LONDON ¨C A report published in the journal Space Weather this past week makes for sobering reading. In four scenarios envisaging the economic impact of a solar storm, the mildest triggers a daily loss to the U.S. economy of $6.2 billion, or 15 percent of daily output; the worst case sees a cost of $41.5 billion, wiping out every dollar the world¡¯s largest economy generates each day.

What sort of event could do that? Something, say, along the lines of the massive explosion on the sun akin to ¡°thousands of nuclear bombs exploding at the same time¡± that happened on March 10, 1989, according to the U.S. National Aeronautics and Space Administration. The explosion released a vast cloud of solar plasma that raced toward the earth at 1.6 million kilometers an hour. When it hit Canada, the electrically charged storm knocked out Quebec¡¯s power grid, leaving 6 million people without power for nine hours.

The World Economic Forum¡¯s annual assessment of global risks, published last week, rates extreme weather events as the most likely risk to the world and the second-most impactful (detonating weapons of mass destruction was perceived as the risk with the greatest consequences, though deemed unlikely to happen).