Webinar offers skills for managing risk, climate change
By KAREN SCHWALLER
While global temperatures overall have warmed about 1.5 degrees in the last century, scientists are now seeing a plateau in that trend.
That assessment came from Jeff Johnson, chief science officer at DTN during a May 19 webinar geared to help farmers adjust crop management with climate change in mind.
Temperatures are not rising as steadily as they did in the 1980s and 1990s, Johnson said. Those years saw more El Nino occurrences, which causes warmer temperatures.
The last few years have seen more La Nina weather patterns, which typically indicate cooler weather.
Also affecting weather patterns are the North Atlantic Oscillation, which causes the jet stream to run a north-to-south pattern.
When in a negative mode the NAO brings colder air from central Canada into the eastern U.S.
During an El Nino and positive NAO combination, milder temperatures typically occur during the winter. But if the NAO is in a negative mode with El Nino, much less warming occurs in the northern U.S. and significantly colder temps prevail in the southern U.S.
“We’ve been in the warm Atlantic phase since the mid 1990s,” Johnson said. “We’re likely to be in this (same pattern) for the next decade or two.”
Johnson said a good part of North America, as well as Europe and Asia, tend to be warmer when the Atlantic Ocean is in the warm phase, and he said it could explain why scientists have seen warmer temperatures.
Other phenomena affecting weather cycles include the solar cycle – currently the U.S. is seeing a weak solar cycle, which could result in cooler temperatures.
Volcanic activity, land use changes (planting and tree clearing) and greenhouse gasses and emissions also combine to affect weather patterns.
Johnson said scientists are seeing more weather volatility than they have seen in the last 20 to 30 years and that extreme weather events are occurring more often than natural variability would suggest.
Examples include extended and warmer seasons, increased incidents of extreme dryness or wetness, more persistent periods of abnormal warmth or cold, extreme rainfall events and more frequency of extreme rainfall events, more concentrated periods of severe weather, more extreme heat.
Johnson said warming is occurring in the Arctic areas. The jet stream is becoming slightly weaker and Arctic sea ice measurements have been shrinking since 1992.
He said if “blockier” jet streams continue and the weather stalls out more, it could mean several impacts, including:
- Extended warm and cold periods.
- Increased wildfires in areas that have extended dry periods.
- Increased flash flooding due to stalled weather patterns.
- Increased drought conditions-particularly in the southwest U.S., which is currently in a pattern for drought over the next 12 years.
He predicted hurricanes to be more intense due to warmer water temperatures, and an increase in surprise events such as Hurricane Sandy, which made an unusual and unexpected left turn, which is not normal for hurricane activity.
Bryce Anderson, senior ag meteorologist for DTN, said the central part of the U.S. has seen rainfall “crowding itself” into the spring instead of spreading out through the spring and summer.
“That’s made a big difference in how producers have to manage their crops,” he said. “You have increased soil erosion with heavy rainfall on rolling ground, and there are also problems with heavy spring rains causing delayed planting.”
Anderson said acreage losses in the central U.S. occurred because of this, and that drainage tile has become a high priority because of it, even with its high cost of around $500 per acre.
“It has becomes essential not only in flat areas but in uplands,” he said. “Agriculture is having to adapt to a changing climate, especially with the timing of the amount of rainfall at a time.”
Summer rainfall in the Midwest and Eastern Corn Belt has not been as predictable as it once was, Anderson said, and as a result he is seeing an increase in center pivot irrigation systems.
He said drought is a big part of what occurs naturally in a changing climate.
“There has been a surge in droughts overall since 2000,” Anderson said. “In 2012, we had a drought that took in much of the country. The maximum area – 65.5 percent of the contiguous U.S. – was covered with drought. It was close to the drought of the mid-1950s.”
Anderson said not only is drought more of a feature of a changing climate, but also the speed in which drought develops is a hallmark.
“We have had flash droughts now, where drought conditions form over weeks instead of months, (and) twice in the last three years – 2011 and 2012,” Anderson said.
Anderson said these phenomena are items of concern that producers will need to keep in mind as they manage their crops over the next five to 10 years especially.
Johnson said weather forecasters predict El Nino conditions this year, bringing the chance of warmer weather patterns, and that the 2014 crop production year should be compared to the weather that occurred in 2009.
Anderson said with that benchmark, the discussion the U.S. Department of Agriculture has about yields possibly being above 165 bushels per acre is “right in step.”