While surface temperatures across most of the globe are on the rise, the eastern U.S. appears to be slowly cooling. Scientists say the trend could be a result of increasing cloud cover triggered by warming Pacific waters. Much of the Earth has warmed over the last half-century, but the eastern half of the United States has shown a cooling trend. Eastern U.S. temperatures have displayed a cooling trend of 0.1 degrees Celsius per decade, while global temperatures warmed by that same amount from 1950 to 1997. The researchers used a computer climate model to see if this regional cooling could be caused by changes in sea surface temperature.
Clouds appear bright white when viewed from above because they reflect sunlight back into space.
The ground and atmosphere below these clouds absorb less solar radiation and therefore release less heat into the environment. Image taken by NASA's SeaWiFS satellite. The brightness of a cloud causes a large percentage of incoming solar radiation to be reflected back into space, thus keeping the atmosphere cooler than if the cloud wasn't there. Using the climate simulations, Robinson found the amount of water vapor in the Gulf of Mexico follows closely the water vapor released by the warm sea surface temperatures in the Pacific Ocean. Water vapor from the Pacific moves east to the Gulf of Mexico and is then carried over the eastern U.S. by the clockwise circulation around an Atlantic subtropical high pressure system.