What does the data show?
This data shows
the monthly averages of maximum surface temperature (°C) for 2040-2069 using a
combination of the CRU TS (v. 4.06) and UKCP18 global RCP2.6 datasets. The
RCP2.6 scenario is an aggressive mitigation scenario where greenhouse gas
emissions are strongly reduced.
The data combines
a baseline (1981-2010) value from CRU TS (v. 4.06) with an anomaly from UKCP18
global. Where the anomaly is the change in temperature at 2040-2069 relative to
1981-2010.
The data is
provided on the WGS84 grid which measures approximately 60km x 60km (latitude x
longitude) at the equator.
Limitations of the data
We recommend the use of multiple grid cells or an average of
grid cells around a point of interest to help users get a sense of the
variability in the area. This will provide a more robust set of values for
informing decisions based on the data.
What are the naming conventions
and how do I explore the data?
This data contains a field for
each month’s average over the period. They are named 'tmax' (temperature maximum),
the month and ‘upper’ ‘median’ or ‘lower’. E.g. ‘tmax Mar Lower’ is the average of the daily minimum
temperatures in March throughout 2040-2069, in the second lowest ensemble
member.
To understand how to explore the data, see this page: https://storymaps.arcgis.com/stories/457e7a2bc73e40b089fac0e47c63a578
Please note, if viewing in ArcGIS Map Viewer, the map will
default to ‘tmax Jan Median’ values.
What do the ‘median’,
‘upper’, and ‘lower’ values mean?
Climate models are numerical representations of the climate
system. To capture uncertainty in projections for the future, an ensemble, or
group, of climate models are run. Each ensemble member has slightly different
starting conditions or model set-ups. Considering all of the model outcomes
gives users a range of plausible conditions which could occur in the future.
To
select which ensemble members to use, the
monthly averages of maximum surface temperature for the period 2040-2069 were calculated
for each ensemble member and they were then ranked in order from lowest to
highest for each location.
The ‘lower’ fields
are the second lowest ranked ensemble member.
The ‘upper’ fields
are the second highest ranked ensemble member.
The ‘median’ field is the central value of the
ensemble.
This gives a median value, and a
spread of the ensemble members indicating the range of possible outcomes in the
projections. This spread of outputs can be used to infer the uncertainty
in the projections. The larger the difference between the lower and upper
fields, the greater the uncertainty.
Data source
CRU TS v. 4.06 -
(downloaded 12/07/22)
UKCP18 v.20200110
(downloaded 17/08/22)
Useful links
Further information on CRU TS
Further information on the UK Climate Projections (UKCP)
Further information on understanding climate data within the Met Office Climate Data Portal