Loutre, Marie-France
[UCL]
Mouchet, Anne
[Université de Liège]
Fichefet, Thierry
[UCL]
Goosse, Hugues
[UCL]
Goelzer, Heiko
[Vrije Universiteit Brussels]
Huybrechts, Philippe
[Vrie Universiteit Brussels]
Many sources of uncertainty limit the accuracy of
climate projections. Among them, we focus here on the parameter uncertainty, i.e. the imperfect knowledge of the values of many physical parameters in a climate model. There-
fore, we use LOVECLIM, a global three-dimensional Earth
system model of intermediate complexity and vary several
parameters within a range based on the expert judgement of
model developers. Nine climatic parameter sets and three
carbon cycle parameter sets are selected because they yield
present-day climate simulations coherent with observations
and they cover a wide range of climate responses to doubled
atmospheric CO2 concentration and freshwater flux perturbation in the North Atlantic. Moreover, they also lead to a large
range of atmospheric CO2 concentrations in response to prescribed emissions. Consequently, we have at our disposal
27 alternative versions of LOVECLIM (each corresponding
to one parameter set) that provide very different responses
to some climate forcings. The 27 model versions are then
used to illustrate the range of responses provided over the
recent past, to compare the time evolution of climate variables over the time interval for which they are available (the
last few decades up to more than one century) and to identify
the outliers and the “best” versions over that particular time
span. For example, between 1979 and 2005, the simulated
global annual mean surface temperature increase ranges from
0.24 !C to 0.64 !C, while the simulated increase in atmospheric CO2 concentration varies between 40 and 50 ppmv.
Measurements over the same period indicate an increase in global annual mean surface temperature of 0.45 !C (Brohan
et al., 2006) and an increase in atmospheric CO2 concentration of 44 ppmv (Enting et al., 1994; GLOBALVIEW-CO2,
2006). Only a few parameter sets yield simulations that reproduce the observed key variables of the climate system
over the last decades. Furthermore, our results show that the
model response, including its ocean component, is strongly
influenced by the model sensitivity to an increase in atmospheric CO2 concentration but much less by its sensitivity
to freshwater flux in the North Atlantic. They also highlight
weaknesses of the model, in particular its large ocean heat
uptake
Bibliographic reference |
Loutre, Marie-France ; Mouchet, Anne ; Fichefet, Thierry ; Goosse, Hugues ; Goelzer, Heiko ; et. al. Evaluating climate model performance with various parameter sets using observations over the recent past. In: Climate of the Past, Vol. 7, p. 511-526 (2011) |
Permanent URL |
http://hdl.handle.net/2078.1/75257 |