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It’s been a rough couple years for extreme weather. By this point, we all probably know someone who’s been affected by a recent weather catastrophe such as a hurricane, drought, flooding or wildfire. Even the most stubborn climate change skeptic might be starting to ask the question: Is this global warming?

According to Dr. Noah Diffenbaugh, professor of earth system science at Stanford University, the short answer is yes. The long answer may require a bit more explaining.

On Monday night, Diffenbaugh spoke to a crowded Cataldo Globe room about the connection between recent extreme weather events and global warming as part of Gonzaga’s annual O’Leary Lecture. Prior to this, Diffenbaugh gave a scientific lecture to students at noon in Hemmingson Auditorium titled “Quantifying the influence of global warming on unprecedented extreme climate events.”

During the public lecture, Diffenbaugh gave a general review of the mechanisms causing an increase in global surface temperature before diving into the primary literature he’s produced from his research.

According to Diffenbaugh, the atmosphere is mostly transparent to the shortwave wavelengths the sun emits, allowing them to enter our atmosphere and warm the Earth. Because of greenhouse gases, the atmosphere is mostly opaque to the longwave wavelengths the Earth is reflecting back, which traps the heat within.

This natural heating mechanism is important, because with only solar input, the Earth’s surface temperature would be about negative 18 degrees Celsius. However, human activity is increasing the concentrations of these greenhouse gases. When we increase the concentration, we increase the amount of heat being trapped in the atmosphere.

“Global warming is an observation or a measurement,” Diffenbaugh said, noting that Earth’s surface temperature has increased by one degree Celsius over the last century. “If you believe in thermometers, you have no choice but to believe the Earth is warming. If you believe we can measure temperature, that’s the result.”

Unfortunately, we can’t model climate change like a regular science experiment because we don’t have 100,000 Earths we can sample to figure out what will happen with a century of warming, but we can accurately simulate historical warming with high fidelity.

According to these models, the warming we’ve experienced so far is not consistent with natural forces such as volcanoes and solar variability alone. The model that fits with our observations is the one that accounts for human activity.

In recent years, we’ve been experiencing more extreme weather events and greater damage associated with these events. In 2017, the cost associated with this weather was $306 billion. Relatively, we now have more record hot days than record cold days, and severe heat has had an influence on the droughts in California, east Africa and Syria.

In California, despite an increase in average temperature, there has been no change in average precipitation. If this is the case, why have there been so many droughts? Diffenbaugh set out to answer this question with his research and found that all droughts happened in years with low precipitation (shocking, right?), but not all years with low precipitation caused drought.

According to his research, a year with low precipitation was twice as likely to produce drought if the low precipitation coexisted with warm temperatures. In the past two decades, 80 percent of years have been counted as warm. By 2040, it’s predicted that 100 percent of low precipitation years will coincide with extremely warm temperatures.

Despite this ominous-sounding news, Diffenbaugh encouraged the audience there is hope still out there. If we can transition to a carbon-free energy system by 2050, we have more than a 50 percent chance of staying below two degrees Celsius of warming. But as long as we keep releasing excess carbon into the atmosphere, the Earth’s temperature will continue to rise and we will continue to see hurricanes and floods wipe out our cities.

Rachael Snodgrass is an opinion editor. Follow her on Twitter: @ RachaelReneeee.

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