Met Office Hadley Centre observations datasets
Home > CRUTEM3 >

Change in the urbanisation component of the CRUTEM3 error series

In October 2006, we corrected a bug in the bias error estimates for CRUTEM3 distributed from this website. Note that the best estimate values are unchanged, the effect of the bug was to make the error ranges slightly too big.

When the CRUTEM3 dataset was developed, the uncertainty due to possible biases arising from changes in the environment of the stations caused by increasing urbanisation was assessed to have a 1 sigma value increasing from 0 in 1900 to 0.005C in 1990, and extrapolated linearly after that. (For details, see the paper). Unfortunately, when calculating the error fields and time-series provided on this website we used an urbanisation uncertainty estimate that was twice this size. This caused a slight overestimate in the total error ranges; the two figures below illustrate the difference.

Timeseries with incorrect estimates
CRUTEM3 global annual series with the doubled urbanisation uncertainties
Timeseries with correct error estimates
CRUTEM3 global annual series with the corrected urbanisation uncertainties

If you downloaded CRUTEM3 uncertainties data from this site before October 2006, please download replacements. Note that the best-estimate data is unaffected, only the uncertainties have changed. We're sorry for this error, if you want any further information, please contact us.

This change also effects HadCRUT3.

Commercial and media enquiries

You can access the Met Office Customer Centre, any time of the day or night by phone, fax or e-mail. Trained staff will help you find the information or products that are right for you.
Contact the Met Office Customer Centre