Two Disturbing Tales of Warming
Seen from the air this spring, the Midwest looked like a marsh, not the fertile fields that grow the nation’s most lucrative crops. This has been one of the rainiest springs on record for the region, forcing many farmers to leave their flooded fields untended.
It is difficult to causally link a single weather event to climate change. Still climate scientists say the devasting rains falling over the Midwest were in line with what they’ve been predicting. In future they expect an increase in total precipitation there, especially in winter and spring, coming as ever more dramatic weather events.
Early June is the latest corn can be planted, and mid-June is the latest for soybeans. After that, temperatures climb too high and too little rain falls for a successful crop. The Department of Agriculture reported that on May 28 only 58% of the corn and 29% of the soybeans had been planted—a big problem for farmers who supply a quarter of the world's grains.
Much of the rain falling over midwestern states originates over the warming waters of the Gulf of Mexico. As the atmosphere there warms, it absorbs more moisture, which it ultimately must dump somewhere. The 2018 National Climate Assessment projects the U.S. to face more catastrophic flooding that will affect crops and infrastructure as the atmosphere continues to warm.
Rain does more than just prevent crops from being put in the ground. Young roots can be damaged by too much moisture, making it difficult for the plants to grow. Extreme rainfall can be just as bad for crops as drought or intense heat.
The economic impact on farmers and consumers depends on this summer’s weather. Late-planted crops will be pollinating at a hot time, which could stress those crops. Corn used in cattle feed will likely be more expensive. A poor harvest will affect other industries and drive up prices in the grocery store.
As for a strategy for the future, geneticists can modify crops to withstand floods or drought, but to do both will be challenging. And while climate change has yet to push farmers to change their practices, after a year like this that might finally change.
Meanwhile farther north, scientists at the University of Alaska Fairbanks report in the journal Geophysical Research Letters that unusually warm summers in the Canadian high arctic between 2003 and 2016 resulted in 150% to 240 % greater permafrost melt than the 1979‐2000 average. The change in such a short time is unprecedented. Scientists had predicted the permafrost wouldn't melt for another 70 years. However, those early forecasts didn't anticipate the unusually warm summers of recent years. The three areas of melting permafrost studied in remote northern Canada are believed to have been frozen for thousands of years.
The disappearing permafrost leaves behind thermokarst, a sinking landscape pockmarked with ponds, holes and mounds. In one area the researchers studied, the ground sank as much as 3 feet over a 12-year period. When the research team started monitoring these sites back in the early 2000s, the landscape was fairly flat and easily walkable. They did not expect it would change so rapidly. Now there are troughs up to 3 feet deep, small ponds, and vegetation never before seen in the area.
Rapidly melting permafrost exacerbates the problem of climate change by exposing thawing biological material to the atmosphere where it decomposes and releases CO2 and methane, powerful greenhouse gases both. The loss of permafrost wreaks havoc on animal habitat, migration patterns and food supply in the wild, and agriculture and infrastructure in populated areas. Houses are sinking into the ground in parts of Alaska, Canada and Russia. The destabilizing land caused by melting permafrost has seriously damaged a 92-mile road in Alaska's Denali National Park.
The data illustrate that despite low mean annual ground temperatures, very cold (under ‐10°C) permafrost with massive ground ice close to the surface is highly vulnerable to rapid degradation and thermokarst development. This is due to scant thermal buffering from soil organic layers and surface vegetation, and to the presence of near-surface ground ice. Observed maximum thaw depths at the studied sites already exceed those previously projected to occur in 2090.
The Midwest and the North. Two separate areas, two distinct effects. The common thread is a warming climate and its impact on Earth’s hydrology.