Hours before Donald Trump announced that the United States would abandon the carbon-reduction treaty signed in Paris, the U.N. Secretary-General António Guterres went on Twitter to declare that climate change is “unstoppable.” The clear message, reinforced by the leaders of the EU and China, is that the rest of the world will continue with the Paris Treaty without the participation of the United States. Their resolution will quickly stumble upon three incontrovertible truths.

Firstly, the Paris climate agreement will be the most expensive global agreement ever. Reducing emissions without accessible and effective substitutes for fossil fuel means more expensive energy and lower economic growth. Estimated calculations using the best peer-reviewed economic models show that the global price of the treaty pledges would reach $1 billion to $2 billion a year, starting in 2030. The treaty also depends on delivering $100 billion a year in “climate aid” to developing countries from 2020, a promise that came originally from the United States.

These enormous costs have jeopardized the treaty since it was signed. It is not difficult to imagine other leaders resisting slower growth, or rich nations that refuse to give the promised aid.

Secondly, the agreement was always going to have a small impact on temperatures, but without the U.S. it will have even less of an effect.

The little that we do remember from the Paris climate agreement is the energetic rhetoric of the leaders who said they were committed to keeping the temperature increases at less than 1.5 degrees Celsius. It was a surprising compromise.

But the speech masked the reality that the true promises of the carbon reduction treaty – which are not legally binding – only last until 2030 and only commit the world to achieving less than 1 percent of the carbon emission reductions that would be needed to maintain temperature increases below 2 degrees Celsius. In other words, the Paris climate agreement leaves 99 percent of the problem unchanged.

No doubt we will hear many politicians preach about future cuts, but the experience is not a good omen for such promises. The Kyoto Protocol was sold to the world in 1998 as the solution to global warming and began to crumble almost as quickly as Paris.

Thirdly, and what is more problematic, green energy is far from being ready to supplant fossil fuels.

The rhetoric is inexorably optimistic: a typical quote from Bloomberg New Energy Finance chairman Michael Liebreich is that “renewable energy is entering the era of undercutting” fossil fuel prices. We have heard this for decades, but it remains at the level of illusion. Green energy is so inefficient that its implementation depends almost entirely on subsidies. Spain was paying almost 1 percent of its gross domestic product in subsidies for renewable energy, more than it spends in higher education. When it reduced the subsidies, the new production of wind energy collapsed completely.

Subsidizing the implementation of renewable energy to reduce our carbon dioxide emissions has been a dead end. After hundreds of billions of dollars in annual subsidies, we only get, according to the International Energy Agency, 0.5 percent of the global energy needs of wind and 0.1 percent of photovoltaic solar energy. Even if by 2040 the Treaty of Paris had remained fully in force, after spending $3 trillion in direct subsidies, the International Energy Agency expects that wind and solar energy will only provide between 1.9 percent and 1 percent of the world’s energy.

All of this means that it is absurd for world leaders to continue to be obsessed with the Paris climate agreement, because it will not only fail, but will be enormously costly and will do almost nothing to solve climate change.

President Trump's decision provides an opportunity to rethink the approach. What is desperately needed is a significantly greater investment in research and development of green energy, so that renewable technology can compete with fossil fuels. Initiatives such as the Breakthrough Energy Coalition, in which Bill Gates has invested $2 billion, is a good start. But a panel of Nobel Prize winners convened for the Copenhagen Consensus on the climate project found that we should not only double the funding of research, but increase it more than sixfold to $100 billion a year.

A commitment to research and development of green energy is what the planet now needs from world leaders, much more than bravado.

Bjorn Lomborg is the director of the Copenhagen Consensus Center and the author of the best-selling "The Ecologist Skeptic" and "Cool It." Considered one of the 100 most influential people in the world by Time magazine, one of the 75 most influential people of the 21st century by Esquire magazine and one of 50 people capable of saving the planet by the U.K.'s Guardian newspaper. He is also a visiting professor at the Copenhagen Business School.