Global Climate Desk: Scientists are examining the potential for climate change to increase the frequency and geographical reach of droughts lasting several consecutive years, raising concerns about long-term pressure on water supplies, agriculture and ecosystems.

New climate research suggests that prolonged drought events could become more common in many parts of the world as temperatures rise, with the magnitude of the changes depending strongly on future greenhouse-gas emissions.

What are multi-year droughts?

Unlike a drought lasting a single season, a multi-year drought continues for two or more consecutive years.

Such events can be particularly difficult to manage because water reserves may not have enough time to recover between dry periods.

Reservoirs, groundwater systems, agricultural soils and ecosystems can all experience cumulative stress when precipitation remains below normal for extended periods.

Climate change can increase drought risk

A warmer atmosphere can hold more water vapour, potentially increasing evaporation from land and vegetation.

When elevated temperatures occur alongside insufficient rainfall, soils can lose moisture more rapidly.

This combination can intensify drought conditions even in areas where annual precipitation does not decline dramatically.

Different emission scenarios produce different outcomes

Climate researchers use different greenhouse-gas emission scenarios to examine possible future conditions.

A study highlighted by the U.S. National Oceanic and Atmospheric Administration examined changes in multi-year drought risk under different warming scenarios.

The research found that the geographical area exposed to prolonged drought could expand substantially under higher-emission conditions.

Under a lower-emission scenario, researchers estimated that roughly one-third of global land areas could experience increased multi-year drought risk. Under a high-emission pathway, the affected area could rise to approximately 62%.

These figures represent modelled future changes rather than predictions that every location within those areas will experience continuous drought.

Agriculture faces major challenges

Long-lasting drought can have serious consequences for agriculture.

Reduced soil moisture can lower crop yields and increase demand for irrigation.

If drought continues across several growing seasons, farmers may have fewer opportunities to recover from one failed harvest before another dry period begins.

Livestock can also be affected by shortages of water and pasture.

Water supplies can decline

Multi-year droughts can reduce water stored in reservoirs, rivers and groundwater systems.

This creates difficulties for cities and industries that depend on reliable freshwater supplies.

Hydropower generation can also be affected when reservoirs and rivers fall below normal levels.

Water managers therefore need to prepare not only for individual dry years but also for the possibility of drought continuing for several years.

Ecosystems can face cumulative stress

Natural ecosystems can sometimes recover from short-term droughts.

Repeated or prolonged dry conditions, however, can increase tree mortality, reduce vegetation growth and alter habitats.

Wildlife may also face shortages of food and water.

In some ecosystems, drought combined with extreme heat and wildfire can create additional environmental pressure.

Drought is not only about rainfall

Scientists emphasize that drought conditions are influenced by several factors.

Rainfall is important, but temperature, evaporation, soil moisture, snowpack, groundwater and human water consumption can also determine how severe a drought becomes.

Climate change can therefore affect drought risk even when changes in precipitation are relatively modest.

Better planning will become increasingly important

Long-term water planning can help communities prepare for more persistent dry conditions.

Measures may include improving water-use efficiency, protecting groundwater, increasing reservoir flexibility, developing drought-resistant agricultural practices and restoring ecosystems that help retain water.

Early-warning systems can also provide governments and communities with more time to respond when drought conditions begin to develop.

Emissions influence future risks

The research highlights the relationship between greenhouse-gas emissions and future drought exposure.

Lower emissions would reduce the amount of additional warming and therefore limit some of the climate changes that can intensify drought risk.

Higher emissions would lead to greater warming and potentially more extensive areas experiencing prolonged drought conditions.

A growing climate challenge

Multi-year droughts represent a particularly difficult climate risk because their impacts can accumulate over time.

Understanding where these events could become more frequent can help governments, farmers and water managers prepare for changing conditions.

The research does not mean that every region will experience increasing drought. Instead, it shows that climate change can substantially alter the geographical distribution and persistence of drought risks, making long-term adaptation and water planning increasingly important.