By Robert Pore

With the Senate likely to postpone debate on a climate change bill until next year, studies continue to point to possible problems facing agriculture if the atmoshpere continues to warm.

For example, Kansas State University’s Joseph Craine, research assistant professor in the Division of Biology, and KC Olson, associate professor in animal sciences and industry, have teamed up with some other scientists from across the United States to look into the possible effects of climate change on cattle nutrition.

Nebraska’s cattle industry is the biggest segement of the state’s ag industry at nearly $7 billion annually.

“Owing to the complex interactions among climate, plants, cattle grazing and land management practices, the impacts of climate change on cattle have been hard to predict,” said Craine, principal investigator for the project.

The lab measured the amount of crude protein and digestible organic matter retained by cattle in the different regions, according to the research.  The pattern of forage quality observed across regions suggests that a warmer climate would limit protein availability to grazing animals, Craine said.

“This study assumes nothing about patterns of future climate change; it’s just a what if,” Olson said. “What if there was significant atmosphere enrichment of carbon dioxide? What would it likely do to plant phenology? If there is atmospheric carbon dioxide enrichment, the length of time between when a plant begins to grow and when it reaches physiological maturity may be condensed.”

Currently, cattle obtain more than 80 percent of their energy from rangeland, pastureland and other sources of roughage, according to the study. With projected scenarios of climate warming, plant protein concentrations will diminish in the future, the study found. If weight gain isn’t to drop, ranchers are likely going to have to manage their herds differently or provide supplemental protein, Craine said.

Any future increases in precipitation would be unlikely to compensate for the declines in forage quality that accompany projected temperature increases, the research found. 

As a result, cattle are likely to experience greater nutritional stress in the future if these geographic patterns hold as a actual example of future climates, Craine said.

“The trickle-down to the average person is essentially thinking ahead of time of what the consequences are going to be for the climate change scenarios that we are looking at and how ranchers are going to change management practices,” Craine said.

“In my opinion these are fully manageable changes,” Olson said. “They are small, and being prepared just in case it does happen will allow us to adapt our management to what will essentially be a shorter window of high-quality grazing.”

In related news, new research found that spurred by a warming climate, daily record high temperatures occurred twice as often as record lows over the last decade across the continental United States.

The ratio of record highs to lows is likely to increase dramatically in coming decades if emissions of greenhouse gases continue to climb, the research found.

“Climate change is making itself felt in terms of day-to-day weather in the United States,” said National Center for Atmospheric Research (NCAR) scientist Gerald Meehl, the lead author. “The ways these records are being broken show how our climate is already shifting.”

The research was funded by the National Science Foundation (NSF), NCAR’s sponsor, the U.S. Department of Energy, and Climate Central.

“This intriguing study provides new evidence of climate change,” says Steve Nelson, NSF program director for NCAR. “And it’s change that’s affecting our daily lives.”

If temperatures were not warming, according to the research, the number of record daily highs and lows being set each year would be approximately even.

Instead, the research found that for the period from January 1, 2000, to September 30, 2009, the continental United States set 291,237 record highs and 142,420 record lows, as the country experienced unusually mild winter weather and intense summer heat waves.

A record daily high means that temperatures were warmer on a given day than on that same date throughout a weather station’s history.

The authors used a quality control process to ensure the reliability of data from thousands of weather stations across the country, while looking at data over the past six decades to capture longer-term trends.

This decade’s warming was more pronounced in the western United States, where the ratio was more than two to one, than in the eastern United States, where the ratio was about one-and-a-half to one, according to the study.

The study also found that the two-to-one ratio across the country as a whole could be attributed more to a comparatively small number of record lows than to a large number of record highs.

According to the study, much of the nation’s warming is occurring at night, when temperatures are dipping less often to record lows.

This finding, according to the research, is consistent with years of climate model research showing that higher overnight lows should be expected with climate change.

According to the study, if nations continue to increase their emissions of greenhouse gases in a “business as usual” scenario, the U.S. ratio of daily record high to record low temperatures would increase to about 20-to-1 by mid-century and 50-to-1 by 2100.

The mid-century ratio could be much higher if emissions rose at an even greater pace, or it could be about 8-to-1 if emissions were reduced significantly, the model showed.

The authors caution that such predictions are, by their nature, inexact.

Researchers said that climate models are not designed to capture record daily highs and lows with precision, and it remains impossible to know future human actions that will determine the level of future greenhouse gas emissions.

Researchers said the model used for the study, the NCAR-based Community Climate System Model, correctly captured the trend toward warmer average temperatures and the greater warming in the West, but overstated the ratio of record highs to record lows in recent years.

However, researchers said the model results are important because they show that, in all likely scenarios of future greenhouse gas emissions, record daily highs should increasingly outpace record lows over time.

“If the climate weren’t changing, you would expect the number of temperature records to diminish significantly over time,” says Claudia Tebaldi, a statistician with Climate Central who is one of the paper’s co-authors.

“As you measure the high and low daily temperatures each year, it normally becomes more difficult to break a record after a number of years. But as the average temperatures continue to rise this century, we will keep setting more record highs.”

The study team focused on weather stations that have been operating since 1950. They found that the ratio of record daily high to record daily low temperatures slightly exceeded one to one in the 1950s, dipped below that level in the 1960s and 1970s, and has risen since the 1980s.

The results reflect changes in U.S. average temperatures, which rose in the 1950s, stabilized in the 1960s, and then began a warming trend in the late 1970s, according to the study.

Even in the first nine months of this year, when the United States cooled somewhat after a string of unusually warm years, the ratio of record daily high to record daily low temperatures was more than three to two, the study found.

Despite the increasing number of record highs, there will still be occasional periods of record cold, Meehl said.

“One of the messages of this study is, you still get cold days,” Meehl says. “Winter still comes. Even in a much warmer climate, we’re setting record low minimum temperatures on a few days each year. But the odds are shifting so there’s a much better chance of daily record highs instead of lows.”

The study team analyzed several million daily high and low temperature readings taken over the span of six decades at about 1,800 weather stations across the country, thereby ensuring ample data for statistically significant results.

The readings, collected at the National Oceanic and Atmospheric Administration’s National Climatic Data Center, undergo a quality control process at the data center that looks for such potential problems as missing data as well as inconsistent readings caused by changes in thermometers, station locations, or other factors.

Meehl and his colleagues then used temperature simulations from the Community Climate System Model to compute daily record highs and lows under current and future atmospheric concentrations of greenhouse gases.