Earth has a message for global warming skeptics: Its effects are starting to appear where it really counts. Antarctic glaciers are melting faster than scientists had thought. The tropical "firebox" that drives the atmosphere's weather machine is running hotter. These two developments could significantly change our planet's weather patterns.
Roughly speaking, Earth's weather machine is like a steam engine with a boiler (the tropical and subtropical oceans) and a condenser (the cooler higher latitudes). Masses of water vapor flow into the atmosphere from the boiler and travel north or south. These masses condense into rain or snow, releasing the heat they absorbed when they evaporated. Much of the water finds its way to the polar seas and flows back to the tropics.
This interchange maintains our planet's distribution of solar heat and fresh water. Research suggests that this heat/moisture distribution is changing, which could shift the location and timing of rainfall, droughts, and floods.
The telltale signal: salt. When the boiler evaporates seawater, it leaves salt behind. The hotter the boiler, the saltier the water. Indeed, the tropical seas across the Atlantic are getting saltier, according to a Nature article last December by Ruth Curry at the Woods Hole Oceanographic Institution in Massachusetts and colleagues - and an update by her last month.
To suggest that this condition is causing the rise in Atlantic hurricane activity would be a stretch. But Dr. Curry and her associates think the accumulation of salt probably is linked to global warming.