  We study the asymptotic behaviour of the nodal length of random
$2d$-spherical harmonics $f_{\ell}$ of high degree $\ell \rightarrow\infty$,
i.e. the length of their zero set $f_{\ell}^{-1}(0)$. It is found that the
nodal lengths are asymptotically equivalent, in the $L^{2}$-sense, to the
"sample trispectrum", i.e., the integral of $H_{4}(f_{\ell}(x))$, the
fourth-order Hermite polynomial of the values of $f_{\ell}$. A particular
by-product of this is a Quantitative Central Limit Theorem (in Wasserstein
distance) for the nodal length, in the high energy limit.
