At the UN Climate Summit in Glasgow (COP26), President Biden is projecting the image of a climate trailblazer: "The United States is not only back at the table, but hopefully leading by the power of our example."

But a pledge of expensive emission cuts by American elites isn't going to make much of a difference, particularly when neither voters back home, nor leaders of developing countries, are willing to give up cheap and reliable energy.

Historically, most climate promises have fared badly. Since negotiations started almost three decades ago, grand promises have been followed by spectacular letdowns and large emission increases. In a startlingly honest review of climate policies of the last decade, the UN Environment Program found that global emissions since 2005 were indistinguishable from business as usual. For all the last decade's many lofty climate promises, including the Paris agreement, emissions have increased as if there is no climate policy whatsoever.

It is easy and popular for politicians to talk up the dangers of climate change and promise safety with grandiose policies for 2030 or 2050. But it is much less popular when it is time to ask voters to pay for these draconian climate policies. When French president Emmanuel Macron enacted a tiny gasoline tax, he was met with years of yellow-vest protests. In June, Swiss voters said no to a new carbon tax, and the UK government backed off on even introducing a new, costly mandate to replace gas-fired home heating.

In Glasgow, Biden has restated his goal to have the US emissions net-zero by 2050, but this will have a surprisingly small impact. Even if he managed to get the US to zero today and keep it there for the rest of the century, the standard UN climate model shows this would only reduce the temperature rise by the end of the century by 0.3°F.Yet doing so would be spectacularly costly. A new study in the journal Nature shows that reducing emissions 95 percent by 2050 – almost the President's promise of net-zero – would cost 11.9 percent of GDP or more than $11,000 present-day dollars for each American citizen, every year.

These costs are far higher than what most people are willing to spend – in one Washington Post survey, a majority was unwilling to spend even $24 per year.

Most emissions in the 21st century will come from China and India along with poor countries in Asia, Africa and Latin America. It is important to design climate solutions that work for them. For developing countries, the current climate approach of paying large sums for achieving negligible temperature reductions in a hundred years is spectacularly unattractive. As their citizens live off as little as a few hundred dollars annually, they understandably care more about their kids surviving malaria and malnutrition. They want to escape misery, poor education and low job prospects. They care about lifting themselves and their children out of poverty with strong economic growth.

Just days before the Glasgow summit, 24 emerging economies including China and India said that the demand for them to achieve net zero by 2050 was unjust because it stopped poor countries from developing their economies. The President of Uganda put it even more bluntly: "Africans have a right to use reliable, cheap energy."

If the rich world wants the developing world to cut their emissions, it will have to pay. As India's Environment Secretary Rameshwar Prasad Gupta said in a stunningly honest interview: "If you want that I don't emit carbon, then provide finance. It will be much more than $100 billion per year for developing nations."

In Glasgow, there is talk of the rich world paying $750 billion each year or even $1.3 trillion. Most rich world voters simply won't pay that kind of bill.

Instead, we need a smarter way forward. We should focus on innovation to make green energy more effective. While politicians often claim green is already cheaper, they are belied by the evidence – if it was cheaper, we wouldn't need years of haggling to get hundreds of nations to grudgingly promise more green.

World leaders should dramatically ramp up investment into research and development of cheaper, low-CO₂ energy, from fusion and fission, solar, wind and batteries to second generation biofuels and many other brilliant ideas. Not only would it be much cheaper than current climate policies, it would also drive major breakthroughs for new, better and greener energy.

At COP26, Biden would be well-advised not to follow the decades-long tradition of empty promises with eyewatering costs and little climate benefits. Instead, he should lead the world by drastically ramping up funding for green innovation. If we can innovate the price of green energy below fossil fuels, everyone will switch.

Bjorn Lomborg is President of the Copenhagen Consensus and Visiting Fellow at Stanford University's Hoover Institution. His latest book is "False Alarm: How Climate Change Panic Costs Us Trillions, Hurts the Poor, and Fails to Fix the Planet."