Researcher Seeks to Improve Climate Models for Future Water Projections

According to a wider scientific consensus, the western part of the United States will have less water and the northeastern United States will have more due to climate change.

However, how much less and how much more is mostly uncertain, posing a crucial difficulty for the researchers, policymakers, and public servants tasked with guaranteeing water supply to the nation.

Flavio Lehner, assistant professor of earth and atmospheric sciences, is looking for ways to decrease that uncertainty, by enhancing the climate models on which future water projections rely. Lehner has been awarded a three-year, $500,000 grant from the National Oceanic and Atmospheric Administration (NOAA) to perform the study, starting this fall.

According to Dan Barrie, a program manager in NOAA’s Climate Program Office, Lehner’s study will enhance NOAA’s climate models and allow the agency to make better short-lived anticipations of floods and droughts and improved long-term predictions of the way in which surface water systems will develop in the 21^st century.

The United States is experiencing profound changes in its regional water resources. It is more urgent than ever to have the best modeling tools to provide a vision of these future changes so that we can take cost-effective measures now to mitigate and adapt to them.

Dan Barrie, Program Manager in Climate Program Office National Oceanic and Atmospheric Administration

Lehner’s study, which will enhance climate modeling throughout the world, is dependent on similar research he started in the Colorado River. Present estimates forecast that for every degree Celsius of global warming, the Colorado River will lose between 3% to 15% of its streamflow.

Lehner made a comparison of the variations in climate models to the discrepancy in human reactions to COVID-19—evaluating whether an individual has COVID-19 is comparatively simple, but anticipating how sick the virus will make each person is much harder. He said that a similar principle comes into play in climate modeling.

For example, for the Colorado River, all of the numbers point in the same direction–in a warmer climate, there will be less water. But the big uncertainty is how much less.

Flavio Lehner, Assistant Professor of Earth and Atmospheric Sciences, Cornell University

For the sensitivity of climate models to be tested, Lehner’s group is analyzing seven decades of data on temperature, precipitation, and streamflow to evaluate how well existing models would have anticipated what has taken place.

Lehner stated, “The most important question to us is: How sensitive are these models to changing environmental factors, such as changes in temperature and atmospheric greenhouse gases? And is their sensitivity consistent with what we see in reality?

The models employed by Lehner and his collaborators are highly complex and eventually more useful since they consider several interacting systems. Instead of just quantifying groundwater or rainwater, Lehner is analyzing how terrestrial, atmospheric, and hydrologic systems interplay, in the existence of growing temperatures and atmospheric greenhouse gases.

For instance, currently, there is 40% more carbon dioxide in the air compared to what there was 10 decades ago, and the earth is 1 °C warmer. Also if precipitation stayed neutral, those variations would make plants change their behavior—using up more groundwater to avoid parching and hence leaving less to become stream runoff available to humans. However, more complexity relates to more uncertainty.

We already have a sizable uncertainty because we don’t know how much precipitation is going to change, but if you go one step further and say, how does runoff or streamflow change? The uncertainty becomes even larger.

Flavio Lehner, Assistant Professor of Earth and Atmospheric Sciences, Cornell University

According to Barrie, there was considerable expansion of modern climate modeling in the 1980s, which has offered beneficial and precise data to assist researchers and policymakers plan and adapt. From 1980, the United States has undergone an average of 7.1 significant weather or climate disasters per year, each amounting to losses of over $1 billion. However, as per NOAA, in the last five years, the annual average of major disasters has increased to 16.2.

Barrie stated, “Improving climate models is one step to ensuring that equitable adaptation efforts can be implemented to minimize net negative impacts on people and the economy. The cost of investments like Dr. Lehner’s research project pales in comparison to the magnitude of the potential benefits.”