Greenhouse gas emissions affect rainfall and future climate patterns in Africa, according to a new report. Thousands of years ago, the release of greenhouse gases resulted in increased levels of rainfall in two areas of the African continent.
About 21,000 years ago, ice sheets covering North America and northern Europe began to recede. The climate in Africa responded in a way that led modern researchers to question their models. Precipitation on the continent became more common, from around 14,700 years ago until 3,000 years before the Common Era.
Known as the African Humid Period (AHP), this era saw deserts turn to savannas rich with life. The great question facing researchers was why these conditions were seen in two widely separated regions, on opposite sides of the equator, at the same time.
Migration of the Earth's axis moved the planet so that the northern hemisphere was closest to the Sun during summer. The Earth is currently closest to our stellar companion while the northern hemisphere experiences winter. Thousands of years ago, additional solar heating would have fueled monsoon winds in the northern half of the globe, fueling rainfall.
"The future impact of greenhouse gases on rainfall in Africa is a critical socioeconomic issue. Africa's climate seems destined to change, with far-reaching implications for water resources and agriculture," Bette Otto-Bliesner of the National Center for Atmospheric Research (NCAR) said.
Sediment was analyzed, along with other methods of measuring past rainfall. This data was used in a computer simulation, in an effort to understand ancient climatic changes on the world's second-largest continent.
The southeastern equatorial region of Africa experienced similar climatic changes when summers were cooler than normal. Researchers discovered a change in currents within the Atlantic Ocean, and natural releases of carbon dioxide led to increased precipitation around large areas of the continent. About 11,000 years ago, carbon dioxide reached levels nearly as high as those seen near the beginning of the industrial revolution.
As the last major ice age began to recede around 17,000 years ago, polar ice caps in the north and south started to melt, releasing vast quantities of fresh water into the salty oceans, altering natural currents, affecting the environment. When ice sheets ceased their retreat, normal circulation resumed, leading to increased precipitation in southern Africa.
This study provides new evidence that the contemporary release of carbon dioxide and other greenhouse gases could have a profound impact on climate in Africa.
The effect of greenhouse gas emissions on the climate of Africa was detailed in the journal Science.
