MANHATTAN, Kan. – If ever there was a year to make one think about climate change, it may be this year.
“July marked the 36th consecutive July and 329th consecutive month with a global temperature above the 20th century average,” said Johannes Feddema, professor of geography at the University of Kansas. “The last below-average temperature July was July 1976 and the last below-average temperature month was February 1985.”
Feddema, who was speaking at the recent “Adapting to a Changing Climate on the Central Great Plains Conference” hosted by Kansas State University, said that so far, 2012 is the 10th warmest year on record globally, but in the U.S. it is the warmest year on record.
“Farmers already know how dry it is, coming into planting season in the context of their crops,” he said. “We as a society need to think about that, too.”
In more than 117 years of records, July 2012 stands alone as not only the hottest July on record in the lower 48 United States, but also the hottest of any month on record in that time span, according to the National Oceanic and Atmospheric Agency (NOAA). To put it another way, July 2012 was the hottest of more than 1,400 months that we've gone through since 1895.
The average temperature for the contiguous United States during July was 77.6 degrees F., which was 3.3 degrees above the 20th century average, marking the warmest July and all-time warmest month on record for the nation in a period that dates back to 1895, he added. The previous warmest July for the nation was July 1936, when the average U.S. temperature was 77.4 degrees.
“Our low temperatures now are much higher than they were in the ‘30s,” Feddema said, in comparing this year with the infamous drought years of the 1930s. “If we look back at the 1930s, average global temperatures were not that exceptional globally. The drought generally only affected the central U.S.”
He cited Environmental Protection Agency records covering 100 years from 1900 to 2000, that illustrated the average last spring frost and the first fall frost in the U.S. (excluding Hawaii and Alaska). Since 1970, the first fall frost has been trending later.
Climate Change and Agriculture
Agriculture contributes to climate change, but also is and will continue to be affected by climate change and variability, said Charles (Chuck) Rice, K-State university distinguished professor in agronomy.
“Citizens are already responding to climate change and some don’t even know it,” said K-State agronomy professor Dan Devlin. “Farmers are planting earlier than they did 30 or 40 years ago. We also have more double-cropping.”
Some conference speakers presented data showing that in general, the first fall freeze is coming later and the last spring freeze is coming earlier.
Even with evidence of earlier frost-free dates in the spring, however, farmers have to gauge the risk – if they plant early, they can still end up with the devastation of a killing freeze, said Stacy Hutchinson, professor of biological and agricultural engineering at K-State.
In most crops so far, there’s been a negative impact on yields from the changes occurring in the climate, Rice said, adding that yields have generally gone up in Kansas because of the development of better varieties, better management and better equipment. But there’s more variability in growing conditions.
“Every one of these dips has been related to weather,” said Rice as he displayed a chart showing crop yield trends. “Irrigation can moderate that, but can’t make up for the whole impact of the variability.”
Diseases that infect plants can be an indicator of climate change, said Karen Garrett, who is a plant pathologist at K-State. She gave the example of soybean rust, a disease that she and a team of researchers are currently studying. Soybean rust overwinters in the south and infects soybean plants as it moves north during the warmer months of the growing season. What happens if overwintering for diseases like this becomes easier farther north?
Rice, who served on the United Nations Intergovernmental Panel on Climate Change, provided the IPCC report’s projected changes for the climate of the U.S. Midwest, including fewer extreme high temperatures in summer in the short term, but more in the long term, as well as higher nighttime temperatures in both summer and winter. The report also predicted increased temperature variability.
The IPCC report also projected about 10 percent more precipitation annually in the Midwest, as well as a change in seasonality. Most of the increase in precipitation is expected to come in the first half of the year, meaning wetter springs and drier summers. There is also more variability in summer precipitation expected, including more intense rain events which could mean more runoff.
Rice said changes in agriculture practices have the potential to make a significant impact on climate change. As a soil scientist, he studies carbon sequestration – the process of transforming carbon in the air (carbon dioxide, or CO2) into stored soil carbon. Carbon dioxide is taken up by plants through photosynthesis, and incorporated into living plant matter. As the plants die, the carbon-based leaves, stems, and roots decay in the soil and become soil organic matter.
How can carbon sequestration aid in the fight against climate change? Atmospheric carbon dioxide, and other greenhouse gases trap heat that is reflected from the earth’s surface. This heat buildup could lead to global warming. Through carbon sequestration, atmospheric carbon dioxide levels are reduced as soil organic carbon levels are increased. If the soil organic carbon is undisturbed, it can stay in the soil for many years as stable organic mat¬ter. This carbon is then sequestered, or removed from the pool available to be recycled to the atmosphere. This process reduces CO2 levels in the atmosphere, reducing the chances of global warming.
Rice estimated that 20 percent or more of targeted CO2 emission reductions could be met by agricultural soil carbon sequestration. In cropland, some steps farmers can take to reduce greenhouse gas include: reduce tillage; rotate crops so as to have less bare fallow and increased crop intensity; plant cover crops; use fertilizer efficiently; and use irrigation efficiently.
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