In the context of which of the following do some scientists suggest the use of cirrus cloud thinning technique and the injection of sulphate aerosols into the stratosphere?

* Cirrus clouds do not reflect a lot of solar radiation into space. As they form at high altitudes and cold temperatures, they trap long-wave radiation and have a climate impact similar to greenhouse gases. Thus, thinning cirrus clouds would reduce the absorption of infrared radiation and are proposed as a form of climate engineering to reduce global warming. * Another proposed Geo-engineering technique involves injecting reflective sulphate aerosol particles into Earth's lower stratosphere to cast a small proportion of the inbound sunlight back into space and cool the planet off. Thus, both are climate engineering/ Geo-engineering techniques to reduce global warming.