The UN secretary-general declares that climate poses “sweeping risks” while we’re heading toward a “cataclysm”. Yet, according to the IPCC, the total cost of climate change by the 2070s would be less than 2 percent of world GDP. This is a problem but not the end of the world. Weigh the 2 percent loss to the 800 percent richer the UN expects the world to be in 2070.

Compare it to the very real challenges that the world faces today. About 1.2 billion people are still living in abject poverty, and they need economic growth. Over the past 30 years, China has lifted 680 million people out of poverty — the biggest poverty reduction rate ever — and it did so with lots of cheap if very polluting coal.

Yet well-meaning Western leaders will descend on New York to reiterate the solution to global warming that has failed for more than two decades: we must switch to renewables, they will say.

But this is hypocritical. According to the International Energy Agency, the rich world gets just 8 percent of its energy from renewables and just 0.9 percent from solar and wind. In contrast, Africa gets almost 50 percent from renewables, but that is because it is poor — the renewables are mostly firewood that kills more than half a million people a year with indoor pollution, forces women to waste 10 hours each week collecting firewood and contributes to deforestation.

Not surprisingly, when African leaders came to Washington at the invitation of US President Barack Obama recently, they said they wanted to use more coal. Even the climate-worried World Bank president accepted that “there’s never been a country that has developed with intermittent power”.

A new study by the Center for Global Development shows the cost of pushing renewables. Spending $10 billion on renewables in Africa can lift 20 million people out of poverty. But spending $10 billion on gas would lift 90 million people out of poverty. Insisting on renewables means deliberately leaving 70 million people in poverty.

This does not mean we shouldn’t tackle global warming. But we need to realize renewables are still too expensive. Some campaigners claim that renewables are “already competitive”. But this is wishful thinking — if they were, they wouldn’t need subsidies. Look at Spain. With lower but still substantial wind subsidies, Spain has this year put up just one wind turbine.

Instead of wasting billions of dollars in subsidies, we should invest much more in green innovation to reduce the cost of future generations of clean energy. When we innovate the price of green energy below fossil fuels, everyone will switch.

But in a world where 4 million people die each year from burning firewood and dung cakes in open fires inside homes, while poverty, lack of clean water, infectious diseases, poor education and too little food afflict billions, we cannot with a straight face claim that climate should be our top priority.

The author is director of the Copenhagen Consensus Centre.