Study provides independent source for assessing global warming impacts
By Bob Berwyn
SUMMIT COUNTY — A comprehensive study of global satellite data shows surface temperatures of large lakes around the planet warmed significantly in the past 25 years in response to climate change.
Researchers Philipp Schneider and Simon Hook of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., used satellite data to measure the surface temperatures of 167 large lakes worldwide, finding an average warming of 0.81 degrees per decade, with some lakes warming as much as 1.8 degrees Fahrenheit per decade.
The warming trend spans the globe, but is most pronounced in the mid- to high-latitudes of the Northern Hemisphere. Warming was weaker in the tropics and in the mid-latitudes of the Southern Hemisphere. That’s consistent with what’s expected based on most existing climate models, said Hook.
“Our analysis provides a new, independent data source for assessing the impact of climate change over land around the world,” said Schneider, lead author of the study published this week in the journal Geophysical Research Letters.
The researchers said warming could have serious consequences for some lake ecosystems, where small changes in water temperature can result in toxic algae blooms, or enable non-native species to survive and disrupt existing ecosystems.
Northern Europe showed the most significant warming trend, decreasing in southeastern Europe around the Black and Caspian seas and Kazakhstan. The trends increased slightly farther east in Siberia, Mongolia and northern China.
In North America, the warming trend was stronger in the southwest United States than in the Great Lakes region.
The surface temperature of lakes was warming faster than air temperatures, and Hook said he’s aren’t sure why, but more studies are planned to try and answer that question.
The NASA researchers used thermal infrared imagery from National Oceanic and Atmospheric Administration and European Space Agency satellites. They focused on summer temperatures (July-September in the Northern Hemisphere and January-March in the Southern Hemisphere) because of the difficulty in collecting data in seasons when lakes are ice-covered and/or often hidden by clouds. Only nighttime data were used in the study.
Hook said using nighttime readings helps reduce confusion from other nearby heat signals that may occur during the day.
The bodies studied were selected from a global database of lakes and wetlands based on size (typically at least 193 square miles or larger) or other unique characteristics of scientific merit. The selected lakes also had to have large surface areas located away from shorelines, so land influences did not interfere with the measurements. Satellite lake data were collected from the point farthest from any shoreline.
Filed under: Environment, global warming, Summit County Colorado Tagged: | European Space Agency, Geophysical Research Letters, global warming, global warming and lakes, Jet Propulsion Laboratory, JPL, NASA, National Oceanic and Atmospheric Administration, Summit County Colorado, Summit County News, Summit Voice