Climate Change in Qube

Qube allows you to estimate the climate change adjusted FDC and annual+monthly mean flows. The various acronyms used below are explained in the glossary at the end.

Climate change estimates are based on the UKCP18 eFLaG meteorological datasets and the CERF2-HadUK generalised rainfall-runoff model.

A summary of the datasets and process is presented below. Please see the 'Development of CERF2-HadUK' and 'Development of climate change adjusted flow statistics in Qube' reports for more details.

Climate forcing data

The eFLaG gridded meteorological datasets were used as meteorological forcing data. These are based on UKCP18 12km resolution RCM using RCP 8.5 with a 12-member PPE for the period December 1980 to November 2080. In Qube these are identified as RCM01, RMC02 etc to 15. RCP 8.5 is a pathway where greenhouse gas emissions continue to grow unmitigated, leading to a best estimate global average temperature rise of 4.3°C by 2100.

The hydrological rainfall-runoff model and calculation of climate change

The meteorological forcing data, above, were input to the CERF2-HadUK generalised rainfall-runoff model for the ~11,000 TSEP catchments across Great Britain.

Key percentiles (Q10, Q20, Q30, Q40, Q50, Q60, Q70, Q80, Q90, Q95) and annual+monthly mean flows were extracted for each epoch:

  • Baseline: Jan 1989 - Dec 2018
  • Near future: Jan 2020 - Dec 2049
  • Far future: Jan 2050 - Dec 2079

Via comparison with the baseline, percentage changes were calculated for each RCM and near and far future, for both the FDC percentiles and annual+monthly mean flows.

Application in Qube

Qube selects the most similar TSEP catchment to the ungauged catchment, based on distance and catchment descriptors. It then applies the percentage changes from the selected TSEP catchment both to the ungauged natural FDC and the annual+monthly mean flows (based on the full period of record) to calculate climate change adjusted flows.

Note on uncertainty

When interpreting the climate-change-adjusted flows it is important to note the limitations and uncertainties associated with the generation of the datasets. The meteorological forcing datasets from eFLaG represent only one climate model, using one emissions scenario, and one bias correction and downscaling method. The RCM PPE, and the associated widely varying meteorological and hydrological outcomes, illustrates some of the uncertainty related to the parameterisation of the RCM.

The results from Qube are based on one model; CERF2-HadUK. It is recognised that there can be large differences between the magnitudes of the changes using different hydrological models, particularly at low flows. However, when percentage changes at key percentiles on the FDC are compared at gauging stations to the other hydrological models used in the eFLaG project, Qube's results are shown to be comparable.

Climate change glossary

  • UKCP18: UK climate projections and tools that form part of the Hadley Centre Met Office Climate Programme.
  • eFLaG: Enhanced Future Flows And Groundwater. A project led by the UK Centre for Ecology and Hydrology (UKCEH) which used UKCEP18 data to produce downscaled and bias-corrected meteorological datasets and future flow projections for a selection of catchments.
  • CERF2-HadUK: the second iteration of the Continuous Estimation of River Flows model, calibrated using the Met Office's Hadley Centre historical dataset
  • RCM: regional climate model
  • PPE: perturbed parameter ensemble
  • RCP: representative concentration pathway
  • TSEP catchments: catchments for which a time series of exceedence percentiles is available
  • FDC: flow duration curve