The evidence that greenhouse gases have a major impact on climate continues to pile up. Scientists have conducted a number of studies demonstrating that carbon dioxide and other gases do create a “greenhouse effect” that can cause global warming.
This new research looks at historical data that suggest increased levels of greenhouse gas concentrations thousands of years ago were a significant factor in huge amounts of rainfall in two major regions of Africa.
Greenhouse gases were the answer to an African climatological puzzle
Climate scientists have long puzzled about the changes in the African climate when the glaciers retreated from North America and northern Europe around 21,000 years ago. The rainfall level in Africa began to go up dramatically around 14,700 years ago and the trend continued until 5000 years ago.
The level of rainfall was so high that the Sahara desert was converted into savanna and grassland, hence the scientists called this time the African Humid Period. What scientists didn’t understand was why the same precipitation phenomenon occurred at the same time in two well-separated regions, one north of the equator and one to the south. This was the first time that natural global warming has been directly associated with a known increase in the concentration of carbon dioxide and other greenhouse gases.
Statement from researchers
“This study is a step toward solving the puzzle of what triggered abrupt changes in rainfall over southeastern equatorial and northern Africa during early deglaciation,” explained Anjuli Bamzai, the program director in NSF’s Division of Atmospheric and Geospace Sciences, who sponsored the study.
Bamzai continued: “Through an analysis of proxy records and climate model simulations, the team demonstrated that the recovery of what’s called the Atlantic Meridional Overturning Circulation, or AMOC, played a role as an initial trigger to wetter conditions.”