Comparing CMIP5 & observations

[Given recent interest in previous comparisons of CMIP5 simulations and observations of global mean surface air temperature, this is now a permanent page which will be incrementally updated as more data accumulates]

The figure below shows a comparison of CMIP5 simulations & observations of global mean surface air temperature, using a 1986-2005 reference period, and is an updated version of Figure 11.25 from IPCC AR5. The HadCRUT4 observations are shown in black with their 5-95% uncertainty in red. The Cowtan & Way v2.0 global temperature fills the gaps in the HadCRUT4 data and is shown in blue.

The grey shading shows the CMIP5 5-95% range for historical (pre-2005) & all future forcing pathways (RCPs, post-2005); the grey lines show the min-max range. The red hatching indicates the IPCC AR5 assessed likely (>66%) range for the 2016-2035 period. The UK Met Office forecast for 2014 is shown by the green error bar.

Notes: (1) Post-2005, the RCP forcings are used in the simulations rather than observational estimates of the forcing. (2) Whether the recent observations are inside or outside the 5-95% CMIP5 range is strongly dependent on the reference period chosen. (3) As the HadCRUT4 dataset has gaps over the Arctic it is likely to be a slight underestimate of the true recent global temperature anomaly, as the Cowtan & Way infilling technique suggests. (4) In this figure, the CMIP5 simulations are NOT masked to the HadCRUT4 observational coverage, unlike some previous examples on this blog.

Updated version of IPCC AR5 Figure 11.25 with HadCRUT4 (black & red) and Cowtan & Way (blue) global temperature timeseries. The CMIP5 model projections are shown relative to 1986-2005 (light grey). The red hatching is the IPCC AR5 assessed likely range for global temperatures in the 2016-2035 period.

UPDATES:
31st January 2014: Added “Note (4)” about masking.
30th January 2014: Added “Note (3)” about missing data in the Arctic.
27th January 2014: Page created.

One Response to Comparing CMIP5 & observations

  1. Pingback: Updates to comparison of CMIP5 models & observations | Climate Lab Book

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