A Multicointegration Model of Global Climate Change

We model the role of the ocean in climate change, using the concept of
multicointegration. Surface temperature and radiative forcing cointegrate and the
accumulated cointegration disequilibria represent the change in Earth system heat
content, which is predominantly stored in the ocean. System heat content in turn
cointegrates with surface temperature. Using a multicointegrating I(2) model, we find that
the climate sensitivity is 2.8ºC and the rate of adjustment to equilibrium is realistically
slow. These results contrast strongly with those from I(1) cointegration models and are
more consistent with global circulation models. We also estimate Earth system heat
content as a latent variable for the full period, 1850-2014, and this predicted heat content
cointegrates with available ocean heat content observations for 1940-2014.