and global temperatures will require far-reaching advances in green energy, and that will mean massive investment in research and development—an annual global commitment of some $100 billion, according to analysis by the Copenhagen Consensus. When green energy is economically competitive, the whole world will rush to use it.

The real misfortune for the planet isn’t that Mr. Trump withdrew the U.S. from the Paris treaty. Rather, it is that his administration has shown no interest in helping to launch the green-energy revolution that the world so urgently needs.

—Mr. Lomborg is the president of the Copenhagen Consensus Center and the author of “The Skeptical Environmentalist” and “Cool It.”