What is the effect of increase in temperature on viscosity of gas

It increases. Rising temperature boosts molecular speeds and momentum exchange between layers, raising a gas’s internal friction (viscosity). Engineers model this with Sutherland’s law (μ ∝ T^{3/2}/(T+S)), widely applied for air and other gases in aerodynamics/CFD. 

Remember the contrast: liquids usually show decreased viscosity with temperature. In an exam, define viscosity briefly, state the trend for gases, quote Sutherland’s relation, and, if asked, contrast with liquids.