As fossil fuel emissions continue to climb, reducing the amount of sunlight hitting the Earth would definitely have a cooling effect on surface temperatures.
The reduction in sunlight can be accomplished by geoengineering schemes. There are two classes: the so-called “sunshade” geoengineering scheme, which would mitigate climate change by intentionally manipulating the solar radiation on the earth's surface; the other category removes atmospheric CO2 and sequesters it into the terrestrial vegetation, oceans or deep geologic formations.
However, a new study from Lawrence Livermore National Laboratory, led by atmospheric scientist Govindasamy Bala, shows that this intentional manipulation of solar radiation also could lead to a less intense global water cycle. Decreasing surface temperatures through “geoengineering” also could mean less rainfall.
In the new climate modeling study, Bala and his colleagues Karl Taylor and Philip Duffy demonstrate that the sunshade geoengineering scheme could slow down the global water cycle.
The sunshade schemes include placing reflectors in space, injecting sulfate or other reflective particles into the stratosphere, or enhancing the reflectivity of clouds by injecting cloud condensation nuclei in the troposphere. When CO2 is doubled as predicted in the future, a 2 percent reduction in sunlight is sufficient to counter the surface warming.
This new research investigated the sensitivity of the global mean precipitation to greenhouse and solar forcings separately to help understand the global water cycle in a geoengineered world.
While the surface temperature response is the same for CO2 and solar forcings, the rainfall response can be very different.
“We found that while climate sensitivity can be the same for different forcing mechanisms, the hydrological sensitivity is very different,” Bala said.
The global mean rainfall increased approximately 4 percent for a doubling of CO2 and decreases by 6 percent for a reduction in sunlight in his modeling study.
“Because the global water cycle is more sensitive to changes in solar radiation than to increases in CO2, geoengineering could lead to a decline in the intensity of the global water cycle” Bala said.
A recent study showed that there was a substantial decrease in rainfall over land and a record decrease in runoff and discharge into the ocean following the eruption of Mount Pinatubo in 1991. The ash emitted from Pinatubo masked some of the sunlight reaching the earth and therefore decreased surface temperatures slightly, but it also slowed down the global hydrologic cycle.
“Any research in geoengineering should explore the response of different components of the climate system to forcing mechanisms,” Bala said.
For instance, Bala said, sunshade geoengineering would not limit the amount of CO2 emissions. CO2 effects on ocean chemistry, specifically, could have harmful consequences for marine biota because of ocean acidification, which is not mitigated by geoengineering schemes.
“While geoengineering schemes would mitigate the surface warming, we still have to face the consequences of CO2 emissions on marine life, agriculture and the water cycle,” Bala said.
- PHYSICAL SCIENCES
- EARTH SCIENCES
- LIFE SCIENCES
- SOCIAL SCIENCES
Subscribe to the newsletter
Stay in touch with the scientific world!
Know Science And Want To Write?
- Prevent Alzheimer's Disease By Drinking Beer?
- Acceptance Of Evolution Is Far Higher Than Acceptance Of Other Biology
- Planck on BICEP2 "It turns out that the part of the dust had been significantly underestimated."
- Hardwired For Miscommunication? Why Women Think Sex When Men Just Want To Be Friends
- The ATLAS Top Production Asymmetry And One Thing I Do Not Like Of It
- Extended Telomeres Slow Cell Aging
- "I find that very interesting. On the one hand, I certainly understand what you mean in not wanting..."
- "Hi KJ,you never do that, as changing your inputs after looking at your answer is anathema - it..."
- "You went from 0 to Crackpot in two short comments. ..."
- "Save your lectures on the scientific method for the academic 'cuspy halo problem' deniers when..."
- "Right, and if 90 percent of science media focused on the anti-science beliefs of Democrats I would..."