CO2 Concentrations Linked to Flood Size

Investigators from the United States Geological Survey (USGS) have determined in a new research that the concentrations of carbon dioxide (CO2) in Earth's atmosphere is only weakly correlated to the size of floods affecting North America.

The team is however keen to point out that these results do not exclude finding a much stronger link in upcoming investigations. For the current research, scientists found that only one in four regions in the US exhibited a statistically significant correlation between the two.

USGS scientists tested for links spanning back as much as 100 years. They discovered that the southwestern region of the US experienced smaller floods since atmospheric CO2 levels increased.

Full details of this research will appear in a paper that has already been accepted for publication in an upcoming issue of the Hydrologic Sciences Journal. Climate experts expect increased flood frequency to be one of the main discernible effects of global warming.

Estimating future flood risks and developing effective flood mitigation strategies for the future has therefore become an important objective for authorities around the world. The USGS investigation is part of such an effort conducted in the United States.

The datasets the team used spanned a total of 127 years, between 1881 and 2008. Experts analyzed all the historical records of floods that happened during this interval in the country. The investigations covered more than 200 sites across the nation.

“Currently we do not see a clear pattern that enables us to understand how climate change will alter flood conditions in the future, but the USGS will continue to collect new data over time and conduct new analyses as conditions change,” researcher Robert Hirsch explains.

“Changes in snow packs, frozen ground, soil moisture and storm tracks are all mechanisms that could be altered by greenhouse gas concentrations and possibly change flood behavior. As we continue research, we will consider these and other factors in our analyses,” he adds.

Hirsch holds an appointment as a research scientist at the USGS, and was also the lead author of the study. He explains that the data the team found on the southwestern region of the country is in tune with other studies, showing that climate change is now bringing less precipitations to this area.

“The relationship between greenhouse gas concentrations and floods is complex, demonstrating the need for long-term streamflow data to help guide future flood hazard mitigation and water resources planning,” USSGS Climate and Land Use Change associate director Matthew Larsen explains.

“USGS streamgages provide real-world data to help scientists understand this relationship. Planning for water supplies and flood hazards should be informed by a combination of predictive modeling approaches as well as statistical approaches such as this study,” he concludes.