Climate change to decrease average number of mild weather days


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Residents enjoy pleasant weather at Noelridge Park in Cedar Rapids, Iowa. (Louis/flickr)
Jenna Ladd | January 24, 2017

The first of its kind, a recent study found that climate change is likely to decrease the number of “nice weather” days worldwide.

The authors of the study, scientists from the National Oceanic and Atmospheric Association and Princeton University, define “nice” or “mild” days as those days when temperatures are between 64 and 86 degrees Fahrenheit, dew points are below 68 degrees Fahrenheit and less than half of an inch of rain falls. Currently there are an average of 74 nice days globally per year, but that number is likely to drop to 70 in the next twenty years and to 64 by 2081.

Karin van der Wiel is a postdoctoral researcher at Princeton University and lead author of the study. She said,

“We used a climate model to simulate the current climate. In that simulation we counted the number of mild days. Then, we increased greenhouse gases in the climate model to simulate the future effects of climate change. This leads to increasing temperatures, changes in humidity, changes in precipitation over the whole world and with very specific patterns. In this new, future climate, we counted the number of mild days again. We could then calculate the change — increase or decrease — of mild weather days for each location globally.”

Not all corners of the Earth will be affected equally, however. Tropical regions are expected to lose the most nice days, with some areas losing up to 50 per year by the end of this century. Meanwhile, London is expected to gain 24 nice days each year.

Predictions for Cedar Rapids, Iowa mirror global averages. Eastern Iowa currently enjoys 76 nice days annually; researchers say that number is expected to drop to an average of 72 between 2016 and 2035 and to 66 each year between 2081 through 2100.

Frequent high humidity makes it tough for Iowa to meet the pleasant weather criteria outlined in the study. Absolute humidity has risen by 13 percent during the summer months in Des Moines since 1970, according to Iowa State climate scientist Gene Takle. Increased humidity also contributes to the extreme rain events that have plagued Iowa in recent years.

van der Wiel said, “Mild weather is something everyone knows, experiences, and has memories of,” she continued, “Our study shows that human-caused climate change is going to lead to changes in mild weather all over… The changes are happening now, and where people live.”

Wild reindeer shrink in size and number


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A recent study found that the largest herd of wild reindeer in the world’s population is decreasing rapidly due to warming temperatures in northern Russia. (Hermanni Tommonen/flickr)
Jenna Ladd | December 13, 2016

The wild reindeer, a holiday icon, is facing sharp population decline due to climate change.

Andrey Petrov, director of the University of Northern Iowa Arctic Center, led a study of the largest reindeer herd in the world, located on the Taimyr Peninsula in the northernmost tip of Russia. Petrov’s work shows that the herd’s population has dropped from 1 million reindeer in 2000 to about 600,000 today. Scientists say rising temperatures in the region may be the cause.

Petrov said, “Climate change is at least one of the variables.” He added, “We know in the last two decades that we have had an increase in temperatures of about 1.5C overall. And that definitely impacts migration patterns.” During his presentation at the Fall Meeting of the American Geophysical Union (AGU) in San Francisco on Monday, Petrov explained that the longer distance the animals have to travel in order to find cold weather is increasing calf mortality. When the reindeer have to travel further and to higher elevations in the winter, it is also more difficult to find land bearing food in the summer months. Petrov also explained that the region’s rivers are growing wider as ice in the area melts, causing more deaths as the herd attempts to swim across bodies of water.

“Reindeer are tremendously important for biodiversity – they are part of the Arctic food chain and without them other species would be in trouble,” he said. Petrov added, “Thousands and thousands of people rely on wild reindeer; it is the basis of their subsistence economy. So it’s about human sustainability too.”

Wild reindeer are also shrinking in size. Scottish and Norwegian researchers recently released a study which found that the average weight of reindeer on Svalbard, a chain of islands north of Norway, has fallen from 121 lb. in the 1990’s to 106 lb. today. Professor Steve Albon, an ecologist at the James Hutton Institute in Scotland, said, “Warmer summers are great for reindeer but winters are getting increasingly tough.” The researchers explained that less snowfall during warmer winters means that the reindeer have to traverse sheets of ice, making it harder for the animals to reach food sources.

In contrast to the Tamiyr population, the Svalbard herd is growing in size.”So far we have more but smaller reindeer,” Albon said. He added that the growing population means competition for food has become more intense.

Researchers perplexed by tornado clusters’ growing size


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An image of a tornado touching down in Oklahoma in May of 1981 from the National Oceanic and Atmospheric Administration’s photo archive. (NOAA/flickr)
Jenna Ladd | December 2, 2016

A recent study in the journal Science reveals that tornado outbreaks are growing in size, and scientists are unsure why.

