Declines in cooling sulfates combined with increases in greenhouse gas concentrations have increased the intensity and frequency of African
Excerpt from this story from Inside Climate News:
When Southern Europe was hit by a catastrophic heat wave last month, it dominated global news cycles. Spain experienced its longest heat wave on record: lasting 16 days with temperatures reaching 109 degrees. By August 19, wildfires stoked by the heat had torched more than 40,000 acres in France. At the peak of the heat wave, 60 percent of Italian cities were placed under the highest alerts for deadly temperatures. The death toll from the heat in Europe is still being tallied, but includes a four-year-old boy who died of heat stroke in Italy.
When higher-latitude, and thus cooler, regions that haven’t prepared for health-threatening high temperatures endure waves of unusual heat, they become obvious examples of heat stress brought on by a warming climate. But places that we assume are always hot have also been burdened by more extreme heat, Joyce Kimutai, principal meteorologist and climate scientist at the Kenya Meteorological Department, said.
“There was the misconception that, because Africa is warm anyway, people are tolerant to the heat,” she said. “I think that tolerance level is now superseded.”
Recent research published in Nature has found that the frequency and intensity of heat waves throughout Africa have increased significantly since the end of the 20th century. But the steep upward trend in temperatures on the continent is due not only to increases in the emissions that warm the climate. A decline in emissions that cool the Earth’s surface is also increasing the heat.
As greenhouse gas emissions, like carbon dioxide, have been increasing, efforts to clean up energy supplies have led to a decrease in coal burning in many areas, including Africa. While reductions in coal burning substantially reduce how much carbon dioxide is emitted to warm the climate in the long term, they also reduce the emissions of sulfates that reflect some heat away from the Earth in the short term. The combination of long-term climate warming and short-term reductions in planet-cooling sulfates has increased the frequency and intensity of heat waves throughout the continent over the past 30 years.
As sunlight warms the Earth’s surface, the planet sends some of this energy back to space. Carbon dioxide, methane and even water vapor in the atmosphere hold some of that heat in like a blanket—the more of those greenhouse gases in the atmosphere, the warmer the blanket. But certain aerosols—like sulfate particles, which are emitted along with carbon dioxide when coal is burned—act like mirrors that reflect some solar radiation away from the planet, thus cooling it.
In Africa, sulfate emissions from coal-producing and consuming countries such as Zimbabwe, Democratic Republic of the Congo and Namibia increased until the late 1980s along with greenhouse gas emissions.
