Future climatic changes: Are we entering an exceptionally long interglacial?

Abstract

Various experiments have been conducted using the Louvain-la-Neuve two-dimensional Northern Hemisphere climate model (LLN 2-D NH) to simulate climate for the next 130 kyr into the future. Simulations start with values representing the present-day Northern Hemisphere ice sheet, using different scenarios for future CO2 concentrations. The sensitivity of the model to the initial size of the Greenland ice sheet, and to possible impacts of human activities, has also been tested. Most of the natural scenarios indicate that: (i) the climate is likely to experience a long lasting (~50 kyr) interglacial; (ii) the next glacial maximum is expected to be most intense at around 100 kyr after present (AP), with a likely intersradial at ~60 kyr AP; and (iii) after 100 kyr AP continental ice rapidly melts, leading to an ice volume minimum 20 kyr later. However, the amplitude and, to a lesser extent, the timing of future climatic changes depend on the CO2 scenario and on the initial conditions related to the assumed present-day ice volume. According to our modelling experiments, man's activities over the next centuries may significantly affect the ice-sheet's behaviour for approximately the next 50 kyr. Finally, the existence of thresholds in CO2 and insolation, earlier shown to be significant for the past, is confirmed to be also important for the future.