Related: Why does rain smell good? What's interesting to climate scientists about the Green Sahara is how abruptly it appeared and vanished. The termination of the Green Sahara took only years, Johnson said. The change in solar radiation was gradual, but the landscape changed suddenly. The next Northern Hemisphere summer insolation maximum — when the Green Sahara could reappear — is projected to happen again about 10, years from now in A.
But what scientists can't predict is how greenhouse gases will affect this natural climate cycle. Paleoclimate research "provides unequivocal evidence to what [humans] are doing is pretty unprecedented," Johnson said. Even if humans stop emitting greenhouse gases today, these gases would still be elevated by the year That said, there's geologic evidence from ocean sediments that these orbitally-paced Green Sahara events occur as far back as the Miocene epoch 23 million to 5 million years ago , including during periods when atmospheric carbon dioxide was similar to, and possibly higher, than today's levels.
So, a future Green Sahara event is still highly likely in the distant future. Today's rising greenhouse gases could even have their own greening effect on the Sahara, though not to the degree of the orbital-forced changes, according to a March review published in the journal One Earth.
But this idea is far from certain, due to climate model limitations. Meanwhile, there is another way to turn parts of the Sahara into a green landscape; if massive solar and wind farms were installed there, rainfall could increase in the Sahara and its southern neighbor, the semiarid Sahel, according to a study published in the journal Science.
Wind and solar farms can increase heat and humidity in the areas around them, Live Science previously reported. An increase in precipitation, in turn, could lead vegetation growth, creating a positive feedback loop, the researchers of that study said. However, this huge undertaking has yet to be tested in the Sahara Desert, so until such a project gets funding, humans might have to wait until the year or longer to see whether the Sahara will turn green again.
Live Science. Image 1 of 6. Image 2 of 6. Image 3 of 6. When most people imagine an archetypal desert landscape—with its relentless sun, rippling sand and hidden oases—they often picture the Sahara. The now-dessicated northern strip of Africa was once green and alive, pocked with lakes, rivers, grasslands and even forests.
So where did all that water go? Archaeologist David Wright has an idea: Maybe humans and their goats tipped the balance, kick-starting this dramatic ecological transformation. In a new study in the journal Frontiers in Earth Science , Wright set out to argue that humans could be the answer to a question that has plagued archaeologists and paleoecologists for years.
The Sahara has long been subject to periodic bouts of humidity and aridity. With more rain, the region gets more greenery and rivers and lakes. All this has been known for decades.
But between 8, and 4, years ago, something strange happened: The transition from humid to dry happened far more rapidly in some areas than could be explained by the orbital precession alone, resulting in the Sahara Desert as we know it today.
The northeastern winds dry out the air over the desert and drive hot winds toward the equator. These winds can reach exceptional speeds and cause severe dust storms that can drop local visibility to zero. Dust from the Sahara travels on trade winds all the way to the opposite side of the globe. Precipitation in the Sahara ranges from zero to about 3 inches of rain per year, with some locations not seeing rain for several years at a time.
Occasionally, snow falls at higher elevations. Daytime summer temperatures are often over degrees Fahrenheit 38 degrees Celsius and can drop to near-freezing temperatures at nighttime. The area of the Sahara desert has grown nearly 10 percent since , according to a study published in the Journal of Climate. While all deserts, including the Sahara, increase in area during the dry season and decrease during the wet season, human-caused climate change in conjunction with natural climate cycles, are causing the Sahara desert to grow more and shrink less.
The study's authors estimated that approximately a third of the desert's expansion was due to human-made climate change.
One proposal for mitigating the effects of climate change is to install large-scale wind and solar farms in the Sahara. The farms would provide clean energy and reduce the amount of greenhouse gases entering the atmosphere, and may also promote increased precipitation in the vicinity, according to a study published in the journal Science.
Simulations showed that in areas with wind farms, there would be warmer temperatures, especially at night, caused by the wind turbines bringing warm air to the surface from higher in the atmosphere. The researchers also estimated that precipitation over the wind farms would double on average, thereby increasing vegetation by an estimated 20 percent. The solar farm simulations produced similar results. The study authors predicted that a large-scale Saharan wind farm would produce approximately 3 terawatts of electrical power, while a large-scale Saharan solar farm would produce about 79 terawatts, which greatly exceeds the 18 terawatts of electrical power that were consumed in
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