Global warming scare stories, like the one that links it to declining wheat production, do more harm than good.

Scare stories have been an integral part of the global warming narrative for a long time. Back in 1997, Al Gore told us that global warming was making the El Niño winds stronger and more severe. That has not happened. Greenpeace and many others have told us for years that we will see more violent hurricanes. In fact, over the last six years, global hurricane energy has dropped to its lowest level since the 1970s, while the United States has had the longest absence of severe hurricanes ever (Sandy was a "superstorm, " not a hurricane, when it hit the vulnerable East Coast in October).

But the scares do not stop there. The World Wildlife Fund declared in 2004 that polar bears would go extinct by the end of the century, and that the calamity would start in Hudson Bay, where they would stop reproducing by 2012. The bears are still reproducing. And stories abound of global warming bringing malaria to Europe or Vermont. But here, too, the evidence contradicts such fears;in fact, malaria deaths have dropped more than 25 per cent over the last ten years.

It is understandable that pundits, worried about global warming and frustrated with the near-absence of political interest or solutions, see exaggeration as an easy way to garner attention. The problem is that when these scare stories are later shown to be wrong, people become less willing to listen even to reasonable arguments about global warming. Indeed, scepticism about global warming has gone up, not down, as the false alarms have become increasingly high-pitched.

Moreover, by casting every problem as mainly caused by global warming, the solution almost automatically becomes cutting CO2 emissions, though this often is the slowest and costliest way to achieve the least good.

Consider the newest global-warming exaggeration : an article from Newsweek shrilly claiming that rising temperatures are heralding "The End of Pasta. " All of the major grains - rice, corn, and wheat - are already suffering from global warming, the article explains, but wheat is the most vulnerable to high temperatures. So, as warming increases, we will see "shockingly high prices" for pasta and bread. Its central message is straightforward : "If humans want to keep eating pasta, we will have to take much more aggressive action against global warming. "

The argument is almost entirely wrong. Yields of all major crops have been rising dramatically in recent decades, owing to higher-yielding crop varieties and farmers' greater use of fertiliser, pesticides, and irrigation. Moreover, CO2 acts as a fertilizer, and its increase has probably raised global yields more than 3 per cent over the past 30 years.

But increasing temperatures will harm some crops while benefiting others. Because most crops are already grown where they do best, it is not surprising that climate models show that temperature increases will reduce yields if farmers change little or nothing. In fact, farmers will adapt, especially over the course of a century. They will plant earlier, grow more heat-loving varieties, or change their crop entirely. And, as growing wheat and grains becomes possible higher north in Canada and Russia, even more opportunities will open up.

The largest study, conducted by the International Institute for Applied Systems Analysis, includes temperature impacts, CO2 fertilisation, and adaptation, and projects a 40. 7 per cent increase in grain production by 2050. Without global warming, production might have been half a percentage point higher. With global warming, prices will most likely be slightly lower. Our linguine supplies are safe.

Of course, this does not mean that global warming has no impact on crops. But cutting back on CO2 is a particularly ineffective way to help the world's poor and hungry. Even if we managed - at very high cost - a significant reduction, we would achieve only a slightly slower rise in global temperatures. Meanwhile, by embracing biofuels, for example, we are essentially burning food in our cars, which drives up food prices and exacerbates hunger.

We could do much more good if we focused on allowing poor countries to use the benefits of extra CO2 fertilisation while adapting to the problems caused by higher temperatures. That means greater investment in crop research to produce more robust and higher-yielding varieties, as well as making more irrigation, pesticides, and fertiliser available. Furthermore, even the poorest parts of the developing world will be much richer by midcentury;most people will live in cities and earn their incomes outside agriculture. As in today's developed countries, their consumption of wheat will not depend on whether it is produced in their own country, but on global food prices and local income.

This underscores the importance of striving for free trade, thereby enabling cheaper agricultural production while increasing wages in nonagricultural sectors. Global-warming scare stories merely shift our focus to the least effective ways to help.


The writer teaches at Copenhagen Business School;Copyright: Project Syndicate, 2013