New study sheds light on global warming trends
TALLAHASSEE, Fla. — New research by a team of Florida State University scientists shows the first detailed look at global land surface warming trends over the last 100 years, illustrating precisely when and where different areas of the world started to warm up or cool down.
The research indicates that the world is indeed getting warmer, but historical records show that it hasn’t happened everywhere at the same rate.
And that new information even took scientists by surprise.
“Global warming was not as understood as we thought,” said Zhaohua Wu, an assistant professor of meteorology at FSU.
Wu led a team of climate researchers including Fei Ji, a visiting doctoral student at FSU’s Center for Ocean-Atmospheric Prediction Studies (COAPS); Eric Chassignet, director of COAPS; and Jianping Huang, dean of the College of Atmospheric Sciences at Lanzhou University in China. The group, using an analysis method newly developed by Wu and his colleagues, examined land surface temperature trends from 1900 onward for the entire globe, minus Antarctica.
Previous work by scientists on global warming could not provide information of non-uniform warming in space and time due to limitations of previous analysis methods in climate research.
The research team found that noticeable warming first started around the regions circling the Arctic and subtropical regions in both hemispheres. But the largest accumulated warming to date is actually at the northern midlatitudes. They also found that in some areas of the world, cooling had actually occurred.
“The global warming is not uniform,” Chassignet said. “You have areas that have cooled and areas that have warmed.”
For example, from about 1910 to 1980, while the rest of the world was warming up, some areas south of the equator — near the Andes — were actually cooling down, and then had no change at all until the mid 1990s. Other areas near and south of the equator didn’t see significant changes comparable to the rest of the world at all.
The team’s work is featured in the May 4 edition of the journal Nature Climate Change.
The detailed picture of when and where the world has warmed or cooled will provide a greater context to global warming research overall, Wu said.
The paper: Fei Ji, Zhaohua Wu, Jianping Huang, Eric P. Chassignet. Evolution of land surface air temperature trend. Nature Climate Change, 2014; DOI: 10.1038/nclimate2223
Evolution of land surface air temperature trend
The global climate has been experiencing significant warming at an unprecedented pace in the past century1, 2. This warming is spatially and temporally non-uniform, and one needs to understand its evolution to better evaluate its potential societal and economic impact. Here, the evolution of global land surface air temperature trend in the past century is diagnosed using the spatial–temporally multidimensional ensemble empirical mode decomposition method3. We find that the noticeable warming (>0.5 K) started sporadically over the global land and accelerated until around 1980. Both the warming rate and spatial structure have changed little since. The fastest warming in recent decades (>0.4 K per decade) occurred in northern mid-latitudes. From a zonal average perspective, noticeable warming (>0.2 K since 1900) first took place in the subtropical and subpolar regions of the Northern Hemisphere, followed by subtropical warming in the Southern Hemisphere. The two bands of warming in the Northern Hemisphere expanded from 1950 to 1985 and merged to cover the entire Northern Hemisphere.