Joe and Mary built a house.
They built it on an old flood plain of a small river, though there’d not been a flood in years. This was a 500-year flood plain. Not a very floody flood plain at all.
The local zoning code required that for a new house at their location the bottom of the basement needed to be above a certain elevation, with fill brought in around the house to raise the surrounding landscape. But Joe’s uncle was on the zoning board, and it wasn’t that hard to get a variance. This saved them thousands of dollars, and they built the house without the raised foundation or the fill.
Over the previous fifty years much of the hilly wooded land up river from Joe and Mary’s house had been converted to agriculture. This changed the nature of the flow of rain across the land surface and into the groundwater. It caused the streams to rise more quickly when it rained, rather then slowly over several days fed by springs linked underground to the forest. Downstream, a century ago, engineers built a bridge for the new road, and they put the pilings closer than would be done in modern times. This caused flotsam from spring floodwaters to accumulate at the bridge, backing up water quite a good distance upstream. A large marsh that fed into the river, upstream from Joe and Mary’s house, normally flooded during high water, holding much of the excess. But about a decade ago, Joe’s uncle built a large housing development there, filling the marsh. There was controversy, and it was even covered in the local Pennysaver, but he got the variance. All these things would have made flooding near Joe and Mary’s house to be much worse than otherwise, but that never happened. The 500-year flood zone hadn’t had any 500-year floods in a long time, maybe 500 years.
Meanwhile, while the forest was being cleared, the road and its bridge built, the housing development constructed over the marsh, and Joe and Mary’s house erected, everybody was putting CO2, a greenhouse gas, into the atmosphere. By the last decade or so of the 20th century, there was significant global warming. The increase in global surface temperature was not even; The Arctic warmed more than the rest of the planet. This caused a change in the behavior of the polar jet stream. Instead of occasionally becoming curvy and kinky and slow moving, the jet stream started to do this all the time. Then these waves went “quasi resonant” meaning that the large curves and loops would sit in one place for a long time, weeks or months. Meanwhile the heated up atmosphere started to take on more water vapor. Air that was wet enough to rain in the old days held the vapor longer because of the warmth, but when the super saturated air let the water out in the form of rain or snow, there was a lot of it. Since the weather systems follow the jet stream, they slowed down and would hang around for a long time in one region, raining and raining and raining while elsewhere there would be short term droughts.
One day, at Joe and Mary’s house, it started to rain. It rained four or five inches in a week. The basement got wet. The tomatoes were overwatered, and their leaves cringed. Everybody’s shoes started to smell. The dark, cloudy, wet days produced a sense of ennui.
Then, on the eight day, it really rained. It rained four inches in one day. The groundwater had been saturated, the streams and the river were already high. The torrential rainstorm raised the river to the 100 year flood level. Then to the 500 year flood level. Then a few feet more. Joe’s uncle’s housing development flooded. The bridge with its jam of flotsam became a dam. The water flowed around Joe and Mary’s house, filling the first floor with three feet of dirty water. Snakes took refuge on their roof. Their car floated away.
Eventually the water receded and Joe and Mary’s home was a total loss. The insurance guy had come by to give them the good news. They would receive a full payout for replacement cost of the home. While they were chatting, the insurance guy noted that the flood was caused by the dam of tree branches and house parts down at the bridge. Joe remembered his uncle’s housing development, the controversy about the flood basin, and noted that may have been a problem. The insurance guy agreed. Mary said she had read about how replacing forest with corn fields made runoff worse, so the streams and rivers would flood more. Joe and the insurance guy nodded. Yes, yes, that was a factor too. Nobody mentioned the fact that Joe and Mary had failed to build their home to code, but they were thinking it. They didn’t mention it because, really, they would only have raised the whole house by about two and a half feet, and the flood was higher than that, so what did that matter?
A few days later Joe and Mary were down at the coffee shop to meet a contractor to talk about using their insurance money to build a new house. They were sitting with the contractor going over preliminary plans, but were distracted by two graduate students form the nearby university sitting at the table next to them. They were talking about the flooding. They were talking about how global warming, caused by that CO2 being released into the atmosphere all these years, had caused the flooding. They were talking about the amplification of warming in the Arctic, the jet streams getting curvy and slowing down, the quasi resonant waves and the extra moisture in the atmosphere.
The contractor became annoyed. He had heard about global warming and all that, everybody had. But he also knew that the last four winters were unusually cold and snowy. His cousin had bought a Tesla electric car a few months earlier, and his cousin was an annoying tree hugging hippie. And, he remembered, he had heard an actual climate scientist on the TV the other day saying something about global warming and storms. In fact, he remembered quite clearly what the scientist had said. And now he wanted to say it too.
The contractor turned to the two graduate students, and got their attention. “Couldn’t help overhear your conversation,” he said to them. “But you know, you can’t attribute a single flood, or other weather event, to global warming. This was just a flood.”
Global warming. Dancing backwards and in high heels for more than 20 years.*