Climate Crystal Ball
By Emma Macmillan
If someone told you they could accurately predict how different the climate of a specific city would be forty years from now, you probably would be a bit skeptical. But a trio of UT civil and environmental engineering researchers crunched some huge numbers to develop the first local climate models to calculate what conditions will be like in 2050.
Joshua Fu, associate professor, John Drake, research professor, and Yang Gao, a former graduate research assistant, devised a method called dynamical downscaling to link existing global and regional models to measure climate impact for a small area.
Drawing data from multiple sources, the Community Earth System Model (CESM) combines atmosphere, land, ocean, and ice models spanning from 1850 to 2000 to make predictions based on various levels of greenhouse gas emissions. A Weather Research Forecast (WRF) model is then used to downscale the data to a resolution as small as four square kilometers.
“Combined models are a more precise representation of the real world than models that only look at one component,” Fu says. “By ensuring that the models can picture the past 150 years, and comparing that picture with observational data, we can make reasonable predictions about future climate change.”
The CESM/WRF process would not be possible without the supercomputing power of Oak Ridge National Laboratory’s Titan and UT’s Kraken. Fu’s team logged ten million combined hours on these machines, comparable to 100 years on a personal computer.
To mirror the majority of other climate models, the researchers targeted 2050. “Thirty years of change translates to climate change, whereas weather has to do with the daily forecast,” Fu says. “We’re not trying to find the weather conditions on a certain day.”
Fu’s research group focused on densely populated cities such as New York, Chicago, Detroit, Baltimore, and Boston because climate changes in such areas affect more people. The results indicate an increased likelihood of severe weather events and higher average temperatures.
“What we’re predicting are more intense and longer heat waves, which could ultimately cause more deaths,” Fu says. In fact, Chicago’s 1995 heat wave was blamed for over 450 deaths.
While the Southeast has the highest intensity in heat waves, the Northeast is likely to experience the highest average temperature increase. “We are looking at increases of 3 to 5 degrees Celsius, with New York experiencing the highest hike,” Fu says.
But heat waves aren’t the only issue. A significant rise in precipitation is also in the cards. The cities of Philadelphia, Baltimore, Washington, DC, Virginia Beach, and Boston are projected to be a lot wetter. More specifically, Fu expects Philadelphia will experience a 105 percent increase, Baltimore a 76 percent increase, and Virginia Beach a 67 percent increase–which suggests a greater risk of dangerous flooding.
“We looked into cities because the Centers for Disease Control and the Environmental Protection Agency can use that information immediately to make plans of action,” Fu explains. “Global models give information, but decision-makers cannot necessarily use that information with as much relevance or immediacy.” Fu also points out that looking at cities can actually help inform global models by improving the model resolutions.
The study’s predictions of heat waves and higher precipitation levels are based on current fossil fuel emissions. “If we continue to use coal as a fuel source, we will continue to have extreme weather,” Fu says. “If we switch to natural gas and renewable energy now, we can prevent or reduce these extreme weather occurrences.”
Additionally, Fu emphasizes the importance of energy policy to slow down climate change. “If we continue to emit the same level of greenhouse gases, there is a greater chance that we will have very high temperatures happening in the future,” Fu says. “You might have low temperatures some days, but we’re looking at an average. We’re also looking at acute damage to human health, since very high temperatures cause human death, along with the loss of crops, livestock, animals, and forests.”
Fu is planning additional research that will investigate even narrower areas of land. For instance, the CDC requested a one-square-kilometer resolution to predict temperature and precipitation increases. “You could look at specific neighborhoods in a city,” Fu says. “With that type of specificity, scientists could more accurately explore the locations with more or less intense extreme weather events, and encourage policy makers to take immediate action to reduce the impact of these events.”
The advent of this new technology allows us to see the future with confidence. It has the potential to save thousands of lives. But it also reminds us of the permanent damage that might occur if energy production methods are not changed. Believe it or not.