The study was published just days after 18 tornadoes devastated parts of the Southeast United States Tuesday night into Wednesday morning. The study’s lead author, Michael Tippett of Columbia University, said that 50 years ago tornado clusters, may have involved about 12 tornados, now they average roughly 20. The researchers studied the most extreme outbreaks, which happen about once every five years, and discovered a steady increase in tornado cluster size since the mid-1960’s.

Before the outbreak on Tuesday, 2016 had seen a record low number of tornadoes. In an interview with the Associated Press, Tippett said,“Something’s up. The tornadoes that do occur are occurring in clusters. It’s not any increase in the (total) number of tornadoes.” In contrast with upticks in other kinds of extreme weather, researchers are not seeing a connection between human-induced climate change and larger tornado clusters. Tippett said, “It’s not what we expected. Either it’s not climate change because not everything is, or it is some aspect of climate change we don’t understand yet.”

The article mentioned that the circulation of warm water in the Pacific and Atlantic oceans could be responsible for the tornado clusters’ growth over the years, but there is no evidence yet to support this claim.

Other scientists question the validity of Tippett’s study, claiming that increased reporting and the prevalence of urban sprawl may be responsible for the perceived growth of tornado outbreaks. One critic is Howard Bluestein, a meteorology professor at the University of Oklahoma. He said, “It’s a useful exercise, but I would be very, very careful in accepting it.”

Seven people were killed by this week’s tornado cluster, several more were injured.

Precipitation in Iowa falls below average for first time since June


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Streamflow remains above average for much of northeastern Iowa as the state heads into the driest season of the year. (Iowa DNR)
Jenna Ladd | November 8, 2016

The Iowa Department of Natural Resources (DNR) recently released its latest Water Summary Update. Each update provides an overview of the status of Iowa’s water resources using four categories: precipitation, streamflow, drought, and shallow groundwater. The latest update provides a water resource snapshot of trends from October 10 through November 3.

As Iowa heads into the driest season of the year, stretching from November through February, October was recorded as the first month since June in which rainfall fell below normal levels. “Abnormally dry,” or drought conditions persisted for south-central Iowa, with the lowest reported October rainfall of 0.54 inches recorded in Story County. Areas of north central and northeastern Iowa, which had experienced heavy rainfall throughout much of September, saw drier conditions at last.

Temperatures throughout the month of October were warmer than they have been since 2007, averaging about 4.5 degrees above normal. This season’s first freeze is yet to occur for the Des Moines metro area, as well as far eastern and southeastern Iowa. The northwest two-thirds portion of the state experienced its first deep freeze on October 13.

Since the previous Water Summary Update, streamflow in the Chartion River Basin in south central Iowa has decreased to normal levels. However, streamflow for most of Iowa remains above average. More specifically, streamflow in the Cedar, Des Moines, and Upper Iowa River basins remain far above average. The forthcoming four months not only mark the driest season of the year, but also the most hydrologically stable. During this period of time Iowa usually receives about 15 percent of the year’s total rainfall, or 5.5 inches of precipitation. In contrast, summer months in the state bring more than 18 inches of precipitation on average.

Water Summary Updates are released every two weeks or as water resource conditions in Iowa significantly change. They are prepared by the Iowa DNR in partnership with Iowa Department of Agriculture and Land Stewardship, the U.S. Geological Survey, and The Iowa Homeland Security and Emergency Management Division. A complete record of Iowa Water Summary Updates can be found here.

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(Iowa DNR)

NOAA expects Iowa winter to be unpredictable


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Iowa falls between regions of the country that will a experience particularly  cold winter and those that will have a particularly warm winter. (NOAA)
Jenna Ladd | October 21, 2016

The National Oceanic and Atmospheric Administration (NOAA) released its predictions for winter weather on Thursday.

Last year the midwest experienced the warmest winter on record in 121 years, but this year NOAA says that Iowans can expect a grab bag of both warm and cold temperatures. Both temperature and precipitation are expected to hover around average from December through February for much of the state, except for the northern most part of the state, which is expected to be colder than usual.

NOAA also expects a weak La Niña this year. La Niña is characterized by particularly cold ocean temperatures in the Equatorial Pacific, and often affects weather trends in the United States. Variances in La Niña’s strength and duration from year to year can make forecasting winter temperatures difficult. Mike Halpert is deputy director with NOAA’s Climate Prediction Center, he said, “Because there is still some uncertainly about when La Niña will develop and persist through the winter, probabilities on the maps this year are fairly conservative.”

Winter 2015-2016 was the wettest Iowa winter on record in 101 years. Other parts of the Midwest and the Western U.S. are predicted to receive high amounts precipitation this year, with Idaho, North Dakota and the Ohio Valley all among those that will be affected. Unusually cool temperatures are on the forecast from Eastern Montana through Wisconsin.

