After its third-wettest September on record, Iowa can expect a rainy October, too. The DesMoines Register reported that 4 to 5 inches of rain are forecasted to fall over most of the state in next few days. For some localities, it’s already started.
Southwest Iowa may be hit the hardest. Forecasts there predict 6 or more inches of rain.
The rain is expected to fall almost endlessly at least into early next week. National Weather Service meteoroligst Brooke Hagenhoff told the Register that the widespread nature of the forecast will likely increase the rainfall’s impacts on rivers and low-lying areas.
Some parts of the state are already saturated. Despite a fairly dry start to the month, flood alerts have been active for parts of the Des Moines, Cedar and Iowa Rivers throughout this week thanks to late-September rains in northern Iowa. The Iowa Flood Information System gauged a major flood stage for the Wapsipinicon River at DeWitt as of Wednesday afternoon.
May 2018 is the warmest month of May ever recorded in the United States according to the National Oceanic and Atmospheric Administration. It broke the long held record, which was set back in 1934, during the Dust Bowl. The average temperature recorded in May 2018 was 65.4 degrees, compared to the 64.7 degree average from May 1934.
This may come as a shock to Midwesterners, who saw several inches of snow fall this Sunday, April 15th. So what’s going on?
Among some other factors, the Greenland Block has a lot to do with the snowy spring of 2018, according to Dr. David Mechem of the University of Kansas. Mechem, a professor of geography and atmospheric science, explained that there is a persistent atmospheric area of high pressure above Greenland which funnels cold air from the poles straight into the mid-latitudes of North America. He told KCUR that the block was in place throughout February and March and is finally starting to break down, which would bring long-awaited warmer temperatures to the midwest.
Further research is needed to establish exactly what kind of effect climate change has on spring weather, but scientists are noticing some changes. Winter storms (even if they happen in April) have increased in frequency and intensity in the Northern hemisphere since 1950 according to the National Climate Assessment. Nor’easter winter storms plague the eastern U.S. and are caused by the the cold air from the Arctic and warm air from the Atlantic interplaying. This year, that region of the U.S. saw several Nor’easters in very quick succession, which is unusual. A recent study in the journal Nature Communications found that as the Arctic’s climate continues to warm at an alarming rate, winter storms becoming more likely in the eastern U.S.
The good news is that as the Greenland block continues to break down, residents of the mid-latitudes can expect spring to finally arrive. The bad news is that unpredictable spring weather can be expected to continue coming years as the climate continues to change.
Given that spring snow fell across Iowa this weekend, it may be hard to believe that the frost-free season across the U.S. is actually getting longer.
A recent report found that, on average, the last spring freeze is occurring earlier while the first fall freeze is happening later. Researchers define the frost-free season as the total number of days between the last day of 32 degree Fahrenheit or lower weather in the spring and the first day of 32 degree Fahrenheit weather in the fall.
The lengthening of this season means that pollen-producing plants have a longer growing period. One study in particular found that the growing season for ragweed, a common allergen in the U.S., lengthened by two to four weeks between 1995 and 2009. This data was collected from ten sites from the southern U.S. through Canada. Iowa has added nine days to the average length of its frost-free season from 1986-2015 when compared with the average from 1901-1960.
Dr. Joseph Shapiro, an allergist and immunologist from California told CBS news, “A recent study showed that pollen counts are likely to double by the year 2040, so in a little more than 20 years we’re going to see a significant increase [in seasonal allergies].”
Climate Central’s recent report provides an interactive graph that allows users to select a U.S. city and see how the frost-free season’s length there may have changed since 1970.
As the Northern Hemisphere enters warmer seasons where severe weather and flooding are more likely, it is yet to be seen whether 2018 will top 2017 as the most costly year for natural disasters ever.
Since 1980, the yearly average for natural disasters in the U.S. that cause more than $1 billion in damages has been 5.8 events. Last year, the country saw 16 such events, including three tropical cyclones, eight severe storms, two inland floods, a crop freeze, drought and wildfire. While this number technically ties with 2011, 2017 had more extreme weather as wildfires are tallied by region rather than single events, and last year brought more wildfires costing upwards of $1 billion than ever before.
The midwest U.S. saw at least two severe storms last year that caused more than $1 billion in damages, both of them in mid-June. Flooding associated with storms like these has caused some $13.5 billion in economic losses from 1988 to 2015 in Iowa alone, according to a recent op-ed by Iowa Flood Center Director Witold Krajewski. Midwesterners also faced early tornado outbreaks in 2017, which tore across the region in late February and early March. Both events cause more than $1 billion in damages.
The National Centers for Environmental Information point out that increased development in vulnerable areas like coastlines, floodplains and fire-prone areas are causing the increase in billion dollar disasters. Climate change plays a role too. They write,
“Climate change is also paying an increasing role in the increasing frequency of some types of extreme weather that lead to billion-dollar disasters. Most notably the rise in vulnerability to drought, lengthening wildfire seasons and the potential for extremely heavy rainfall and inland flooding events are most acutely related to the influence of climate change.”
The study analyzed U.S. Department of Agriculture data from more than 800 counties across North Dakota, South Dakota, Wyoming, Nebraska, Iowa, Colorado, Kansas, Oklahoma and Texas from 1968 through 2013. Collectively, they found that climate change caused about 25 percent of crop yield variance during that time. While temperature and precipitation changes were responsibile for 52 percent of crop fluctuations in some counties, they did not have any effect in others.
Similarly, the three crops that were studied: corn, soy and sorghum, all responded to the changing climate differently. Corn is more likely than the other two to be impacted by rising temperatures. When corn plants are not irrigated, yields are twice as likely to be harmed by increased temperatures. However, irrigated corn seemed to do relatively well in these conditions. Irrigated soy and sorghum plants were much less likely than non-irrigated plants to be negatively impacted by precipitation and temperature shifts too.
Suat Irmak and Meetpal Kukal are the study’s authors. They say that their work makes the case for continued climate change studies which consider different climate variables, crop types and growing conditions.
“I hope we are successful in getting across the message that there are changes in temperature and precipitation, (but) those changes are different over time and location, and they are having different impacts on our agricultural productivity,” Dr. Irmak said to the University of Nebraska. “That can help high-level advisers, decision-makers and policymakers to identify locations where those impacts are greatest so that resource allocation or re-allocation can make (fields) even more productive.”
Unfortunately, scientists say that the existing emission-reduction pledges by the world’s nations are not enough to keep temperatures from rising above 2 degrees Celsius. The study finds that if temperatures were to rise to 3 degrees hotter than preindustrial levels, North America would see at least a 300 percent increase in extreme weather events, for example.
Dr. Noah Diffenbaugh is a climate scientist at Stanford University and the study’s lead author. He said to the Scientific American, “In addition to not meeting the global temperature target, those commitments also imply substantial increase in the probability of record-setting events. Not only hot events but wet events, and also in other regions of the world, dry events as well.”
The study found that extreme heat records are the most likely to be affected by unabated climate change. Scientists focused primarily on North America, Western Europe and East Asia. They found that hotter-than-ever night time temperatures have been occurring much more frequently in recent years. If the climate warms to the 3 degree threshold, extreme heat events are expected to happen five times more frequently in half of Europe and at least three times more frequently in parts of Eastern Asia.
The study reads, “However, even if cumulative emissions are sufficiently constrained to ensure that global warming is held to 1° to 2°C, many areas are still likely to experience substantial increases in the probability of unprecedented [extreme weather] events.”