Since the start of the Industrial Age, the atmosphere and the oceans have warmed up, the amount of snow and ice has diminished and the sea level has risen. These are observed changes that no set of circumstances can explain without factoring in the increase in the greenhouse effect that has been caused by the emission of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N20) from human activities over the past 100 years.
“It is settled science,” says Forrest Melton, senior research scientist at California State University Monterey Bay and associate program manager for water resources with the NASA Applied Sciences Program. He recently gave a webinar on the subject to Western Growers members through the association’s Science & Technology Department, and also discussed the topic with WG&S.
Melton said there is consensus among the climate science community that global warming is a fact and caused in great part by the burning of fossil fuels for energy and transportation, with deforestation and some types of agriculture also contributing emissions. The good news is that there is still time to alter the course of the future and increase the likelihood that our climate in the U.S. in 2100 is not vastly different than the one we have today. However, make no mistake about it that best case scenario future will not exist unless global, coordinated action is soon enacted…and we are not yet on that path.
Melton said climate scientists have modeled four scenarios for the next 85 years, each assuming a different level of CO2 emissions over that time period. If we stay on the current path, the worst case scenario will persevere. That assumes a continued increase in CO2 emission with a more than doubling of current levels in the atmosphere by 2100. According to the modeling Melton articulated, that would result in an average global temperature increase of 5-9 degrees F. Under that scenario, Omaha, Nebraska, and similar northern U.S. regions, would register summertime temperatures similar to what Phoenix experiences today. In fact, if that scenario plays out, the vast majority of the United States will have summertime temperature similar to what we see in Southwest desert regions today.
Under the best case scenario, CO2 and other greenhouse gases in the atmosphere will continue to increase until about mid-century. At that point, actions instituted today, or at least very soon, would start to result in a reduction of CO2 in the atmosphere and by 2100, be back close to current levels of around 400 ppm, which is where they are today. The amount of CO2 in the atmosphere first topped 400 ppm in May of 2013, higher than it has been for the past 800,000 years, and 40% higher than at the start of the Industrial Age. Because these emissions have a lifespan of decades to centuries, Melton said current emissions, as well as those released in the past century, have already committed us to a future that can only be altered incrementally and slowly.
During the climate change webinar, Melton focused on the effects global warming will have on agriculture. He opined that the very real global temperature rise has set the world on a course of “the greatest experiment ever conducted on agriculture in the United States.” In general, wet areas are becoming wetter and dry areas are becoming dryer. Extreme weather conditions — be they drought or floods — are increasing
Just how will production agriculture respond to the conditions that it will almost surely face in the coming decades? Regardless of any course correction that may be enacted in the next decade or so, temperatures will rise in the coming decades and agriculture will be affected. Melton said there will be more frost free days, less chilling hours and warmer temperatures on average. The added CO2 in the atmosphere may result in greater growth and increased yields in some crops such as wheat and cotton in the short term. However, those conditions will also create greater weed growth and more pests. Some of the more northern environs in the United States will have longer frost free seasons, but desert growing regions, as well as some current productive land in the San Joaquin Valley and other like environments, will most likely see the summer growing season impacted by increasing maximum temperatures and changes in water supplies for irrigation. With less chilling hours, tree and nut crops may also have difficulty producing crops as they do today.
Melton said new varieties will need to be developed that are more drought and heat tolerant. Over the long run, research has shown that as temperatures rise, yields will decline in many different crop types. Because increased temperatures are coming and it could take years and even decades to develop new varieties, Melton said resources need to be allocated for that research as soon as possible.
Though the webinar painted a fairly dire picture, Melton did indicate there is room for optimism. In the first place, he said there is a clear path toward change. For example, Spain has altered its energy course through the use of renewable and nuclear energy. Currently 33 percent of Spain’s energy comes from renewable resources and 21 percent comes from nuclear power. The United States lags far behind with 9 percent from renewable sources and 8 percent from nuclear power. But he is encouraged as the cost of renewable power — most notably solar energy — has come way down in price in the past five years.
The climate scientist also pointed to California’s energy use over the past four decades as a successful model. While all the other states in the United States have nearly doubled their per capita use of energy over those 40 years, California’s residential use has remained flat, largely because of increased energy efficiency. Others could follow suit and make a dent in fossil fuel use and associated greenhouse gas emissions.
Melton said most of the initial steps to reduce CO2 emissions involve actions that have a net economic savings as well, such as the use of more fuel efficient cars and better lighting technology as well as switching to better tillage methods and more efficient use of fertilizer and irrigation through better management.
However, Melton was quick to point out that agriculture’s contribution to CO2 emissions is only about 10 percent of the total, with methane gas from livestock production and rice paddies being the largest ag contributors. Hence whatever mitigation efforts agriculture takes, it cannot solve the problem by itself. He reiterated that the burning of fossil fuels is the chief contributor to CO2 emissions and climate change.
But Melton said agriculture does have a very important role to play in the debate to take substantive action to change the current course. “The agricultural industry can have a very strong voice in this discussion,” he said. “Agriculture is one of the most vulnerable industries to climate change. By speaking up they could change the political conversation on climate change.”
He added that one of the most important things anyone can do is to contact their elected representatives and discuss the issue and their concerns. “Farmers have a truly powerful voice on this topic and have the ability to influence policy in ways that climate change scientist never will. That is one of the most powerful mitigation options available today for the agricultural industry.”
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