In short, NOAA expects wetter and colder than usual temperatures for the far northern Midwest and warmer with drier winter conditions for the Southern U.S., and most of Iowa falls somewhere in the middle. Much like most winters, Iowans should prepare for anything.

CGRER members Jerry Schnoor, Larry Weber and Gene Takle share climate and flood prevention expertise with Iowans


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The Iowa River overflows onto the University of Iowa campus following the 2008 flood. (rachaelvoorhees/flickr)
Jenna Ladd | October 18, 2016

In the face of more frequent flooding and much heavier rains, it is estimated that Iowa will need $4 to $5 billion to protect its communities moving forward. 

Flood mitigation efforts in the state thus far have centered around building levees, flood walls, and protecting utilities, but Iowa researchers have found that upstream structures like wetlands and detention pounds are an effective means of flood prevention. Sen. Rob Hogg of Cedar Rapids said that some lawmakers have acknowledged the need to ramp up these strategies, but the conversation is often buried by health care and education budget arguments. Hogg said, “If you can’t reach agreement over funding the basics, it’s really hard to get to the next level, to discuss funding water management.”

The increasing frequency of extreme rainfall may demand that flood mitigation take center stage at the capital. “We were hard-pressed to get 4-inch rainfalls 100 years ago, and now it’s very common,” said Jerry Schnoor, co-director at the University of Iowa’s Center for Global and Regional Environmental Research. Eugene Takle, director of the climate science program at Iowa State University, agreed, “In the Cedar River basin, we found the 100-year flood a century ago is now very likely to be a 25-year flood.” The Cedar basin’s record flood in 2008 had a $5 billion price tag.

Takle and other experts say these changes are primarily due to climate change. Rising greenhouse gases in the atmosphere allow it to hold more water vapor. “When you have more water vapor, you can expect more rain events,” he said. Takle’s data support this claim: atmospheric water vapor has increased by 31 percent in the winter months since 1970 and by 14 percent in the spring; average annual rainfall in Iowa has risen by 33 percent since 1970. Takle said, “This is consistent with what the climate models said would happen. The Midwest has experienced a big increase in extreme events.” According to NOAA National Centers for Environmental Information, Iowa has had 26 flood disasters with damages adding up to more than $1 billion since 1980.

Larry Weber, director at the University of IIHR – Hydroscience & Engineering, parent organization of the Iowa Flood Center, said that the loss of prairie potholes and wetlands, which can soak up heavy rainfalls, has contributed to these flooding events. He said, “We’ve taken away a lot of those natural storage areas.”

Iowa lawmakers passed a sales-tax funding plan in 2012 to provide $1.4 billion in flood prevention structures, but more funding is needed. Eight-nine towns and cities have identified $35 million in flood prevention structures that do not have funding. Some Iowa lawmakers are working to increase the sales tax by three-eighths of 1 cent in order to fund the Natural Resources and Outdoor Recreation Trust Fund, which would provide $180 million each year to restore wetlands, protect wildlife habitat, reduce runoff and improve trails, and more.

One and a half million dollars in federal supplemental aid money allocated to the Iowa Flood Center’s Iowa Watersheds Project after the 2008 flood has reduced flooding downstream by 15-20 percent in the Otter, Beaver and South Chequest watersheds. The center received $98 million in federal grant money this year for similar flood mitigation projects in 25 additional watersheds. Weber said, “We’re making great strides in the places where we work, we just need to be working in more places — whether it’s through our projects, or the work of other state and federal agencies, private landowners, and nonprofit groups.”

On The Radio – Attributing extreme weather to climate change


An aerial shot of the 2008 flood along the Iowa River in Iowa City. (Tom Jorgensen/University of Iowa Libraries)
An aerial shot of flooding along the Iowa River just south of the University of Iowa campus in 2008. (Tom Jorgensen/University of Iowa Libraries)
Nick Fetty | May 2, 2016

This week’s On The Radio segment looks at a recent study that examines how climate change affects extreme weather events such as floods and droughts.

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Transcript: Attributing extreme weather to climate change

Scientists are becoming increasingly confident attributing extreme weather events to human-caused climate change.

This is the Iowa Environmental Focus.

A March study led by The National Academy of Sciences concludes that scientists are more able to determine how climate change affects the intensity and likelihood of some extreme weather events like floods and droughts. Extreme event attribution, a relatively new science according to the study, has made rapid advancements in the last ten years.

After extreme weather events like the record-breaking precipitation Iowans experienced in the winter of 2015, scientists are often asked if these events can be attributed to climate change. While few if any phenomena can be explained by climate change alone, scientists are now better able to determine how much of an effect climate change may have.

For more information about the study and climate modeling, visit IowaEnvironmentalFocus.org.

From the UI Center for Global & Regional Environmental Research, I’m Betsy Stone.