Humans have contributed to increased global risks of drought for more than a century, scientists say, in findings that also point to "severe" consequences ahead with climate change.

The research by US-based scientists and published in Nature journal on Thursday comes as the latest Bureau of Meteorology data showed the first four months of 2019 were the hottest on record for Australia as drought tightened its grip on the country's south-east.

Australia is among the regions of the world where the drying trend is clearest. Credit:Christopher Lorrimer

The scientists, led by Kate Marvel at NASA's Goddard Institute for Space Studies, used so-called drought atlases derived from tree-ring data combined with satellite observations and climate models to identify how soil moisture has changed.

They found drought increased during the first half of the 20th century, eased in the quarter century to 1975 and worsened again. The pause in the trend coincided with increased aerosol pollution.