Reciprocal climate-sensitivity uncertainty ($\Delta T_{2\times }=F_{2\times }/\lambda$)

A symmetric positive uncertainty interval for a stabilizing feedback coefficient produces asymmetric uncertainty in its reciprocal. With both cooling magnitude $x$ and forcing magnitude $f$ uncertain, constant-sensitivity lines are rays $x/f=\mathrm{constant}$; tangents from the origin to a Gaussian covariance ellipse give a one-parameter profile interval for the ratio. A unit-radius two-variable covariance ellipse is not itself a 68 percent joint confidence region.