A team of scientists traced back the planet's history of drought in the past century, discovering clear signals of global warming affecting drought patterns as far back as 100 years ago.

More significantly, humanity's fingerprints are all over the research, showing that people have been influencing the climate — specifically, drought patterns — for longer than expected.

Researchers Link Global Warming To Hydroclimate

In a new study published in the journal Nature, scientists used advanced computer models and long-term observations of ancient tree rings to look at drought patterns historically. Findings show that global warming have been influencing the hydroclimate for a long time.

"This important paper offers new insights into the link between increasing atmospheric greenhouse gases and regional droughts, both in the past and increasingly in the future," said Peter Gleick, who cofounded the California's Pacific Institute and an expert on climate and water issues, in a news release from Columbia University.

He added that the study also confirms the increasingly sophisticated climate models and tools that are able to identify the impact of humans on extreme hydrologic events.

Three Drought Periods

The researchers identified three distinct periods in their period of study with the events of each period appearing to be linked to human activities.

During the first period from 1900 to 1949, there was a marked increase in global warming. Droughts were found to have increased globally with drying observed in Australia, Central America, North America, Europe, the Mediterranean, Western Russia, and Southeast Asia. Meanwhile, some regions became wetter, including Western China, Central Asia, Indonesia, Central Canada, and the Indian subcontinent.

The second period, from 1950 to 1975, stood out for its seemingly random events with no identifiable patterns in drought. Study authors note that massive amounts of aerosols were being released into the air during this period, which could have greatly affected the weather and masked the effects of greenhouse gases.

With the rise of clean-air regulations in 1970s onward, the amount of aerosols in the air began to stop increasing even with industrial activities continuing to rise. However, greenhouse gas emissions and global temperatures are still on the rise.

During this third period at the end of the 20th century, the global warming signature on hydroclimate emerged once again in the 1980s. While the connection isn't as it was in the early 20th century, scientists predict that it will become more apparent.

"If we don't see it coming in stronger in, say, the next 10 years, we might have to wonder whether we are right," said lead author Kate Marvel from Goddard and Columbia University. "But all the models are projecting that you should see unprecedented drying soon, in a lot of places."

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