Fewer Basins Will Follow Their Budyko Curves Under Global Warming and Fossil-Fueled Development

Area of Science:

• Hydrology
• Climate Science
• Environmental Science

Background:

• The Budyko framework describes the relationship between water availability and evaporative demand in river basins.
• Basin hydroclimatic changes are visualized by movements within the Budyko space, indicating shifts in evaporation and aridity.
• Long-term aridity changes typically move basins along Budyko curves, while human activities can cause deviations.

Purpose of the Study:

• To investigate whether river basins will follow or deviate from their Budyko curves under future global warming and human development.
• To quantify projected movements in Budyko space for numerous river basins using climate model outputs.
• To assess the influence of different potential evaporation models and emissions scenarios on these projected movements.

Main Methods:

• Analysis of hydroclimatic changes in 405 river basins from 1901-1950 to 2051-2100.
• Utilized outputs from seven Coupled Model Intercomparison Project - Phase 6 (CMIP6) models.
• Compared results using two different potential evaporation models and considered low- and high-emissions scenarios (SSP1-2.6 and SSP5-8.5).

Main Results:

• Significant differences in projected basin movement within Budyko space were observed based on the potential evaporation model used.
• Over 72% of river basins are projected to deviate from their reference Budyko curves, irrespective of the potential evaporation estimate or emissions scenario.
• The proportion of deviating basins is higher under high greenhouse gas emissions (SSP5-8.5) and across both dry and wet climate regimes.

Conclusions:

• Future hydroclimatic conditions, influenced by climate change and human development, will likely cause widespread deviations from established Budyko relationships.
• High emissions scenarios exacerbate the deviation from Budyko curves, highlighting the significant impact of unchecked global warming and development.
• Further research is needed to fully understand the complex drivers behind these projected deviations from theoretical hydroclimatic pathways.