The phrase "large gradient" refers to a steep change or difference between two points. It is used to describe how quickly or drastically something changes, either in terms of quantity, direction, or position. Full definition
On the contrary, independent data on both ocean sediments in the Sargasso Sea and dendrology favor repeated strong temperature oscillations with comparably large gradients in historic times. (link.springer.com)
(Also, with respect to the T ^ 4 issue, the lower gradients results in smaller radiative losses than a planet with large gradients — all things being equal. (rabett.blogspot.ru)
That is why small temperature gradients result in small amounts of energy transfer and large gradients result in large energy transfers. (theinconvenientskeptic.com)