Pakistan, July 17 -- Soccer had a fierce reckoning with heat at the recently concluded FIFA Club World Cup in the United States - a sweltering preview of what players and fans may face when the U.S. co-hosts the World Cup with Mexico and Canada next summer.

With temperatures rising worldwide, scientists warn that staging the World Cup and other soccer tournaments in the Northern Hemisphere summer is getting increasingly dangerous for both players and spectators. Some suggest that FIFA may have to consider adjusting the soccer calendar to reduce the risk of heat-related illnesses.

"The deeper we go in the decade, the greater the risk without considering more dramatic measures, such as playing in the winter months and/or cooler latitudes,...